Arctic Sea Ice : Forum

Cryosphere => Antarctica => Topic started by: prokaryotes on November 23, 2017, 07:07:57 PM

Title: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: prokaryotes on November 23, 2017, 07:07:57 PM
Rapid collapse of Antarctic glaciers could flood coastal cities by the end of this century. Based on an article written by Eric Holthaus.

http://www.youtube.com/watch?v=Pp5kK0Td-Vc
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: gerontocrat on November 23, 2017, 09:51:13 PM
Why a dedicated thread for this?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Neven on November 24, 2017, 12:06:03 AM
Why a dedicated thread for this?

On the one hand, I agree. On the other hand, it's an interesting video.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: prokaryotes on November 24, 2017, 10:06:54 AM
This is kind of a summary, though planning to publish a video on surface melt vs basal.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: GeoffBeacon on November 24, 2017, 05:41:12 PM
Was the article by Holthaus this one on grist (https://grist.org/article/antarctica-doomsday-glaciers-could-flood-coastal-cities/)?

It was criticised by Tamsin Edwards in the Guardian (https://www.theguardian.com/science/head-quarters/2017/nov/23/climate-change-how-soon-will-the-ice-apocalypse-come-antarctica) e.g.

Quote
But Eric is wrong to say Antarctica’s ‘ice budget’ has tipped out of balance due to our burning of fossil fuels. Not only has it been out of balance before – such as the ancient West Antarctic collapse that causes concern – but the reason for the Amundsen Sea changes, where most ice is being lost, is that the ring of deep warm water around Antarctica has welled up onto the continental shelf and is melting the ice from underneath. We don’t know if human activities made this more likely.

Any comments?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 24, 2017, 09:28:44 PM
Any comments?

Geoff,

I enjoyed watching the short video, as it offers a nice summary in a manner that the general public can digest.  Regarding Tamsin Edwards' criticism, I would say that it is irrelevant whether we know, as a proven fact, that human activity has caused the Amundsen Sea Embayment, ASE, marine glaciers to cross their tipping points, as climate models combined with field observation make an almost certain fact.  For example:

1. Proistosescu & Huybers (2017) demonstrate convincingly that since 1750 anthropogenic activity has slowly been increasing the heat content of both the Tropical Pacific Ocean and the Southern Ocean; which not only increases ocean driving ice mass loss from West Antarctic marine glaciers, but also has activated a slow-response positive feedback mechanism that is currently increasing ECS to at least the upper end of the AR5 range.

Cristian Proistosescu and Peter J. Huybers (05 Jul 2017), "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Science Advances, Vol. 3, no. 7, e1602821, DOI: 10.1126/sciadv.1602821

http://advances.sciencemag.org/content/3/7/e1602821

Thus, not only are humans responsible for increasing the heat content of the Southern Ocean but the associated increase of the current ECS value means that the hydrofracturing mechanism described by DeConto & Pollard could begin as soon as 2040; which would greatly accelerate ice mass loss from all of the WAIS.

2.  There is no serious doubt that human activity caused the ozone hole over Antarctica, which accelerated the westerly wind velocities into a 'sweet spot' for promoting the increased upwelling of relatively warm circumpolar deepwater, CDW, onto the continental shelves that lead to key marine glaciers in the ASE (and other Antarctic marine glaciers).  Thus not only are we responsible for increasing the heat content of the CDW, but we are responsible for the mechanism that delivers this heat content to the grounding line of key marine glaciers.

3.  It is my opinion that human activity has accelerated surface ice mass loss from Greenland (including due to both decreased albedo from air pollution and from increased surface temperatures), which most likely caused a 'cold spot' in the North Atlantic, which most likely has somewhat slowed the Meridional Overturning Circulation, MOC.  Hansen et al (2016) indicates that this slowing of the MOC has reduced the formation of polynas in the Weddell Sea area, which has promoted an increase in Antarctic sea ice area, which has protected the upwelled CDW from cooling as much as it use to; which promotes grounding line retreat of key Antarctic marine glaciers.  This bipolar seesaw action contributes to Hansen's ice-climate feedback which further increases ECS and which further increases the risk of hydrofracturing of key ASE marine glaciers circa 2040.

I could go on, but my main point is that reticent scientists do not hesitate to dream-up any highly improbably scenario (like SSP1) to indicate that we may never cross the 2C limit; but then they do not hesitate to imply that much more probable scenarios that lead to GMSTAs approaching at least 2.7C (at which point DeConto & Pollard's ice cliff and hydrofracturing mechanisms kick into high gear) are not absolutely proven and thus do not merit serious consideration by busy decision makers who are bedeviled by other fat-tailed risks.  Such a reticent scientific posture is not good science.

Best,
ASLR

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Neven on November 24, 2017, 09:45:33 PM
Tamsin Edwards is an apologist for climate risk denial, like a good Brit phlegmatically adding a couple of big paving stones to the road to hell.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: magnamentis on November 24, 2017, 09:54:35 PM
Any comments?

Geoff,

I enjoyed watching the short video, as it offers a nice summary in a manner that the general public can digest.  Regarding Tamsin Edwards' criticism, I would say that it is irrelevant whether we know, as a proven fact, that human activity has caused the Amundsen Sea Embayment, ASE, marine glaciers to cross their tipping points, as climate models combined with field observation make an almost certain fact.  For example:

1. Proistosescu & Huybers (2017) demonstrate convincingly that since 1750 anthropogenic activity has slowly been increasing the heat content of both the Tropical Pacific Ocean and the Southern Ocean; which not only increases ocean driving ice mass loss from West Antarctic marine glaciers, but also has activated a slow-response positive feedback mechanism that is currently increasing ECS to at least the upper end of the AR5 range.

Cristian Proistosescu and Peter J. Huybers (05 Jul 2017), "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Science Advances, Vol. 3, no. 7, e1602821, DOI: 10.1126/sciadv.1602821

http://advances.sciencemag.org/content/3/7/e1602821

Thus, not only are humans responsible for increasing the heat content of the Southern Ocean but the associated increase of the current ECS value means that the hydrofracturing mechanism described by DeConto & Pollard could begin as soon as 2040; which would greatly accelerate ice mass loss from all of the WAIS.

2.  There is no serious doubt that human activity caused the ozone hole over Antarctica, which accelerated the westerly wind velocities into a 'sweet spot' for promoting the increased upwelling of relatively warm circumpolar deepwater, CDW, onto the continental shelves that lead to key marine glaciers in the ASE (and other Antarctic marine glaciers).  Thus not only are we responsible for increasing the heat content of the CDW, but we are responsible for the mechanism that delivers this heat content to the grounding line of key marine glaciers.

3.  It is my opinion that human activity has accelerated surface ice mass loss from Greenland (including due to both decreased albedo from air pollution and from increased surface temperatures), which most likely caused a 'cold spot' in the North Atlantic, which most likely has somewhat slowed the Meridional Overturning Circulation, MOC.  Hansen et al (2016) indicates that this slowing of the MOC has reduced the formation of polynas in the Weddell Sea area, which has promoted an increase in Antarctic sea ice area, which has protected the upwelled CDW from cooling as much as it use to; which promotes grounding line retreat of key Antarctic marine glaciers.  This bipolar seesaw action contributes to Hansen's ice-climate feedback which further increases ECS and which further increases the risk of hydrofracturing of key ASE marine glaciers circa 2040.

I could go on, but my main point is that reticent scientists do not hesitate to dream-up any highly improbably scenario (like SSP1) to indicate that we may never cross the 2C limit; but then they do not hesitate to imply that much more probable scenarios that lead to GMSTAs approaching at least 2.7C (at which point DeConto & Pollard's ice cliff and hydrofracturing mechanisms kick into high gear) are not absolutely proven and thus do not merit serious consideration by busy decision makers who are bedeviled by other fat-tailed risks.  Such a reticent scientific posture is not good science.

Best,
ASLR

another top post as always, must be mentioned from time to time
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: A-Team on November 24, 2017, 11:28:32 PM
Quote
Tamsin Edwards is an apologist for climate risk denial.
Here is an amusing commentary on their low-ball Antarctic scenario from G Laden and RB Alley.

I did not care for the timing (as it undercut a good public outreach effort from E Holthaus) nor the self-promotional tone of the Guardian piece, nor the barrage of followup tweets, from a minor figure in climate science seemingly assuming a major role as media spokesperson.

I wonder if she will morph into another Dahl-Jensen, Judith Curry, Andrew Rifken, or Bjorn Lomberg, the last thing we need right now in communicating climate risk. Or maybe just naive (as only a scientist can be) to how the Guardian post will be utilized by industry to muddy the risk waters.

I located her researchgate page and the never--published, never-cited 2006 dissertation on Z bosons; this constant recitation of being a particle physicist despite never having worked in that area in a professional capacity. It's not a qualification any more than neurosurgery because the physics of climate change is entirely nineteenth century newtonian (outside a few things like isotopes).

http://gregladen.com/blog/2015/11/22/antarctic-ice-sheet-deterioration-study-left-out-important-factors/
http://www.annualreviews.org/doi/abs/10.1146/annurev-earth-060614-105344?journalCode=earth
http://www.annualreviews.org/doi/abs/10.1146/annurev-earth-060614-105344?journalCode=earth
https://www.researchgate.net/profile/Tamsin_Edwards/contributions
https://www-d0.fnal.gov/results/publications_talks/thesis/edwards/thesis.pdf

"An engineer, a theoretical physicist [ie TE], and a paleoclimatologist are at a wedding. There is a ice large sculpture of a swan on a flat topped table, for decoration. The three start a betting pool on how long it will take for the entire swan, which has already started to melt, to end up on the floor.

The engineer notices some of the meltwater dribbling off the back of the table. She places a set of beer mugs under the streams of water, and records how long it takes for a measured amount of liquid to accumulate. She uses this to generate a graph showing melting over time, estimating the volume of the swan by looking it up in his manual on Ice Sculpture Specifications, and suggests that it will take eleven hours.

The theoretical physicist estimates the volume of ice by assuming a spherical swan, measures the air temperature, and calculates the rate of conversion from ice to water using thermodynamics. He comes up with a different estimate, because the engineer forgot to account for density differences in ice vs water. He estimates that the swan will be entirely the floor in eight and a half hours.

The paleoclimatologist disagrees, and says, “It will take between one and three hours for that swan to be on the floor.”

“Why do you think that, you are clearly an idiot, and I am clearly a physicist, so I must be right!” says the theoretical physicist.

Just as the paleoclimatologist is about to answer, the already melting neck of the swan breaks, and the upper part of the neck and head fall backwards, knocking off one of the large wings. All of those pieces slide off the table and crash on the floor. The stress of the impact causes the second wing to break off, but it stays on the table, but it begins to slowly slide toward the edge, clearly about to fall off as well.

“Because,” the paleoclimatologist says. “Last wedding I went to, that happened.”
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 25, 2017, 03:59:46 AM
I concur that paleo researchers can share a lot of insights with ESM modelers (see the linked open access reference), and one insight that CMIP6 modelers could learn would be to make some of their runs including subroutines of DeConto and Pollard's ice cliff failure and hydrofracturing mechanism, because without the introduction of such freshwater hosing into their models, they will never be able to match the climate responses indicated in the paleo record for Super Interglacials:

Anna S. von der Heydt, Peter Ashwin (Submitted on 12 Apr 2016), "State-dependence of climate sensitivity: attractor constraints and palaeoclimate regimes",    arXiv:1604.03311


http://arxiv.org/abs/1604.03311
&
http://arxiv.org/pdf/1604.03311v1.pdf

Abstract: "Equilibrium climate sensitivity is a frequently used measure to predict long-term climate change. However, both climate models and observational data suggest a rather large uncertainty on climate sensitivity (CS). The reasons for this include: the climate has a strong internal variability on many time scales, it is subject to a non-stationary forcing and it is, on many timescales, out of equilibrium with the changes in the radiative forcing. Palaeo records of past climate variations give insight into how the climate system responds to various forcings although care must be taken of the slow feedback processes before comparing palaeo CS estimates with model estimates. In addition, the fast feedback processes can change their relative strength and time scales over time. Consequently, another reason for the large uncertainty on palaeo climate sensitivity may be the fact that it is strongly state-dependent. Using a conceptual climate model, we explore how CS can be estimated from unperturbed and perturbed model time series. Even in this rather simple model we find a wide range of estimates of the distribution of CS, depending on climate state and variability within the unperturbed attractor. For climate states perturbed by instantaneous doubling of CO2, the sensitivity estimates agree with those for the unperturbed model after transient decay back the attractor. In this sense, climate sensitivity can be seen as a distribution that is a local property of the climate attractor. We also follow the classical climate model approach to sensitivity, where CO2 is prescribed and non-dynamic, leading to CS values consistently smaller than those derived from the experiments with dynamic CO2. This suggests that climate sensitivity estimates from climate models may depend significantly on future dynamics, and not just the level of CO2."

Extract: “... the presence of variability on the attractor on a number of timescales means there are clear and non-trivial distributions of sensitivities, even for unperturbed climates. The distribution of sensitivities depends strongly on the background state as well as on the timescale considered. This suggests that it could be useful to think of the unperturbed climate sensitivity as a local property of the “climate attractor”. For a perturbed system (we have considered instantaneously doubled CO2) this is still useful once an initial transient has decayed. This transient will depend in particular on ocean heat uptake, though also on carbon cycle and biosphere processes that act on time scales roughly equivalent with the forcing time scale. If the climate system has more than one attractor, the perturbed system may clearly evolve to a completely different set of states than the original attractor – a situation that did not occur in the climate model used here. In less extreme cases, there may still be very long transients for some perturbations associated parts of the climate system that are associated with slow feedbacks.

Such perturbations (illustrated in Fig. 1b,d) are not normally applied in climate models used for climate predictions [IPCC, 2013], where climate sensitivity is derived from model simulations considering prescribed, non-dynamic atmospheric CO2. In our conceptual model, we have derived climate sensitivities from both types of perturbations and find that the classical climate model approach (section 2.2, Fig. 4f) leads to significantly lower values of the climate sensitivity than the perturbations away from the attractor with dynamic CO2 (section 2.3, Fig. 11a). This emphasises the importance of including dynamic carbon cycle processes into climate prediction models. Moreover, it supports the idea that the real observed climate response may indeed be larger than the model predicted."

Edit, see also:

https://link.springer.com/article/10.1007/s40641-016-0049-3
&
https://pubs.geoscienceworld.org/gsa/geology/article-abstract/45/7/643/207872/el-nino-southern-oscillation-like-variability-in-a?redirectedFrom=fulltext
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: GeoffBeacon on November 25, 2017, 01:00:40 PM
I've just posted excerpts of one of AbruptSLR's comments and Neven's on the Guardian's site.

I might go back later to add some of A-Team's comment.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: GeoffBeacon on November 25, 2017, 03:17:52 PM
Not much of a surprise when the Guardian removed my comment and left

Quote
This comment was removed by a moderator because it didn't abide by our community standards. Replies may also be deleted. For more detail see our FAQs.

This may be off-topic. I have started a new thread Censorship by the good guys (http://Censorship by the good guys)
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: prokaryotes on November 25, 2017, 04:43:07 PM
There is another new study on winds due to CO2 increase, causing more upwelling, and may cause through this mechanism warm water intrusion at Totten glacier -- holds more than 11 feet of sea level rise, located in East Antarctica
http://www.youtube.com/watch?v=Le-4HrUXT4w

Press release https://news.utexas.edu/2017/11/01/winds-driving-warm-water-under-east-antarctic
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 25, 2017, 06:51:14 PM
I've just posted excerpts of one of AbruptSLR's comments and Neven's on the Guardian's site.

I might go back later to add some of A-Team's comment.

Geoff,

It can be tiresome to play games with reticent scientists/denialist as they hide behind the inherent complexity and uncertainties of climate change, with the essence of their game plan captured by Cardinal Richelieu's following quote:

"If you give me six lines written by the hand of the most honest of men, I will find something in them which will hang him."

https://en.wikiquote.org/wiki/Cardinal_Richelieu

Nevertheless, as I believe that this is a topic of some fundamental importance, I will try to provide a series of posts, over the coming days/weeks, that can provide some counter arguments to Tamsin Edwards' points, in order to illustrate that the risks of the possible early collapse of the WAIS is likely higher than she implies.

In this regards:

My first image shows NOAA's 2017 SLR guidance; which recommends that significant coastal structures (such as power plants, etc.) should consider 2.5m of SLR by 2100; which is improbably without significant SLR contribution from the WAIS.  I start with this image because NOAA is a conservative US authority on SLR and their guidance can be used as a baseline to which more possible SLR contributions from the WAIS this century and be added.

My second image from DeConto & Pollard (2016) extended data, illustrates that Edwards is correct that in this initial assessment using RCP 8.5 with ECS about 3C, that the peak SLR contribution from the WAIS does not occur until about 2150; however, when DeConto & Pollard use RCP 8.5 together with Hansen's ice-climate interaction, the peak SLR contribution from the WAIS shifts to about 2100 (which is more contribution than assumed by NOAA's 2017 guidance).

Next, DeConto & Pollard's work indicates that their cliff failure and hydrofracturing mechanisms become highly activated before GMSTA reaches 2.7C.  However, as the third image indicates that when following CMIP5 (as DeConto & Pollard (2016) did) this threshold is not reached until about 2070; while if one uses the paleo-calibrated estimate of ECS provided by Tobias Friedrich et al (2016), one sees that we may cross this threshold around 2045 (I note that Hansen's ice-climate work assumed a value for ECS that was compatible with CMIP5).  Thus DeConto & Pollard's extended data peak contribution with ice-climate interaction of about 2100 could be moved forward in time to about 2075, using Friedrich et al's estimate for ECS.

Lastly (for this post), the fourth image from SkS's response to work by Cristian Proistosescu and Peter J. Huybers (05 Jul 2017), therein PH17, indicate that there is substantial fat-tailed risk that Friedrich et al's value for ECS may be two low, and that more advanced ESM projections indicate a risk that ECS may be between 6 and 8C (which could move the date for the peak SLR contribution from the WAIS to a date meaningful earlier than 2075).

Best,
ASLR


Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 25, 2017, 07:03:25 PM
As a follow-on to my last post, the Bakker et al (2017) reference, cited below, presents a worked example of how to calibrate a scenario (see the first image for part of the calibration process using both paleo ,and observed, data) for the potential collapse of the WAIS this century.  Bakker et al (2017) then effectively summarize the findings from their calibrated scenario, w.r.t. to its impact on SLR, in an easily understood plot (see the second attached image) of Sea level with time and scenarios with varying degrees of 'deep uncertainty.  Also, I note that Bakker et al (2017) indicate that: "Around 2040-2050, a large and uncertain contribution of the GIS becomes important …"

Alexander M. R. Bakker, Tony E. Wong, Kelsey L. Ruckert & Klaus Keller (2017), "Sea-level projections representing the deeply uncertain contribution of the West Antarctic ice sheet", Scientific Reports 7, Article number: 3880; doi:10.1038/s41598-017-43134-5

http://www.nature.com/articles/s41598-017-04134-5

Abstract: "There is a growing awareness that uncertainties surrounding future sea-level projections may be much larger than typically perceived. Recently published projections appear widely divergent and highly sensitive to non-trivial model choices. Moreover, the West Antarctic ice sheet (WAIS) may be much less stable than previous believed, enabling a rapid disintegration. Here, we present a set of probabilistic sea-level projections that approximates the deeply uncertain WAIS contributions. The projections aim to inform robust decisions by clarifying the sensitivity to non-trivial or controversial assumptions. We show that the deeply uncertain WAIS contribution can dominate other uncertainties within decades. These deep uncertainties call for the development of robust adaptive strategies. These decision-making needs, in turn, require mission-oriented basic science, for example about potential signposts and the maximum rate of WAIS-induced sea-level changes."

Extract: "Our sea-level projections are constructed to support robust decision frameworks by i) being explicit about the relevant uncertainties, both shallow and deep; ii) communicating plausible ranges of sea-level rise, including the deep uncertainties surrounding future climate forcings and potential WAIS collapse; and iii) tending to err on the side of underconfident versus overconfident when possible.

Model design. We design the projections to be probabilistic where reasonable and explicit about deep uncertainties (e.g. resulting from non-trivial model choices) when needed. Robust decision frameworks often apply plausible rather than probabilistic ranges to represent and communicate uncertainties. In the case of sea-level projections, the bounding of the plausible range usually involves both a probabilistic interpretation of the surrounding uncertainties and estimates of which probabilities are still relevant. For example, a full disintegration of the major ice sheets is often not taken into account because the probabilities of this occurring are considered too
small to be relevant. What probability is relevant is highly dependent on the decision context and therefore it makes sense to be explicit about the probabilities. Moreover, probabilities are the easiest and most unambiguous way to communicate uncertainties.

Our projections are designed to highlight the relatively large deep uncertainties, notably those resulting from future climate forcings and those surrounding potential WAIS collapse (even though representations of deep uncertainty often implicitly encompass probabilistic interpretations). The future climate forcing is, to a large extent, controlled by future human decisions.

The probability of a WAIS collapse is potentially much larger than previously thought due to the combined effects of Marine Ice Sheet Instability (MISI), ice cliff failure and hydrofracturing. The discovery of this new mechanism puts earlier expert elicitations in a different light as it is unclear if those were based on this combined effect. One approach when faced with deeply uncertain model structures and priors is to present a potential WAIS collapse as deeply uncertain by means of a plausible range. We stress that this range is not meant to represent an implicit probabilistic projection of the WAIS contribution to sea-level rise.

We merge some small deep uncertainties into the probabilistic part of the projections. According to Herman et al. “… a larger risk lies in sampling too narrow a range (thus ignoring potentially important vulnerabilities) rather than too wide a range which, at worst, will sample extreme states of the world in which all alternatives fail”.  Thus, in the context of informing robust decision making, it can be preferable to be slightly under- than slightly overconfident. To minimize the risk of producing overconfident projections we only use observational data with relatively uncontroversial and well-defined error structure.

Model setup. We use a relatively simple (39 free physical and statistical parameters), but a mechanistically motivated model framework to link transient sea-level rise to radiative concentration pathways applying sub-models for the global climate, thermal expansion (TE), and contributions of the Antarctic ice sheet (AIS), Greenland ice sheet (GIS) and glaciers and small ice caps (GSIC) (see Methods). This approach extends on the semi-empirical model setup recently reported by Mengel et al..

We use a Bayesian calibration method, wherein paleoclimatic data is assimilated with the AIS model separately from the calibration for the rest of the model, which assimilates only modern observations. Modern model simulations are then run at parameters drawn from the two resulting calibrated parameter sets (AIS and rest-of-model) and compared to global mean sea-level (GMSL) data (see Methods). Only model realizations which agree with each GMSL data point to within 4σ are admitted into the final ensemble for analysis. 4σ was chosen so the spread in the model ensemble characterizes well the uncertainty in the GMSL data (Fig. 1f). We choose, at this time, not to use paleo-reconstructions nor reanalyses, beyond incorporating a windowing
approach into our calibration method for the Antarctic ice-sheet parameters. This choice is motivated by the highly complex and uncertain error structure of these data sets. Failure to account for such complex error structure can result in considerable overconfidence, especially for low-probability events."

Furthermore, Bakker et al (2017) cite the second linked reference which provides a worked example of how the potential bias of a current model can be quantified by comparing its projections against the projections of a dynamical model with 'deep uncertainty', in this cases one that includes the dynamical mechanism of cliff failures and hydrofracturing w.r.t. to SLR contributions from the Antarctic ice sheet.  To the best of my understanding none of the Earth System Models in CMIP6 include the dynamical cliff failures, and hydrofracturing, mechanisms, apparently due to 'deep uncertainty'.  Nevertheless, even if CMIP6/AR6 do not present projections including the impacts of the dynamical cliff failures, and hydrofractuing, mechanisms, they could still numerically present the potential bias of their projections by following the methodology presented by Ruckert et al (2017), & in this regards see the last two attached images.


Kelsey L. Ruckert, Gary Shaffer, David Pollard, Yawen Guan, Tony E. Wong, Chris E. Forest &Klaus Keller (2017), "Assessing the impact of retreat mechanisms in a simple Antarctic ice sheet model using Bayesian Calibration", PLoS ONE, 12, 1-15, https://doi.org/10.1371/journal.pone.0170052

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0170052

Abstract: "The response of the Antarctic ice sheet (AIS) to changing climate forcings is an important driver of sea-level changes. Anthropogenic climate change may drive a sizeable AIS tipping point response with subsequent increases in coastal flooding risks. Many studies analyzing flood risks use simple models to project the future responses of AIS and its sea-level contributions. These analyses have provided important new insights, but they are often silent on the effects of potentially important processes such as Marine Ice Sheet Instability (MISI) or Marine Ice Cliff Instability (MICI). These approximations can be well justified and result in more parsimonious and transparent model structures. This raises the question of how this approximation impacts hindcasts and projections. Here, we calibrate a previously published and relatively simple AIS model, which neglects the effects of MICI and regional characteristics, using a combination of observational constraints and a Bayesian inversion method. Specifically, we approximate the effects of missing MICI by comparing our results to those from expert assessments with more realistic models and quantify the bias during the last interglacial when MICI may have been triggered. Our results suggest that the model can approximate the process of MISI and reproduce the projected median melt from some previous expert assessments in the year 2100. Yet, our mean hindcast is roughly 3/4 of the observed data during the last interglacial period and our mean projection is roughly 1/6 and 1/10 of the mean from a model accounting for MICI in the year 2100. These results suggest that missing MICI and/or regional characteristics can lead to a low-bias during warming period AIS melting and hence a potential low-bias in projected sea levels and flood risks."

Extract: " We calibrate a simple AIS model (that does not include a cliff instability mechanism nor is able to capture regional characteristics) with observational constraints over the past 240,000 years using a Bayesian inversion considering the heteroskedastic nature of the data. Using the hindcasts and projections, we compare our results to those from a pre-calibration method and expert assessments with potentially more realistic models. We approximate how neglecting fast processes (i.e., the MICI mechanism) in an AIS model can lead to biases in the AIS hindcasts and projections during warming periods. For the specific example considered, we show how missing MICI produces a lower mean hindcast (roughly 26% or 1 m smaller) during the LIG, a period when the marine ice sheet is suggested to have deglaciated. Additionally, the model is unable to account for roughly 96 and 100% of future AIS contributions predicted by a physically more realistic model accounting for MISI, MICI, and hydro-fracturing yet reproduces the projected median melt in other expert assessments in the year 2100. Overall, accounting for retreat mechanisms can potentially increase warming period AIS melt and reduce model discrepancy."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 25, 2017, 08:07:00 PM
Edwards' claim that BAU is best represented by the Paris Accord path forward, is nothing more than her personal opinion, as the first attached image issued by the Global Carbon Project compares the SSP scenarios vs the observed projected thru 2017 for the fossil fuel and land use change CO2 emissions.  This plot indicates that we are currently following the SSP5 Baseline pathway, and not SSP3 which roughly represents the Paris Accord path forward.  This point is clarified by the second attached image where the authors of the Shared Socioeconomic Pathways, SSPs, label both SSP5 and SSP3 as baseline scenario depending on the decision maker's point of view.  However, I note that even SSP5 baseline can be taken to be optimistic as the third image indicates that SSP5 assumes a world population of about 8.5 billion by 2050; while the fourth image of the 2017 UN projection of global population gives a 50-50 chance that the world population will be 9.8 billion by 2050.  Thus taking SSP5/RCP 8.5 as BAU is fully supported by the IPCC process.

Also, I note that NASA's 12-month running GISTEMP value for GMSTA corrected to a pre-industrial baseline thru October 2017 is currently 1.159C, which is high, and that CO2e is over 521ppm to 530ppm (depending on how one treats ozone's contribution), which is also high.  So both of these parameters support the idea that we are currently following a SSP5/RCP 8.5 pathway.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: A-Team on November 25, 2017, 08:28:43 PM
Quote
Not much of a surprise when the Guardian removed my comment and left "This comment was removed by a moderator because it didn't abide by our community standards. Replies may also be deleted.
Right, good effort Geoff. They probably wanted you to express views in your own words. Copy/paste opens too many doors to mass orchestrated submissions.

However ... newspapers are always looking for free content and seeking 'balance'. The Guardian is driven financially by investment income from its giant charitable endowment. I don't imagine they are invested in high risk, low-return Puerto Rican reconstruction bonds nor feel-good green energy projects but rather have a conventional large cap stock portfolio, meaning their income -- and the paper's very survival -- rises and falls with capitalism and ponzical growth. So it 'makes sense' to have climate coverage in alignment.

While we don't know if the Guardian has contracted with T Edwards to spin future climate coverage, I don't expect them to hit rock bottom like the NYTimes, all those years of Revkin followed by firing the entire environmental desk. Meanwhile Chris Mooney for the WaPo/Bezos is making them look stupid; and Masters/Benson climate commentary at Wunderground is so far being tolerated by new owner IBM.

Quote
tiresome to play games with reticent scientists/denialist/delayers/minimizers
Right. Some climate scientists are not going to stay on message, no matter what the societal costs. The whole idea is be different, get noticed as an iconoclastic paradigm-challenger. Journals favor controversy-engendering articles that bump citation rankings; universities hire full-time PR staff to hype mundane faculty accomplishments. The planets are in alignment.

How many times has Antarctica been modeled in the last twenty years? I'm going to say 1000 papers. Picture yourself in early career about to write #1001, knowing a choice of internal parameters for your ensemble runs that merely affirms #1000 would be unpublishable and possibly fatal to your livelihood.  Whereas a different choice would get you noticed, all the more so if backed by non-stop horn-tooting.

Alternatively, imagine you ran down your machine time budget before finally realizing what you should have done -- what to do with what you did? Publish it.

There's no need to feel guilty because 'everyone does it' plus #1002 will come along soon enough, overwriting your societal damage because those authors need to conflict with #1001. There are unrealistic pressures on young researchers today.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 25, 2017, 09:59:34 PM
T. Edwards' comment that no other model other than Pollard and DeConto (2016) indicates such rapid ice mass loss from the WAIS ignores the significance of modeling efforts such as the following:

David Pollard, Won Chang, Murali Haran, Patrick Applegate, and Robert DeConto (2016), "Large ensemble modeling of the last deglacial retreat of the West Antarctic Ice Sheet: comparison of simple and advanced statistical techniques", Geosci. Model Dev., 9, 1697–1723, doi:10.5194/gmd-9-1697-2016

http://www.geosci-model-dev.net/9/1697/2016/gmd-9-1697-2016.pdf
www.geosci-model-dev.net/9/1697/2016/


Abstract. A 3-D hybrid ice-sheet model is applied to the last deglacial retreat of the West Antarctic Ice Sheet over the last ~20 000 yr. A large ensemble of 625 model runs is used to calibrate the model to modern and geologic data, including reconstructed grounding lines, relative sea-level records, elevation–age data and uplift rates, with an aggregate score computed for each run that measures overall model–data misfit. Two types of statistical methods are used to analyze the large-ensemble results: simple averaging weighted by the aggregate score, and more advanced Bayesian techniques involving Gaussian process-based emulation and calibration, and Markov chain Monte Carlo. The analyses provide sea-level-rise envelopes with well-defined parametric uncertainty bounds, but the simple averaging method only provides robust results with full-factorial parameter sampling in the large ensemble. Results for best-fit parameter ranges and envelopes of equivalent sea-level rise with the simple averaging method agree well with the more advanced techniques.  Best-fit parameter ranges confirm earlier values expected from prior model tuning, including large basal sliding coefficients on modern ocean beds.

&

Won Chang, Murali Haran, Patrick Applegate, David Pollard (October 7, 2015), "Improving Ice Sheet Model Calibration Using Paleoclimate and Modern Data"

http://arxiv.org/pdf/1510.01676.pdf

Abstract: "Human-induced climate change may cause significant ice volume loss from the West Antarctic Ice Sheet (WAIS). Projections of ice volume change from ice-sheet models and corresponding future sea-level rise have large uncertainties due to poorly constrained input parameters. In most future applications to date, model calibration has utilized only modern or recent (decadal) observations, leaving input parameters that control the long-term behavior of WAIS largely unconstrained. Many paleo-observations are in the form of localized time series, while modern observations are non-Gaussian spatial data; combining information across these types poses nontrivial statistical challenges. Here we introduce a computationally efficient calibration approach that utilizes both modern and paleo-observations to generate better-constrained ice volume projections.

Using fast emulators built upon principal component analysis and a reduced dimension calibration model, we can efficiently handle high-dimensional and non-Gaussian data. We apply our calibration approach to the PSU3D-ICE model which can realistically simulate long-term behavior of WAIS. Our results show that using paleo observations in calibration significantly reduces parametric uncertainty, resulting in sharper projections about the future state of WAIS. One benefit of using paleo observations is found to be that unrealistic simulations with overshoots in past ice retreat and projected future regrowth are eliminated."

&

David Pollard, Robert DeConto, Won Chang, Patrick Applegate and Murali Haran (Dec 18, 2015), "Modeling of past and future variations of the Antarctic Ice Sheet with Large Ensembles" AGU Fall Meeting, Paper 60833.

https://agu.confex.com/agu/fm15/meetingapp.cgi/Paper/60833

Abstract: "Recent observations of thinning and retreat of the Pine Island and Thwaites Glaciers identify the Amundsen Sea Embayment (ASE) sector of West Antarctica as particularly vulnerable to future climate change. To date, most future modeling of these glaciers has been calibrated using recent and modern observations. As an alternate approach, we apply a hybrid 3-D ice sheet-shelf model to the last deglacial retreat of Antarctica, making use of geologic data from ~20,000 years BP to present, focusing on the ASE but including other sectors of Antarctica.
Following several recent ice-sheet studies, we use Large Ensemble statistical methods, performing sets of ~600 runs over the last 30,000 years with systematically varying model parameters. Objective scores for each run are calculated using modern data and past reconstructed grounding lines, relative sea level records, cosmogenic elevation-age data and uplift rates. Two types of statistical methods are used to analyze the Large-Ensemble results: simple averaging weighted by the aggregate score, and more advanced Bayesian emulation and calibration methods that rigorously account for some of the uncertainties in the model and observations.

Results for best-fit parameter ranges and envelopes of equivalent sea-level rise with the simple averaging method agree quite well with the more advanced techniques, but only for a Large Ensemble with dense (Full Factorial) parameter sampling. Runs are extended into the future using RCP scenarios, with drastic retreat mechanisms of hydrofracturing and structural ice-cliff failure. In most runs this produces grounding-line retreat into the West Antarctic interior, and into East Antarctic basins for RCP8.5, and the Large Ensemble analysis provides sea-level-rise envelopes with well defined parametric uncertainty bounds."

&

E. Gasson, R.M. DeConto, D. Pollard, and R.H. Levy (2016), "Dynamic Antarctic ice sheet during the early to mid-Miocene", Proceedings of the National Academy of Sciences, pp. 201516130, doi: 10.1073/pnas.1516130113

http://www.pnas.org/content/early/2016/02/17/1516130113

Significance: "Atmospheric concentrations of carbon dioxide are projected to exceed 500 ppm in the coming decades. It is likely that the last time such levels of atmospheric CO2 were reached was during the Miocene, for which there is geologic data for large-scale advance and retreat of the Antarctic ice sheet. Simulating Antarctic ice sheet retreat is something that ice sheet models have struggled to achieve because of a strong hysteresis effect. Here, a number of developments in our modeling approach mean that we are able to simulate large-scale variability of the Antarctic ice sheet for the first time. Our results are also consistent with a recently recovered sedimentological record from the Ross Sea presented in a companion article."

Abstract: "Geological data indicate that there were major variations in Antarctic ice sheet volume and extent during the early to mid-Miocene. Simulating such large-scale changes is problematic because of a strong hysteresis effect, which results in stability once the ice sheets have reached continental size. A relatively narrow range of atmospheric CO2 concentrations indicated by proxy records exacerbates this problem. Here, we are able to simulate large-scale variability of the early to mid-Miocene Antarctic ice sheet because of three developments in our modeling approach. (i) We use a climate–ice sheet coupling method utilizing a high-resolution atmospheric component to account for ice sheet–climate feedbacks. (ii) The ice sheet model includes recently proposed mechanisms for retreat into deep subglacial basins caused by ice-cliff failure and ice-shelf hydrofracture. (iii) We account for changes in the oxygen isotopic composition of the ice sheet by using isotope-enabled climate and ice sheet models. We compare our modeling results with ice-proximal records emerging from a sedimentological drill core from the Ross Sea (Andrill-2A) that is presented in a companion article. The variability in Antarctic ice volume that we simulate is equivalent to a seawater oxygen isotope signal of 0.52–0.66‰, or a sea level equivalent change of 30–36 m, for a range of atmospheric CO2 between 280 and 500 ppm and a changing astronomical configuration. This result represents a substantial advance in resolving the long-standing model data conflict of Miocene Antarctic ice sheet and sea level variability."

&

Dewi Le Bars, Sybren Drijfhout and Hylke de Vries (3 April 2017), "A high-end sea level rise probabilistic projection including rapid Antarctic ice sheet mass loss",
Environmental Research Letters, Volume 12, Number 4 , https://doi.org/10.1088/1748-9326/aa6512

http://iopscience.iop.org/article/10.1088/1748-9326/aa6512
&
http://iopscience.iop.org/article/10.1088/1748-9326/aa6512/pdf

Abstract: "The potential for break-up of Antarctic ice shelves by hydrofracturing and following ice cliff instability might be important for future ice dynamics. One recent study suggests that the Antarctic ice sheet could lose a lot more mass during the 21st century than previously thought. This increased mass-loss is found to strongly depend on the emission scenario and thereby on global temperature change. We investigate the impact of this new information on high-end global sea level rise projections by developing a probabilistic process-based method. It is shown that uncertainties in the projections increase when including the temperature dependence of Antarctic mass loss and the uncertainty in the Coupled Model Intercomparison Project Phase 5 (CMIP5) model ensemble. Including these new uncertainties we provide probability density functions for the high-end distribution of total global mean sea level in 2100 conditional on emission scenario. These projections provide a probabilistic context to previous extreme sea level scenarios developed for adaptation purposes."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 25, 2017, 10:04:32 PM
Furthermore, T. Edwards ignores the linked reference which discusses state of the art surface temperature at the West Antarctic Divide for the past ~ 40,000 years, that indicate that current climate models are challenged to hind cast the observed findings and that models with low climate sensitivities can be eliminated from consideration.  Furthermore, they find that an Antarctic Amplification of 2 to 3 time GMSTA. 

Kurt M. Cuffey, Gary D. Clow, Eric J. Steig, Christo Buizert, T. J. Fudge, Michelle Koutnik, Edwin D. Waddington, Richard B. Alley, and Jeffrey P. Severinghaus (2016), "Deglacial temperature history of West Antarctica", PNAS, vol. 113 no. 50, 14249–14254, doi: 10.1073/pnas.1609132113

http://www.pnas.org/content/113/50/14249

Abstract: "The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth’s climate responds to various forcings, including a rise in atmospheric CO2. This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes’ sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was 11.3±1.8 ∘  11.3±1.8∘ C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted."

Extract: "Of greatest immediate interest, however, is our demonstration that the global deglacial temperature change was amplified by a factor of 2–3 in the Antarctic, that Antarctic warming was largely achieved by 15 ka in coherence with records from Southern Hemisphere mountain ranges, and that climate models of the deglaciation perform well on average, but that the ones with lowest sensitivity can be discounted. The early warming of the Southern Hemisphere, which our study helps to quantify, arose from combined effects of reduced northward oceanic heat transport, increased insolation, and increasing atmospheric CO2. Quantitative simulation of this phenomenon could provide an illuminating challenge for model studies."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 25, 2017, 10:11:53 PM
Furthermore, T. Edwards ignores the already increasing risks of hydrofracture events in the WAIS as illustrated by the two linked sources (the attached image comes from the first linked source):

"Scientists stunned by Antarctic rainfall and a melt area bigger than Texas"

https://www.washingtonpost.com/news/energy-environment/wp/2017/06/15/scientists-just-documented-a-massive-melt-event-on-the-surface-of-antarctica/?utm_term=.526054dc4fdf

Extract: "Scientists have documented a recent, massive melt event on the surface of highly vulnerable West Antarctica that, they fear, could be a harbinger of future events as the planet continues to warm.

In the Antarctic summer of 2016, the surface of the Ross Ice Shelf, the largest floating ice platform on Earth, developed a sheet of meltwater that lasted for as long as 15 days in some places. The total area affected by melt was 300,000 square miles, or larger than the state of Texas, the scientists report."
&
The second linked reference finds that: "The increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major surface melt events.":

Julien P. Nicolas et. al. (2017), "January 2016 extensive summer melt in West Antarctica favoured by strong El Niño", Nature Communications 8, Article number: 15799, doi:10.1038/ncomms15799

http://www.nature.com/articles/ncomms15799

Abstract: "Over the past two decades the primary driver of mass loss from the West Antarctic Ice Sheet (WAIS) has been warm ocean water underneath coastal ice shelves, not a warmer atmosphere. Yet, surface melt occurs sporadically over low-lying areas of the WAIS and is not fully understood. Here we report on an episode of extensive and prolonged surface melting observed in the Ross Sea sector of the WAIS in January 2016. A comprehensive cloud and radiation experiment at the WAIS ice divide, downwind of the melt region, provided detailed insight into the physical processes at play during the event. The unusual extent and duration of the melting are linked to strong and sustained advection of warm marine air toward the area, likely favoured by the concurrent strong El Niño event. The increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major melt events."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 25, 2017, 10:24:07 PM
T. Edwards also ignores the implications of both the extensive subglacial meltwater drainage system and the high subglacial geothermal heat flux as indicated in the linked references and attached images:

The linked reference studies a subglacial draining event beneath Thwaites Glacier from June 2013 to January 2014:

Smith et. al. (2017), "Connected subglacial lake drainage beneath Thwaites Glacier, West Antarctica", The Cryosphere, 11, 451–467, doi:10.5194/tc-11-451-2017

http://www.the-cryosphere.net/11/451/2017/tc-11-451-2017.pdf

&

Yasmina M. Martos, Manuel Catalan, Tom A. Jordan,Alexander Golynsky, Dmitry Golynsky, Graeme Eagles & David G. Vaughan (6 November 2017), "Heat flux distribution of Antarctica unveiled", Geophysical Research Letters, DOI: 10.1002/2017GL075609 

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075609/abstract?utm_content=buffer4cbb3&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2017, 12:44:13 AM
Furthermore, T. Edwards ignores the dynamical periodic multistate nature of the Earth's Systems; where ENSO is but one of several different interacting positive reinforcements of various Earth Systems (Arctic Amplification, Bipolar Seesaw, Permafrost degradation, PDO/ENSO, Ice-Climate Feedback, Hadley Cell expansion, etc.); which Chaos Theory calls Strange (or Lorenz) Attractors.  I believe that such strange attractors can progressively/interactively ratchet-up different Earth System States (see the first attached image) so as to increase the effective climate sensitivity so that some "slow-response" feedbacks (see the second figure from Andrew – Ringberg 2015, where the middle panel indicates an effective climate sensitivity of about 5C) occur within decades rather than millennia. This potential acceleration of the rate of activation of "slow-response" feedbacks is driven by anthropogenic behavior including:

(a) We are radiatively forcing the Earth at well over 10 times the rate experienced during the PETM;

(b) Rapid deforestation and ocean acidification are slowly decreasing the capacity of both land and the ocean, respectively, to serve as CO₂ sinks.

(c) Anthropogenic aerosols have been temporarily masking the impacts of anthropogenic radiative forcing; much as dust in paleo times resulted in negative forcing that caused cooling.  However, reticent science has discounted the efficiency of both of these mechanisms leaving the modern world subject to unexpectedly high rates of GMST increases due to the GHGs that accumulated in the atmosphere during the recent faux hiatus.

Indeed the first linked reference indicates that when analyzing modern day observations: "Severe testing is applied to observed global and regional surface and satellite temperatures and modelled surface temperatures to determine whether these interactions are independent, as in the traditional signal-to-noise model, or whether they interact, resulting in steplike warming."  The reference concludes that indeed steplike warming occurs due to "… a store-and-release mechanism from the ocean to the atmosphere…" like the classical Lorenzian attractor case of ENSO decadal cycles.  Such steplike behavior confirms the mechanism that I call "Ratcheting of Quasi-static Equilibrium States" (see the first attachment).  As the authors point-out reticent science likely missed this behavior because: "This may be due in part to science asking the wrong questions."; and they advise that such reticent AR5/CMIP5 researchers should change how they view the output from their models.  For example, the third attached image (see panel "e" of that Figure 6) from the reference shows global warming increasing much faster for a steplike response if ECS is 4.5 than for a the traditional AR5/CMIP5 interpretation; which means that ESLD researchers are exposing society to far more risk of the consequences of high ECS values than AR5/CMIP5 are leading us to believe:

Jones, R. N. and Ricketts, J. H.: Reconciling the signal and noise of atmospheric warming on decadal timescales, Earth Syst. Dynam. Discuss., doi:10.5194/esd-2016-35, in review, 2016.

http://www.earth-syst-dynam-discuss.net/esd-2016-35/
&
http://www.earth-syst-dynam-discuss.net/esd-2016-35/esd-2016-35.pdf


Extract: "This finding does not invalidate the huge literature that assesses long-term (>50 years) climate change as a relatively linear process, and the warming response as being broadly additive with respect to forcing (e.g., Lucarini et al., 2010; Marvel et al., 2015). However, on decadal scales, this is not the case – warming appears to be largely governed by a storage and release process, where heat is stored in the ocean and released in bursts projecting onto modes of climate variability as suggested by Corti et al. (1999). We discuss this further in another paper (Jones and Ricketts, 2016).

This has serious implications for how climate change is understood and applied in a whole range of decision-making contexts.  The characterisation of changing climate risk as a smooth process will leave climate risk as being seriously underdetermined, affecting how adaptation is perceived, planned and undertaken (Jones et al., 2013).

The interaction of change and variability is typical of a complex, rather than mechanistic, system. The possibility of Lorenzian attractors in the ocean-atmosphere acting on decadal time scales was raised by Palmer (1993) and, despite later discussions about the potential for nonlinear responses on those timescales (e.g., Lucarini and Ragone, 2011;Tsonis and Swanson, 2012), very little progress has been made in translating this into applied research that can portray a better understanding of changing climate risk. This may be due in part to science asking the wrong questions.

The signal to noise model of a gradually changing mean surrounded by random climate variability poorly represents warming on decadal timescales. The separation of signal and noise into ‘good’ and ‘bad, likewise, is poor framing for the purposes of understanding and managing risk in fundamentally nonlinear systems (Koutsoyiannis, 2010; Jones, 2015b). However, as we show, the presence of such changes within climate models shows their current potential for investigating nonlinearly changing climate risks. Investigating step changes in temperature and related variables does not indicate a need to fundamentally change how climate modelling is carried out. It does, however, indicate a need to change how the results are analysed."

The second reference indicates global warming is increasing the frequency of extreme El Ninos.  As strong El Ninos increase both the temperature and induce droughts in the tropics it is clear that CO₂ emissions increase from the tropical land vegetation during strong El Ninos:

Wenju Cai, Agus Santoso, Guojian Wang, Sang-Wook Yeh, Soon-Il An, Kim M. Cobb, Mat Collins, Eric Guilyardi, Fei-Fei Jin, Jong-Seong Kug, Matthieu Lengaigne, Michael J. McPhaden, Ken Takahashi, Axel Timmermann, Gabriel Vecchi, Masahiro Watanabe & Lixin Wu (2015), "ENSO and greenhouse warming", Nature Climate Change, Volume: 5, Pages: 849–859, doi:10.1038/nclimate2743


http://www.nature.com/nclimate/journal/v5/n9/full/nclimate2743.html

Abstract: "The El Niño/Southern Oscillation (ENSO) is the dominant climate phenomenon affecting extreme weather conditions worldwide. Its response to greenhouse warming has challenged scientists for decades, despite model agreement on projected changes in mean state. Recent studies have provided new insights into the elusive links between changes in ENSO and in the mean state of the Pacific climate. The projected slow-down in Walker circulation is expected to weaken equatorial Pacific Ocean currents, boosting the occurrences of eastward-propagating warm surface anomalies that characterize observed extreme El Niño events. Accelerated equatorial Pacific warming, particularly in the east, is expected to induce extreme rainfall in the eastern equatorial Pacific and extreme equatorward swings of the Pacific convergence zones, both of which are features of extreme El Niño. The frequency of extreme La Niña is also expected to increase in response to more extreme El Niños, an accelerated maritime continent warming and surface-intensified ocean warming. ENSO-related catastrophic weather events are thus likely to occur more frequently with unabated greenhouse-gas emissions. But model biases and recent observed strengthening of the Walker circulation highlight the need for further testing as new models, observations and insights become available."

In summary, I provide the fourth image that illustrates how periodic climate attractors (triggered by the combination of anthropogenic radiative forcing and freshwater hosing from the collapse of the WAIS) could stepwise drive us into a very dynamical anthropogenic state, with high sea level, high storm activity and high temperatures.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2017, 04:32:56 PM
Furthermore, T. Edwards ignores the fact that all glacial models included in CMIP5 and CMIP6 cannot match the paleo-record, nor the observed-record, for ice mass loss from marine glaciers, and that they all err far on the side of least drama.  Therefore I post selected images (from a slide show compiled by Bill Lipscomb's team from the US - DOE and Los Alamos National Lab.) regarding recent research using the Community Ice Sheet Model (CISM), that illustrate the challenges that such models face (which will take decades to resolve to the point where they could match the paleo-record):

- The first image shows key software in CISM
- The second image shows the concept of using software packages to fight on many challenging fronts at once for both GIS and WAIS types of ocean, atmosphere, land, ice situations.
- The third image shows a listing of progress by the team on these many fronts.
- The fourth image shows the coupling required between the various software packages

Due to the four image limit per post I will present images related to a  BISICLES analysis for the West Antarctic in my next post.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2017, 04:43:36 PM
The following images continue from the preceeding post with figures related to analysis for the Western Antarctic focused on marine glaciers and ice shelves:

- The first shows the boundary layer conditions for such an analysis.
- The second images shows future/planned moving boundaries for such models to account for subglacial cavity growth and sub-ice-shelf melting.
- The third images shows the results of a convergence study for the LCM indicating that they need a resolution of at least 1 km which means that there model is too local to capture advective interactions between PIG and Thwaites (as I discuss in the "Surge" thread).  Thus computers will need to become bigger and faster before complex regional interactions can be captured
- The fourth image shows the subglacial hydrological system used in the LCM which does not include geothermal heating comparable to that measured in the BSB (Byrd Subglacial Basin) that is creating relatively large volumes of basal meltwater, sufficient to feed a key subglacial lake, which is also not included in the LCM system.  Furthermore, I have postulated that the basal meltwater entering the ocean through the Thwaites Gateway Trough act as a positive feedback for the advective formation of a subglacial cavity in the trough (which is not captured in this LCM model).

These images show how much work remains to be done (including refinement of the gird resolution of non-linear models) before projections from the combined GCM, RCM, and LCM efforts can be depended upon for reasonably accurate SLR projections.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2017, 07:05:57 PM
The following extracts come from the linked Scribbler article entitled: "From Ice Apocalypse to Mega-Thunderstorms, Continuing to Burn Fossil Fuels Makes the World Scary as all Hell", which also has a link to the 'Chasing Ice' video of a 2012 ice cliff failure event at the Jakobshavn Glacier.  Scribbler provides some descriptions of ice cliff failures that the general public can relate too; however, he: (1) limits his stated concerns about DeConto & Pollard (2016)'s findings to issues related to sea level rise; which ignores dynamical issues such as ice-climate interaction and associated mega-storms cited by Hansen; and (2) his mentioning of a relatively low probability of occurrence of 10 to 20 percent for DeConto & Pollard's scenario is highly subjective and is likely to bias readers to err on the side of least drama as the true probability is certainly much higher than 10 to 20 percent.

https://robertscribbler.com/2017/11/22/from-ice-apocalypse-to-mega-thunderstorms-continuing-to-burn-fossil-fuels-makes-the-world-scary-as-all-hell/

Extract: "Ice cliff stability is a pretty technical term. One that may make the eyes of your typical reader gloss over. But when we consider that the glaciers of Greenland and Antarctica can be upwards of two miles high, then the question of whether or not the cliffs of those great ice mountains are stable may start to generate a flicker of warning. May conjure up a phantom of the titanic roar set off when such ice giants tumble away into the sea as has happened throughout the deep history of Earth whenever the world warmed up by a certain amount.
When I think of the words ice cliff stability, my mind’s eye pictures a vast wall of numbing white-blue stretching hundreds of feet high. It expands both left and right as far as I can see. And it looms over an endless warming ocean. Waiting for a colossal fall if just that right amount of extra heat is applied.
Ice is fragile. It’s not like stone. It doesn’t flex much. It doesn’t give much. And even minor stresses are enough to make it shatter.

But the problem with the DeConto study, as with any other form of serious climate risk, is that there are plausible scenarios in which terrible catastrophic events are possible even if their degree of likelihood is still somewhat debatable. And reasonable precaution would dictate that even if there were just a 10-20 percent chance of DeConto like events coming to pass, we would do everything we could to avoid them. The risk of this scenario emerging, however, is probably a bit higher. As numerous studies have identified the potential for 6, 8, or even 12 feet of sea level rise by as early as 2100."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2017, 08:03:02 PM
Perhaps T. Edwards' most valid issue for debate is: How long will it take for the ice plug in the Thwaites Gateway to degrade to the point that cliff failures will begin in earnest in this part of the WAIS?  In this regards, the first attached image of the ice sheet in the Wilkes Basin illustrates how an ice plug (that is similar to that for Thwaites) can temporarily make a marine glacier stable for a relatively long period until ocean/atmospheric heat (or hydrofracturing) causes a sufficient retreat down a negative bottom slope for cliff failures (and hydrofracturing) to drive a rapid retreat as per DeConto & Pollard.

DeConto & Pollard (2016)'s ice sheet model has a relatively coarse grid resolution, and thus largely relies on hydrofracturing to both eliminate the ice shelf buttressing and the ice plug for Thwaites; which is why their projections rely on GMSTA approaching 2.7C (I note that conservative estimates give less than a 5% chance that we will stay below 2C) before significant cliff failure activity occurs.  DeConto & Pollard's reliance on hydrofracturing to kick-start serious cliff failure activity not only saves then from using a fine grid resolution but also from the trouble of modeling the influence of:

(a) The basal meltwater drainage system and high geothermal heat flux for Thwaites (which I previously mentioned);

(b) The PIG-Thwaites interaction especially via the Southwest, SW, Tributary Glacier, whose activation by the retreat of the Pine Island Ice Shelf, PIIS, calving face upstream of the SW Tributary Glacier's calving face (which per the second attached image could occur in the next year or two), would reduce the ice flow restraint associated with Thwaites' eastern shear margin (see the third image);

(c) The fourth image shows that several years ago both the Thwaites Eastern Ice Shelf and the Thwaites Ice Tongue, were pinned by offshore submerged seamounts, but now the Thwaites Ice Tongue is no longer pinned, and the Eastern Ice Shelf shows signs that it may break apart (largely due to basal melting from ocean heat) long before hydrofracturing may begin.

This post just cites some of the reasons that DeConto & Pollard (2016)'s projection of how soon the Thwaites ice plug may be lost, likely errs on the side of least drama; while in future posts, I plan to cite several other reasons (including the influence of the 'trough' that passes through the Thwaites ice plug shown in the fourth image).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2017, 08:40:14 PM
As a follow-on to my last post [focused on specific local reasons that the Thwaites Ice Plug could degrade earlier than projected by DeConto & Pollard (2016)], in this post I provide the two more reasons:

(a) The first image shows a Nov 1 2017 image of the degraded conditions of both the Thwaites Eastern Ice Shelf and the Thwaites Ice Tongue, while the second image shows portions of these features before January 2012 together with superimposed coloring indicating where an abrupt drop in surface ice elevation occurred after January 2012 near the bases of both the Ice Shelf and the Ice Tongue, in the area of the 'trough' shown in the fourth image of my last post.  Furthermore the third image shows a 2013 close-up of this collapsed area of ice indicating a 'checkerboard' pattern of floating icebergs that are currently trapped by the outboard ice mélange of the residual Thwaites Ice Tongue, that could readily float away once ocean currents/storms have adequately cleared away this ice mélange.  This 'checkerboard' of penned-in icebergs are located in the 'trough' through the Thwaites Ice Plug shown in the fourth image of my last post, and thus once these penned-in icebergs float away, the water depth in the 'trough' is deep enough to initiate local cliff failures that could accelerate the degradation of the ice plug together with the loss of buttressing associated with the potential early loss of the ice shelf (discussed in my last post).

(b) The fourth image (from Fogt et al 2011) shows how atmospheric Rossby waves telecommunicate atmospheric heat energy directly from the Tropical Pacific to the WAIS according to the indicated patterns of La Nina, El Nino and SAM events.  This telecommunicated heat energy could accelerate rapidly in the next few decades as global warming is projected to accelerate the frequency of Super El Nino (& to a lesser extent Super La Nina) events.  If so this could start hydrofracturing around the WAIS sooner than assumed by DeConto & Pollard (2016).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2017, 10:44:09 PM
Further to my last two posts about local considerations that could lead to an early (relative to DeConto & Pollard 2016's projection) degradation of the Thwaites ice plug, this post focuses on the influence of the ENSO cycle on the Amundsen Sea Low (or Amundsen Bellingshausen Sea Low), ASL (or ABSL) and the advection of more than usual wind-driven warm CDW into the ASE.
In this regards, the first attached image from Bertler et al 2006 (see reference below), which shows pictorially the relationship between the location of the ASL (or ABSL) and either a La Nina or an El Nino event.  This implies that future El Nino events will shift the location of the ASL to blow wind directly into the ASE.  Furthermore, the winds blowing into the ASE will likely be stronger than in the past recent past due both to the lower Amundsen sea pressure associated with AMO effect and the projected increase in the frequency of Super El Nino events with continued global warming.

The second image shows the deepwater changes across the Amundsen Sea continental shelf through which the warm CDW flows towards the grounding lines of key marine glaciers.
The third image shows a computer simulation of the pattern of warm CDW flow in the Amundsen Sea continental shelf area; which indicates how warm CDW can flow from the PIG to the Thwaites grounding line.

The fourth image shows that the submerged ridge seaward of Thwaites can help direct the warm CDW come from the PIG towards the 'trough' that crosses the Thwaites ice plug.

Bertler, N.A., Naish, T.T., Mayewski, P.A. and Barrett, P.J., (2006), "Opposing oceanic and atmospheric ENSO influences on the Ross Sea Region, Antarctica", Advances in Geosciences, 6, pp 83-88, SRef-ID: 1680-7359/adgeo/2006-6-83.

Next, the second linked reference indicates that from January to June the ASL typically moves from about 110 degrees W (where it is in position to help direct warm CDW into the ASE) to about 150 degrees W (where it does not help to direct warm CDW into the ASE).  I note also that:
(a) As the SAM has become more positive, due to global warming, the ASL has become more intensity and has tended to drift more to the west than previously; and

(b) El Nino events do not typically occur in the January to June timeframe but rather in the October to Dec timeframe, which helps to explain way more warm CDW flows into the ASE during El Nino events

Turner, J., Phillips, T., Hosking, J. S., Marshall, G. J. and Orr, A. (2013), The Amundsen Sea low. Int. J. Climatol., 33: 1818–1829. doi: 10.1002/joc.3558

http://onlinelibrary.wiley.com/doi/10.1002/joc.3558/abstract

Abstract: "We develop a climatology of the Amundsen Sea low (ASL) covering the period 1979–2008 using ECMWF operational and reanalysis fields. The depth of the ASL is strongly influenced by the phase of the Southern annular mode (SAM) with positive (negative) mean sea level pressure anomalies when the SAM is negative (positive). The zonal location of the ASL is linked to the phase of the mid-tropospheric planetary waves and the low moves west from close to 110°W in January to near 150°W in June as planetary waves 1 to 3 amplify and their phases shift westwards. The ASL is deeper by a small, but significant amount, during the La Niña phase of El Niño-Southern Oscillation (ENSO) compared to El Niño. The difference in depth of the low between the two states of ENSO is greatest in winter. There is no statistically significant difference in the zonal location of the ASL between the different phases of ENSO. Over 1979–2008 the low has deepened in January by 1.7 hPa dec−1 as the SAM has become more positive. It has also deepened in spring and autumn as the semi-annual oscillation has increase in amplitude over the last 30 years. An increase in central pressure and eastward shift in March has occurred as a result of a cooling of tropical Pacific SSTs that altered the strength of the polar front jet."

Next, the third linked reference ties the warming of the Tropical Atlantic SST to a strengthening of both the Antarctic Circumpolar Winds and the Amundsen Bellingshausen Sea Low (ABSL/ASL) via atmospheric Rossby waves in all seasons except the austral summer. 

XICHEN LI, EDWIN P. GERBER, DAVID M. HOLLAND, AND CHANGHYUN YOO, (2015), "A Rossby Wave Bridge from the Tropical Atlantic to West Antarctica", J. Climate, 28, 2256–2273, doi: http://dx.doi.org/10.1175/JCLI-D-14-00450.1


http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00450.1
&
http://polarmet.osu.edu/ACCIMA/li_gerber_jc_2015.pdf

Abstract: "Tropical Atlantic sea surface temperature changes have recently been linked to circulation anomalies around Antarctica during austral winter. Warming in the tropical Atlantic associated with the Atlantic multidecadal oscillation forces a positive response in the southern annular mode, strengthening the Amundsen–Bellingshausen Sea low in particular. In this study, observational and reanalysis datasets and a hierarchy of atmospheric models are used to assess the seasonality and dynamical mechanism of this teleconnection.  Both the reanalyses and models reveal a robust link between tropical Atlantic SSTs and the Amundsen–Bellingshausen Sea low in all seasons except austral summer. A Rossby wave mechanism is then shown to both explain the teleconnection and its seasonality. The mechanism involves both changes in the excitation of Rossby wave activity with season and the formation of a Rossby waveguide across the Pacific, which depends critically on the strength and extension of the subtropical jet over the west Pacific. Strong anticyclonic curvature on the poleward flank of the jet creates a reflecting surface, channeling quasi-stationary Rossby waves from the subtropical Atlantic to the Amundsen–Bellingshausen Sea region. In summer, however, the jet is weaker than in other seasons and no longer able to keep Rossby wave activity trapped in the Southern Hemisphere. The mechanism is supported by integrations with a comprehensive atmospheric model, initial-value calculations with a primitive equation model on the sphere, and Rossby wave ray tracing analysis."

Extract: "Antarctic climate is also influenced by other tropical–polar teleconnections (Fogt et al. 2011; Ding et al. 2012), and key questions remain concerning the relative importance of these effects. The time scales of tropical SST variability differs significantly from one region to another (e.g., ENSO and the east Pacific dominate on interannual time scales, while the AMO and Pacific decadal oscillation are more significant on longer time scales). Moreover, SSTs in different tropical ocean basins may interact with each other through tropical ocean interbasin teleconnections. It is thus important to further investigate the relative importance and the relationship between the teleconnections from different tropical ocean sectors as a function of time scale."

Finally, the fourth linked 2017 reference confirms that the ENSO is directly associated with surface air temperatures across the interior of West Antarctica, and I note that the frequency of Super El Nino events is projected to double when the global mean surface temp. anom. gets to 1.5C:

Kyle R. Clem, James A. Renwick, and James McGregor (2017), "Large-Scale Forcing of the Amundsen Sea Low and its Influence on Sea Ice and West Antarctic Temperature", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0891.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0891.1?utm_content=buffer2e94d&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Using empirical orthogonal function (EOF) analysis and atmospheric reanalyses, we examine the principal patterns of seasonal West Antarctic surface air temperature (SAT) and their connection to sea ice and the Amundsen Sea Low (ASL). During austral summer, the leading EOF (EOF1) explains 35% of West Antarctic SAT variability and consists of a widespread SAT anomaly over the continent linked to persistent sea ice concentration anomalies over the Ross and Amundsen Seas from the previous spring. Outside of summer, EOF1 (explaining ~40-50% of the variability) consists of an east-west dipole over the continent with SAT anomalies over the Antarctic Peninsula opposite those over western West Antarctica. The dipole is tied to variability in the Southern Annular Mode (SAM) and in-phase El Niño-Southern Oscillation (ENSO) / SAM combinations that influence the depth of the ASL over the central Amundsen Sea (near 105°W). The second EOF (EOF2) during autumn, winter, and spring (explaining ~15-20% of the variability) consists of a dipole shifted approximately 30 degrees west of EOF1 with a widespread SAT anomaly over the continent. During winter and spring, EOF2 is closely tied to variability in ENSO and a tropically-forced wavetrain that influences the ASL in the western Amundsen / eastern Ross Seas (near 135°W) with an opposite sign circulation anomaly over the Weddell Sea; the ENSO-related circulation brings anomalous thermal advection deep onto the continent. We conclude the ENSO-only circulation pattern is associated with SAT variability across interior West Antarctica, especially during winter and spring, while the SAM circulation pattern is associated with an SAT dipole over the continent."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2017, 11:32:00 PM
Another reason that DeConto & Pollard (2016)'s projection for the loss of the Thwaites ice plug may be too slow, is that they (and essentially all other modelers) have based their estimates of current ice mass loss from the ASE largely on data from the GRACE satellite.  However, the past GRACE data may have been corrected using a conservative estimate of the associated glacial isostatic adjustment, GIA, in this area.

Thus I post the following abstract which indicates that after updated GIA correction the Amundsen Sea sector is contributing more to SLR than previously projected:

An investigation of Glacial Isostatic Adjustment over the Amundsen Sea sector, West Antarctica
by: A. Groh; H. Ewert, M. Scheinert, M. Fritsche, A. Rülke, A. Richter, R. Rosenau, R. Dietrich
http://dx.doi.org/10.1016/j.gloplacha.2012.08.001

Abstract
The present study focuses on the Amundsen Sea sector which is the most dynamical region of the Antarctic Ice Sheet (AIS). Based on basin estimates of mass changes observed by the Gravity Recovery and Climate Experiment (GRACE) and volume changes observed by the Ice, Cloud and Land Elevation Satellite (ICESat), the mean mass change induced by Glacial Isostatic Adjustment (GIA) is derived. This mean GIA-induced mass change is found to be 34.1 ± 11.9 Gt/yr, which is significantly larger than the predictions of current GIA models. We show that the corresponding mean elevation change of 23.3 ± 7.7 mm/yr in the Amundsen Sea sector is in good agreement with the uplift rates obtained from observations at three GPS sites. Utilising ICESat observations, the observed uplift rates were corrected for elastic deformations due to present-day ice-mass changes. Based on the GRACE-derived mass change estimate and the inferred GIA correction, we inferred a present-day ice-mass loss of − 98.9 ± 13.7 Gt/yr for the Amundsen Sea sector. This is equivalent to a global eustatic sea-level rise of 0.27 ± 0.04 mm/yr. Compared to the results relying on GIA model predictions, this corresponds to an increase of the ice-mass loss or sea-level rise, respectively, of about 40%.

The first accompanying figure shows an overview of the Amundsen Sea sector, West Antarctica. The red line defines the generalised drainage basins of Pine Island Glacier, Thwaites Glacier and Smith Glacier (PITS). Locations of three GPS campaign sites are marked by red triangles.

The second image shows how post-glacial rebound for current ice mass loss from a marine glacier consists of both quick elastic rebound and slower rebound due to the flow of magma in the mantle.  I note that the current GIA corrections to GRACE data are based on conservative assumptions about the viscosity of the magma beneath the Byrd Subglacial Basin, BSB; but numerous indications are that this magma has a slower viscosity than assumed, which may mean that the GRACE ice mass loss projections for the ASE glaciers may need to be increased by more 40%.

The third and fourth images show the GRACE data from 2003 to 2009 which likely needs to be increase by more 40% than previously reported.  I note that the GRACE satellite has now fallen out of obit, but should be replaced by an upgraded system in 2018.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 27, 2017, 02:01:42 AM
While my last series of posts have focused on factors that could accelerate (earlier than assumed by DeConto & Pollard 2016) ice mass loss from the ASE marine glaciers, in this post I provide some factors that could cause ice mass losses from other portions of the WAIS earlier than assumed by DeConto & Pollard (2016).

The first four following references on both Oceanic Rossby Waves (see the first attached image) and Oceanic Infragravity Waves that telecommunicate energy from the Pacific Ocean to West Antarctica, and which promote ice calving events.

Pierre St-Laurent, John M. Klinck and Michael S. Dinniman (2012), "On the Role of Coastal Troughs in the Circulation of Warm Circumpolar Deep Water on Antarctic Shelves", JPO.

Bromirski, P.D., Miller, A.J., Flick, R.E, and Auad, G., (2011), "Dynamical Suppression of Sea Level Rise Along the Pacific Coast of North America: Indications for Imminent Acceleration" Journal of Geophysical Research, Vol. 116, C07005, doi: 10.1029/2010JC006759, July 2011.

Bromirski, P. D., O. V. Sergienko, and D. R. MacAyeal (2010), Transoceanic infragravity waves impacting Antarctic ice shelves, Geophys. Res. Lett., 37, L02502, doi:10.1029/2009GL041488.

The fourth (linked) reference provides recent field evidence of the impacts of tsunami and infragravity waves on the Ross Ice Shelf and concludes that such very long period waves can reduce the stability of Antarctic ice shelves; which could then reduce the buttressing on the associated marine glacial, and thus can serve to accelerate the rate of sea level rise (and the ice-climate feedback mechanism).

P. D. Bromirski et al. (20 July 2017), "Tsunami and infragravity waves impacting Antarctic ice shelves", JGR Oceans, DOI: 10.1002/2017JC012913 

http://onlinelibrary.wiley.com/doi/10.1002/2017JC012913/full

Abstract: "The responses of the Ross Ice Shelf (RIS) to the 16 September 2015 8.3 (Mw) Chilean earthquake tsunami (>75 s period) and to oceanic infragravity (IG) waves (50–300 s period) were recorded by a broadband seismic array deployed on the RIS from November 2014 to November 2016. Here we show that tsunami and IG-generated signals within the RIS propagate at gravity wave speeds (∼70 m/s) as water-ice coupled flexural-gravity waves. IG band signals show measureable attenuation away from the shelf front. The response of the RIS to Chilean tsunami arrivals is compared with modeled tsunami forcing to assess ice shelf flexural-gravity wave excitation by very long period (VLP; >300 s) gravity waves. Displacements across the RIS are affected by gravity wave incident direction, bathymetry under and north of the shelf, and water layer and ice shelf thicknesses. Horizontal displacements are typically about 10 times larger than vertical displacements, producing dynamical extensional motions that may facilitate expansion of existing fractures. VLP excitation is continuously observed throughout the year, with horizontal displacements highest during the austral winter with amplitudes exceeding 20 cm. Because VLP flexural-gravity waves exhibit no discernable attenuation, this energy must propagate to the grounding zone. Both IG and VLP band flexural-gravity waves excite mechanical perturbations of the RIS that likely promote tabular iceberg calving, consequently affecting ice shelf evolution. Understanding these ocean-excited mechanical interactions is important to determine their effect on ice shelf stability to reduce uncertainty in the magnitude and rate of global sea level rise."

Plain Language Summary
"A major source of the uncertainty in the magnitude and rate of global sea level rise is the contribution from Antarctica. Ice shelves buttress land ice, restraining land ice from reaching the sea. We present the analysis of seismic data collected with a broadband seismic array deployed on the Ross Ice Shelf, Antarctica. The characteristics of ocean gravity-wave-induced vibrations, that may expand existing fractures in the ice shelf and/or trigger iceberg calving or ice shelf collapse events, are described. The mechanical dynamic strains induced can potentially affect ice shelf integrity, and ultimately reduce or remove buttressing restraints, accelerating sea level rise."

&

The second attached figure by Fogt et al 2011 indicates that trends for cyclones storm in both the Ross Sea, and Bellingshausen Sea, Basins has been of increased intensity (ie lower cental pressure) and increase storm frequency.  This will tend to increase calving from ice shelves/tongues in these areas.

&

I note that the conventional thinking is that the cold FRIS/RIS ice shelves will largely remain intact until well after 2300 possibly due to their belief in the stationary nature of both: (a) the water adjoining the FRIS/RIS  in the Continential Zone, within the Continental Water Boundary, CWB, shown in the third attached image; and (b) the protective circulation pattern beneath a cold ice shelf that helps to keep warm CDW out from beneath as cold ice shelf, per Hellmer et al 2012.  However, in the next linker reference, Hellmer et al (2017) demonstrates that warm CDW will circulate beneath the FRIS circa 2070.

Hartmut H. Hellmer et al. (2017), "The Fate of the Southern Weddell Sea Continental Shelf in a Warming Climate", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0420.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0420.1
http://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-16-0420.1

Abstract: "Warm water of open ocean origin on the continental shelf of the Amundsen and Bellingshausen Seas causes the highest basal melt rates reported for Antarctic ice shelves with severe consequences for the ice shelf/ice sheet dynamics. Ice shelves fringing the broad continental shelf in the Weddell and Ross Seas melt at rates orders of magnitude smaller. However, simulations using coupled ice–ocean models forced with the atmospheric output of the HadCM3 SRES-A1B scenario run (CO2 concentration in the atmosphere reaches 700 ppmv by the year 2100 and stays at that level for an additional 100 years) show that the circulation in the southern Weddell Sea changes during the twenty-first century. Derivatives of Circumpolar Deep Water are directed southward underneath the Filchner–Ronne Ice Shelf, warming the cavity and dramatically increasing basal melting. To find out whether the open ocean will always continue to power the melting, the authors extend their simulations, applying twentieth-century atmospheric forcing, both alone and together with prescribed basal mass flux at the end of (or during) the SRES-A1B scenario run. The results identify a tipping point in the southern Weddell Sea: once warm water flushes the ice shelf cavity a positive meltwater feedback enhances the shelf circulation and the onshore transport of open ocean heat. The process is irreversible with a recurrence to twentieth-century atmospheric forcing and can only be halted through prescribing a return to twentieth-century basal melt rates. This finding might have strong implications for the stability of the Antarctic ice sheet."

Extract: "Our experiments indicate that the link between the hydrography on the southern Weddell Sea continental shelf and melt rates beneath the Filchner–Ronne Ice Shelf is controlled by a positive feedback mechanism: Once the reversal of the near-bottom density gradient across the Filchner Trough, together with a rising coastal thermocline, facilitates the direct inflow of the slope current into the trough, warm deep water flushes the ice shelf cavity, causing its warming, enhanced basal mass loss, and a vigorous outflow of glacial meltwater. The latter further freshens the shelf water and thus maintains a density and flow structure at the sill that supports further access of warm water to the ice shelf cavity. The increase in basal melting accelerates the cavity circulation, drawing in even more warm water of open ocean origin—a self-intensifying mechanism. Although the initial trigger for this transition is freshening on the continental shelf as a result of atmosphere–ocean interactions, once the system is in the warm-shelf phase, the only way to stop the inflow of the warm water is to return to twentieth-century atmospheric conditions and to reduce the meltwater input. At first, the latter could be realized by a reduction in the floating portion of the ice sheet. However, the resulting loss of buttressing of the inland ice sheet would accelerate the draining ice streams. The discharge of ice from the relevant catchment basin and a significant contribution to global sea level will be inevitable."

&

Lastly I note that the following linked (open access) reference cites research on four decades of marine glacier grounding line retreat in the Bellingshausen margin (see fourth attached image), which is losing ice mass faster than most researchers previously expected, primarily due to oceanic heat effects:

Frazer D.W. Christie, Robert G. Bingham, Noel Gourmelen, Simon F.B. Tett & Atsuhiro Muto (22 May 2016), "Four-decade record of pervasive grounding line retreat along the Bellingshausen margin of West Antarctica", Geophysical Research Letters, DOI: 10.1002/2016GL068972

http://onlinelibrary.wiley.com/doi/10.1002/2016GL068972/abstract

Abstract: "Changes to the grounding line, where grounded ice starts to float, can be used as a remotely-sensed measure of ice-sheet susceptibility to ocean-forced dynamic thinning. Constraining this susceptibility is vital for predicting Antarctica's contribution to rising sea levels. We use Landsat imagery to monitor grounding line movement over four decades along the Bellingshausen margin of West Antarctica, an area little monitored despite potential for future ice losses. We show that ~65% of the grounding line retreated from 1990-2015, with pervasive and accelerating retreat in regions of fast ice flow and/or thinning ice shelves. Venable Ice Shelf confounds expectations in that despite extensive thinning, its grounding line has undergone negligible retreat. We present evidence that the ice shelf is currently pinned to a sub-ice topographic high which, if breached, could facilitate ice retreat into a significant inland basin, analogous to nearby Pine Island Glacier."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 27, 2017, 02:28:06 AM
In my last post I cited some factors that may contribute to significant ice mass loss, before 2100, from key regions of the WAIS in addition to the Amundsen Sea Embayment, ASE, marine glaciers.  Here I present the first two images (& I note that the second image show up to 120 meters of total post glacial rebound in the BSB, which was not considered by DeConto & Pollard's model) from Vaughan et al. 2011, that indicate that during previous collapses of the WAIS, seaways opened between the various regions of the WAIS.  If such seaways were to open during the future WAIS collapse postulated by DeConto & Pollard (2016), the associated oceanic heat impacts and loss of ice surface elevations would likely result in faster image mass loss than DeConto & Pollard (2016) assumed.  In this regards, I note that the main reason that current Antarctic Amplification is lower than current Arctic Amplification, is due to the high elevation of the glacial ice in Antarctica.  Thus, if a postulated collapse of the WAIS were to occur this century, Antarctic Amplification would increase to the range of 2 to 3 times GMSTA.

Also, I note that the third image illustrates a clear bipolar seesaw mechanism between freshwater hosing events since MIS 5 (the Eemian), thus as both the Greenland Ice Sheet and the WAIS are concurrently losing ice mass during the Anthropocene, one can expect more impact on/from the MOC than for the paleo periods the DeConto & Pollard (2016) conservatively calibrated their model for.

Lastly, for this post, I note that researchers have identified numerous positive feedback mechanisms related to the methane cycle that could result in significant natural pulses of methane emissions into the atmosphere in the 2050 to 2100 timeframe including from: flooded tropical peatlands/rainforests, methane hydrates beneath the WAIS and from Arctic thermokarst lakes (see the fourth attached image for RCP 8.5 forcing), none of which were including in DeConto & Pollard (2016)'s forcing scenario.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 27, 2017, 03:06:31 AM
In my last post, I briefly mentioned the risk of abrupt release of methane from hydrate beneath the WAIS, during a potential near-future collapse of the WAIS. In this regards, the linked reference provides paleo evidence that subglacial gas hydrates within zones of the basal sediment served to reduce ice flow velocities in the marine glaciers of the Barents-Sea-Fennoscandian ice sheet approximately 20,000 years ago.  As there are projected to be large amounts of gas hydrates in the marine sediments beneath the WAIS, these findings may help to partially explain why the ice flow velocities of key WAIS marine glaciers like the PIG and Thwaites have plateaued recently (rather than continuing to accelerate rapidly).  However, if this is the case and if cliff failures and hydrofracturing occurs in the WAIS before GMST anoms reach 2.7C (as forecast by DeConto 2016), then such postulated basal hydrates could release significant volumes of methane if/when the WAIS collapses:

Monica Winsborrow, Karin Andreassen, Alun Hubbard, Andreia Plaza-Faverola, Eythor Gudlaugsson, Henry Patton. Regulation of ice stream flow through subglacial formation of gas hydrates. Nature Geoscience, 2016; DOI: 10.1038/ngeo2696

http://www.nature.com/ngeo/journal/v9/n5/full/ngeo2696.html


Abstract: "Variations in the flow of ice streams and outlet glaciers are a primary control on ice sheet stability, yet comprehensive understanding of the key processes operating at the ice-bed interface remains elusive. Basal resistance is critical, especially sticky spots-localized zones of high basal traction-for maintaining force balance in an otherwise well-lubricated/high-slip subglacial environment. Here we consider the influence of subglacial gas-hydrate formation on ice stream dynamics, and its potential to initiate and maintain sticky spots. Geophysical data document the geologic footprint of a major palaeo-ice-stream that drained the Barents Sea-Fennoscandian ice sheet approximately 20,000 years ago. Our results reveal a ∼250 km2 sticky spot that coincided with subsurface shallow gas accumulations, seafloor fluid expulsion and a fault complex associated with deep hydrocarbon reservoirs. We propose that gas migrating from these reservoirs formed hydrates under high-pressure, low-temperature subglacial conditions. The gas hydrate desiccated, stiffened and thereby strengthened the subglacial sediments, promoting high traction-a sticky spot-that regulated ice stream flow. Deep hydrocarbon reservoirs are common beneath past and contemporary glaciated areas, implying that gas-hydrate regulation of subglacial dynamics could be a widespread phenomenon."

https://www.sciencedaily.com/releases/2016/04/160413084735.htm

Extract: "One of the major questions today is: What are the ice sheets going to do in an ever-warming climate? Ice sheets of Greenland and Antarctica are major contributors to the sea level rise, which can make life difficult for many coastal nations in the near future.

To understand the ice sheets we need to understand their drainage system -- a key component of this is ice streams, fast-flowing rivers of ice, that deliver ice from the centre of the ice sheet to the oceans. Many of these ice streams are speeding up, which may be seen as the logical consequence of the warming climate. But some are slowing down, even stopping, examples of this may be found in the Ross ice streams of West Antarctica.

A new study in Nature Geoscience suggests that a 250km2 sticky spot made up of sediments with gas hydrates in them, slowed down an ice stream in the Barents Sea. This happened sometime during the last ice age, 20,000 years ago, when the Barents Sea was covered with an ice sheet.

Gas hydrate sticky spots under ice streams are a potentially widespread feature also today.
"If there are gas hydrates under today's ice sheets, they can slow the ice streams. There are studies indicating that there may be vast reservoirs of hydrates under the West Antarctic Ice sheet. Anywhere you have a hydrocarbon reservoir, water, high pressure and low temperature, you will get gas hydrate." says Winsborrow.

Ice streams of today are extensively monitored with GPS tracking systems, but it is very difficult to gaze beneath three kilometres of ice to see what is going on at the bottom. But scars left by the Barents Sea Ice sheet are visible on the ocean floor today. That makes this ancient ice sheet an important analogue, especially for the modern West Antarctica Ice Sheet, as both are based in marine environments.

"We need these analogies from the past. Understanding what is happening at the base of ice streams is important for modelling and predicting the future of the ice sheets.""

&

The following linked reference presents new findings that the retreat of the Barents Sea Ice Sheet at the end of the last ice age resulted in the explosive release of methane from Arctic seafloor hydrates as overpressure from the ice sheet disappeared.  The researchers find that serves as a good past analogy of what may likely happen in the near-term future if the WAIS were to collapse (see the attached image).  As methane has a GWP100 of about 35 such explosive releases of methane could have a significant impact on global warming this century.  Such short-term methane forcings would be superimposed on top of Hansen's ice-climate feedback mechanism.

K. Andreassen, A. Hubbard, M. Winsborrow, H. Patton, S. Vadakkepuliyambatta, A. Plaza-Faverola, E. Gudlaugsson, P. Serov, A. Deryabin, R. Mattingsdal, J. Mienert & S. Bünz (02 Jun 2017), "Massive blow-out craters formed by hydrate-controlled methane expulsion from the Arctic seafloor", Science, Vol. 356, Issue 6341, pp. 948-953
DOI: 10.1126/science.aal4500

http://science.sciencemag.org/content/356/6341/948

Abstract: "Widespread methane release from thawing Arctic gas hydrates is a major concern, yet the processes, sources, and fluxes involved remain unconstrained. We present geophysical data documenting a cluster of kilometer-wide craters and mounds from the Barents Sea floor associated with large-scale methane expulsion. Combined with ice sheet/gas hydrate modeling, our results indicate that during glaciation, natural gas migrated from underlying hydrocarbon reservoirs and was sequestered extensively as subglacial gas hydrates. Upon ice sheet retreat, methane from this hydrate reservoir concentrated in massive mounds before being abruptly released to form craters.  We propose that these processes were likely widespread across past glaciated petroleum provinces and that they also provide an analog for the potential future destabilization of subglacial gas hydrate reservoirs beneath contemporary ice sheets."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 27, 2017, 06:38:01 PM
At around minute 42 of the linked video entitled: ""Sea-Level Rise: Inconvenient, or Unmanageable?" Richard B. Alley", Alley notes that the ASE marine glaciers could begin to hydrofacture with subsequent cliff failures in about 50-years +/- 50 years:

https://www.youtube.com/watch?v=WE9Gqy8Yy9w
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: A-Team on November 27, 2017, 07:27:14 PM
I sure hope you are planning to pull all this together into a comprehensive arXiv-type journal review article as hosted by Cornell. They have a section called Atmospheric and Oceanic Physics with el nino articles etc where it would fit in and receive a permanent citable doi. It might involve less quoting and more paraphrasing of source material and endnotes for the refs (though I haven't looked at their exact requirements). Such posts can then serve as a springboard to submission to regular peer-reviewed journals if you want to go that route.

https://arxiv.org/list/physics.ao-ph/recent

Scribbler note on Holthaus:
https://robertscribbler.com/category/climate-change-2/
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 28, 2017, 12:21:47 AM
I sure hope you are planning to pull all this together into a comprehensive arXiv-type journal review article as hosted by Cornell. They have a section called Atmospheric and Oceanic Physics with el nino articles etc where it would fit in and receive a permanent citable doi. It might involve less quoting and more paraphrasing of source material and endnotes for the refs (though I haven't looked at their exact requirements). Such posts can then serve as a springboard to submission to regular peer-reviewed journals if you want to go that route.

https://arxiv.org/list/physics.ao-ph/recent

Scribbler note on Holthaus:
https://robertscribbler.com/category/climate-change-2/

Thanks for the pointer, but as I work as a fulltime engineer, I find it easier to critique the work of real scientists rather than to pretend to be one myself.  Nevertheless, the following linked abstract (I do not have access to EGU papers), indicates that DeConto & Pollard are working hard to improve the calibration of the model that they used in the 2016 paper.

Rob DeConto, David Pollard, and Ed Gasson (2017), "Potential for future sea-level contributions from the Antarctic ice sheet", Geophysical Research Abstracts, Vol. 19, EGU2017-15929,

http://meetingorganizer.copernicus.org/EGU2017/EGU2017-15929.pdf

Abstract: "Recent Antarctic ice-sheet modeling that includes the effects of surface meltwater on ice-sheet dynamics (through hydrofracturing and ice-cliff collapse) has demonstrated the previously underappreciated sensitivity of the ice sheet to atmospheric warming in addition to sub-ice oceanic warming. Here, we improve on our modeling of future icesheet retreat by using time-evolving atmospheric climatologies from a high-resolution regional climate model, synchronized with SSTs, subsurface ocean temperatures, and sub-ice melt rates from the NCAR CCSM4 GCM. Ongoing improvements in ice-sheet model physics are tested and calibrated relative to observations of recent and ancient (Pliocene, Last InterGlacial, and Last Deglaciation) ice-sheet responses to warming. The model is applied to a range of future greenhouse-gas emissions scenarios, including modified RCP scenarios corresponding to the 1.5º and 2.0º targets of the Paris Agreement and higher emissions scenarios including RCP8.5. The results imply that a threshold in the stability of the West Antarctic Ice Sheet and outlet glaciers in East Antarctica might be exceeded in the absence of aggressive mitigation policies like those discussed in Paris. We also explore the maximum potential for Antarctica to contribute to future sea-level rise in high greenhouse gas emissions scenarios, by testing a range of model physical parameters within the bounds of observations."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: FishOutofWater on November 28, 2017, 12:48:15 AM
Let me add that the southward expansion of the subtropical highs is an known predicted consequence of adding heat to the climate system. There are numerous papers on it. The combination of the southward expansion of the high pressure areas and the cooling caused by ozone killing chemicals has increased the temperature gradient north of Antarctica. That has caused an increase of westerly winds closer to the continent.

Our theoretical physicist is ignorant of the meteorology and oceanography of the southern ocean. The tightening winds around Antarctica are driving the warm waters under the ice shelves. There are papers on the effects of the tightening winds on the ocean currents around the Antarctic Peninsula.

That joke about the paleoclimatologist, physicist and engineer was good for a big laugh. Thanks.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: FishOutofWater on November 28, 2017, 01:10:00 AM
Thanks for the video. There are a few redundancies but it has excellent visualizations that will help non-scientists and scientists alike understand what's happening.

Another piece of information our theroetical physicist doesn't know. The fresh water layer caused by melting will greatly reduce heat loss from warmer water below. It will act as a lid on heat loss.  A blanket of insulating ice in the winter may actually expand in area, but the glaciers will continue to melt from below because warm intermediate water will not be caught up in deep convection.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: FishOutofWater on November 28, 2017, 01:14:00 AM
ASLR if you can't access scientific reports any other way try this link.
http://sci-hub.bz/
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 28, 2017, 02:35:33 AM
ASLR if you can't access scientific reports any other way try this link.
http://sci-hub.bz/

Thanks, but I already looked there & I could not find DeConto & Pollard's 2017 EGU paper (if it exists).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: GeoffBeacon on November 28, 2017, 12:30:56 PM
A-Team

Quote
I sure hope [A-team is] planning to pull all this together into a comprehensive arXiv-type journal review article as hosted by Cornell.

But who is going to get the message through to Guardian readers?  These might even include some policy makers or policy influencers.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 28, 2017, 05:46:25 PM
It seems to me that when glacial scientists like Richard Alley says that major portions of the WAIS could begin rapid ice cliff failures and hydrofracturing within 50-years plus or minus 50-years; and when climate scientists like James Hansen warned that global mean sea level could be up to 5m higher than pre-industrial by 2100, and when Bakker et al. 2100 carefully layout the probabilities for scenarios leading up to 5m of sea level rise by 2100 (see the first image); then both decision makers and the public have already been adequately warned, and it societies addiction to cheap power (largely fossil fuels) that will keep us on a RCP8.5/SSP5 pathway through about 2050 (when a socio-economic collapse will unfold until about 2060).

The second image shows that by 2050 following RCP 8.5 (which does not include any freshwater hosing events) that anthropogenic radiative forcing (planetary energy imbalance) will be about 5 Watts/sq meter, which herein I will assume will stop increasing (due to socio-economic collapse) but will remain constant thru 2100 (due to the long life of CO₂ in the atmosphere).  However, the third image (from Hansen et al 2016) shows that an abrupt freshwater hosing event circa 2050 will cause pulse increase of radiative forcing of about 2.5 Watts/sq meter that is additive to the 5 Watts/sq meter, for a total radiative forcing of about 7.5 Watts/sq meter circa 2060; which is very close to RCP 8.5's assumed 8.5 Watts/sq meter of radiative forcing by 2100.

Now, the two following Bintanja et al. (2017) referencing indicate that in the 2091 to 2100 timeframe most of the strongly increase volume of precipitation in the Arctic will fall as rain, rather than as show; which my by logic cited in the preceding paragraph would begin circa 2060 if the WAIS collapse reaches a peak circa 2060.  However, the fourth attached image (from Hansen & Sato 2012) indicates that with an albedo flip (herein assumed to occur due to Arctic rainfall), together with the assumed freshwater hosing event, that ECS would reach about 7C.  Also, the possible pulses of methane discussed in Replies #30 & 31 (from thermokarst lakes, tropical wetlands and from Antarctic marine hydrates), we could be on a pathway to a runaway-greenhouse (with an equable climate in the NH) effect indicated in the fourth image to occur when radiative forcing reaches about 8.5 Watts/sq meter.

Richard Bintanja and Olivier Andry (2017), “Towards a rain-dominated Arctic”, Geophysical Research Abstracts Vol. 19, EGU2017-4402

http://meetingorganizer.copernicus.org/EGU2017/EGU2017-4402.pdf

Abstract: “Current climate models project a strong increase in Arctic precipitation over the coming century, which has been attributed primarily to enhanced surface evaporation associated with sea-ice retreat. Since the Arctic is still quite cold, especially in winter, it is often (implicitly) assumed that the additional precipitation will fall mostly as snow. However, very little is known about future changes in rain/snow distribution in the Arctic, notwithstanding the importance for hydrology and biology. Here we use 37 state-of-the-art climate models in standardised twenty-first century (2006–2100) simulations to show that 70◦ – 90◦N average annual Arctic snowfall will actually decrease, despite the strong increase in precipitation, and that most of the additional precipitation in the future (2091– 2100) will fall as rain. In fact, rain is even projected to become the dominant form of precipitation in the Arctic region. This is because Arctic atmospheric warming causes a greater fraction of snowfall to melt before it reaches the surface, in particular over the North Atlantic and the Barents Sea. The reduction in Arctic snowfall is most pronounced during summer and autumn when temperatures are close to the melting point, but also winter rainfall is found to intensify considerably. Projected (seasonal) trends in rain/snowfall will heavily impact Arctic hydrology (e.g. river discharge, permafrost melt), climatology (e.g. snow, sea ice albedo and melt) and ecology (e.g. water and food availability).”

See also:

R. Bintanja et al. Towards a rain-dominated Arctic, Nature Climate Change (2017). DOI: 10.1038/nclimate3240

http://www.nature.com/nclimate/journal/v7/n4/full/nclimate3240.html

Extract: "Rain causes more (extensive) permafrost melt, which most likely leads to enhanced emissions of terrestrial methane  (a powerful greenhouse gas), more direct runoff (a smaller seasonal delay) and concurrent freshening of the Arctic Ocean. Rainfall also diminishes snow cover extent and considerably lowers the surface albedo of seasonal snow, ice sheets and sea ice, reinforcing surface warming and amplifying the retreat of ice and snow; in fact, enhanced rainfall will most likely accelerate sea-ice retreat by lowering its albedo (compared with that of fresh snowfall)."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: A-Team on November 28, 2017, 06:00:02 PM
Quote
I do not have access to EGU papers
That is just an abstract for a talk at EGU2017. There is no further pdf associated with it. The powerpoints shown during the talk are not available either. An older paper with a very similar title was written by these authors from 2016, DOI 10.1038/nature17145. Neither author is on ResearchGate.

However RE Kopp is there, co-authoring this April 2017 arxiv preprint (comments accepted) with DeConto et al:

Implications of ice-shelf hydrofracturing and ice-cliff collapse mechanisms for sea-level projections
https://arxiv.org/abs/1704.05597

A title search of the 2016 paper at google reveals 275 follow-up citations by subsequent articles which is a lot. These hits can be sorted by date. Some of them are on-topic, others off in the weeds.

Here are some other 2017 DeConto resources (in addition to Google Scholar 2017 hits):

https://www.youtube.com/watch?v=StHiUgF2iU4

http://www.scientia.global/dr-david-pollard-dr-robert-deconto-birth-death-ice-sheets-understanding-past-predicting-future-pennsylvania-state-university-university-massachusetts/

Quote
But who is going to get the message through to Guardian readers?  These might even include some policy makers or policy influencers.
Good question, Geoff. Outreach at that level is a full-time job. In the meantime "A lie can travel halfway around the world while the truth is still putting on its shoes".

Jonathan Swift on this in “The Examiner” back in 1710:

"Besides, as the vilest Writer has his Readers, so the greatest Liar has his Believers; and it often happens, that if a Lie be believ’d only for an Hour, it has done its Work, and there is no farther occasion for it. Falsehood flies, and the Truth comes limping after it; so that when Men come to be undeceiv’d, it is too late; the Jest is over, and the Tale has had its Effect…"

https://quoteinvestigator.com/2014/07/13/truth/
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 28, 2017, 08:19:52 PM
In my last post, I truncated the RCP 8.5 anthropogenic radiative forcing at 2050 (due to an assumed socio-economic collapse), and then added radiative forcing from a freshwater hosing event (per Hansen et al 2016) & an Arctic Albedo Flip (per Hansen and Sato 2012) & unspecified amount of methane emissions from thermokarst lakes, Antarctic methane hydrates and tropical wetlands.  In this post, I discuss some of the implications of decision makers being out of date on the implications of current methane concentrations.  In this regards, the first image shows the CO2e concentrations (per Wikipedia) for the various RCP scenarios, assume the conversion factors assumed prior to AR5.  This image shows an assumed CO2e concentration for RCP 8.5 of about 425 for 2017 and of about 630 ppm by 2050.

However, the total radiative forcings, RFs, from the linked ORNL website article by Blasing, T.J. (that updates such RF values reported in April 2016) are used in the linked Wikipedia article to calculate a CO2e value of 526.6ppm; which assuming the current rate of annual increase in CO2e of about 3.5ppm indicates that early in 2017 CO2e exceeded 530ppm:

https://en.wikipedia.org/wiki/Carbon_dioxide_equivalent


Extract: "To calculate the CO2e of the additional radiative forcing calculated from April 2016's updated data: ∑ RF(GHGs) = 3.3793, thus CO2e = 280 e3.3793/5.35 ppmv = 526.6 ppmv."

http://cdiac.ornl.gov/pns/current_ghg.html


This value of 530ppm for CO2e for 2017 is well above the 425ppm value assumed by RCP 8.5 (used to force climate models for AR5); thus it seems highly likely that the true CO2e value in 2050 will be well above 750ppm

Also, see the associated 2008 article entitled: "Possible Origin of Methane in Ice Core Records"; which concludes that the methane in both Antarctic and Greenland ice cores for the Late Quaternary period (0.5-1.0 million years ago) is likely associated with methane emitted from marine hydrates

https://www.sciencedaily.com/releases/2008/02/080217093816.htm

Next, I provide a links to Jagniecki et al. (2015) (and an associated article); indicating that early Eocene climatic optimum (EECO) conditions (with an equable climate) may have occurred with atmospheric CO₂ concentrations between 680ppm and 1260ppm (see the second attached image); and that under such conditions the effective climate sensitivity (ESS) may have been twice that previously assumed by Royer et al (2012) (see link to reference below) as indicates in the third attached image, and could be very high for a CO2e concentration over 750ppm per the fourth image.

Jagniecki,Elliot A. et al. (2015), "Eocene atmospheric CO2from the nahcolite proxy", Geology, http://dx.doi.org/10.1130/G36886.1


http://geology.gsapubs.org/content/early/2015/10/23/G36886.1

ftp://rock.geosociety.org/pub/reposit/2015/2015357.pdf

Abstract: "Estimates of the atmospheric concentration of CO2, [CO2]atm, for the "hothouse" climate of the early Eocene climatic optimum (EECO) vary for different proxies. Extensive beds of the mineral nahcolite (NaHCO3) in evaporite deposits of the Green River Formation, Piceance Creek Basin, Colorado, USA, previously established [CO2]atm for the EECO to be >1125 ppm by volume (ppm). Here, we present experimental data that revise the sodium carbonate mineral equilibria as a function of [CO2] and temperature. Co-precipitation of nahcolite and halite (NaCl) now establishes a well-constrained lower [CO2]atm limit of 680 ppm for the EECO. Paleotemperature estimates from leaf fossils and fluid inclusions in halite suggest an upper limit for [CO2]atm in the EECO from the nahcolite proxy of ∼1260 ppm. These data support a causal connection between elevated [CO2]atm and early Eocene global warmth, but at significantly lower [CO2]atm than previously thought, which suggests that ancient climates on Earth may have been more sensitive to a doubling of [CO2]atm than is currently assumed."

Extract: "These results show that [CO₂]atm may not have been as high as previously thought during the warmest interval of the Cenozoic, implying a climate sensitivity for CO₂ that is roughly twice as high as is currently assumed (Royer et al., 2012)."

See also:
https://www.sciencenews.org/article/eocene-temperature-spike-caused-half-much-co2-once-thought

Extract: "During the Eocene around 50 million years ago, climbing CO2 levels heated the planet by more than 5 degrees Celsius. By examining crystals grown in this “hothouse” climate, researchers discovered that Eocene CO2 levels were as low as 680 parts per million. That’s nearly half the 1,125 ppm predicted by previous, less accurate crystal experiments, the researchers report online October 23 in Geology."

This supports my concern that if we stay on a BAU pathway until 2050, we could trigger a runaway climate change situation driven by methane from hydrates (see the following Wikipedia article on the Clathrate gun hypothesis) after say 2100, even if humans stop new GHG emissions all together in 2050.

Title: "Clathrate gun hypothesis"

https://en.wikipedia.org/wiki/Clathrate_gun_hypothesis

Extract: "The sudden release of large amounts of natural gas from methane clathrate deposits in runaway climate change could be a cause of past, future, and present climate changes. The release of this trapped methane is a potential major outcome of a rise in temperature; some have suggested that this was a main factor in the planet warming 6 °C, which happened during the end-Permian extinction, as methane is much more powerful as a greenhouse gas than carbon dioxide. Despite its atmospheric lifetime of around 12 years, it has a global warming potential of 72 over 20 years, 25 over 100 years, and 33 when accounted for aerosol interactions. The theory also predicts this will greatly affect available oxygen and hydroxyl radical content of the atmosphere.

Another kind of exception is in clathrates associated with the Arctic ocean, where clathrates can exist in shallower water stabilized by lower temperatures rather than higher pressures; these may potentially be marginally stable much closer to the surface of the sea-bed, stabilized by a frozen 'lid' of permafrost preventing methane escape.

The so-called self-preservation phenomenon has been intensively studied by Russian geologists starting in the late 1980s. This metastable clathrate state can be a basis for release events of methane excursions, such as during the interval of the last glacial maximum. A study from 2010 concluded with the possibility for a trigger of abrupt climate warming based on metastable methane clathrates in the East Siberian Arctic Shelf (ESAS) region."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Susan Anderson on November 28, 2017, 10:46:07 PM
[edit and further apology for not reading from the beginning: I see Prokaryotes opened this discussion with a reference to this article. The continuing discussion is fascinating if a bit above my level.]

With apologies for an amateur interruption, while admiring all this excellent work. Just caught up my reading on a link I'd saved for when I had time from Eric Holthaus (Grist, 21 November 2017). It is a layperson's overview. I'm inclined to tamp down on exaggeration, but this is both convincing and terrifying. https://grist.org/article/antarctica-doomsday-glaciers-could-flood-coastal-cities/ (https://grist.org/article/antarctica-doomsday-glaciers-could-flood-coastal-cities/)

Quote
Ice Apocalypse: Rapid collapse of Antarctic glaciers could flood coastal cities by the end of this century.
....
The glaciers of Pine Island Bay are two of the largest and fastest-melting in Antarctica. (A Rolling Stone feature earlier this year dubbed Thwaites “The Doomsday Glacier.”) Together, they act as a plug holding back enough ice to pour 11 feet of sea-level rise into the world’s oceans — an amount that would submerge every coastal city on the planet. For that reason, finding out how fast these glaciers will collapse is one of the most important scientific questions in the world today.

To figure that out, scientists have been looking back to the end of the last ice age, about 11,000 years ago, when global temperatures stood at roughly their current levels. The bad news? There’s growing evidence that the Pine Island Bay glaciers collapsed rapidly back then, flooding the world’s coastlines — partially the result of something called “marine ice-cliff instability.”

The ocean floor gets deeper toward the center of this part of Antarctica, so each new iceberg that breaks away exposes taller and taller cliffs. Ice gets so heavy that these taller cliffs can’t support their own weight. Once they start to crumble, the destruction would be unstoppable.

“Ice is only so strong, so it will collapse if these cliffs reach a certain height,” explains Kristin Poinar, a glaciologist at NASA’s Goddard Space Flight Center. “We need to know how fast it’s going to happen.”

In the past few years, scientists have identified marine ice-cliff instability as a feedback loop that could kickstart the disintegration of the entire West Antarctic ice sheet this century — much more quickly than previously thought.

Minute-by-minute, huge skyscraper-sized shards of ice cliffs would crumble into the sea, as tall as the Statue of Liberty and as deep underwater as the height of the Empire State Building. The result: a global catastrophe the likes of which we’ve never seen.

There are more references and caveats in the article, which appears to me to raise the probability of sea level rise which will inundate good parts of, for example, my home city Boston sooner than previously projected and make the low estimates for 2100 less likely than the higher ones.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 28, 2017, 10:46:45 PM
As I only attach four images per post, I provide the four attached images to catch-up to the points made in by last two posts. 

The first image from Tobias Friedrich et al. (2016), indicates that when using an effective ECS based on calibration to data during warm conditions over the past 784,000 years, the global mean SAT could become as high as 8C above pre-industrial with radiative forcing of 6 Watts/sq meter (see also the following associated caption)

Caption for the first image: "Fig. 3  Sensitivity of global mean SAT anomalies to radiative forcing anomalies:  Scatter diagram (circles) of reconstructed global mean SAT anomalies (K) (Fig. 2B) versus net radiative forcing anomalies (W/m2) (Fig. 2D) for the last 784,000 years. Anomalies are calculated with respect to PI values. Two-dimensional kernel density estimate of paleo-SAT/radiative forcing data (blue shading). The thick dashed yellow curve represents nonlinear regression of paleo-SAT/radiative forcing data, along with uncertainty ranges (dashed black curves; see Materials and Methods). The thick cyan line represents linear regression for cold phases. The slope represents Scold. The thick red line represents linear regression for warm phases. The slope represents Swarm. Dashed horizontal lines denote warm (orange) and cold (blue) phases using 1 SD of the reconstructed global mean SAT anomalies as a separator. Cold (warm) phases are defined by SAT anomalies of <−5.12 K (>−1.66 K). The CMIP5 transient model projections using the RCP8.5 forcing scenario are presented by purple circles. Using Swarm (orange shading) and taking into account the ocean heat uptake efficiency, we can calculate the transient response to the RCP8.5 radiative forcing. The resulting paleo-based projection with the corresponding uncertainty ranges is represented by cyan shading (see Materials and Methods)."

The second image shows a table of CH4 direct, CH4 indirect and associate indirect radiative forcing from O3/H₂O/CO₂ from the indicated change in CH4 burden in the atmosphere; which is associated with the third image that describes the cases, with a highest case associated with a pulse of methane from hydrates.  The second & third images are from Isaksen et al. (2011).

The fourth image shows the total net positive cloud feedback per degree C increase in GMSTA (global mean surface temperature anom.); which helps to explain why ECS increases with increasing GMSTA.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 28, 2017, 11:31:48 PM
The linked reference studies the paleo decay of the Cordilleran ice sheet and finds that it lost most of its ice mass earlier than consensus science previously thought, and it lost much of its ice mass over a relatively short period.  Personally, I am concerned about the impact of rainfall at increasingly high latitudes (with warming) on both the Greenland Ice Sheet, GIS, on Arctic permafrost, and on the WAIS and the EAIS, and I note that some researchers indicate that based on these new findings that the GIS could lose all of its ice mass in as little as 500 years (which would contribute to freshwater hosing from both the WAIS and the EAIS):

B. Menounos et al (10 Nov 2017), "Cordilleran Ice Sheet mass loss preceded climate reversals near the Pleistocene Termination", Science, Vol. 358, Issue 6364, pp. 781-784, DOI: 10.1126/science.aan3001

http://science.sciencemag.org/content/358/6364/781

Abstract: "The Cordilleran Ice Sheet (CIS) once covered an area comparable to that of Greenland. Previous geologic evidence and numerical models indicate that the ice sheet covered much of westernmost Canada as late as 12.5 thousand years ago (ka). New data indicate that substantial areas throughout westernmost Canada were ice free prior to 12.5 ka and some as early as 14.0 ka, with implications for climate dynamics and the timing of meltwater discharge to the Pacific and Arctic oceans. Early Bølling-Allerød warmth halved the mass of the CIS in as little as 500 years, causing 2.5 to 3.0 meters of sea-level rise. Dozens of cirque and valley glaciers, along with the southern margin of the CIS, advanced into recently deglaciated regions during the Bølling-Allerød and Younger Dryas."

Disappearance of an ice sheet

The Cordilleran Ice Sheet is thought to have covered westernmost Canada until about 13,000 years ago, even though the warming and sea level rise of the last deglaciation had begun more than a thousand years earlier. This out-of-phase behavior has puzzled glaciologists because it is not clear what mechanisms could account for it. Menounos et al. report measurements of the ages of cirque and valley glaciers that show that much of western Canada was ice-free as early as 14,000 years ago—a finding that better agrees with the record of global ice volume (see the Perspective by Marcott and Shakun). Previous reconstructions seem not to have adequately reflected the complexity of ice sheet decay.

In the attached image showing the results of a straw-man poll of experts, I would believe that the risk of a WAIS collapse, and ENSO amplitude increase, are seriously underestimated (but the risk of the GIS collapse seems reasonable).  Also, I note that a dynamical analysis would clearly demonstrate that all of these indicated tipping mechanisms are interlinked and feedback on each other.  Also, I note that rainfall in the Arctic would do more that just reduce sea ice albedo, but would also reduce the albedo of snow-covered land.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2017, 12:15:32 AM
Here are four more misc. images that are relevant to this topic.

The first image shows how warm ocean water can leak from the West Pacific Warm Pool into the Southern Ocean, and this mechanism should result in more advected warm water with continued global warming and with increase amplitude of El Nino events.

The second images observed data illustrating how quickly the volume of warm CDW has increase in the Southern Ocean in recent years.  This not only promotes ice mass loss from Antarctic marine glaciers, but it also promotes the slow response positive feedback mechanism between the Tropical Pacific and the Southern Ocean.

The third image shows how the discharge of fresh basal meltwater at the cliff face of a marine glacier produces turbulent convection at the ice face, which can promote the occurrence of cliff failures.

The fourth image shows how relatively thin the lithosphere is in much of West Antarctica, which not only promotes geothermal heat flux, but also promotes both seismic and volcanic activity; both of which can be triggered by sufficient ice mass loss.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2017, 12:38:35 AM
While the ice in the Totten Glacier Catchment (see the first image) in East Antarctica, may not collapse until 2100 or later, this issue is still a serious concern.  The second image shows the Totten Gateway with a deep channel in the seafloor leading to the warm CDW indicated in the third and fourth attached images.

See also the video linked in Reply #12.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on November 29, 2017, 05:57:33 AM
" I note that some researchers indicate that based on these new findings that the GIS could lose all of its ice mass in as little as 500 years "

Do tell ? References would be helpful. Losing all icemass from GIS in 500 years is not something I have seen.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: A-Team on November 29, 2017, 02:14:27 PM
Quote
Losing all ice from GIS in 500 years is not something I have seen
Right, sidd. No such claim has ever been made in a peer-reviewed article. For Greenland's floating ice shelves, those are all but gone already. These do not contribute to sea level rise, nor does what's left significantly buttress ice streams in the case of Jakobshavn and Petermann, contrary to repeated nonsense in newspapers. Zachariae - Nioghalvfjerdsfjorden's shelves might, but like the name says it's at 79ºN and adjacent to a steady stream of Fram ice floes.

Instead, there has been a long-running argument between the soil surface Be10 people and the Danish PI of ice core drilling about whether Greenland even melted out during the last interglacial, the Eemian, which was warmer than today and lasted for a few thousand years.

The beryllium data shows beyond any reasonable doubt that central and western Greenland did in fact melt out. (Note no one is suggesting that the 3000 m marginal mountains on the east side were snow-free.) Moderately old bottom ice in Greenland has been identified but drilling to date has taken place elsewhere.

The focus today is getting additional soil and rock cores from beneath the ice sheet, both for geothermal gradient and melt history. Stay tuned while the back-and-forth continues over Greenland's paleo contributions to sea level rise.
 
The whole problem with paleo setting risk policy is when you get it wrong, like here, Storegga, and numerous late Pleistocene - early Holocene event correlations now known from gold standard dendrochronology to be incorrectly dated by C14 plateauing and ice core annual layer mis-counting.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2017, 05:39:42 PM
Quote
Losing all ice from GIS in 500 years is not something I have seen
Right, sidd. No such claim has ever been made in a peer-reviewed article.

Applegate et al. 2015 is a peer-reviewed reference that with a GMSTA of 9C indicates a 7m, or a with a GMSTA of 12C indicates an 8m, contribution to SLR by 2500 from the GIS (see the first attached image & the second linked pdf).  While these values of GMSTA seem high, my discussion above (see the second attached image, while Rohling et al 2013 indicates that sea level could increase as much as 18m by 2500, see the third image, which implies major contributions from the GIA) indicates that if we stay on a BAU pathway until 2050 they may occur before 2100.

Applegate, P.J., Parizek, B.R., Nicholas, R.E. et al. (2015), "Increasing temperature forcing reduces the Greenland Ice Sheet’s response time scale", Clim Dyn 45: 2001. https://doi.org/10.1007/s00382-014-2451-7

https://link.springer.com/article/10.1007/s00382-014-2451-7#citeas
&
https://static-content.springer.com/esm/art%3A10.1007%2Fs00382-014-2451-7/MediaObjects/382_2014_2451_MOESM1_ESM.pdf

Abstract: "Damages from sea level rise, as well as strategies to manage the associated risk, hinge critically on the time scale and eventual magnitude of sea level rise. Satellite observations and paleo-data suggest that the Greenland Ice Sheet (GIS) loses mass in response to increased temperatures, and may thus contribute substantially to sea level rise as anthropogenic climate change progresses. The time scale of GIS mass loss and sea level rise are deeply uncertain, and are often assumed to be constant. However, previous ice sheet modeling studies have shown that the time scale of GIS response likely decreases strongly with increasing temperature anomaly. Here, we map the relationship between temperature anomaly and the time scale of GIS response, by perturbing a calibrated, three-dimensional model of GIS behavior. Additional simulations with a profile, higher-order, ice sheet model yield time scales that are broadly consistent with those obtained using the three-dimensional model, and shed light on the feedbacks in the ice sheet system that cause the time scale shortening. Semi-empirical modeling studies that assume a constant time scale of sea level adjustment, and are calibrated to small preanthropogenic temperature and sea level changes, may underestimate future sea level rise. Our analysis suggests that the benefits of reducing greenhouse gas emissions, in terms of avoided sea level rise from the GIS, may be greatest if emissions reductions begin before large temperature increases have been realized. Reducing anthropogenic climate change may also allow more time for design and deployment of risk management strategies by slowing sea level contributions from the GIS."

Also, the Purdue researchers who studied the Cordilleran Ice Sheet feel that the GIS could lose around half of its ice mass in as little as 500-years.

Title: "Research shows ice sheets as large as Greenland’s melted fast in a warming climate"

https://www.purdue.edu/newsroom/releases/2017/Q4/research-shows-ice-sheets-as-large-as-greenlands-melted-fast-in-a-warming-climate.html

Extract: "New research published in Science shows that climate warming reduced the mass of the Cordilleran Ice Sheet by half in as little as 500 years, indicating the Greenland Ice Sheet could have a similar fate.

The Cordilleran Ice Sheet covered large parts of North America during the Pleistocene - or last ice age - and was similar in mass to the Greenland Ice Sheet. Previous research estimated that it covered much of western Canada as late as 12,500 years ago, but new data shows that large areas in the region were ice-free as early as 1,500 years earlier. This confirms that once ice sheets start to melt, they can do so very quickly."

Edit: In Reply #40, I discuss how high values of radiative forcing (Watts/sq meter) could be reached when following RCP 8.5 until 2050.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2017, 05:43:00 PM
" I note that some researchers indicate that based on these new findings that the GIS could lose all of its ice mass in as little as 500 years "

Do tell ? References would be helpful. Losing all icemass from GIS in 500 years is not something I have seen.

sidd

See my response to A-Team.  While a GMSTA of 9C may seem extreme, even without that much forcing the Purdue team thinks that the GIS could contribute 4m to SLR by 2500 (which is a lot).

Furthermore, my point in raising the issue of ice mass loss from the GIS is that even after mankind stops making large GHG emissions, the bipolar seesaw could stay very active in a run away greenhouse situation.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2017, 06:33:16 PM
While it is not necessary to follow a RCP 8.5/SSP5 pathway until 2050 for the peak ice mass discharge of a WAIS collapse to occur this century; nevertheless, the following is a short list of conceptual Catch 22's associated with climate change that may keep society on such a pathway until a socioeconomic collapse by 2050 stops significant further anthropogenic GHG emissions:

1. For developing countries: Developing nations need to strengthen their economies to mitigate the issues facing their populations, issues that will be exacerbated by climate change. However strengthening their economies requires energy. Energy production currently causes greenhouse gas, which causes climate change.

2.  For consensus climate science:  Consensus climate science needs to be taken seriously by both the public and by decision makers; therefore they tend to err on the side of least drama.  Consequently, both the public and decision makers underestimate climate risks and tend to focus on other right-tailed risks such as those posed by terrorists, recessions, immigration, etc.  This results in the increase of climate risks with each passing month.

3. For military organizations: Military organizations facilitate the BAU fossil-fuel driven global economy that has set global population to have a 50-50 chance or reaching 9.8 billion by 2050.  However, the current socioeconomic landscape is generating increased tensions that result in epicenters of potential violence (stressed by climate change) that will require military organizations to increasing deal with such issues as food shortages, water shortages and nationalism/regionalism.

See also the linked study entitled: "Epicenters of Climate and Security"

https://climateandsecurity.org/epicenters/

Extract: "… security experts identify 12 key climatic risks to international security that may shape the geostrategic landscape of the 21st century. In the wake of extraordinary upheaval in the international effort to address climate change, the report presents a compelling case for why tackling these climate and security “epicenters” – major categories of climate-driven risks to international security – should be a top priority for governments and institutions around the world. The report also outlines the key tools for managing systemic risks that should be included in every climate security practitioner’s and policy-maker’s toolbox."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2017, 06:46:45 PM
I have repeatedly noted that Hansen's ice-climate feedback mechanism results in a warming of the tropical oceans which results in an expansion of the Hadley cells (see the attached image); and the linked reference indicates that the ITCZ moves poleward with the Hadley cell expansion, and that it narrows as it migrates.  This will cause a lot of changes to effected local climates, and could lead to an equable climate in the NH if the WAIS collapses this century due to anthropogenic radiative forcing:

Byrne, M. P., and T. Schneider (2016), "Narrowing of the ITCZ in a warming climate: Physical mechanisms", Geophys. Res. Lett.,
43, doi:10.1002/2016GL070396.

https://climatedynamics.ethz.ch/people/mike/byrne_schneider_2016b.pdf

Abstract: "The Intertropical Convergence Zone (ITCZ) narrows in response to global warming in both observations and climate models. However, a physical understanding of this narrowing is lacking. Here we show that the narrowing of the ITCZ in simulations of future climate is related to changes in the moist static energy (MSE) budget. MSE advection by the mean circulation and MSE divergence by transient eddies tend to narrow the ITCZ, while changes in net energy input to the atmosphere and the gross moist stability tend to widen the ITCZ. The narrowing tendency arises because the meridional MSE gradient strengthens with warming, whereas the largest widening tendency is due to increasing shortwave heating of the atmosphere. The magnitude of the ITCZ narrowing depends strongly on the gross moist stability and clouds, emphasizing the need to better understand these fundamental processes in the tropical atmosphere."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: A-Team on November 29, 2017, 08:18:28 PM
Quote
reference that with a GMSTA of 9C indicates a 7m
Cheap shot there. Sure, with a preposterous enough temperature rise scenario, anything is possible in models. Greenland could melt tomorrow if enough neutron bombs were detonated over it.

No one has the slightest idea what the planet would be like given feedbacks at those temperatures. No one has the slightest idea what policy changes will be instituted in the next decade.

For air temperatures, a lot could be done; with ocean temperatures very little can be done and WAIS  etc may well be in irreversible decline but not so much Greenland, eg Petermann has a prograde interior.

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on November 29, 2017, 09:34:49 PM
That Applegate paper does not use global T increase, but rather greenland T increase. So 12 K over greenland would be more like 6K global, as in fig 4 of the paper. I attach. This is for RCP 8.5 showing 12 K is reached over greenland around 2200.

They model ice volume going to zero using the concept of an e-folding time which drops to order 100 yr for greenland temperature anomaly of 12K. I see i have posted fig 2a in this forum already, so i must have read the paper.

The models used are SICOPOLIS and a a profile model along 72N by Parizek and Alley. Then an e-folding time is estimated from the model runs with a simple exponential decay formula. The uncertainty for the 12K anomaly is about the same as the efolding time on the order of a century or two.

I seem to have forgotten all about that paper. I wonder if other models have been used like PISM or Elmer ?

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2017, 10:37:41 PM
That Applegate paper does not use global T increase, but rather greenland T increase. So 12 K over greenland would be more like 6K global, as in fig 4 of the paper. I attach. This is for RCP 8.5 showing 12 K is reached over greenland around 2200.

sidd,

Thank you very much for correcting my error regarding the 9 to 12C being Greenland T increase, roughly corresponding to a 4.5 to 6C GMSTA increase.  These topics are complicated and I always appreciate a check from a second pair of eyes.  That said, I will slip back into my normal erring on the side of maximum drama mode to point-out that:

(a) The SICOPOLIS runs likely do not consider some of the ice mass loss mechanisms from the recent Cordilleran Ice Sheet  studies, and thus they may err on the side of least drama.

(b) As the elevation of the ice surface drops in the GIS the amplification factor from GMSTA may increase from 2 up to 3; which would mean that in the future GMSTA might only need to get to 3 to 4C increase for the GIS to largely disappear circa 2500.

(c)  Per Hansen et al (2016), substantial ice mass loss from Antarctica can cool the Southern Ocean while significantly warming the NH (for periods of decades); thus direct comparison of GMSTA to Greenland T increase can err on the side of least drama.

When I have more time, I will provide more posts on how masking factors (like: aerosols, the recent cooling of the Southern Ocean due to freshwater hosing, multi-decadal metocean cycles, etc.) can lead interpretations of CMIP5 output to underestimate the risks of our current situation.

However, I cannot help but to note in closing that if my previously cited estimate that CO2e is currently close to 530ppm (assuming a GWP100 for methane of 35), then per the attached plot we are currently at conditions that RCP 8.5 assumes that we will not reach until about 2037.

Best regards,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: A-Team on November 29, 2017, 10:50:24 PM
So, 2012 in Greenland was predicted decades in advance? I must have missed it. Then the cold year 2017 thickening of Greenland played out just like they said it would? I must have missed that too, amidst all the doom and gloom coming off 2012.

Someone predicted Jakobshavn's behavior this year? Too bad they didn't share it ahead of time. All that rain in all the wrong places after El Nino? Rain would be a huge deal for Greenland. But then again it could just as well be snow.

How about someone telling us where the Jakobshavn calving front will be 2018-2038. Right here, right on this forum. Draw lines over a satellite image. Put some skin in the game. Stop blowing smoke. You know, a testable prediction in our lifetime, not pie-in-the-sky stuff about Y2.5k. Not when we have 800kg gorillas in the room who are eating our pie right now.

Climate change: focus on actionable near-term monitoring and high priorities, forget the rest.

Ask for something specific and testable by 2028, the silence is deafening. Better to play it safe and talk about 2100. No accountability. Maybe catastrophic sea level rise five centuries from now.

Frankly nobody around here gives a hoot about NYC or Miami, much less some faraway foreign port. Talk about a dumb incentiviser: "long after you are dead, some people you don't known may be terribly inconvenienced." Look at the apathy around Puerto Rico -- that actually happened and continues to happen. To someone else.

I see very few working scientists venturing testable predictions say for Arctic sea ice. No one has any real idea when or what comes next for mid-latitude. That doesn't exactly inspire confidence in model ruminations for 2025 or beyond. There's plenty of vapor steaming out of the cubicles though.
 
Consider a range of scenarios? Sure why not. Andorra unleashing a barrage of missiles against Liechtenstein? It could happen, fat tail risk. So the Pentagon long ago wrote up a scenario for that. It's sitting on the shelf: there are far more pressing risks by orders of magnitude than further documentation of impacts to Monaco.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on November 29, 2017, 11:08:50 PM
"As the elevation of the ice surface drops ..."

The ice elevation SMB feedback is already in SICOPOLIS.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2017, 11:43:55 PM
As I am promoting that ESM modelers adopt a more dynamical interpretation (considering possible chain reactions of smaller trigger mechanisms) of their results, I will also try to make future posts that describe a probable chain of events that could trigger the WAIS to make a peak contribution to SLR by/before 2100, and in this regards, I begin with Jakobshavn Glacier.

I have repeatedly cited the bipolar seesaw (with both fast atmospheric and slower oceanic energy advections), and I have noted that DeConto, Pollard and Alley largely calibrated their Antarctic Ice Sheet model with hydrofracturing and cliff failures, based on Jakobshavn.  Thus, I suspect that based on the first attached image (for Jakobshavn retreating up a slope) and the linked findings led by Rignot, that by 2028 (following a BAU pathway until then) the ice mass loss from Jabokshavn will increase significantly as its grounding line retreats down its retrograde slope.

I then speculate that that this bipolar seesaw input together with BAU warming will lead to cliff failures for Thwaites by about 2040 (as I assume that ECS is about 4.5C, and that GMSTA will approach 2.7C around that time per the second image).

Title: "Scientists uncover troubling news about Greenland’s most enormous glacier"

http://www.pressherald.com/2017/04/11/scientists-just-uncovered-troubling-news-about-greenlands-most-enormous-glacier/

Extract: "But until now, researchers have not been sure how far Jakobshavn’s ice extends below sea level – or how much deeper it gets farther inland. That’s crucial because Jakobshavn is undergoing a dangerous “marine ice sheet instability,” in which ocean-front glaciers that grow deeper farther inland are prone to unstoppable retreat down what scientists call a “retrograde” slope.

That’s where the new science comes in: Researchers who flew over Jakobshavn in a helicopter toting a gravimeter, used to detect the gravitational pull of the ice and deduce its mass, say they’ve found the glacier extends even deeper below sea level than previously realized, a configuration that sets the stage for further retreat.

“The greater depth of the trough indicated by the new data will favor faster retreat, but it is such a narrow trough that some stabilization from the sides is likely to continue, so that there is still no worry of the whole ice sheet suddenly falling in the ocean,” said Richard Alley, a glaciologist at Penn State University who was not involved in the study. Alley said this still makes Jakobshavn less of a worry than Thwaites glacier in West Antarctica, which is far wider and less constrained."

I also note that monitoring snowfall and surface mass balance is a secondary issue to ice cliffs and hydrofracturing, as in the WAIS at least more snowfall until 2040 will increase the gravitational driving force on Thwaites after 2040.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2017, 11:54:28 PM
"As the elevation of the ice surface drops ..."

The ice elevation SMB feedback is already in SICOPOLIS.

sidd

Thanks, and I note that they appear to drive their SICOPOLIS model using RCP 8.5

Edit: I repost the attached image to indicate that CO2 emissions are tracking SSP5/RCP 8.5 thru 2017.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on November 30, 2017, 12:22:28 AM
I have made my prediction for Jacobshawn grounding line in the Jacobshawn thread.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2017, 12:46:59 AM
I have made my prediction for Jacobshawn grounding line in the Jacobshawn thread.

sidd

sidd,

Thanks.  I assume that you mean that by 2028 the Jakobshavn grounding line will be upstream of location A15 on the attached image that you provided from doi:10.1002/2017GL073245.

Best,
ASLR

Edit, For what it is worth, I note that the linked reference indicates that surface meltwater is increasing ice flux from Jakobshavn:

Joseph, C. A. and Lampkin, D. J.: Spatial and temporal variability of water-filled crevasse hydrologic states along the shear margins of Jakobshavn Isbrae, Greenland, The Cryosphere Discuss., doi:10.5194/tc-2017-86, in review, 2017.

http://www.the-cryosphere-discuss.net/tc-2017-86/

Abstract. The impact of melt water injection into ice streams over the Greenland Ice Sheet is not well understood. Water-filled crevasses along the shear margins of Jakobshavn Isbræ are known to fill and drain, resulting in weakening of the shear margins due to reduced basal friction. Seasonal variability in the hydrologic dynamics of these features has not been quantified. In this work, we characterize the spatial and temporal variability in the hydrological state (filled or drained) of these water-filled crevasse systems. A fusion of multi-sensor optical satellite imagery was used to examine hydrologic states from 2000 to 2015. The monthly distribution of crevasse systems observed as water filled is unimodal with peak number of filled days during the month of July at 329 days, while May has the least at 15. Over the study period the occurrence of drainage within a given season increases. Inter-seasonal drain frequencies over these systems ranged from 0 to 5. The frequency of multi-drainage events are correlated with warmer seasons and large strain rates. Over the study period, summer temperatures averaged from −1 and 2 °C and tensile strain rates have increased to as high as ~ 1.2 s. Intermittent melt water input during hydrofracture drainage responsible for transporting surface water to the bed is largely facilitated by high local tensile stresses. Drainage due to fracture propagation may be increasingly modulated by ocean-induced calving dynamics for the lower elevation ponds. Water-filled crevasses could expand in extent and volume as temperatures increase resulting in regional amplification of ice mass flux into the ice stream system.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on November 30, 2017, 05:09:10 AM
No. I mean that the grounding line will be close to A45. But lets take this to the Jacobshawn thread.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on November 30, 2017, 05:52:39 AM
In a larger sense, and more to the topic of this thread (threat?), the great glaciers will not, i think, be the dominant factor in greenland ice mass waste. As Enderlin saw and the models in Applegate indicate, dynamic ice loss in greenland becomes less and less important wth larger forcing.

"Consistent with the conclusions of these earlier studies, the agreement between the ice volume curves from the mass balance-only runs and the dynamic runs becomes progressively better as ΔTgrl increases (Fig. 3b; see also Huybrechts and de Wolde 1999). This result suggests that ice dynamics are an important determinant of the time scale of GIS response for small temperature anomalies, but the ice sheet’s response is dominated by surface mass balance changes at high ΔTgrl values." -- Applegate(2014)

 ΔTgrl is the temperature anomaly imposed over greenland.

Surface mass imbalance is already majority of mass loss in greenland. It's all surface mass balance in greenland  from here on out. Watch out for moisture rich air on greenland, even more than rain, moisture packs 540 cal+80cal/g rather than just 80.

There is another indicator would like to know, which is the elevation of the saddle at 67N between north and south domes in greenland. Some years ago, i posted to realclimate that the equilibrium line had climbed above the saddle. Gregoire(2012 doi:10.1038/nature11257 ; 2016 doi:10.1002/2016GL070356 ) describe saddle collapse and i have posted on this before. That saddle should be dropping now as the collapse begins. I would like some time series of that saddle elevation (and a pony ... )

I think  Greenland will sit and melt in place, all the heat has to get there thru the air.

But WAIS is a different matter. The ocean is already delivering heat there 300meter depth and below. When the atmosphere gets involved as in Mercer's comments about midsummer 0C isotherm on ice shelves, it will be too late.

Jacobshawn is the only collapsing icecliff instability we see, 5Km wide, sinuous channel, sidewall and frozen melange buttressing and the rest. Thwaites is at least ten times as wide and exposed. How fast could that go ? As Alley and Rignot say, it could be just decades, then the seaways to the ross and the ronne open and all WAIS is gone, Totten and the Aurora Basin on deck.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2017, 06:12:26 PM
Just for the record, I generally concur with sidd's analysis (in Reply #64) of the stability of the GIS, including his opinion that the groundling line for Jakobshavn will have retreated to location A45 by 2028 (which Rignot et al 2017 indicates represents at least a 50% increase in annual ice mass loss from Jakobshavn).  However, my point is that consensus climate scientists do not adequately the dynamical/periodic climate attractor associated with the on-going synergy between such Earth Systems as: the bipolar seesaw, ice-climate feedback, ENSO trends/cycles, cloud feedback, polar amplification Hadley cell expansion and precipitation patterns.  For example, an acceleration of ice mass loss from Jakobshavn thru 2028 would contribute to the North Atlantic cold spot (regardless of possible increased net snowfall on Greenland in this timeframe); which will serve to somewhat slow the MOC, which in turn will increase the absorption of heat by the tropical oceans, and thus will contribute somewhat to increased extreme ENSO events.

However, Proistosescu & Huybers (2017) has demonstrated, using CMIP5 output, that a slow response feedback associated with the ocean heat content of the Tropical Pacific and the Southern Ocean has already been building since 1750 and is now contributing to ECS.  This can be seen directly in the first & second images, and indirectly in the middle panel of the third image (from Andrew's 2015 Ringberg presentation), and in the red 'time-dependence' curve of the forth image (which supports my assumed mean ECS value of 4.5) from Amour (2016).

So getting by to A-Teams request for verifiable short-term projects (besides Jakobshavn's increased discharge, which is a somewhat small contributor to a slow MOC increasing ECS this century); if ECS is about 4.5C then I roughly expect that GMSTA will increase about 0.07C per year (at least following BAU until 2040).  Thus conservatively taking GMSTA by the end of 2017 to be 1.1C this indicates that we should reach 1.5C by about 2024,  As the linked Wang et al. (2017) reference indicates that extreme El Nino events could double in frequency if/when we reach a 1.5C increase in GMSTA, I thus predict that the period between Super El Nino events will first drop to one every ten years by about 2025 and to once every eight years by about 2033; which will drive-up not only global warming, but will advect substantial heat from the Tropical Pacific to both the North Pacific and directly to the WAIS, where it will promote/accelerate ice mass loss:

Guojian Wang, et. al. (2017), "Continued increase of extreme El Niño frequency long after 1.5 °C warming stabilization", Nature Climate Change, doi:10.1038/nclimate3351

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3351.html?foxtrotcallback=true

Abstract: "The Paris Agreement aims to constrain global mean temperature (GMT) increases to 2 °C above pre-industrial levels, with an aspirational target of 1.5 °C. However, the pathway to these targets and the impacts of a 1.5 °C and 2 °C warming on extreme El Niño and La Niña events—which severely influence weather patterns, agriculture, ecosystems, public health and economies—is little known. Here, by analysing climate models participating in the Climate Model Intercomparison Project’s Phase 5 (CMIP5) under a most likely emission scenario, we demonstrate that extreme El Niño frequency increases linearly with the GMT towards a doubling at 1.5 °C warming. This increasing frequency of extreme El Niño events continues for up to a century after GMT has stabilized, underpinned by an oceanic thermocline deepening that sustains faster warming in the eastern equatorial Pacific than the off-equatorial region. Ultimately, this implies a higher risk of extreme El Niño to future generations after GMT rise has halted. On the other hand, whereas previous research suggests extreme La Niña events may double in frequency under the 4.5 °C warming scenario, the results presented here indicate little to no change under 1.5 °C or 2 °C warming."

See also: "‘Extreme’ El Niños to double in frequency under 1.5C of warming, study says"

https://www.carbonbrief.org/extreme-el-ninos-double-frequency-under-one-point-five-celsius-warming-study

Extract: "Now a new study, published in Nature Climate Change, suggests that similar “extreme” El Niño events could become more frequent as global temperatures rise.

If global warming reaches 1.5C above pre-industrial levels – the aspirational limit of the Paris Agreement – extreme El Niño events could happen twice as often, the researchers find.

That means seeing an extreme El Niño on average every 10 years, rather every 20 years."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2017, 06:46:58 PM
I provide the first linked paleo research as evidence that ice mass loss from the GIS can contribute to MIS 11 type value for ECS, and the second linked paleo research that shows that the MIS 11 ECS was higher than current ESM models can simulate.  This is indirect evidence supporting my assumption that ECS is now about 4.5C (which supports my projection of significant cliff failures for Thwaites circa 2040, when GMSTA may approach 2.7C).

Kandiano et al. (2017), "Response of the North Atlantic surface and intermediate ocean structure to climate warming of MIS 11" Scientific Reports 7, Article No. 46192, doi:10.1038/srep46192

http://www.nature.com/articles/srep46192

Extract: "Our results underscore the intricate interdynamic behavior of the North Atlantic climate system.  Furthermore, if the present-day rapid summer melting of the GIS continues, the resulting freshening of the surface ocean may well lead to fundamental structural changes in both ocean and atmospheric circulation as reconstructed for MIS 11."

&

Coletti, A. J., DeConto, R. M., Brigham-Grette, J., and Melles, M.: A GCM comparison of Pleistocene super-interglacial periods in relation to Lake El'gygytgyn, NE Arctic Russia, Clim. Past, 11, 979-989, doi:10.5194/cp-11-979-2015, 2015.

http://www.clim-past.net/11/979/2015/cp-11-979-2015.pdf
http://www.clim-past.net/11/979/2015/cp-11-979-2015.html

Abstract: "Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stages (MISs) 1 (9 ka), 5e (127 ka), 11c (409 ka) and 31 (1072 ka) with new proxy climate data recovered from Lake El'gygytgyn, NE Russia. Climate reconstructions of the mean temperature of the warmest month (MTWM) indicate conditions up to 0.4, 2.1, 0.5 and 3.1 °C warmer than today during MIS 1, 5e, 11c and 31, respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer (JJA) orbital forcing, the extraordinary warmth of MIS 11c compared to the other interglacials in the Lake El'gygytgyn temperature proxy reconstructions remains difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El'gygytgyn, we isolated the influence of vegetation, sea ice and circum-Arctic land ice feedbacks on the modeled climate of the Beringian interior. Simulations accounting for climate–vegetation–land-surface feedbacks during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on northeast Asian temperature during the warmth of stages 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic Ocean does have some effect on Lake El'gygytgyn's regional climate, but the exceptional warmth of MIS 11c remains enigmatic compared to the modest orbital and greenhouse gas forcing during that interglacial."

Extract: "The timing of significant warming in the circum-Arctic can be linked to major deglaciation events in Antarctica, demonstrating possible interhemispheric linkages between the Arctic and Antarctic climate on glacial–interglacial timescales, which have yet to be explained."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2017, 07:17:03 PM
To continue with my list of near-term predictions, I predict that satellite observations will continue to observe that "… high clouds are likely to get higher, cloudy and clear bands may shift from lower latitudes towards the poles, and clouds may become less icy and more watery…"; which will contribute to positive cloud feedback, and an ECS near 4.5C this century, partially due to the tropical atmospheric convective mixing shown in the first image from Sherwood et al. 2014, and the second image that shows how this deep convection help expands the Hadley cell.

Sherwood, S.C., Bony, S. and Dufresne, J.-L., (2014) "Spread in model climate sensitivity traced to atmospheric convective mixing", Nature; Volume: 505, pp 37–42, doi:10.1038/nature12829

http://www.nature.com/nature/journal/v505/n7481/full/nature12829.html

Next, the second linked SciAm article by Kate Marvel confirms that the net feedback from clouds is currently positive and may well become more positive with continued global warming.  This will result in more global warming than was previously anticipated for the same radiative forcing:

Kate Marvel (2017), "The Cloud Conundrum", Scientific American 317, doi:10.1038/scientificamerican1217-72

http://www.nature.com/scientificamerican/journal/v317/n6/full/scientificamerican1217-72.html
&
https://www.scientificamerican.com/article/will-changing-cloud-cover-accelerate-global-warming/

Brief: "To accurately predict how much warmer climate change will make the earth, scientists must determine the influence of clouds, which is significant.  Computer models have difficulty simulating the changing nature of clouds, but improved satellite data are providing some strong clues: high clouds are likely to get higher, cloudy and clear bands may shift from lower latitudes towards the poles, and clouds may become less icy and more watery.  Data indicate that the trends that amplify warming are strong and the trends that slow warming are weaker than anticipated."

Finally, the third linked reference provides satellite data (see the third attached image) from CloudSat & CALIPSO within the A-Train, that show a dramatic increase (more positive) in observed net cloud feedback as compared to prior assumptions.  This of course means that ECS is higher than previously assumed.

Graeme Stephens et. al. (2017), "CloudSat and CALIPSO within the A-Train: Ten years of actively observing the Earth system", BAMS, https://doi.org/10.1175/BAMS-D-16-0324.1

http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-16-0324.1?utm_content=bufferebbb9&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer
or
http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-16-0324.1

Abstract: "The more than 10 years of observations jointly collected by CloudSat and CALIPSO satellites has resulted in new ways of looking at aerosol, clouds, and precipitation and new discoveries about processes that connect them.

One of the most successful demonstrations of an integrated approach to observe Earth from multiple perspectives is the A-Train satellite constellation (e.g. Stephens et al., 2002). The science enabled by this constellation flourished with the introduction of the two active sensors carried by the NASA CloudSat and the NASA/CNES Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellites that were launched together on April 28th, 2006. These two missions have provided a 10-year demonstration of coordinated formation flying that made it possible to develop integrated products and that offered new insights on key atmospheric processes. The progress achieved over this decade of observations, summarized in this paper, clearly demonstrate the fundamental importance of the vertical structure of clouds and aerosol for understanding the influences of the larger scale atmospheric circulation on aerosol, the hydrological cycle, the cloud-scale physics and on the formation of the major storm systems of Earth. The research also underscored inherent ambiguities in radiance data in describing cloud properties and how these active systems have greatly enhanced passive observation. It is now clear that monitoring the vertical structure of clouds and aerosol is essential and a climate data record is now being constructed. These pioneering efforts are to be continued with EarthCARE mission planned for launch in 2019."

Caption for the third image: "Figure 5 Upper three panels are from Hartmann et al (1992) who estimate the contribution to the cloud radiative effects (CRE) of five classes of clouds as defined according to the ISCCP radiance classification (upper left). The bottom panels are the equivalent analysis but with classification determined by the radar-lidar data of CloudSat and CALIPSO where true cloud heights establish the types and cloud thickness (x axis) are from water and ice path information which is proportional to cloud optical depth. The differences in CRE between this latter analysis and that of Hartmann et al underscores the effects of misclassification of clouds on the interpretation of their radiative effects. Ci=cirrus, D.C.=Deep Convection, M.L.=multi-layer, AS=Altostratus, AC-Alto-cumulus, NS=Nimbostratus, St=stratus, SC=stratocumulus and Cu=cumulus."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2017, 09:36:54 PM
With regards to a more specific near-term cryosphere prediction, I predict that in less than 2.5-years, the PIIS and the SW Tributary Ice Shelf will experience a concurrent major calving event (along the intersecting cracks shown in the attached Sentinel-1 image from Nov 28 2017) that will temporarily cause the ice velocities in the SW Tributary Glacier to accelerate.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2017, 10:48:36 PM
Based on my interpretation of the two linked references, I predict that local ice cliff failures near the base of the Thwaites Ice Tongue (see the four images) will begin sometime 2025 and 2033, and will be initiated due to influences from Super El Nino events in that timeframe:

Yu, H., Rignot, E., Morlighem, M., & Seroussi, H. (2017). Iceberg calving of Thwaites Glacier, West Antarctica: full-Stokes modeling combined with linear elastic fracture mechanics. The Cryosphere, 11(3), 1283, doi:10.5194/tc-11-1283-2017

https://www.the-cryosphere.net/11/1283/2017/tc-11-1283-2017.pdf
https://www.the-cryosphere.net/11/1283/2017/tc-11-1283-2017-assets.html

Abstract. "Thwaites Glacier (TG), West Antarctica, has been losing mass and retreating rapidly in the past few decades.  Here, we present a study of its calving dynamics combining a two-dimensional flow-band full-Stokes (FS) model of its viscous flow with linear elastic fracture mechanics (LEFM) theory to model crevasse propagation and ice fracturing.  We compare the results with those obtained with the higher-order (HO) and the shallow-shelf approximation (SSA) models coupled with LEFM. We find that FS/LEFM produces surface and bottom crevasses that are consistent with the distribution of depth and width of surface and bottom crevasses observed by NASA’s Operation IceBridge radar depth sounder and laser altimeter, whereas HO/LEFM and SSA/LEFM do not generate crevasses that are consistent with observations.  We attribute the difference to the nonhydrostatic condition of ice near the grounding line, which facilitates crevasse formation and is accounted for by the FS model but not by the HO or SSA models. We find that calving is enhanced when pre-existing surface crevasses are present, when the ice shelf is shortened or when the ice shelf front is undercut. The role of undercutting depends on the timescale of calving events. It is more prominent for glaciers with rapid calving rates than for glaciers with slow calving rates. Glaciers extending into a shorter ice shelf are more vulnerable to calving than glaciers developing a long ice shelf, especially as the ice front retreats close to the grounding line region, which leads to a positive feedback to calving events. We conclude that the FS/LEFM combination yields substantial improvements in capturing the stress field near the grounding line of a glacier for constraining crevasse formation and iceberg calving."

Extract: "In our simulations, we find that crevasses propagate significantly faster near the ice front when the ice shelf is shortened.

The reason for the propagation of crevasses is the existence of a nonhydrostatic condition of ice immediately downstream of the grounding line, which is not accounted for in simplified models that assume hydrostatic equilibrium everywhere on the ice shelf.  We also find that calving is enhanced in the presence of pre-existing surface crevasses or shorter ice shelves or when the ice front is undercut.  We conclude that it is important to consider the full stress regime of ice in the grounding line region to replicate the conditions conducive to calving events, especially the nonhydrostatic condition that is critical to propagate the crevasses."

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The second linked reference confirms that the ENSO is directly associated with surface air temperatures across the interior of West Antarctica, and I note that the frequency of extreme El Nino events is projected to double when the global mean surface temp. anom. gets to 1.5C:

Kyle R. Clem, James A. Renwick, and James McGregor (2017), "Large-Scale Forcing of the Amundsen Sea Low and its Influence on Sea Ice and West Antarctic Temperature", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0891.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0891.1?utm_content=buffer2e94d&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Using empirical orthogonal function (EOF) analysis and atmospheric reanalyses, we examine the principal patterns of seasonal West Antarctic surface air temperature (SAT) and their connection to sea ice and the Amundsen Sea Low (ASL). During austral summer, the leading EOF (EOF1) explains 35% of West Antarctic SAT variability and consists of a widespread SAT anomaly over the continent linked to persistent sea ice concentration anomalies over the Ross and Amundsen Seas from the previous spring. Outside of summer, EOF1 (explaining ~40-50% of the variability) consists of an east-west dipole over the continent with SAT anomalies over the Antarctic Peninsula opposite those over western West Antarctica. The dipole is tied to variability in the Southern Annular Mode (SAM) and in-phase El Niño-Southern Oscillation (ENSO) / SAM combinations that influence the depth of the ASL over the central Amundsen Sea (near 105°W). The second EOF (EOF2) during autumn, winter, and spring (explaining ~15-20% of the variability) consists of a dipole shifted approximately 30 degrees west of EOF1 with a widespread SAT anomaly over the continent. During winter and spring, EOF2 is closely tied to variability in ENSO and a tropically-forced wavetrain that influences the ASL in the western Amundsen / eastern Ross Seas (near 135°W) with an opposite sign circulation anomaly over the Weddell Sea; the ENSO-related circulation brings anomalous thermal advection deep onto the continent. We conclude the ENSO-only circulation pattern is associated with SAT variability across interior West Antarctica, especially during winter and spring, while the SAM circulation pattern is associated with an SAT dipole over the continent."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2017, 11:27:52 PM
While Transient Climate Response, TCR, only addresses fast feedback mechanisms (and not the slow feedback confirmed by PH17), I note that the linked reference indicates that a "... stronger constraint on forcing will bring a significant reduction in the uncertainty of observation-based estimates of the transient climate response, with a 50% reduction in its uncertainty range expected by 2030.  This will help to verify my assumption that ECS is currently around 4.5C:

Gunnar Myhre, Olivier Boucher, François-Marie Bréon, Piers Forster & Drew Shindell, (2015), "Declining uncertainty in transient climate response as CO2 forcing dominates future climate change", Nature Geoscience, doi:10.1038/ngeo2371

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2371.html

Abstract: "Carbon dioxide has exerted the largest portion of radiative forcing and surface temperature change over the industrial era, but other anthropogenic influences have also contributed. However, large uncertainties in total forcing make it difficult to derive climate sensitivity from historical observations. Anthropogenic forcing has increased between the Fourth and Fifth Assessment Reports of the Intergovernmental Panel of Climate Change (IPCC) although its relative uncertainty has decreased. Here we show, based on data from the two reports, that this evolution towards lower uncertainty can be expected to continue into the future. Because it is easier to reduce air pollution than carbon dioxide emissions and because of the long lifetime of carbon dioxide, the less uncertain carbon dioxide forcing is expected to become increasingly dominant. Using a statistical model, we estimate that the relative uncertainty in anthropogenic forcing of more than 40% quoted in the latest IPCC report for 2011 will be almost halved by 2030, even without better scientific understanding. Absolute forcing uncertainty will also decline for the first time, provided projected decreases in aerosols occur. Other factors being equal, this stronger constraint on forcing will bring a significant reduction in the uncertainty of observation-based estimates of the transient climate response, with a 50% reduction in its uncertainty range expected by 2030."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2017, 05:37:43 PM
As it is relevant to my prior posts in this thread, I provide the linked article and subsequent associated linked references, address efforts to improve/advance climate forecasting.  While the article addresses a range of efforts from correcting model bias to predicting snow (& associated albedo effects) distribution, in this post I only extract sections related to efforts to better understand the telecommunication of tropical heat energy to the Arctic (see the attached image & caption, which does not show telecommunications of tropical heat energy to Antarctica, which also occurs).  While climate modelers are working hard to improve their projections, I noted that none of the efforts discussed consider the impacts of freshwater hosing events (such as the possible collapse of the WAIS this century).  A major freshwater hosing event (or events) and its associated telecommunications and a snow albedo flip, would have major consequences on future climate that are not adequately addressed in current publically available forecasts.

Merryfield, W. J., F. J. Doblas-Reyes, L. Ferranti, J.-H. Jeong, Y. J. Orsolini, R. I. Saurral, A. A. Scaife, M. A. Tolstykh, and M. Rixen (2017), Advancing climate forecasting, Eos, 98, https://doi.org/10.1029/2017EO086891

https://eos.org/project-updates/advancing-climate-forecasting?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz120117

Extract: "The heaviest rainfall on Earth occurs over tropical oceans. As water vapor condenses to form droplets in the moist tropical air, the water releases substantial amounts of latent heat. This heat produces deep convection currents that propel the resulting clouds to great heights. The accompanying uplift turns into divergent horizontal winds near the tops of these clouds, high in the troposphere.

Variations in climate alter the patterns of tropical rainfall from year to year. Shifts in upper level divergent winds drive disturbances in atmospheric circulation. These disturbances, known as Rossby or planetary waves, propagate eastward and poleward away from the equator in the winter hemisphere and affect atmospheric circulation in the extratropical regions, outside of the tropics. Such tropical influences on extratropical climate are known as teleconnections (Figure 1).

In some regions of the tropics, climate variations are relatively predictable because strong couplings between the tropical ocean and atmosphere modulate climate on relatively slow oceanic timescales. The most prominent such modulation is the El Niño–Southern Oscillation.
Because the predictable tropical climate influences the less predictable extratropical climate through teleconnections, tropical predictability could enable skillful predictions of the extratropical climate.

These interconnections raise several important and related questions:
•   How much do tropical teleconnections contribute to extratropical climate variability?
•   How well are extratropical circulation responses to tropical climate variability represented in current climate models?
•   To what extent can improvements in the modeling of teleconnections improve the skill of extratropical climate forecasts?

To address these questions, the WGSIP teleconnection initiative is examining how well climate forecast models represent the chain of causation connecting variations in tropical rainfall to planetary wave forcing and propagation and hence to modulation of extratropical climate. A pilot analysis of one model [Scaife et al., 2017] is being extended to many models, drawing on the CHFP archive and other hindcast data sources.

Recent results [Molteni et al., 2015] indicate that teleconnections are more directly connected to tropical rainfall than sea surface temperature, which has often been used to infer teleconnection driving. In addition, climate forecast models show encouraging levels of skill at predicting seasonal rainfall in all tropical ocean basins during the Northern Hemisphere’s winter months, especially in the eastern and western Pacific.

Ongoing efforts will determine how well different models represent the sources and propagation of planetary waves driven by tropical rainfall. We will then relate those model attributes to skill in forecasting winter climate variations in the northern extratropics, including the Arctic and North Atlantic oscillations."

Caption: "Fig. 1. Averaged atmospheric response during winter in the Northern Hemisphere to recent El Niño events, connecting atmospheric changes in the tropics with those at latitudes farther north and south. Dots represent approximate pathways of planetary waves [after Scaife et al., 2017]. Colors show associated changes in sea level pressure (SLP) in hectopascals (hPa), indicative of atmospheric circulation changes. In the Northern Hemisphere, changes are clockwise for positive contours, represented by warm colors, and counterclockwise for negative contours, represented by cool colors; these directions are opposite in the Southern Hemisphere. Credit: Adam Scaife"

See also:
Scaife, A. A., et al. (2017), Tropical rainfall, Rossby waves and regional winter climate predictions, Q. J. R. Meteorol. Soc., 143, 1–11, https://doi.org/10.1002/qj.2910.

http://onlinelibrary.wiley.com/doi/10.1002/qj.2910/abstract?systemMessage=Wiley+Online+Library+will+be+unavailable+on+2nd+Dec+2017+starting+from+0800+EST+%2F+1300+GMT+%2F+21.00+SGT+for+2.5+hours+due+to+urgent+server+maintenance.+Apologies+for+the+inconvenience.

Abstract: "Skilful climate predictions of the winter North Atlantic Oscillation and Arctic Oscillation out to a few months ahead have recently been demonstrated, but the source of this predictability remains largely unknown. Here we investigate the role of the Tropics in this predictability. We show high levels of skill in tropical rainfall predictions, particularly over the Pacific but also the Indian and Atlantic Ocean basins. Rainfall fluctuations in these regions are associated with clear signatures in tropical and extratropical atmospheric circulation that are approximately symmetric about the Equator in boreal winter. We show how these patterns can be explained as steady poleward propagating linear Rossby waves emanating from just a few key source regions. These wave source ‘hotspots’ become more or less active as tropical rainfall varies from winter to winter but they do not change position. Finally, we show that predicted tropical rainfall explains a highly significant fraction of the predicted year-to-year variation of the winter North Atlantic Oscillation."
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Tompkins, A. M., et al. (2017), The Climate-system Historical Forecast Project: Providing open access to seasonal forecast ensembles from centers around the globe, Bull. Am. Meteorol. Soc., https://doi.org/10.1175/BAMS-D-16-0209.1.

http://journals.ametsoc.org/doi/10.1175/BAMS-D-16-0209.1

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Sanchez-Gomez, E., et al. (2016), Drift dynamics in a coupled model initialized for decadal forecasts, Clim. Dyn., 46, 1819–1840, https://doi.org/10.1007/s00382-015-2678-y.

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2017, 07:02:20 PM
I point-out that I have already made a lot of other predictions (related to an Ice Apocalypse) in a variety of other threads, e.g. I provided the attached image in Reply #21 of the "Potential Collapse Scenario for the WAIS" on February 24, 2013; which is still relevant to all I have stated in this thread so long as one understands that the green areas (that I drew on Vaughan et al. 2011's plan of the WAIS) represent grounding line retreats, to 2040, with cliff faces only near the base of the Thwaites Ice Tongue, and with grounding line retreats beneath ice shelves everywhere else.  Therefore, I will stop summarizing past predictions here, unless someone asks some specific questions about my assumed scenario (which I acknowledge has evolved somewhat since 2013, and which requires BAU forcing at least until about 2040) for a WAIS collapse this century.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2017, 08:59:51 PM
The linked Climate Feedback article gives Holthaus' "Ice Apocalypse" a 'high' credibility rating by a panel of experts, including Richard Alley who highlights the fact that DeConto & Pollard (2016) ice mass loss projections for the WAIS in the coming 500-years may be very conservative due to the deep uncertainty associated with this issue.  While the following linked reference by Scambos et al (2017) indicates that this matter is sufficiently important to warrant a major research effort.

Title: "Grist article on an “Ice Apocalypse” mostly accurate, but doesn’t make the likelihood of that apocalypse clear enough to readers"

https://climatefeedback.org/evaluation/antarctica-doomsday-glaciers-could-flood-coastal-cities-grist-eric-holthaus/

Extract: "Six scientists analyzed the article and estimate its overall scientific credibility to be 'high'

The DeConto-Pollard numbers (and earlier, the Pollard-DeConto-Alley numbers, so note that I was involved with earlier parts of this research) assumed that if triggered, the retreat in West Antarctica would not be as fast as the fastest rates already observed in Greenland (a maximum retreat rate was set in the model); the notably greater sea-level contribution of West Antarctica in the new modeling arises from the much broader calving front that would be activated. But, the greater depth and width of West Antarctica’s deep marine basins than in Greenland could produce much faster calving than in Greenland. Hence, the DeConto-Pollard simulations are not a worst-case scenario.

Much work remains to be done to narrow the uncertainties, including analyses of the “mélange” of broken-up icebergs mentioned by Ted Scambos—but note that such a mélange is present in the narrow fjord of Jakobshavn, providing a backstress that has still allowed the rapid retreat observed there.

See also:

T.A. Scambos et al. (2017), "How much, how fast?: A science review and outlook for research on the instability of Antarctica's Thwaites Glacier in the 21st century", Global and Planetary Change
Volume 153, June 2017, Pages 16-34, https://doi.org/10.1016/j.gloplacha.2017.04.008

http://www.sciencedirect.com/science/article/pii/S092181811630491X
https://ac.els-cdn.com/S092181811630491X/1-s2.0-S092181811630491X-main.pdf?_tid=20819862-d928-11e7-8063-00000aacb360&acdnat=1512415383_a13a8187d40a64981160a7b173487514

Abstract: "Constraining how much and how fast the West Antarctic Ice Sheet (WAIS) will change in the coming decades has recently been identified as the highest priority in Antarctic research (National Academies, 2015). Here we review recent research on WAIS and outline further scientific objectives for the area now identified as the most likely to undergo near-term significant change: Thwaites Glacier and the adjacent Amundsen Sea. Multiple lines of evidence point to an ongoing rapid loss of ice in this region in response to changing atmospheric and oceanic conditions. Models of the ice sheet's dynamic behavior indicate a potential for greatly accelerated ice loss as ocean-driven melting at the Thwaites Glacier grounding zone and nearby areas leads to thinning, faster flow, and retreat. A complete retreat of the Thwaites Glacier basin would raise global sea level by more than three meters by entraining ice from adjacent catchments. This scenario could occur over the next few centuries, and faster ice loss could occur through processes omitted from most ice flow models such as hydrofracture and ice cliff failure, which have been observed in recent rapid ice retreats elsewhere. Increased basal melt at the grounding zone and increased potential for hydrofracture due to enhanced surface melt could initiate a more rapid collapse of Thwaites Glacier within the next few decades."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2017, 11:45:22 PM
The paleo findings of the following linked reference indicate to me that we are playing Russian roulette w.r.t. the possible collapse of the WAIS this century.  The extreme storm activity and high sea levels in the Bahamas cited in Hearty & Tormey (2017) and in Rovere et al. (2017) indicate to me that the ice-climate feedback was very strong during the late MIS 5e highstand (circa 119.5 kya).  Furthermore, when one looks at the sea level error bars in the attached image [from O'Leary et al. (2013)] around 119.5 kya it is clear that there is a reasonable probability that the WAIS could substantially collapse in less than a century.  People who demand absolute proof of such a possible event, are likely to be able to directly observe it from 2040 to 2100.

P.J. Hearty & B.R. Tormey (1 August 2017), "Sea-level change and superstorms; geologic evidence from the last interglacial (MIS 5e) in the Bahamas and Bermuda offers ominous prospects for a warming Earth", Marine Geology, Volume 390, Pages 347-365, https://doi.org/10.1016/j.margeo.2017.05.009

http://www.sciencedirect.com/science/article/pii/S0025322717302700

Extract: "Geological observations from last interglacial (LIG; MIS 5e, Eemian) carbonate landscapes in the Bahamas and Bermuda reveal a turbulent climate transition at the close of the peak interglacial. The interval is associated with rapid, multi-meter shifts in sea level as major ice sheets melted and/or collapsed. Sedimentary evidence from the eastern Bahamas includes wave-transported megaboulders, lowland chevron storm ridges, and hillside runup deposits. This “trilogy” collectively provides direct geological evidence of frequent, intense storms generating sustained long-period waves from the northeast Atlantic Ocean. Penecontemporaneous with wave deposits is the subtidal production and flux of a massive volume of ooid sediments associated with amplified winds and storminess during the latter half of MIS 5e that resulted in exponential island growth. Steeper temperature and pressure gradients were evident in the North Atlantic Ocean, while the Southern Ocean appears to have had a major role in affecting atmospheric CO2, as warming of the Southern Ocean drives ventilation of the deep ocean. CO2 in turn, acts as a tight control knob on global climate.

The dramatic oceanographic and island building events of late MIS 5e are unique among other interglacial periods of the past half million years. The LIG record reveals that strong climate forcing is not required to yield major impacts on the ocean and ice caps. Antarctic ice cores document that LIG atmospheric CO2 was ~ 275 ppm, while global temperature was < 1 °C warmer than present. Despite only slightly warmer conditions than pre-Industrial times, relative sea level (RSL) persisted at + 2–3 m for several thousand years during the early and mid LIG. Later in the LIG, sea level abruptly rose an additional 3–5 m meters to + 6–9 m RSL.

In terms of Lyellian uniformitarian principles, the trilogy of coeval deposits of MIS 5e described herein do not translate to our modern climate parameters, and further cannot be explained by coincidental megatsunami. In our industrial world, rapidly increasing atmospheric CO2 rates (> 2 ppm/yr) have surpassed 408 ppm, levels not achieved since the Pliocene 3 Ma ago, while global temperature increased ~ 1 °C since the 1870s. With greatly increased CO2 forcing at unmatched rates, except perhaps during global extinction events, dramatic change is certain. In the interest of our future world, we must seek to understand the complex set of linked natural events and field observations that are revealed in the geology of past warmer climates."
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Title: "Geologic evidence is the forerunner of ominous prospects for a warming Earth"

https://www.sciencedaily.com/releases/2017/10/171012114839.htm

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Alessio Rovere et al. (2017), "Giant boulders and Last Interglacial storm intensity in the North Atlantic", PNAS, doi: 10.1073/pnas.1712433114

http://www.pnas.org/content/114/46/12144.abstract

Abstract: "As global climate warms and sea level rises, coastal areas will be subject to more frequent extreme flooding and hurricanes. Geologic evidence for extreme coastal storms during past warm periods has the potential to provide fundamental insights into their future intensity. Recent studies argue that during the Last Interglacial (MIS 5e, ∼128–116 ka) tropical and extratropical North Atlantic cyclones may have been more intense than at present, and may have produced waves larger than those observed historically. Such strong swells are inferred to have created a number of geologic features that can be observed today along the coastlines of Bermuda and the Bahamas. In this paper, we investigate the most iconic among these features: massive boulders atop a cliff in North Eleuthera, Bahamas. We combine geologic field surveys, wave models, and boulder transport equations to test the hypothesis that such boulders must have been emplaced by storms of greater-than-historical intensity. By contrast, our results suggest that with the higher relative sea level (RSL) estimated for the Bahamas during MIS 5e, boulders of this size could have been transported by waves generated by storms of historical intensity. Thus, while the megaboulders of Eleuthera cannot be used as geologic proof for past “superstorms,” they do show that with rising sea levels, cliffs and coastal barriers will be subject to significantly greater erosional energy, even without changes in storm intensity."

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Michael J. O’Leary, Paul J. Hearty, William G. Thompson, Maureen E. Raymo, Jerry X. Mitrovica and Jody M.Webster (2013), "Ice sheet collapse following a prolonged period of stable sea level during the last interglacial", Nature Geoscience 6, 796-800, doi:10.1038/ngeo1890.

https://www.nature.com/articles/ngeo1890

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 11, 2017, 06:41:39 PM
Personally, I think that the first linked article and the associated second linked reference increases the probability that the WAIS will enter a main phase collapse period by 2040.  The article indicates that ice mass loss from Greenland has been contributing to feedback mechanisms that has caused the Beaufort Gyre to progressively stockpile more freshwater than all of the great lakes combined (see the first image).  While some consensus scientists will undoubtable emphasize that an eventual release of this freshwater in coming years will result in a temporary cooling of the North Atlantic and Europe, which may decrease GMSTA; I note that

Title: "How a Wayward Arctic Current Could Cool the Climate in Europe"

http://e360.yale.edu/features/how-a-wayward-arctic-current-could-cool-the-climate-in-europe

Extract: "The Beaufort Gyre, a key Arctic Ocean current, is acting strangely. Scientists say it may be on the verge of discharging a huge amount of ice and cold freshwater that could kick off a period of lower temperatures in northern Europe.

…something is amiss with this vital plumbing system in the Arctic, a region warming faster than any other on the planet. Thanks in part to rising air temperatures, steadily disappearing sea ice, and the annual melting of 270 billion tons of ice from Greenland’s ice cap, the gyre is no longer functioning as it has predictably done for more than a half century. And now, scientists are anticipating that a sudden change in the Beaufort Gyre could set in motion events that — in a steadily warming world — would actually lead to a temporary but significant cooling of the North Atlantic region.

During the second half of the 20th century — and, most likely, earlier — the gyre adhered to a cyclical pattern in which it would shift gears every five to seven years and temporarily spin in a counter-clockwise direction, expelling ice and freshwater into the eastern Arctic Ocean and the North Atlantic. But for more than a dozen years, this carousel of ice and, increasingly, freshwater has been spinning faster in its usual clockwise direction, all the while collecting more and more freshwater from three sources: melting sea ice, huge volumes of runoff flowing into the Arctic Ocean from Russian and North American rivers, and the relatively fresh water streaming in from the Bering Sea….
The gyre’s strange behavior is likely linked, at least in part, to the profound warming of the Arctic, and it demonstrates how disruptions in one rapidly changing region of the world can affect ecosystems hundreds, even thousands, of miles away. In a recent paper, Krishfield, Proshutinsky, and other scientists suggest that frigid freshwater pouring into the north Atlantic Ocean from the rapidly melting Greenland ice sheet is forming a cap on the North Atlantic that results in stratification that prevents storm-triggering heat from the northern end of the Gulf Stream from rising to the surface. The scientists say this may be inhibiting the formation of cyclones that would cause the motion of the gyre to weaken or temporarily reverse.

If that is the case, it may mean the gyre will continue to grow and spin clockwise for years to come."
See also:

Andrey Proshutinsky, Dmitry Dukhovskoy, Mary-Louise Timmermans, Richard Krishfield, Jonathan L. Bamber (2015), "Arctic circulation regimes", Philosophical Transactions of the Royal Society A, DOI: 10.1098/rsta.2014.0160

http://rsta.royalsocietypublishing.org/content/373/2052/20140160

Abstract: "Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability."

&

The third linked Marino & Zahn (2015) reference (and second attached image) shows how a cooling of the North Atlantic can cause warming around Antarctica and an increase of Agulhas Leakage which can interact with the AMOC to strengthen Arctic Amplification and the bipolar seesaw:

Gianluca Marino and Rainer Zahn (January 2015), "The Agulhas Leakage: the missing link in the interhemispheric climate seesaw?", Past Global Changes Magazine, SCIENCE HIGHLIGHTS: Glacial terminations and interglacials

http://www.pages-igbp.org/download/docs/magazine/2015-1/PAGESmagazine_2015(1)_22-23_Marino.pdf

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With continued global warming one can expect more Agulhas leakage (see the third image); which per the fourth linked reference means that one can expect the AMOC to continue slowing; which should work synergistically with Hansen's ice-climate feedback, particularly if the WAIS collapses in coming decades:

Kathryn A. Kelly, Kyla Drushka, LuAnne Thompson, Dewi Le Bars & Elaine L. McDonagh (25 July 2016), "Impact of slowdown of Atlantic overturning circulation on heat and freshwater transports", Geophysical Research Letters, DOI: 10.1002/2016GL069789

http://onlinelibrary.wiley.com/doi/10.1002/2016GL069789/abstract

&

The fifth linked reference about the influence of the recent increased Agulhas leakage on tropical Atlantic warming and the response of the AMOC:

Joke F. Lübbecke, Jonathan V. Durgadoo, and Arne Biastoch (2015), "Contribution of increased Agulhas leakage to tropical Atlantic warming", Journal of Climate, doi: http://dx.doi.org/10.1175/JCLI-D-15-0258.1


http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0258.1

&

The sixth linked reference (with a free access pdf) indicates that the leakage of warm saline water from the Agulhas Current into the Atlantic Ocean, caused a positive feedback mechanism contributing to polar amplification during the Eemian; and that this mechanism could become increasingly important with increasing global warming today:

Turney, C. S.M. and Jones, R. T. (2010), Does the Agulhas Current amplify global temperatures during super-interglacials?. J. Quaternary Sci., 25: 839–843. doi: 10.1002/jqs.1423

http://onlinelibrary.wiley.com/doi/10.1002/jqs.1423/full
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2017, 06:20:51 PM
The linked August 2016 Special Edition of Past Global Changes (PAGES) Magazine examines paleo evidence for multiple different mechanisms for tipping points including the synergistic interactions between various mechanism resulting in a chain reaction leading to abrupt climate change.  While the entire issue is valuable, I extract from two article in the Special Edition by Fogwill et al (2016), and Praetorius & Mix (2016); which highlight the importance of ice (or freshwater hosing)-climate interaction.  The first image, from Fogwill et al (2016), shows that for Pliocene conditions (which we might reach without adequate mitigation), it is impossible to reproduce the paleo reported ice mass loss from Antarctica (both West and East) without invoking both cliff failures and hydrofracturing.  The second image, from Praetorius & Mix (2016), highlight paleo evidence that oceanic feedback mechanisms can synchronize warming of both the North Atlantic and the North Pacific in order contribute to relatively high Arctic Amplification:

Eds: Turney C, Fogwill C, Lenton T, Jones R & von Gunten L (August 2016), "Tipping Points", Past Global Changes Magazine (PAGES), vol. 24(1), 1-52, https://doi.org/10.22498/pages.24.1

http://www.pages-igbp.org/products/pages-magazine/7018-24-1-tipping-points
&
http://www.pages-igbp.org/download/docs/magazine/2016-1/PAGESmagazine_2016(1)_Full_HighREs.pdf

Christopher J. Fogwill, N.R. Golledge, H. Millman and C.S.M. Turney (August 2016), "The East Antarctic Ice Sheet as a source of sea-level rise: A major tipping element in the climate system?", Past Global Changes Magazine (PAGES), Vol 24, No. 1,

Extract: "Sea-level reconstructions suggest significant contributions from the East Antarctic Ice Sheet may be required to reconcile high interglacial sea levels. Understanding the mechanism(s) that drove this loss is critical to projecting our future commitment to sea-level rise."

&

Summer K. Praetorius and Alan C. Mix (August 2016), "Did synchronized ocean warming in the North Pacific and North Atlantic trigger a deglacial tipping point in the Northern Hemisphere?", Past Global Changes Magazine (PAGES), Vol 24, No. 1, 

http://pastglobalchanges.org/download/docs/magazine/2016-1/PAGESmagazine_2016%281%29_10-11_Praetorius.pdf

Extract: "Rapid Northern Hemisphere warming during the last deglaciation involved synchronization of the North Pacific and North Atlantic. Threshold-like transitions to hypoxia occurred in conjunction with abrupt ocean warming, implying synergistic ocean heat transport triggered both physical and ecological tipping points.

Outlook
New high-resolution paleoceanographic records from the subpolar North Pacific document rapid changes during the last deglacial transition similar in timing to those observed in the Greenland ice cores. Rather than deglacial changes in the North Pacific merely reflecting a downstream response to changes in the North Atlantic region, interactions between basins may be a key element in the emergence of abrupt climate transitions in the Northern Hemisphere."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2017, 08:36:25 PM
The linked reference indicates that an abrupt cooling of the subpolar gyre, SPG, (say due to an abrupt release of freshwater from the Beaufort Gyre), could abruptly slow the AMOC. This reference indicates that the CMIP5 ensemble underestimates the risk of future abrupt cooling of the subpolar North Atlantic, SPG.  This increases the probability of the reality of Hansen's ice-climate feedback mechanism.

Giovanni Sgubin, Didier Swingedouw, Sybren Drijfhout, Yannick Mary & Amine Bennabi
(2017), "Abrupt cooling over the North Atlantic in modern climate models", Nature Communications (2017) 8, doi:10.1038/ncomms14375

http://www.nature.com/articles/ncomms14375

Abstract: "Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models’ varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wili on December 12, 2017, 09:14:15 PM
Thanks for this, ASLR, and of course for all of your excellent posts.

So what do you or others think is the likely consequence of this for European and North American weather patterns?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2017, 10:56:20 PM
So what do you or others think is the likely consequence of this for European and North American weather patterns?

wili,

The best advise that I can offer is to down load the linked open access pdf for Hansen et al 2016 and to look as the results for SRES A1B with 10-Doubling for ice melting in both hemispheres.  For your convenience, I have included an extract discussing devastating storms (superstorms) in eastern North America and western Europe and I have attached two relevant images with their captions cited below:

James Hansen, Makiko Sato, Paul Hearty, Reto Ruedy, Maxwell Kelley, Valerie Masson-Delmotte, Gary Russell, George Tselioudis, Junji Cao, Eric Rignot, Isabella Velicogna, Blair Tormey, Bailey Donovan, Evgeniya Kandiano, Karina von Schuckmann, Pushker Kharecha, Allegra N. Legrande, Michael Bauer, and Kwok-Wai Lo (2016), "Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous", Atmos. Chem. Phys., 16, 3761-3812, doi:10.5194/acp-16-3761-2016

http://www.atmos-chem-phys.net/16/3761/2016/acp-16-3761-2016.html

Extract: "Increased baroclinicity produced by a stronger temperature gradient provides energy for more severe weather events. Many of the most significant and devastating storms in eastern North America and western Europe, popularly known as superstorms, have been winter cyclonic storms, though sometimes occurring in late fall or early spring, that generate near-hurricane-force winds and often large amounts of snowfall (Chapter 11, Hansen, 2009)."

&

Caption for first image: "Figure 6. Surface air temperature (oC) relative to 1880–1920 in (a) 2065, (b) 2080, and (c) 2096. Top row is IPCC scenario A1B. Ice melt with 10-year doubling is added in other scenarios.

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Caption for the second image: "Figure 20. Change of seasonal-mean (a) sea level pressure (hPa), (b) wind speed (m s-1) in 2078–2082 relative to 1880–1920, and (c) the wind speed (m s-1) itself, all for the scenario with ice melt in both hemispheres."

Best regards,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2017, 11:59:25 PM
The linked reference shows that ice mass loss from the WAIS is a nonlinear function of ocean forcing period.  While many consensus scientists consider ocean forcing a slow response mechanism, reasons to suspect that such nonlinear behavior could be trigger in the next few decades include:

1. The Southern Ocean has been warming since 1750, which is a long period of ocean forcing.

2. The Antarctic Ozone Hole has been advecting warm CDW to the grounding line of key WAIS marine glaciers since the 1970's (which is a somewhat long period).

3. Due to both the Antarctic Ozone Hole and Greenland Ice Sheet, GIS, ice mass loss, Agulhas Leakage has been documented to be occurring for years; which is increasing Arctic Amplification.

4. The Beaufort Gyre has been increasingly accumulating freshwater for longer periods since the mid-20th century and has not generated a pulsed release of freshwater since 2004 (apparently due to ice mass loss from the GIS and associated changes in ocean currents).  Furthermore, a sharp increase in ice mass loss from Jakobshaven Glacier between 2018 and 2028 could cause the Beaufort Gyre to accumulate several times its typical quantity of freshwater; which might then be released in a large pulse in to the North Atlantic thus slow the AMOC and warming Antarctic (including advecting more warm CDW to key marine glacier grounding lines and ice shelves) via the bipolar seesaw mechanism.

K. Snow et al. (11 December 2017), "The Response of Ice Sheets to Climate Variability", Geophysical Research Letters, DOI: 10.1002/2017GL075745

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075745/abstract?utm_content=buffer74be2&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "West Antarctic Ice Sheet loss is a significant contributor to sea level rise. While the ice loss is thought to be triggered by fluctuations in oceanic heat at the ice shelf bases, ice sheet response to ocean variability remains poorly understood. Using a synchronously coupled ice-ocean model permitting grounding line migration, this study evaluates the response of an ice sheet to periodic variations in ocean forcing. Resulting oscillations in grounded ice volume amplitude is shown to grow as a nonlinear function of ocean forcing period. This implies that slower oscillations in climatic forcing are disproportionately important to ice sheets. The ice shelf residence time offers a critical time scale, above which the ice response amplitude is a linear function of ocean forcing period and below which it is quadratic. These results highlight the sensitivity of West Antarctic ice streams to perturbations in heat fluxes occurring at decadal time scales."

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wili on December 13, 2017, 12:10:08 AM
Thanks again, ASLR. So it's more about the storms than some new 'Little Ice Age'?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2017, 12:27:06 AM
Thanks again, ASLR. So it's more about the storms than some new 'Little Ice Age'?

In my opinion, a 'Little Ice Age' is out of the question (unless government misjudge the implementation of a solar radiation management plan), but in addition to superstorms, Hansen et al (2016) also assumes about 5m of SLR by 2100.  That said the decrease in GMSTA predicted by Hansen et al (2016) masks the significance of the sharp increase in Planetary Energy Imbalance, by 2100 for 10-year ice doubling in both hemispheres, see the red curves in the attached image; as the Planetary Energy Imbalance is driven into the ocean, while the decrease in GMSTA comes from a thin layer of low salinity seawater in the North Atlantic and the Southern Ocean, which soon dissipate, while the heat content in the ocean lasts for millennia.

Furthermore, Hansen et al (2016) assume that ECS is 3C, so if ECS is 4.5C you can expect Arctic Amplification to continue increasing; and also Hansen acknowledges that his model projections are conservative for his assumed inputs.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wili on December 13, 2017, 12:53:44 AM
Ah. Thanks again.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2017, 02:48:04 AM
Ah. Thanks again.

Not to keep qualifying Hansen et al. (2016)'s projections, but:

1. They used a model of intermediate complexity and recent research has shown that more sophisticated models tend to indicate higher values of ECS.  Also, even the most sophisticated models have been able to replicate the ECS values for super interglacials like MIS 11, and we are now driving climate with a higher rate of radiative forcing than during any super interglacial.

2. SRES A1B assumed a GWP100 for methane of about 28 instead of 35.

3. They did not consider possible ESS mechanisms like: methane emissions from thermokarst lakes by 2060, etc. which could drive the effective climate sensitivity this century above ECS values.

Edit: Just to clarify this point about different values for climate sensitivity, the first attached image from Hansen et al 2011 shows three possible representative climate response functions for use in climate models, and notes that models typically use the curve labeled 'slow' response (comparable to ECS =3C).  The curve labeled 'intermediate' response can be compared to ECS equal to 4 to 4.5C, while the curve labeled 'fast' response assumes that several ESS (Earth System Sensitivity) feedback mechanisms kick-in this century and temporarily raise the effective ECS above 4.5C as indicated by the temporary bump up to 7C in second attached image from Hansen & Sato 2012.  The third attached image is from Hansen et al. (2016) and confirms that for that analysis Hansen et al (2016) assumed a slow climate response function.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2017, 05:33:18 PM
While Hansen et al. (2016) used an intermediate ESM with a slow response function (ECS~3C) for their projections, I provide the following references about results using more advance versions of Community Earth Systems Model, CESM; which is the foundation of ACME (for which no results have been published), to indicate that the effective climate sensitivity this century could be well above 4.5C, to which one would need to add the impacts of freshwater hosing not included in the CESM (nor the CMIP5) projections:

The linked reference cites findings from an improved version of CESM that increases ESS from 4.1C to 5.6C.  If this is actually experienced this coming century, this is bad news for both people & the current biota:

William R. Frey & Jennifer E. Kay (2017), "The influence of extratropical cloud phase and amount feedbacks on climate sensitivity", Climate Dynamics; pp 1–20, doi:10.1007/s00382-017-3796-5

https://link.springer.com/article/10.1007%2Fs00382-017-3796-5?utm_content=bufferfdbc0&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Global coupled climate models have large long-standing cloud and radiation biases, calling into question their ability to simulate climate and climate change. This study assesses the impact of reducing shortwave radiation biases on climate sensitivity within the Community Earth System Model (CESM). The model is modified by increasing supercooled cloud liquid to better match absorbed shortwave radiation observations over the Southern Ocean while tuning to reduce a compensating tropical shortwave bias. With a thermodynamic mixed-layer ocean, equilibrium warming in response to doubled CO2 increases from 4.1 K in the control to 5.6 K in the modified model. This 1.5 K increase in equilibrium climate sensitivity is caused by changes in two extratropical shortwave cloud feedbacks. First, reduced conversion of cloud ice to liquid at high southern latitudes decreases the magnitude of a negative cloud phase feedback. Second, warming is amplified in the mid-latitudes by a larger positive shortwave cloud feedback. The positive cloud feedback, usually associated with the subtropics, arises when sea surface warming increases the moisture gradient between the boundary layer and free troposphere. The increased moisture gradient enhances the effectiveness of mixing to dry the boundary layer, which decreases cloud amount and optical depth. When a full-depth ocean with dynamics and thermodynamics is included, ocean heat uptake preferentially cools the mid-latitude Southern Ocean, partially inhibiting the positive cloud feedback and slowing warming. Overall, the results highlight strong connections between Southern Ocean mixed-phase cloud partitioning, cloud feedbacks, and ocean heat uptake in a climate forced by greenhouse gas changes."

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The following linked reference provides satellite evidence that the CMIP5 projections substantially underestimate the positive feedback from precipitating clouds:

J.-L. F. Li, Wei-Liang Lee, Yi-Hui Wang, Mark Richardson, Jia-Yuh Yu, E. Suhas, Eric Fetzer, Min-Hui Lo & Qing Yue (2016), "Assessing the Radiative Impacts of Precipitating Clouds on Winter Surface Air Temperatures and Land Surface Properties in GCMs Using Observations", JGR: Atmospheres, DOI: 10.1002/2016JD025175

http://onlinelibrary.wiley.com/doi/10.1002/2016JD025175/abstract

Abstract: "Using CloudSat-CALIPSO ice water, cloud fraction and radiation; CERES radiation and long-term station-measured surface air temperature (SAT), we identified a substantial underestimation of the total ice water path, total cloud fraction, land surface radiative flux, land surface temperature (LST) and SAT during Northern Hemisphere winter in CMIP5 models. We perform sensitivity experiments with the NCAR Community Earth System Model version 1 (CESM1) in fully coupled modes to identify processes driving these biases. We found that biases in land surface properties are associated with the exclusion of downwelling long-wave heating from precipitating ice during Northern Hemisphere winter. The land surface temperature biases introduced by the exclusion of precipitating ice radiative effects in CESM1 and CMIP5 both spatially correlate with winter biases over Eurasia and North America. The underestimated precipitating ice radiative effect leads to colder LST, associated surface energy-budget adjustments and cooler SAT. This bias also shifts regional soil moisture state from liquid to frozen, increases snow cover and depresses evapotranspiration (ET) and total leaf area index (TLAI) in Northern Hemisphere winter. The inclusion of the precipitating ice radiative effects largely reduces the model biases of surface radiative fluxes (more than 15 W m-2), SAT (up to 2-4 K), snow cover and ET (25-30%), compared with those without snow-radiative effects."

&

The following linked (open access) reference provides a comparison of the best 2014 version of Community Earth Systems Model run to date (CESM-H), and a standard ESM run (CESM-S) such as that used for AR5.  The article, the attached image (and caption) and extracts, make it very clear that while the CESM-H run is not perfect (i.e. there is still a reason to run ACME/E3SM), it is a substantial improvement about the AR5 generation of climate models, and it projects higher increases in mean global temperature increases, and less sea ice (see the figure 1) than the AR5 generation of projections.

R. Justin Small, Julio Bacmeister, David Bailey, Allison Baker, Stuart Bishop, Frank Bryan, Julie Caron, John Dennis, Peter Gent, Hsiao-ming Hsu, Markus Jochum, David Lawrence, Ernesto Muñoz, Pedro diNezio, Tim Scheitlin, Robert Tomas, Joseph Tribbia, Yu-heng Tseng, & Mariana Vertenstein, (December 2014), "A new synoptic scale resolving global climate simulation using the Community Earth System Model", JAMES, Volume 6, Issue 4, Pages 1065–1094, DOI: 10.1002/2014MS000363

http://onlinelibrary.wiley.com/enhanced/doi/10.1002/2014MS000363/

Abstract: "High-resolution global climate modeling holds the promise of capturing planetary-scale climate modes and small-scale (regional and sometimes extreme) features simultaneously, including their mutual interaction. This paper discusses a new state-of-the-art high-resolution Community Earth System Model (CESM) simulation that was performed with these goals in mind. The atmospheric component was at 0.25° grid spacing, and ocean component at 0.1°. One hundred years of “present-day” simulation were completed. Major results were that annual mean sea surface temperature (SST) in the equatorial Pacific and El-Niño Southern Oscillation variability were well simulated compared to standard resolution models. Tropical and southern Atlantic SST also had much reduced bias compared to previous versions of the model. In addition, the high resolution of the model enabled small-scale features of the climate system to be represented, such as air-sea interaction over ocean frontal zones, mesoscale systems generated by the Rockies, and Tropical Cyclones. Associated single component runs and standard resolution coupled runs are used to help attribute the strengths and weaknesses of the fully coupled run. The high-resolution run employed 23,404 cores, costing 250 thousand processor-hours per simulated year and made about two simulated years per day on the NCAR-Wyoming supercomputer “Yellowstone.”"

Extracts: "The high-resolution CESM was run under “present-day” (year 2000) greenhouse gas conditions (fixed CO2 concentration of 367 ppm). This was chosen so that direct comparisons could be made with recent-era observations of fine-scale and large-scale phenomena. The prognostic carbon-nitrogen cycle was not used in this simulation.

In the following, this simulation will be referred to as CESM-High Resolution (CESM-H).

The interpretation of the model data employed in this paper is that the CESM-H and CESM-S are the best simulations available at their respective resolutions, for the same model version, and for year 2000 conditions."


Caption for Figure 1: "Time series of globally averaged quantities for 100 years of CESM-H (thick black line) and 166 years of CESM-S (thin gray line). (a) Top of atmosphere net radiation, positive incoming to Earth. Data are 10 year running mean. (b) Surface (including ocean, land, ice) temperature, 10 year running average. Sea ice area in (c) Northern Hemisphere and (d) Southern Hemisphere. (e) Atlantic Meridional Overturning Circulation (AMOC), 12 month running averages, (f) transport through Drake Passage due to Antarctic Circumpolar Current (ACC), annual values."

The following link provides public access to various model run outputs:

http://www.earthsystemgrid.org/

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 14, 2017, 03:48:56 PM
The linked open access reference estimates sea level rise values by 2100 that are about twice those projected by AR5.  However, due to conservative assumptions made by the study w.r.t. timing of contributions from both the GIS and the AIS, these projected SLR values by 2100 could be increased again in several years time:

Robert E. Kopp, Robert M. DeConto, Daniel A. Bader, Carling C. Hay, Radley M. Horton, Scott Kulp, Michael Oppenheimer, David Pollard & Benjamin H. Strauss (14 December 2017), "Evolving Understanding of Antarctic Ice-Sheet Physics and Ambiguity in Probabilistic Sea-Level Projections", Earth's Future, DOI: 10.1002/2017EF000663

http://onlinelibrary.wiley.com/doi/10.1002/2017EF000663/abstract

Abstract: "Mechanisms such as ice-shelf hydrofracturing and ice-cliff collapse may rapidly increase discharge from marine-based ice sheets. Here, we link a probabilistic framework for sea-level projections to a small ensemble of Antarctic ice-sheet (AIS) simulations incorporating these physical processes to explore their influence on global-mean sea-level (GMSL) and relative sea-level (RSL). We compare the new projections to past results using expert assessment and structured expert elicitation about AIS changes. Under high greenhouse gas emissions (Representative Concentration Pathway [RCP] 8.5), median projected 21st century GMSL rise increases from 79 to 146 cm. Without protective measures, revised median RSL projections would by 2100 submerge land currently home to 153 million people, an increase of 44 million. The use of a physical model, rather than simple parameterizations assuming constant acceleration of ice loss, increases forcing sensitivity: overlap between the central 90% of simulations for 2100 for RCP 8.5 (93–243 cm) and RCP 2.6 (26–98 cm) is minimal. By 2300, the gap between median GMSL estimates for RCP 8.5 and RCP 2.6 reaches >10 m, with median RSL projections for RCP 8.5 jeopardizing land now occupied by 950 million people (versus 167 million for RCP 2.6). The minimal correlation between the contribution of AIS to GMSL by 2050 and that in 2100 and beyond implies current sea-level observations cannot exclude future extreme outcomes. The sensitivity of post-2050 projections to deeply uncertain physics highlights the need for robust decision and adaptive management frameworks."

Extract: "Probabilistic assessment also requires more research on potential bounds for factors that influence the AIS. For example, it is unclear whether even a full ensemble of GCMs would fully constrain the range of plausible distributions of near surface ocean temperature, sea ice, and storm tracks near the AIS. More research is also needed on interactions and feedbacks across the AIS and between the AIS and the rest of the world, including through poorly understood mechanisms like ocean circulation that could over long time scales influence both ice-sheet retreat and other drivers of coastal flood risk (such as tropical cyclones) around the globe."

Caption for the first image: "(a and b) Relationship between the Antarctic ice-sheet contribution to global-mean sea-level (GMSL) in 2020 and that in (a) 2100 or (b) 2300. Black line is the relationship in the K14 projections. Red/blue/green is the DP16 ensemble (red = RCP 8.5; blue = RCP 4.5; green = RCP 2.6; filled = with bias correction; open = without bias correction). (c, e) GMSL projections consistent with 50 ± 10 cm (green) and 200 ± 10 cm (orange) of GMSL rise in 2100 under (c) K14 and (e) DP16. (d, f) GMSL projections for 2100 conditional on observations in a given decade falling within the bounds of the 50 cm (green) or 200 cm (orange) time paths. In (c–f), heavy line = median; dashed/shaded region = 5th–95th percentile."

Caption for second image: "Median DP16 RSL projections under Representative Concentration Pathway (RCP) 8.5 in 2050, 2100 and 2300."


See also:
Title: "Sea level rise may be twice earlier estimates, dooming coastal cities"

http://mashable.com/2017/12/13/sea-level-rise-could-be-double-previous-estimates-climate-change-study/#ZTMaw6OSwSq8
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 21, 2017, 04:57:12 PM
This selected abstract comes from the IGSOC 2017 conference, and concludes that a possible positive feedback between ice mass loss in the WAIS and decompression-melt-induced subglacial volcanism would result in an acceleration of the collapse of the WAIS:

https://www.igsoc.org/symposia/2017/boulder/proceedings/proceedings.html

76A2543
The potential for positive feedback between deglaciation of the West Antarctic Ice Sheet, decompression-melt-induced subglacial volcanism and resultant sea-level rise
John Behrendt, Wesley LeMasurier
Corresponding author: John Behrendt
Corresponding author e-mail: john.behrendt@colorado.edu
Melting of the West Antarctic Ice Sheet (WAIS) would raise global sea level ~3 m. WAIS flows through the volcanically active West Antarctic rift system (WARS); heat flow is high beneath WAIS. Satellite altimetry shows rapid retreat of ice shelves bordering WAIS resulting from climate change. GRACE satellite data indicate accelerating mass loss from WAIS, reducing basal pressure. Aeromagnetic surveys over WAIS revealed >1000 high-amplitude magnetic anomalies, indicative of the late Cenozoic–recent age subglacial volcanic rocks at its base. Increased volcanic activity resulting from decompression mantle melting beneath a thinning WAIS may serve as a positive feedback mechanism that could further destabilize WAIS. In both Iceland and on midocean ridges, dated volcanism suggests decompression mantle melting associated with reductions in either ice or water loads drives significant volcanism. Acceleration of volcanic activity as the WAIS thins could enhance the rate of ice loss and accelerate global sea level rise.


Edit: The following extract is from the Eighteenth Annual WAIS Workshop (2011), illustrates how volcanically active the WAIS is and Behrendt 2011 recommends that its potential contribution should not be ignored when assessing the risks of coming SLR.  The attached figures are also from a Behrendt 2011 pptx.


Extract: "Geophysical evidence of Ice-Magma interactions beneath the West Antarctic Ice Sheet in the West Antarctic Rift System
John C. Behrendt
INSTAAR University of Colorado, Boulder
And USGS, Denver
Radar Ice Sounding and Aeromagnetic Surveys reported over the West Antarctic Ice Sheet WAIS have been interpreted as evidence of subglacial eruptions. Several active volcanoes have shown evidence of eruption through the WAIS and several other active volcanoes are present beneath the WAIS (e.g. Corr et al., 2009; Blankenship et al., 1993) reported from radar ice sounding and aeromagnetic data (Behrendt et al., 1995; 2004). Aeromagnetic profiles (>10,000 km) acquired in the early 1960s over the West Antarctic Ice Sheet (WAIS) combined with coincident aeromagnetic and radar ice sounding in 1978-79 indicated numerous high-amplitude, shallow-source, magnetic anomalies over a very extensive area of the volcanically active West Antarctic rift system interpreted as caused by subglacial volcanic rocks. These early aerogeophysical surveys defined this area as >500,000 km2. Five-kilometer spaced coincident aeromagnetic and radar ice sounding surveys since 1990 provide three dimensional characterization of the magnetic field and bed topography beneath the ice sheet. These 5-50-km width, semicircular magnetic anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick ice have been interpreted as evidence of subglacial eruptions. Behrendt et al, (2005, 2008) interpreted these anomalies as indicating >1000 "volcanic centers." requiring high remanent normal (and at least 10% reversed) magnetizations in the present field direction. These data have shown that >80% of the anomaly sources at the bed of the WAIS, have been modified by the moving ice into which they were injected, requiring a younger age than the WAIS (about 25 Ma). Although exposed volcanoes surrounding the WAIS extend in age to ~34 m.y., Mt Erebus, (<1 Ma) Mt. Melbourne, (<0.26 Ma), and Mt. Takahae (<0.1 Ma) are examples of exposed active volcanoes in the WAIS area. However, the great volume of volcanic centers is buried beneath the WAIS. If only a very small percentage of these >1000 volcanic, magnetic-anomaly sources are active today, or in the recent past, in the drainage area of the WAIS, subglacial volcanism may still have a significant effect on the dynamics of the WAIS. Interpreted active subglacial volcanism is revealed by aerogeophysical data reported by Blankenship et al., (1993, Mt. Casertz), and Corr and Vaughan, (2008, near Hudson Mts.), who raised the question of possible volcanic effects on the regime of the WAIS. Wingham et al. (2009) reported an average rate of volume loss from 2.6 to 10.1 km3 /yr from 1995 to 2006 for the Pine Island Glacier in the vicinity of the active subglacial volcano near the Hudson Mts. Probably wet-based areas of the WAIS would be the most likely to be impacted. Here I discuss these geophysical data over the WAIS, and conclude that even if there is a very low probability, future effects on the stability of the WAIS and associated sea-level rise should not be ignored, as changes observed in the past 20 years resulting from global warming, could be accelerated by subglacial volcanism."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 22, 2017, 12:36:08 AM
The linked reference finds that algae driven darkening of bare ice in Greenland reduced albedo more than nonalgal impurities.  Furthermore, they find that a global warming continues the impact of the algae on albedo will also increase:

Marek Stibal et al. (18 November 2017), "Algae Drive Enhanced Darkening of Bare Ice on the Greenland Ice Sheet", Geophysical Research Letters, DOI: 10.1002/2017GL075958

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075958/full

Abstract: "Surface ablation of the Greenland ice sheet is amplified by surface darkening caused by light-absorbing impurities such as mineral dust, black carbon, and pigmented microbial cells. We present the first quantitative assessment of the microbial contribution to the ice sheet surface darkening, based on field measurements of surface reflectance and concentrations of light-absorbing impurities, including pigmented algae, during the 2014 melt season in the southwestern part of the ice sheet. The impact of algae on bare ice darkening in the study area was greater than that of nonalgal impurities and yielded a net albedo reduction of 0.038 ± 0.0035 for each algal population doubling. We argue that algal growth is a crucial control of bare ice darkening, and incorporating the algal darkening effect will improve mass balance and sea level projections of the Greenland ice sheet and ice masses elsewhere."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 23, 2017, 06:25:53 PM
The first attached image from the conservative DeConto & Pollard (2016) analysis, that in panel "c" the "T" stands for Totten Glacier and the "TG" stands for Thwaites Glacier contribution to SLR, with RCP 8.5 radiative forcing.  If it is not clear, let me note that it is note reasonable that Totten's SLR contribution would peak amore 75 years earlier than that from Thwaites; while in reality this order is a manifestation of DeConto & Pollard (2016)'s arbitrary assumption that cliff failures in Antarctica will occur in the future at a rate of ½ of the current calving rate of Jakobshavn.  Due to the 3D nature of possible future cliff failures for Thwaites it will more reasonably calve at a rate several times higher than that of the current rate of calving for Jakobshavn

Caption for the first image: "Figure 4 | Future ice-sheet simulations and Antarctic contributions to GMSL from 1950 to 2500 driven by a high-resolution atmospheric model and 1° NCAR CCSM4 ocean temperatures. a, Equivalent CO₂ forcing applied to the simulations, following the RCP emission scenarios in ref. 36, except limited to 8 × PAL (preindustrial atmospheric level, where 1 PAL = 280 p.p.m.v.). b, Antarctic contribution to GMSL. c, Rate of sea-level rise and approximate timing of major retreat and thinning in the Antarctic Peninsula (AP), Amundsen Sea Embayment (ASE) outlet glaciers, AS–BS, Amundsen Sea–Bellingshausen Sea; the Totten (T), Siple Coast (SC) and Weddell Sea (WS) grounding zones, the deep Thwaites Glacier basin (TG), interior WAIS, the Recovery Glacier, and the deep EAIS basins (Wilkes and Aurora). d, Antarctic contribution to GMSL over the next 100 years for RCP8.5 with and without a +3 °C adjustment in ocean model temperatures in the Amundsen and Bellingshausen seas as shown in Extended Data Fig. 5d. e–g, Ice-sheet snapshots at 2500 in the RCP2.6 (e), RCP4.5 (f) and RCP8.5 (g) scenarios. Ice-free land surfaces are shown in brown. h, Close-ups of the Amundsen Sea sector of WAIS in RCP8.5 with bias-corrected ocean model temperatures."

The second image shows a typical current calving mechanism for Jakobshavn; which illustrates how the resulting icebergs typically roll on to their sides, so as to float-out with a draft less than 500-m.  If the icebergs resulting from future cliff failure calving of Thwaites exhibit a similar behavior, then these future Thwaites icebergs likely will not become pinned on the sill of the Thwaites Gateway; which would mean that the rate of float-out of future Thwaites icebergs would likely be limited by the rate of calving.

Edit: For clarity, I provide the third image which is a blow-up of panel 'c' from the first image.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 23, 2017, 06:46:00 PM
The first image shows zones of relatively cool to relatively warm ocean heat content around Antarctica, near the depth necessary to melt either grounding line ice of marine glaciers and/or basal ice for ice shelves.  Note that both the Filchner-Ronne Ice Shelf and the Ross Ice Shelf have cool sea water under them.

The second image shows how cool water beneath an ice shelf can stabilize basal crevasses, what warm water can 'burn' through such basal crevasses.

The third image shows how climate change-induced changes in local wind effects on the ocean near the Weddell Sea can direct warm water through the Filchner Trough in order to warm the water beneath the Filchner-Ronne Ice Shelf, FRIS.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 31, 2017, 02:26:18 AM
This is just a quick post to remind people that the CMIP5 projections do not consider freshwater hosing events; however, Antarctic ice shelves have lost so much ice mass in recent decades that Hansen's ice-climate positive feedback mechanism is already being activated even without a large SLR contribution from Antarctica.

In my opinion this initiation of the ice-climate feedback mechanism is already contributing to an increase in the positive nature of the net cloud feedback, by slowing the MOC and thus increasing the net surface temperatures of the tropical ocean regions (which increases evaporation and deep atmospheric convection, which both increases the average height of clouds and moves the net tropical cloud cover poleward; which resulting in increased solar radiation on the tropical oceans).

The attached image illustrates the extent of recent (1994-2012) ice mass loss from Antarctic ice shelves.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wili on December 31, 2017, 03:28:57 AM
"freshwater hosing events"

Sorry, could you briefly explain what that is, or provide a link that does. Thanks.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Tor Bejnar on December 31, 2017, 07:00:05 AM
I searched for "freshwater hosing" and found the following:
Quote
Numerous modelling experiments have now been carried out in which freshwater is introduced into the ocean ('freshwater hosing').

This is the Google search result (screen print):
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: oren on December 31, 2017, 08:43:37 AM
"freshwater hosing events"

Sorry, could you briefly explain what that is, or provide a link that does. Thanks.
Here's a plain language paragraph from an article published in July 2015 about Hansen's paper. Interestingly, since then there have been decreases in sea ice around Antarctica, not increases. But the cold spot near Greenland is still alive and kicking.

Quote
The paper also describes an atmosphere-ocean modeling study of feedback loops caused by ice sheet melting under 2°C conditions. What they found, Hansen says, is that melting ice sheets in Greenland and Antarctica could inject enough fresh water into the seas to slow the formation of two key water masses: the North Atlantic Deepwater and the Antarctic Bottom Water formations. Both are part of the so-called Great Ocean Conveyor Belt of ocean circulation. The injection of so much cold water, they say, could lead to a stratification of the water column, with warm water buried underneath cold surface water. “Instead of emerging at the surface, much of that heat is melting the ice shelves,” Hansen says, producing more fresh water and amplifying the feedback. That is particularly striking, he added, because it’s what we’re observing right now: an increase in cold surface waters around Antarctica and Greenland, as well as increases in sea ice around some parts of Antarctica.
http://www.sciencemag.org/news/2015/07/climate-researcher-blasts-global-warming-target-highly-dangerous (http://www.sciencemag.org/news/2015/07/climate-researcher-blasts-global-warming-target-highly-dangerous)
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wili on December 31, 2017, 12:34:22 PM
Thanks, oren and TB.

That concept was familiar to me, but I hadn't heard the phrase 'freshwater hosing' applied to it. Makes sense, though.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 31, 2017, 05:53:15 PM
Thanks, oren and TB.

That concept was familiar to me, but I hadn't heard the phrase 'freshwater hosing' applied to it. Makes sense, though.

wili,

I used the term 'freshwater hosing events', not only because all the CMIP5/AR5 models do not address this well known feedback mechanism, but also because I am not only concerned about freshwater introduced to the oceans from ice shelves, ice sheets, marine glaciers, subglacial lakes, and surface lakes; but particularly because I am concerned that the Beaufort Gyre will release an atypically large pulse of freshwater into the North Atlantic in the 2025 to 2035 timeframe (see my prior posts in this thread on this mechanism).

Best,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on January 25, 2018, 04:36:51 PM
I provide links to the following 2015 article (& associated 2016 reference) to remind us all that while most consensus discussion of climate sensitivity focuses on feedbacks due to increases in global temperatures, that feedbacks based on increases in polar precipitation can create a positive feedback comparable to a doubling of global carbon dioxide:

Title: "Melting sea ice increases Arctic precipitation, complicates climate predictions"

https://phys.org/news/2015-12-sea-ice-arctic-precipitation-complicates.html

Extract: "The melting of sea ice will significantly increase Arctic precipitation, creating a climate feedback comparable to doubling global carbon dioxide, a Dartmouth College-led study finds."

See also:
Kopec et al (2016), "Influence of sea ice on Arctic precipitation", PNAS, vol. 113 no. 1 46-51, doi: 10.1073/pnas.1504633113

http://www.pnas.org/content/113/1/46

Abstract: "Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. However, the quantitative link between precipitation and sea ice extent is poorly constrained. Here we present observational evidence for the response of precipitation to sea ice reduction and assess the sensitivity of the response. Changes in the proportion of moisture sourced from the Arctic with sea ice change in the Canadian Arctic and Greenland Sea regions over the past two decades are inferred from annually averaged deuterium excess (d-excess) measurements from six sites. Other influences on the Arctic hydrologic cycle, such as the strength of meridional transport, are assessed using the North Atlantic Oscillation index. We find that the independent, direct effect of sea ice on the increase of the percentage of Arctic sourced moisture (or Arctic moisture proportion, AMP) is 18.2 ± 4.6% and 10.8 ± 3.6%/100,000 km2 sea ice lost for each region, respectively, corresponding to increases of 10.9 ± 2.8% and 2.7 ± 1.1%/1 °C of warming in the vapor source regions. The moisture source changes likely result in increases of precipitation and changes in energy balance, creating significant uncertainty for climate predictions."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on January 25, 2018, 04:38:48 PM
The linked reference confirms that most climate simulations do not capture the greater polar amplification during the equable climate of the Eocene.  As CO2e approaches 560ppm this type of information could become highly relevant to modern times:

David Evans, et al (January 22, 2018), "Eocene greenhouse climate revealed by coupled clumped isotope-Mg/Ca thermometry", PNAS, doi: 10.1073/pnas.1714744115

http://www.pnas.org/content/early/2018/01/12/1714744115.abstract

Significance: "Reconstructing the degree of warming during geological periods of elevated CO2 provides a way of testing our understanding of the Earth system and the accuracy of climate models. We present accurate estimates of tropical sea-surface temperatures (SST) and seawater chemistry during the Eocene (56–34 Ma before present, CO2 >560 ppm). This latter dataset enables us to reinterpret a large amount of existing proxy data. We find that tropical SST are characterized by a modest warming in response to CO2. Coupling these data to a conservative estimate of high-latitude warming demonstrates that most climate simulations do not capture the degree of Eocene polar amplification."

Abstract: "Past greenhouse periods with elevated atmospheric CO2 were characterized by globally warmer sea-surface temperatures (SST). However, the extent to which the high latitudes warmed to a greater degree than the tropics (polar amplification) remains poorly constrained, in particular because there are only a few temperature reconstructions from the tropics. Consequently, the relationship between increased CO2, the degree of tropical warming, and the resulting latitudinal SST gradient is not well known. Here, we present coupled clumped isotope (Δ47)-Mg/Ca measurements of foraminifera from a set of globally distributed sites in the tropics and midlatitudes. Δ47 is insensitive to seawater chemistry and therefore provides a robust constraint on tropical SST. Crucially, coupling these data with Mg/Ca measurements allows the precise reconstruction of Mg/Casw throughout the Eocene, enabling the reinterpretation of all planktonic foraminifera Mg/Ca data. The combined dataset constrains the range in Eocene tropical SST to 30–36 °C (from sites in all basins). We compare these accurate tropical SST to deep-ocean temperatures, serving as a minimum constraint on high-latitude SST. This results in a robust conservative reconstruction of the early Eocene latitudinal gradient, which was reduced by at least 32 ± 10% compared with present day, demonstrating greater polar amplification than captured by most climate models."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on February 08, 2018, 05:12:58 PM
As sidd has questions about why abrupt sea level rise from ice mass loss might increase the risks of flipping the Earth's magnetic poles, I am reposting the following from the 'Adapting to the Anthropocene' thread:

"In my opinion, a collapse of the WAIS this century would likely accelerate schedule for the long overdue flipping of the Earth's magnetic poles.  So I hope people prepare accordingly:

Title: "Earth's Magnetic Poles Are Overdue For a Switch And We're Not Prepared"

https://www.sciencealert.com/earth-magnetic-poles-reversal-switch-overdue-turbulent

Extract: "Within the last 20 million years, Earth has fallen into the pattern of pole reversal every 200,000 to 300,000 years, and between successful swaps, the poles sometimes even attempt to reverse and then snap back into place.

About 40,000 years ago, the poles made one such unsuccessful attempt, and the last full swap was about 780,000 years ago, so we're a bit overdue for a pole reversal based on the established pattern.

The planet's magnetic field is already shifting, which could signify the poles are preparing to flip, and while we can't yet confirm that a reversal is on the near horizon, it is well within the realm of possibility.

To try to determine whether or not a flip is imminent, scientists have begun using satellite imagery and complex calculations to study the shifting of the magnetic field.

They've found that molten iron and nickel are draining energy from the dipole at the edge of the Earth's core, which is where the planet's magnetic field is generated.

They also found that the north magnetic pole is especially turbulent and unpredictable. If the magnetic blocks become strong enough to sufficiently weaken the dipole, the poles will officially switch.

Again, while it is not a certainty that the switch will happen soon, this activity at the Earth's core suggests that it is possible in the near future.""
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on February 08, 2018, 05:15:30 PM
Here is another repost regarding possible increased risks of flipping the Earth's magnetic poles


": sidd  Today at 02:26:20 AM

"In my opinion, a collapse of the WAIS this century would likely accelerate schedule for the long overdue flipping of the Earth's magnetic poles. "

Interesting. What leads you to this opinion ? Do tell.

sidd




Here is some background references:


1. Adam C. Maloof Galen P. Halverson Joseph L. Kirschvink Daniel P. Schrag Benjamin P. Weiss Paul F. Hoffman (2006), "Combined paleomagnetic, isotopic, and stratigraphic evidence for true polar wander from the Neoproterozoic Akademikerbreen Group, Svalbard, Norway",  GSA Bulletin, 118 (9-10): 1099-1124, DOI: https://doi.org/10.1130/B25892.1

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/118/9-10/1099/125331/combined-paleomagnetic-isotopic-and-stratigraphic?redirectedFrom=fulltext

Abstract: "We present new paleomagnetic data from three Middle Neoproterozoic carbonate units of East Svalbard, Norway. The paleomagnetic record is gleaned from 50 to 650 m of continuous, platformal carbonate sediment, is reproduced at three locations distributed over >100 km on a single craton, and scores a 5–6 (out of 7) on the Van der Voo (1990) reliability scale. Two >50° shifts in paleomagnetic direction are coincident with equally abrupt shifts in δ13C and transient changes in relative sea level. We explore four possible explanations for these coincidental changes: rapid plate tectonic rotation during depositional hiatus, magnetic excursions, nongeocentric axial-dipole fields, and true polar wander. We conclude that the observations are explained most readily by rapid shifts in paleogeography associated with a pair of true polar wander events. Future work in sediments of equivalent age from other basins can test directly the true polar wander hypothesis because this type of event would affect every continent in a predictable manner, depending on the continent's changing position relative to Earth's spin axis."

2. J. R. Creveling, J. X. Mitrovica, N.-H. Chan, K. Latychev & I. Matsuyama (08 November 2012), "Mechanisms for oscillatory true polar wander", Nature, volume 491, pages 244–248,
doi:10.1038/nature11571

http://www.nature.com/articles/nature11571

Abstract: "Palaeomagnetic studies of Palaeoproterozoic to Cretaceous rocks propose a suite of large and relatively rapid (tens of degrees over 10 to 100 million years) excursions of the rotation pole relative to the surface geography, or true polar wander (TPW). These excursions may be linked in an oscillatory, approximately coaxial succession about the centre of the contemporaneous supercontinent. Within the framework of a standard rotational theory, in which a delayed viscous adjustment of the rotational bulge acts to stabilize the rotation axis, geodynamic models for oscillatory TPW generally appeal to consecutive, opposite loading phases of comparable magnitude. Here we extend a nonlinear rotational stability theory to incorporate the stabilizing effect of TPW-induced elastic stresses in the lithosphere. We demonstrate that convectively driven inertia perturbations acting on a nearly prolate, non-hydrostatic Earth with an effective elastic lithospheric thickness of about 10 kilometres yield oscillatory TPW paths consistent with palaeomagnetic inferences. This estimate of elastic thickness can be reduced, even to zero, if the rotation axis is stabilized by long-term excess ellipticity in the plane of the TPW. We speculate that these sources of stabilization, acting on TPW driven by a time-varying mantle flow field, provide a mechanism for linking the distinct, oscillatory TPW events of the past few billion years."

3. To learn how much the North Pole has shifted in the recent decades due to rapid ice mass loss, see Chen, J..L., C.R. Wilson, J.C. Ries, B.D. Tapley, Rapid ice melting drives Earth's pole to the east, Geophys. Res. Lett., Vol. 40, 1-6, DOI: 10.1002/grl.50552, 2013; which can be found at the prime author's website at the University of Texas, where you can download a preprint (made available by the author):

http://www.csr.utexas.edu/personal/chen/publication.html

and here is a link directly to the preprint pdf:

ftp://ftp.csr.utexas.edu/pub/ggfc/papers/2013GL056164_preprint.pdf

"


Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on February 08, 2018, 05:18:39 PM
Here is my last repost from the 'Adapting to the Anthropocene' thread about increased risk of flipping the Earth's magnetic pole due to abrupt sea level rise associated with abrupt ice mass loss this century:


": sidd  Today at 06:55:23 AM

Do you mean magnetic pole or rotational pole ? both the papers you cite talk about the rotational pole.

sidd




sidd,

I will move this line of discussion to the 'Ice Apocalypse' thread (see the link below) in the Antarctic folder as this topic was meant to be just a word of warning here.  However, my general point is that a some portion of the changes in the magnetic pole can be associated with changes in the rotational pole (the attached image illustrates how fast this is currently changing), due to changes in the magma flow associated with ice mass redistribution.  Furthermore, my point is that due to the current exceptionally high rate of anthropogenic forcing and the bipolar seesaw mechanism that possible abrupt changes in ice mass loss can make faster changes in tectonic behavior than observed in the paleorecord.

https://forum.arctic-sea-ice.net/index.php/topic,2205.50.html

ASLR"
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on February 08, 2018, 06:12:17 PM
As a follow on to my last series of re-posts about correlating true polar wander (shifting of the Earth's rotational axis) and magnetic field reversals and mass redistribution around the Earth; I provide the first linked reference that provides paleo evidence that during periods of little polar wander the is reduced activity of magnetic pole flipping; while the second linked article makes it clear that polar wander is associated with all mass (ice, sea level, groundwater, isostatic rebound) redistribution.  Also, Hansen's ice-climate feedback results in changes in precipitation patterns that will affect polar wander.

I recommend that scientists with the appropriate Earth models that include Earth's interior core-mantle-lithosphere mechanisms should assume some up-bound scenarios for possible future abrupt mass redistributions around the Earth (including: a WAIS ice mass collapse and associated isostatic rebound, increased rainfall at both poles; changes in groundwater distributions, etc.) and then see what happens to tectonic activity (including magnetic fields, volcanism and seismic activity):

Courtillot V & Besse J. (1987 Sep 4), "Magnetic field reversals, polar wander, and core-mantle coupling", Science vol 237, issue (4819), pp 1140-7, DOI:10.1126/science.237.4819.1140

http://science.sciencemag.org/content/237/4819/1140

Abstract: "True polar wander, the shifting of the entire mantle relative to the earth's spin axis, has been reanalyzed. Over the last 200 million years, true polar wander has been fast (approximately 5 centimeters per year) most of the time, except for a remarkable standstill from 170 to 110 million years ago. This standstill correlates with a decrease in the reversal frequency of the geomagnetic field and episodes of continental breakup. Conversely, true polar wander is high when reversal frequency increases. It is proposed that intermittent convection modulates the thickness of a thermal boundary layer at the base of the mantle and consequently the core-to-mantle heat flux. Emission of hot thermals from the boundary layer leads to increases in mantle convection and true polar wander. In conjunction, cold thermals released from a boundary layer at the top of the liquid core eventually lead to reversals. Changes in the locations of subduction zones may also affect true polar wander. Exceptional volcanism and mass extinctions at the Cretaceous-Tertiary and Permo-Triassic boundaries may be related to thermals released after two unusually long periods with no magnetic reversals. These environmental catastrophes may therefore be a consequence of thermal and chemical couplings in the earth's multilayer heat engine rather than have an extraterrestrial cause."

&

Title: "Climate Change Is Moving the North Pole"

https://news.nationalgeographic.com/2016/04/160408-climate-change-shifts-earth-poles-water-loss/

Extract: "As ice melts and aquifers are drained, Earth's distribution of mass is changing—and with it the position of the planet's spin axis."


Edit, also see which indicates that about 66% of the polar wander over the indicated period was due to rapid changes in ice mass loss:

Surendra Adhikari and Erik R. Ivins (08 Apr 2016), "Climate-driven polar motion: 2003–2015", Science Advances, Vol. 2, no. 4, e1501693, DOI: 10.1126/sciadv.1501693

http://advances.sciencemag.org/content/2/4/e1501693

Abstract: "Earth’s spin axis has been wandering along the Greenwich meridian since about 2000, representing a 75° eastward shift from its long-term drift direction. The past 115 years have seen unequivocal evidence for a quasi-decadal periodicity, and these motions persist throughout the recent record of pole position, in spite of the new drift direction. We analyze space geodetic and satellite gravimetric data for the period 2003–2015 to show that all of the main features of polar motion are explained by global-scale continent-ocean mass transport. The changes in terrestrial water storage (TWS) and global cryosphere together explain nearly the entire amplitude (83 ± 23%) and mean directional shift (within 5.9° ± 7.6°) of the observed motion. We also find that the TWS variability fully explains the decadal-like changes in polar motion observed during the study period, thus offering a clue to resolving the long-standing quest for determining the origins of decadal oscillations. This newly discovered link between polar motion and global-scale TWS variability has broad implications for the study of past and future climate."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on February 08, 2018, 09:43:21 PM
While I am not a scientist, the fact that the linked reference associates climate change with a Cambrian true wander event and associated changes in the paleomagnetic data, indicates to me that qualified scientist should model what impacts that abrupt sea level rise this century would have on both Earth's rotational and magnetic axes:

Wen-Jun Jiao et al. (16 January 2018", "Paleomagnetism of a well-dated marine succession in South China: A possible Late Cambrian true polar wander (TPW)", Physics of the Earth and Planetary Interiors, https://doi.org/10.1016/j.pepi.2018.01.009

https://www.sciencedirect.com/science/article/pii/S0031920117301905

Abstract: "The Cambrian true polar wander (TPW) hypothesis remains controversial largely because of the uncertainties in the quality and/or fidelity of the paleomagnetic data as well as their chronological control. Testing the TPW hypothesis requires high-quality paleomagnetic data of sufficient spatial and temporal resolutions. Here, we present paleomagnetic results of a continuous Cambrian shallow marine succession from South China where available detailed biostratigraphy provides exceptional chronological constraints. Forty-three sites of paleomagnetic samples were collected from this limestone-dominated succession. Stepwise thermal demagnetization generally reveals three-component magnetizations. Low- and intermediate-temperature components can be cleaned by ∼330°C, and the high-temperature component (HTC) was isolated typically from ∼350 to ∼450°C. A positive fold test and the presence of reversed polarity in the strata, together with rock magnetic data as well as the scanning electron microscopic (SEM) and transmission electron microscopic (TEM) results, collectively suggest that the HTCs are likely primary. A directional shift of the HTCs occurs between the lower-middle Cambrian and the upper Cambrian strata in the succession and is tentatively interpreted to indicate a ∼57° polar wander from ∼500.5 to 494 Ma. Because the rate of polar wander is too fast to be a tectonic origin, this polar wander is interpreted to represent a Late Cambrian TPW. This TPW appears coeval with the Steptoean positive carbon isotope excursion (SPICE) and the major trilobite mass extinctions, suggesting a potential link between the TPW and the Late Cambrian biotic and climatic changes. Because the proposed TPW event is exceptionally well-dated, it should be testable through examination of other worldwide sections."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: gerontocrat on February 08, 2018, 10:14:35 PM
And on the way to a reversal of poles, some scientists have said the magnetic field will do a polar vortex, i.e. weaken and become erratic. Bad news for our electro-magnetic society when a solar storm hits it.

(No source - dredged up from a rusty filing cabinet in the brain from a long time ago at Uni when plate tectonics was still just a hypothesis and these flipflops played a big part to prove it).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on February 09, 2018, 09:35:14 PM
I thought that I would offer the following comments and associated images regarding ECS in our warming world:

1.  The first image shows calculated values of inferred ECS with latitude based on recent surface temperature observations (and thus do not include slow response contributions.  Things to note include: a. the inferred ECS near the North Pole is approximately 4.2C; b. the inferred ECS over the Southern Ocean is around 1.3C because Antarctic ice shelves have lost so much ice mass that they are already activating Hansen's ice-climate feedback mechanism, and c. the inferred ECS over most of Antarctica is around 2.5C, which is much less than that for the Arctic because of the relatively high surface elevation for most of Antarctica; which will change is the WAIS collapses.

2. The second image shows paleo values for Gain (in 'C per W/sq-m') compared to the AR5 likely range for these values vs frequency (in cycles/year).  This shows both that the IPCC is highlighting linear response for what is a highly non-linear behavior and that long/fat tailed events (like freshwater hosing events) can have Gain values that are 2.5 times higher than assumed by the IPCC; which translates into higher than recognized resists for mankind.

3. The third image shows how the product of the frequency PDF for bad events times the expected magnitude of such bad events results in maximum risk towards 65% to 75% confidence level for the PDF.  This means that policy makers should be working with the upper end of expected ECS range rather than with mean or mode values.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: steve s on February 10, 2018, 01:59:28 AM
"ECS" refers to what?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Bruce Steele on February 10, 2018, 04:24:54 AM
Equilibrium Climate Sensitivity - ECS

https://www.skepticalscience.com/climate-sensitivity-advanced.htm

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: FishOutofWater on February 10, 2018, 05:00:27 AM
Sea level rise is already slowing the earth's rate of rotation.

http://www.climatecentral.org/news/glacial-melt-slowing-of-earths-rotation-19843

To get the rotational pole to wander there must be differential rotation of the crust, mantle and/or core. Angular momentum of the earth moon system is conserved. Over long periods of time tides slow earth's rotation and the rotational energy is transferred to the moon.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on March 14, 2018, 11:02:03 PM
If the findings of the linked reference are correct then "chain-reactions of fast draining lakes" could threaten the stability of key portions of Greenland's ice sheet over the coming 50 years:

Poul Christoffersen et al, Cascading lake drainage on the Greenland Ice Sheet triggered by tensile shock and fracture, Nature Communications (2018). DOI: 10.1038/s41467-018-03420-8

http://www.nature.com/articles/s41467-018-03420-8

Abstract: "Supraglacial lakes on the Greenland Ice Sheet are expanding inland, but the impact on ice flow is equivocal because interior surface conditions may preclude the transfer of surface water to the bed. Here we use a well-constrained 3D model to demonstrate that supraglacial lakes in Greenland drain when tensile-stress perturbations propagate fractures in areas where fractures are normally absent or closed. These melt-induced perturbations escalate when lakes as far as 80 km apart form expansive networks and drain in rapid succession. The result is a tensile shock that establishes new surface-to-bed hydraulic pathways in areas where crevasses transiently open. We show evidence for open crevasses 135 km inland from the ice margin, which is much farther inland than previously considered possible. We hypothesise that inland expansion of lakes will deliver water and heat to isolated regions of the ice sheet’s interior where the impact on ice flow is potentially large."

See also:

Title: "Chain reaction of fast-draining lakes poses new risk for Greenland ice sheet"

https://phys.org/news/2018-03-chain-reaction-fast-draining-lakes-poses.html

Extract: "A growing network of lakes on the Greenland ice sheet has been found to drain in a chain reaction that speeds up the flow of the ice sheet, threatening its stability."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Adam Ash on March 15, 2018, 10:49:06 AM
Comparing the size of the heat sinks represented by the main ice masses:
Arctic              25,600 cu km (mid winter)
Greenland   2,850,000 cu km
Antarctic  26,500,000 cu km

So Arctic peak winter ice volume is about 1% of Greenland's, and Greenland's is 10% of Antarctica's.  Thus the heat which disposes of most of the Arctic's ice in summer, is having a significant input to Greenland's ice mass too.  The less Arctic ice there is, the more the heat goes into the Greenland heat sink, and the adjacent ocean. 

Its kinda the inverse of a scheme to pay off debts.  Pay off the smallest first, then there is much more to pay off the next.  Get rid of Arctic ice, then with that job done that heat will hit Greenland hard.  Hanson's exponential rate of change of SLR becomes more likely every day.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Neven on March 15, 2018, 10:57:35 AM
Hansen, James Hansen.

This is Hanson:

https://www.youtube.com/watch?v=NHozn0YXAeE
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: FishOutofWater on March 15, 2018, 03:31:50 PM
Whoa, Neven, the sea ice has been restored and we're back in the '90s. Kids having innocent fun. These days kids here are acting like adults and the adults are acting like kids.

These are dizzying times. It's so hard to get a handle on the rates of change and the probabilities of extreme events like rapid sea level rise. I wish we could retreat to the innocence of that video but we can't.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on March 15, 2018, 03:52:00 PM
... However, my general point is that a some portion of the changes in the magnetic pole can be associated with changes in the rotational pole (the attached image illustrates how fast this is currently changing), due to changes in the magma flow associated with ice mass redistribution.  Furthermore, my point is that due to the current exceptionally high rate of anthropogenic forcing and the bipolar seesaw mechanism that possible abrupt changes in ice mass loss can make faster changes in tectonic behavior than observed in the paleorecord.

https://forum.arctic-sea-ice.net/index.php/topic,2205.50.html

ASLR"

The first image shows the southern supercontinent Gondwana about 183million year ago at the point of the initial breakup of the supercontinent.  The second image highlights the Euler geometry of hexagons and pentagons bounded by the supercontinent rupture lines that define the lines of minimum energy required to break apart the supercontinent.  These two images illustrate the origins of the area known as the South Atlantic Anomaly – an expanse of the field currently stretching from Chile to Zimbabwe, as discussed in the reference linked (and the last two images) below.  The Hare et al. (2018) linked open access reference indicates that this region is likely a key area of the Earth core-mantle boundary that is likely in the process of triggering a flip in the Earth's magnetic poles.

Vincent J. Hare et al. (15 February 2018), "New Archeomagnetic Directional Records From Iron Age Southern Africa (ca. 425–1550 CE) and Implications for the South Atlantic Anomaly", GRL, DOI: 10.1002/2017GL076007

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076007/full

Abstract: "The paucity of Southern Hemisphere archeomagnetic data limits the resolution of paleosecular variation models. At the same time, important changes in the modern and historical field, including the recent dipole decay, appear to originate in this region. Here a new directional record from southern Africa is presented from analysis of Iron Age (ca. 425–1550 CE) archeological materials, which extends the regional secular variation curve back to the first millennium. Previous studies have identified a period of rapid directional change between 1225 and ∼1550 CE. The new data allow us to identify an earlier period of relatively rapid change between the sixth and seventh centuries CE. Implications for models of recurrent flux expulsion at the core-mantle boundary are discussed. In addition, we identify a possible relationship of changes recorded in these African data with archeomagnetic jerks."

See also:

Title: "A Mysterious Anomaly Under Africa Is Radically Weakening Earth's Magnetic Field"

https://www.sciencealert.com/something-mysterious-under-southern-africa-dramatically-weakening-earth-s-magnetic-field-south-atlantic-anomaly

Extract: "This could be precursor to Earth's poles swapping places.

The region that concerns scientists the most at the moment is called the South Atlantic Anomaly – a huge expanse of the field stretching from Chile to Zimbabwe. The field is so weak within the anomaly that it's hazardous for Earth's satellites to enter it, because the additional radiation it's letting through could disrupt their electronics.

… the artefacts revealed that the weakening in the South Atlantic Anomaly isn't a standalone phenomenon of history.

Similar fluctuations occurred in the years 400-450 CE, 700-750 CE, and 1225-1550 CE – and the fact that there's a pattern tells us that the position of the South Atlantic Anomaly isn't a geographic fluke.

"We're getting stronger evidence that there's something unusual about the core-mantel boundary under Africa that could be having an important impact on the global magnetic field," Tarduno says.

The current weakening in Earth's magnetic field – which has been taking place for the last 160 years or so – is thought to be caused by a vast reservoir of dense rock called the African Large Low Shear Velocity Province, which sits about 2,900 kilometres (1,800 miles) below the African continent.

"It is a profound feature that must be tens of millions of years old," the researchers explained in The Conversation last year.

"While thousands of kilometres across, its boundaries are sharp."

This dense region, existing in between the hot liquid iron of Earth's outer core and the stiffer, cooler mantle, is suggested to somehow be disturbing the iron that helps generate Earth's magnetic field.

There's a lot more research to do before we know more about what's going on here.

As the researchers explain, the conventional idea of pole reversals is that they can start anywhere in the core – but the latest findings suggest what happens in the magnetic field above us is tied to phenomena at special places in the core-mantle boundary."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on March 15, 2018, 10:42:34 PM
The very generation of earths magnetic field is poorly understood. Magnetic pole reversal is even less well understood. The impact of changing tectonics in response to ice unloading is also poorly understood and it's influence on magnetic field generation is not understood at all.  I am aware of no literature suggesting that ice unloading will cause magnetic pole reversal, and i consider the notion quite farfetched.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on March 16, 2018, 12:34:17 AM
While glaciovolcanism (defined as “the interactions of magma with ice in all its forms, including snow, firn and any meltwater”), may still be in its infancy; nevertheless, I provide the following links to relevant information (& two images about geomagnetism), and I note that there is more information in the 'Antarctic Tectonics' thread in the Antarctic folder; for those who are interested in learning more about this topic:

J.L. Smellie (2018), "Chapter 10 – Glaciovolcanism: A 21st Century Proxy for Palaeo-Ice",
Past Glacial Environments (Second Edition), Pages 335–375, https://doi.org/10.1016/B978-0-08-100524-8.00010-5

https://www.sciencedirect.com/science/article/pii/B9780081005248000105

Abstract: "Glaciovolcanism is a young science that has undergone a major transformation during the last 15 years. It is important for a variety of reasons but it is set to play a major role in deriving critical parameters of past ice sheets and thus greatly improve the accuracy of their reconstruction. Glaciovolcanic studies can deduce a wider range of parameters than any other methodology currently existing, including: establishing the presence of ice, its age, ice thickness, ice surface elevation, and basal thermal regime. These attributes can be acquired routinely for many glaciovolcanic sequences and, uniquely, several are quantifiable. Most glaciovolcanic terrains provide punctuated rather than continuous records of the coeval ice sheet, i.e., with numerous time gaps. Despite the gaps, glaciovolcanic studies of ice sheets have been completed successfully in the three major glaciovolcanic regions of the Earth: mainly Antarctica, but also Iceland and British Columbia (Canada). Future studies in these and other glaciovolcanic regions will considerably improve our knowledge of Earth’s water inventory and contribute to a better understanding of past ice dynamics and the impact of the cryosphere on global climate."

&

Title: "Antarctic Glaciovolcanism:

https://www2.le.ac.uk/departments/geology/people/smellie-jl/personal/ant-glaciovolc

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on March 16, 2018, 07:32:29 PM
The linked articles confirm that not only are the Earth's rotation poles wandering rapidly, but so are its magnetic poles:

Title: "Shifting Ice Caps - Magnetic Poles and Ice Caps move in Tandem"

https://planet-earth-2017.com/wandering-poles/

Extract: "“The rate of the magnetic pole’s movement has increased in the last  century compared with fairly steady movement in the previous four centuries”, said Joseph Stoner and the Oregon researchers."

See also:

Title: "Magnetic north pole drifting fast"

http://news.bbc.co.uk/2/hi/science/nature/4520982.stm

Extract: " The Earth's north magnetic pole is drifting away from North America so fast that it could end up in Siberia within 50 years, scientists have said."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on March 31, 2018, 12:38:36 PM

The first image shows the southern supercontinent Gondwana about 183million year ago at the point of the initial breakup of the supercontinent.  The second image highlights the Euler geometry of hexagons and pentagons bounded by the supercontinent rupture lines that define the lines of minimum energy required to break apart the supercontinent.  These two images illustrate the origins of the area known as the South Atlantic Anomaly – an expanse of the field currently stretching from Chile to Zimbabwe, as discussed in the reference linked (and the last two images) below.  The Hare et al. (2018) linked open access reference indicates that this region is likely a key area of the Earth core-mantle boundary that is likely in the process of triggering a flip in the Earth's magnetic poles.

Vincent J. Hare et al. (15 February 2018), "New Archeomagnetic Directional Records From Iron Age Southern Africa (ca. 425–1550 CE) and Implications for the South Atlantic Anomaly", GRL, DOI: 10.1002/2017GL076007

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076007/full

Abstract: "The paucity of Southern Hemisphere archeomagnetic data limits the resolution of paleosecular variation models. At the same time, important changes in the modern and historical field, including the recent dipole decay, appear to originate in this region. Here a new directional record from southern Africa is presented from analysis of Iron Age (ca. 425–1550 CE) archeological materials, which extends the regional secular variation curve back to the first millennium. Previous studies have identified a period of rapid directional change between 1225 and ∼1550 CE. The new data allow us to identify an earlier period of relatively rapid change between the sixth and seventh centuries CE. Implications for models of recurrent flux expulsion at the core-mantle boundary are discussed. In addition, we identify a possible relationship of changes recorded in these African data with archeomagnetic jerks."

See also:

Title: "A Mysterious Anomaly Under Africa Is Radically Weakening Earth's Magnetic Field"

https://www.sciencealert.com/something-mysterious-under-southern-africa-dramatically-weakening-earth-s-magnetic-field-south-atlantic-anomaly

Extract: "This could be precursor to Earth's poles swapping places.

The region that concerns scientists the most at the moment is called the South Atlantic Anomaly – a huge expanse of the field stretching from Chile to Zimbabwe. The field is so weak within the anomaly that it's hazardous for Earth's satellites to enter it, because the additional radiation it's letting through could disrupt their electronics.

… the artefacts revealed that the weakening in the South Atlantic Anomaly isn't a standalone phenomenon of history.

Similar fluctuations occurred in the years 400-450 CE, 700-750 CE, and 1225-1550 CE – and the fact that there's a pattern tells us that the position of the South Atlantic Anomaly isn't a geographic fluke.

"We're getting stronger evidence that there's something unusual about the core-mantel boundary under Africa that could be having an important impact on the global magnetic field," Tarduno says.

The current weakening in Earth's magnetic field – which has been taking place for the last 160 years or so – is thought to be caused by a vast reservoir of dense rock called the African Large Low Shear Velocity Province, which sits about 2,900 kilometres (1,800 miles) below the African continent.

"It is a profound feature that must be tens of millions of years old," the researchers explained in The Conversation last year.

"While thousands of kilometres across, its boundaries are sharp."

This dense region, existing in between the hot liquid iron of Earth's outer core and the stiffer, cooler mantle, is suggested to somehow be disturbing the iron that helps generate Earth's magnetic field.

There's a lot more research to do before we know more about what's going on here.

As the researchers explain, the conventional idea of pole reversals is that they can start anywhere in the core – but the latest findings suggest what happens in the magnetic field above us is tied to phenomena at special places in the core-mantle boundary."

It may (or may not) be a coincidence that a tectonic fissure has recently formed in south-western Kenya, in an area close to the recently identified weakening of the Earth's geomagnetic fields ???:

Title: "Large crack in East African Rift is evidence of continent splitting in two"

https://www.the-star.co.ke/news/2018/03/31/large-crack-in-east-african-rift-is-evidence-of-continent-splitting-in_c1739076

Extract: "A large crack, stretching several kilometres, made a sudden appearance recently in south-western Kenya. The tear, which continues to grow, caused part of the Nairobi-Narok highway to collapse and was accompanied by seismic activity in the area.
...
The East African Rift is unique in that it allows us to observe different stages of rifting along its length. To the south, where the rift is young, extension rates are low and faulting occurs over a wide area. Volcanism and seismicity are limited.

Towards the Afar region, however, the entire rift valley floor is covered with volcanic rocks. This suggests that, in this area, the lithosphere has thinned almost to the point of complete break up. When this happens, a new ocean will begin forming by the solidification of magma in the space created by the broken-up plates. Eventually, over a period of tens of millions of years, seafloor spreading will progress along the entire length of the rift. The ocean will flood in and, as a result, the African continent will become smaller and there will be a large island in the Indian Ocean composed of parts of Ethiopia and Somalia, including the Horn of Africa."

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Daniel B. on March 31, 2018, 02:53:37 PM
I guess it is possible that the fissure was responsible for the weakening.  We would need to seek out someone better knowledgeable in this area.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on March 31, 2018, 06:59:35 PM

The crack is probably the continuing extension of east African Rift system and thinning of the lithosphere the 'crack' is just the latest brittle fault that represents the continuing plate movement. The development of this rift system has been understood for at least 20 years, and has been going on for 10s of millions of years (the red sea is an extension of African plate boundary, Somalia I believe, is considered to be on its own plate)

There may be a relationship between the plate movement (essentially the top of mantle convection cells) and the deep mantle structure, but spreading is happening in may other places (the gulf of California is somewhat analogous to the red sea), and is just part of the normal tectonic cycle. My best guess is that the two aren't casual.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: salbers on April 02, 2018, 12:24:50 AM
As I mentioned elsewhere, a recent PNAS paper shows SLR is accelerating at .08mm/yr^2. One can look at the doubling time of each component and there we see Antarctic Ice Sheets have a relatively low contribution now, though the shortest doubling time, on the order of 6 years. The overall doubling rate of the rise is roughly 35 years.

http://www.pnas.org/content/early/2018/02/06/1717312115

And GRACE data shows the more specific acceleration of the Antarctic Ice Sheets.

Comparing the size of the heat sinks represented by the main ice masses:
Arctic              25,600 cu km (mid winter)
Greenland   2,850,000 cu km
Antarctic  26,500,000 cu km

So Arctic peak winter ice volume is about 1% of Greenland's, and Greenland's is 10% of Antarctica's.  Thus the heat which disposes of most of the Arctic's ice in summer, is having a significant input to Greenland's ice mass too.  The less Arctic ice there is, the more the heat goes into the Greenland heat sink, and the adjacent ocean. 

Its kinda the inverse of a scheme to pay off debts.  Pay off the smallest first, then there is much more to pay off the next.  Get rid of Arctic ice, then with that job done that heat will hit Greenland hard.  Hanson's exponential rate of change of SLR becomes more likely every day.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on April 11, 2018, 12:30:05 AM
The linked open access reference is highly relevant to Hansen's ice-climate feedback mechanism, as an abrupt collapse of key WAIS marine glaciers, would increase ocean temperatures at key Greenland marine-terminating glaciers via the bipolar seesaw:

Tabone, I., Blasco, J., Robinson, A., Alvarez-Solas, J., and Montoya, M.: The sensitivity of the Greenland Ice Sheet to glacial–interglacial oceanic forcing, Clim. Past, 14, 455-472, https://doi.org/10.5194/cp-14-455-2018, 2018.

https://www.clim-past.net/14/455/2018/

Abstract. Observations suggest that during the last decades the Greenland Ice Sheet (GrIS) has experienced a gradually accelerating mass loss, in part due to the observed speed-up of several of Greenland's marine-terminating glaciers. Recent studies directly attribute this to warming North Atlantic temperatures, which have triggered melting of the outlet glaciers of the GrIS, grounding-line retreat and enhanced ice discharge into the ocean, contributing to an acceleration of sea-level rise. Reconstructions suggest that the influence of the ocean has been of primary importance in the past as well. This was the case not only in interglacial periods, when warmer climates led to a rapid retreat of the GrIS to land above sea level, but also in glacial periods, when the GrIS expanded as far as the continental shelf break and was thus more directly exposed to oceanic changes. However, the GrIS response to palaeo-oceanic variations has yet to be investigated in detail from a mechanistic modelling perspective. In this work, the evolution of the GrIS over the past two glacial cycles is studied using a three-dimensional hybrid ice-sheet–shelf model. We assess the effect of the variation of oceanic temperatures on the GrIS evolution on glacial–interglacial timescales through changes in submarine melting. The results show a very high sensitivity of the GrIS to changing oceanic conditions. Oceanic forcing is found to be a primary driver of GrIS expansion in glacial times and of retreat in interglacial periods. If switched off, palaeo-atmospheric variations alone are not able to yield a reliable glacial configuration of the GrIS. This work therefore suggests that considering the ocean as an active forcing should become standard practice in palaeo-ice-sheet modelling.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on April 14, 2018, 06:47:38 PM
As bad as the linked article about a potential collapse of the Atlantic overturning circulation sounds, just consider that the article does not even talk about the impacts of the bipolar seesaw and a potential collapse of the WAIS this century, on the ocean current conveyor belt:

Title: "Avoid Gulf stream disruption at all costs, scientists warn"

https://www.theguardian.com/environment/2018/apr/13/avoid-at-all-costs-gulf-streams-record-weakening-prompts-warnings-global-warming

Extract: "Serious disruption to the Gulf Stream ocean currents that are crucial in controlling global climate must be avoided “at all costs”, senior scientists have warned. The alert follows the revelation this week that the system is at its weakest ever recorded.

Past collapses of the giant network have seen some of the most extreme impacts in climate history, with western Europe particularly vulnerable to a descent into freezing winters. A significantly weakened system is also likely to cause more severe storms in Europe, faster sea level rise on the east coast of the US and increasing drought in the Sahel in Africa.

The new research worries scientists because of the huge impact global warming has already had on the currents and the unpredictability of a future “tipping point”."

Edit, see also:

Title: "Stronger evidence for a weaker Atlantic overturning circulation"

http://www.realclimate.org/index.php/archives/2018/04/stronger-evidence-for-a-weaker-atlantic-overturning-circulation/
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on April 24, 2018, 06:08:05 PM
While the two attached images are not from the linked research, the first image (from 2000 Richard Alley data for Greenland) illustrates how quickly temperatures warmed in Greenland 15,000 kya; while the second image should how 14,700 to 13,5000 kya the subsequent Meltwater pulse 1A rapidly drove-up sea level (& I note that Meltwater pulse 1A appears to have been triggered by a collapse of portions of the Pine Island embayment marine glacier, see the last link about Meltwater pulse 1A).  This paleo-data illustrates how rapidly the bipolar seesaw can change global climate, and I note that we appear to be entering a parallel phase of bipolar seesaw, with rapidly shifting North Atlantic (see the immediate previous post) and North Pacific ocean circulation patterns, and with the PIG and Thwaites marine glaciers at risk of rapidly collapsing due to associated changes in local ocean circulation patterns:

Title: "Shift in ocean circulation triggered the end of the last ice age"

https://www.upi.com/Shift-in-ocean-circulation-triggered-the-end-of-the-last-ice-age/8381524574301/

Extract: ""This gives us an example of the way that different parts of the climate system are connected, so that changes in circulation in one region can drive changes in CO2 and oxygen all the way over on the other side of the planet," researcher Will Gray said.

The end of the last ice age was precipitated by a shift in the circulation of the North Pacific Ocean some 15,000 years ago.

Scientists modeled the ancient shifts in circulation and ocean-atmosphere gas exchange by measuring the chemical composition of foraminifera, the tiny fossil shells left behind by plankton. Their analysis -- published this week in the journal Nature Geoscience -- revealed an uptick in the amount of CO2 released by the North Pacific beginning 15,000 years ago. Previous studies have found evidence of shifting circulation patterns in the Atlantic at roughly the same time.

Earlier this month, another group of researchers published a study showing the Atlantic's circulation is slowing down. Scientists suggest a slowdown could significantly alter climate patterns across the globe.

"In our study we see very rapid changes in the climate of the North Pacific that we think are linked to past changes in ocean currents in the Atlantic," lead researcher Will Gray, an environmental scientist at St. Andrews, said in a news release. "This gives us an example of the way that different parts of the climate system are connected, so that changes in circulation in one region can drive changes in CO2 and oxygen all the way over on the other side of the planet.""

See also:

Gray et al. (2018), "Deglacial upwelling, productivity and CO₂ outgassing in the North Pacific Ocean", Nature Geoscience, doi: 10/1038/s4156-018-0108-6

https://www.nature.com/articles/s41561-018-0108-6

&

Title: "Meltwater pulse 1A"

https://en.wikipedia.org/wiki/Meltwater_pulse_1A
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on April 26, 2018, 10:22:43 PM
The linked 2008 Editor's Note, discusses the 'John Mercer effect' that "… stands for the fact that scientists (in this case glaciologists) are wary of being similarly characterized as alarmists, particularly because of the impact that this may have on future funding."  This is due to what " … Rachel Carson called "the gods of profit and production", and it will likely lead to a "Climate Catastrophe":

https://list.uvm.edu/cgi-bin/wa?A3=ind0802&L=SCIENCE-FOR-THE-PEOPLE&E=0&P=163360&B=--%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D_-1010152671%3D%3D_ma%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D&T=text%2Fhtml;%20charset=us-ascii

Extract: "Twenty years ago climatologist James Hansen of NASA's Goddard Institute of Space Studies, widely considered to be the world's leading authority on global warming, first brought the issue into the public spotlight in testimony before the U.S. Congress. Recently, Hansen published an article entitled "Climate Catastrophe" in the New Scientist (July 28, 2007), http://www.newscientist.com. There he presented evidence suggesting that under "business as usual," in which greenhouse gas emissions continue to increase unchecked, a rise in sea level by several meters during the present century due to the melting of polar ice sheets is a "near certainty."

A sea level rise of this extent (up to five meters or sixteen feet) would mean the loss of land areas on which much of the earth's population lives at present (10 percent of the world's population live less than ten meters above the mid-tide sea level.). Yet, most scientists, even glaciologists, still downplay the full extent of the danger, failing to acknowledge probable nonlinear processes associated with climate change, and are especially reticent when it comes to making public statements in that regard.

Why? Hansen calls this the "John Mercer effect." In the 1970s John Mercer, a glaciologist at Ohio State University's Institute of Polar Studies, drew attention to the West Antarctic Ice Sheet, which is separated from the bulk of Antarctica by a mountain range. Ice shelves floating on its rim put it in a delicate balance so that global warming, Mercer claimed, could within a mere forty years cause it to disintegrate and slide into the sea, raising the sea level by five meters.

Other glaciologists looked into Mercer's model and decided based on the data collected that what he described could indeed happen. But most climatologists and geologists publicly dismissed the idea that an ice sheet as big as Mexico could disintegrate in less than a few centuries (Spencer R. Weart, The Discovery of Global Warming, pp. 79-80). According to Hansen, although it was not obvious at the time whether Mercer or his critics were correct, "researchers who suggested that his paper was alarmist were regarded as more authoritative." Hansen believes that Mercer lost funding opportunities as a result. This discouraged other scientists from speaking out.

The John Mercer Effect then stands for the fact that scientists (in this case glaciologists) are wary of being similarly characterized as alarmists, particularly because of the impact that this may have on future funding. "Scientists downplaying the dangers of climate change [or other threats to the status quo] fare better when it comes to getting funding." Hansen points to his own experience. In 1981, based on the first reliable estimates of average global temperature by NASA, he pointed to the dangers of global warming from fossil fuel use. The result: his research group had some of its funding pulled by the Department of Energy, which specifically criticized aspects of that paper. Hansen argues that such economic/funding constraints have the effect of inhibiting scientific criticisms of the status quo: "I believe there is pressure on scientists to be conservative." To be sure, scientists are trained to be skeptics, but "excessive caution also holds dangers. 'Scientific reticence' can hinder communication with the public about the dangers of global warming. We may rue reticence if it means no action is taken until it is too late to prevent future disasters."

Hansen's description of the John Mercer Effect reflects the way in which a system devoted to what Rachel Carson called "the gods of profit and production" (see the Review of the Month in this issue) constrains scientists (along with everyone else), whenever issues arise that potentially threaten the vested interests-even when it is a question of protecting human life and the planetary environment. In the United States, where so much of the scientific funding comes from the Pentagon and the large corporations, the John Mercer Effect is especially strong in limiting what scientists are willing to say and do. As Richard Levins and Richard Lewontin have written "the irrationalities of a scientifically sophisticated world come not from failure of intelligence but from the persistence of capitalism, which as a by-product also aborts human intelligence" (Dialectical Biologist, p. 208; see also their Biology Under the Influence [Monthly Review Press, 2007])."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on April 26, 2018, 11:01:30 PM
I replied to the previous message at

https://forum.arctic-sea-ice.net/index.php/topic,1053.msg151925.html#msg151925

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on April 27, 2018, 01:03:36 AM
The linked reference provides a current, limited-scale, real-world example of Hansen's ice-climate feedback.

Alessandro Silvano et al. (18 Apr 2018), "Freshening by glacial meltwater enhances melting of ice shelves and reduces formation of Antarctic Bottom Water", Science Advances, Vol. 4, no. 4, eaap9467, DOI: 10.1126/sciadv.aap9467

http://advances.sciencemag.org/content/4/4/eaap9467

Extract: "Strong heat loss and brine release during sea ice formation in coastal polynyas act to cool and salinify waters on the Antarctic continental shelf. Polynya activity thus both limits the ocean heat flux to the Antarctic Ice Sheet and promotes formation of Dense Shelf Water (DSW), the precursor to Antarctic Bottom Water. However, despite the presence of strong polynyas, DSW is not formed on the Sabrina Coast in East Antarctica and in the Amundsen Sea in West Antarctica. Using a simple ocean model driven by observed forcing, we show that freshwater input from basal melt of ice shelves partially offsets the salt flux by sea ice formation in polynyas found in both regions, preventing full-depth convection and formation of DSW. In the absence of deep convection, warm water that reaches the continental shelf in the bottom layer does not lose much heat to the atmosphere and is thus available to drive the rapid basal melt observed at the Totten Ice Shelf on the Sabrina Coast and at the Dotson and Getz ice shelves in the Amundsen Sea. Our results suggest that increased glacial meltwater input in a warming climate will both reduce Antarctic Bottom Water formation and trigger increased mass loss from the Antarctic Ice Sheet, with consequences for the global overturning circulation and sea level rise."

See also:

Title: "One of the most worrisome predictions about climate change may be coming true"

https://bangordailynews.com/2018/04/23/environment/one-of-the-most-worrisome-predictions-about-climate-change-may-be-coming-true/

Extract: "Two years ago, former NASA climate scientist James Hansen and a number of colleagues laid out a dire scenario in which gigantic pulses of fresh water from melting glaciers could upend the circulation of the oceans, leading to a world of fast-rising seas and even superstorms.

Hansen’s scenario was based on a computer simulation, not hard data from the real world, and met with skepticism from a number of other climate scientists. But now, a new oceanographic study appears to have confirmed one aspect of this picture — in its early stages, at least.

The new research, based on ocean measurements off the coast of East Antarctica, shows that melting Antarctic glaciers are indeed freshening the ocean around them. And this, in turn, is blocking a process in which cold and salty ocean water sinks below the sea surface in winter, forming “the densest water on the Earth,” in the words of study lead author Alessandro Silvano, a researcher with the University of Tasmania in Hobart, Australia.

Hansen said that “this study provides a nice small-scale example of processes that we talk about in our paper.”
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on April 29, 2018, 10:50:04 AM
The linked reference finds that:
"… Labrador Sea deep convection and the AMOC have been anomalously weak over the past 150 years or so (since the end of the Little Ice Age, LIA, approximately AD 1850) compared with the preceding 1,500 years.

We suggest that enhanced freshwater fluxes from the Arctic and Nordic seas towards the end of the LIA – sourced from melting glaciers and thickened sea ice that developed earlier in the LIA – weakened Labrador Sea convection and the AMOC.  The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet."

These findings support Hansen's ice-climate feedback mechanism.

Thornalley et al. (2018), "Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years", Nature, doi:10.1038/s41586-018-0007-4

https://www.nature.com/articles/s41586-018-0007-4
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on April 30, 2018, 04:28:24 PM
There is a reason why Thwaites Glacier has been nicknamed the 'doomsday' glacier, and why research institutions keep spending more and more research dollars to study this important marine glacier.

Title: "Penn State researchers join international effort to study Antarctic ‘doomsday’ glacier"

https://stateimpact.npr.org/pennsylvania/2018/04/30/penn-state-researchers-join-international-effort-to-study-antarctic-doomsday-glacier/

Extract: "Researchers from Penn State University will be part of a major, international effort to better understand an Antarctic glacier, dubbed the “doomsday glacier” for its potential to contribute significantly to global sea level rise.

The Thwaites Glacier on the West Antarctic Ice Sheet is about the size of Pennsylvania. The threat of it collapsing is so significant that the National Science Foundation and the United Kingdom’s National Environmental Research Council today announced $25 million in funding for eight research efforts."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on May 07, 2018, 11:38:12 PM
The linked reference provides a mathematical framework for modeling cascading tipping mechanisms resulting in abrupt climate change; and as an illustration of this methodology it provides a conceptual model for coupling the North Atlantic Ocean Overturning Current and the ENSO system in the Pacific.  Consensus climate science should use such a methodology to better evaluate the risks associated with Hansen's ice-climate feedback mechanism:

Dekker, M. M., von der Heydt, A. S., and Dijkstra, H. A.: Cascading transitions in the climate system, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-26, in review, 2018.

https://www.earth-syst-dynam-discuss.net/esd-2018-26/
https://www.earth-syst-dynam-discuss.net/esd-2018-26/esd-2018-26.pdf

Abstract. We provide a theory of cascading tipping, i.e., a sequence of abrupt transitions occurring because a transition in one subsystem changes the background conditions for another subsystem. A mathematical framework of elementary deterministic cascading tipping points in autonomous dynamical systems is presented containing the double-fold, fold-Hopf, Hopf-fold and double-Hopf as most generic cases. Statistical indicators which can be used as early warning indicators of cascading tipping events in stochastic, non-stationary systems are suggested. The concept of cascading tipping is illustrated through a conceptual model of the coupled North Atlantic Ocean – El-Niño Southern Oscillation (ENSO) system, demonstrating the possibility of such cascading events in the climate system.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on May 11, 2018, 05:03:32 PM
The DOE has now released computer code & preliminary results from ACME (Accelerated Climate Model for Energy) while the DOE has renamed the program E3SM (Energy Exascale Earth System Model), and this world's most sophisticated climate model projects that ECS for the rest of this century will be about 5.2C (& this relatively high value is likely attributable to the state-of-the-art way that ACME/E3SM models aerosols and cloud feedback mechanisms).

While some consensus scientists (like Bjorn Stevens) have said that it is difficult to determine whether the ACME findings are any more relevant than other models in the CMIP6 program; I believe that these findings from the world's most advanced ESM warrant the adoptions of the Precautionary Principle, particularly as the ACME results only partially address Hansen's ice-climate feedback mechanism:

Title: "DOE’s maverick climate model is about to get its first test"
doi:10.1126/science.aau0578

http://www.sciencemag.org/news/2018/05/does-maverick-climate-model-about-get-its-first-test

Extract: "In 2017, after President Donald Trump took office and pulled the nation out of the Paris climate accords, DOE dropped "climate" from the project name. The new name, the Energy Exascale Earth System Model (E3SM), better reflects the model's focus on the entire Earth system, says project leader David Bader of Lawrence Livermore National Laboratory in California.
..
One preliminary result, on the climate's sensitivity to carbon dioxide (CO2), will "raise some eyebrows," Bader says. Most models estimate that, for a doubling of CO2 above preindustrial levels, average global temperatures will rise between 1.5°C and 4.5°C. The E3SM predicts a strikingly high rise of 5.2°C, which Leung suspects is due to the way the model handles aerosols and clouds. And like many models, the E3SM produces two bands of rainfall in the tropics, rather than the one seen in nature near the equator.

The first test of the E3SM will be its performance in CMIP6. Nearly three dozen modeling groups, including newcomers from South Korea, India, Brazil, and South Africa, are expected to submit results to the intercomparison between now and 2020."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on May 11, 2018, 07:54:29 PM
" like many models, the E3SM produces two bands of rainfall in the tropics, rather than the one seen in nature near the equator. "

O dear. I had hoped it would do better. But further discussion should probably be i a thread on models, perhaps.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 14, 2018, 12:43:59 AM
Remember that ice mass loss from Antarctica is expected to accelerate nonlinearly with continued global warming, so while the current Antarctic contribution to sea level rise of 0.5mm/y may seem small, when it is increased nonlinearly to 2100, this small value could become big:

Title: "Antarctica’s Ice Sheet Is Melting Three Times Faster Than We Thought"

https://www.thedailybeast.com/antarcticas-ice-sheet-is-melting-three-times-faster-than-we-thought

Extract: "Antarctica’s ice sheet is melting three times faster than previously forecasted, according to a report published Wednesday in the journal Nature by 80 scientists. The team said that the ice sheet is melting so fast that 219 billion tons of ice is pouring into the ocean annually—enough to raise sea levels by a half millimeter per year. Between 1992 and 1997, Antarctica was losing 49 billion times of ice per year; from 2012 to 2017, that number increased more than eightfold, according to the Ice Sheet Mass Balance Inter-comparison Exercise. At this rate of acceleration, scientists warn that oceans would rise faster than ever, which means a reduced amount of time for low-lying communities to prepare adequately. “We’re still talking about roughly a half a millimeter per year,” one scientist told The Washington Post. “That isn’t going to sound horribly unmanageable. But remember for the northern hemisphere, for North America, the fact that the location in West Antarctica is where the action is amplifies that rate of sea level rise by up to an about additional 25 percent in a city like Boston or New York.”"
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 15, 2018, 05:57:33 AM
Recent findings indicate that as the oceans continue to warm the less the oceans will be able to act as a carbon sink for atmospheric CO₂.  This means that the concentration of atmospheric CO₂ will increase faster than previously expected:

Title: "Invisible scum on sea cuts CO2 exchange with air 'by up to 50%'"

https://www.theguardian.com/environment/2018/may/28/invisible-scum-on-sea-cuts-co2-exchange-with-air-by-up-to-50

Extract: "The world’s oceans absorb around a quarter of all man-made carbon dioxide emissions, making them the largest long-term sink of carbon on Earth.

They found surfactants can reduce carbon dioxide exchange by up to 50%.

Dr Ryan Pereira, a Lyell research fellow at Heriot-Watt University in Edinburgh, said: “As surface temperatures rise, so too do surfactants, which is why this is such a critical finding.
“The warmer the ocean surface gets, the more surfactants we can expect, and an even greater reduction in gas exchange.

Rob Upstill-Goddard, professor of marine biogeochemistry at Newcastle University, said: “These latest results build on our previous findings that, contrary to conventional wisdom, large sea surface enrichments of natural surfactants counter the effects of high winds.”"
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 15, 2018, 06:58:03 PM
The linked reference discusses the finding of improved modeling near the Eocene–Oligocene transition (EOT) that are of particular interest for calibrating climate models to including Hansen's ice-climate feedback mechanism (that is highly related to the response of the meridional overturning circulation).  These new finding indicate higher climate sensitivity than projected by earlier (as in those used by AR5) less-sophisticated models.  These findings increase the probability that Hansen's warnings about the risks of abrupt climate change this century are correct:

Hutchinson, D. K., de Boer, A. M., Coxall, H. K., Caballero, R., Nilsson, J., and Baatsen, M.: Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1, Clim. Past, 14, 789-810, https://doi.org/10.5194/cp-14-789-2018, 2018.

https://www.clim-past.net/14/789/2018/

Abstract. The Eocene–Oligocene transition (EOT), which took place approximately 34 Ma ago, is an interval of great interest in Earth's climate history, due to the inception of the Antarctic ice sheet and major global cooling. Climate simulations of the transition are needed to help interpret proxy data, test mechanistic hypotheses for the transition and determine the climate sensitivity at the time. However, model studies of the EOT thus far typically employ control states designed for a different time period, or ocean resolution on the order of 3°. Here we developed a new higher resolution palaeoclimate model configuration based on the GFDL CM2.1 climate model adapted to a late Eocene (38 Ma) palaeogeography reconstruction. The ocean and atmosphere horizontal resolutions are 1°  ×  1.5° and 3°  ×  3.75° respectively. This represents a significant step forward in resolving the ocean geography, gateways and circulation in a coupled climate model of this period. We run the model under three different levels of atmospheric CO2: 400, 800 and 1600 ppm. The model exhibits relatively high sensitivity to CO2 compared with other recent model studies, and thus can capture the expected Eocene high latitude warmth within observed estimates of atmospheric CO2. However, the model does not capture the low meridional temperature gradient seen in proxies. Equatorial sea surface temperatures are too high in the model (30–37 °C) compared with observations (max 32 °C), although observations are lacking in the warmest regions of the western Pacific. The model exhibits bipolar sinking in the North Pacific and Southern Ocean, which persists under all levels of CO2. North Atlantic surface salinities are too fresh to permit sinking (25–30 psu), due to surface transport from the very fresh Arctic ( ∼  20 psu), where surface salinities approximately agree with Eocene proxy estimates. North Atlantic salinity increases by 1–2 psu when CO2 is halved, and similarly freshens when CO2 is doubled, due to changes in the hydrological cycle.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 21, 2018, 09:26:51 PM
Another reason that DeConto & Pollard (2016)'s projection for the loss of the Thwaites ice plug may be too slow, is that they (and essentially all other modelers) have based their estimates of current ice mass loss from the ASE largely on data from the GRACE satellite.  However, the past GRACE data may have been corrected using a conservative estimate of the associated glacial isostatic adjustment, GIA, in this area.

While the linked research, indicating more rapid bedrock uplift in Amundsen Sea Embayment, seems like good news, if one refers to projections from ice sheet models that do not include Pollard's & DeConto's ice cliff and hydrofacturing mechanism and which assume radiative forcing scenarios of RCP 4.5 or less.  However, if one assumes radiative forcing scenarios close to BAU for the next two decades and projections from Pollard & DeConto's recent work, then Barletta et al (2018)'s finding are actually bad news regarding the potential collapse of the WAIS this century.

V.R. Barletta el al. (22 Jun 2018), "Observed rapid bedrock uplift in Amundsen Sea Embayment promotes ice-sheet stability," Science,:
Vol. 360, Issue 6395, pp. 1335-1339, DOI: 10.1126/science.aao1447.

http://science.sciencemag.org/content/360/6395/1335

Abstract
The marine portion of the West Antarctic Ice Sheet (WAIS) in the Amundsen Sea Embayment (ASE) accounts for one-fourth of the cryospheric contribution to global sea-level rise and is vulnerable to catastrophic collapse. The bedrock response to ice mass loss, glacial isostatic adjustment (GIA), was thought to occur on a time scale of 10,000 years. We used new GPS measurements, which show a rapid (41 millimeters per year) uplift of the ASE, to estimate the viscosity of the mantle underneath. We found a much lower viscosity (4 × 1018 pascal-second) than global average, and this shortens the GIA response time scale from tens to hundreds of years. Our finding requires an upward revision of ice mass loss from gravity data of 10% and increases the potential stability of the WAIS against catastrophic collapse.


Title: "Bedrock in West Antarctica rising at surprisingly rapid rate"

https://phys.org/news/2018-06-bedrock-west-antarctica-surprisingly-rapid.html
Extract: "The findings, reported in the journal Science, have surprising and positive implications for the survival of the West Antarctic Ice Sheet (WAIS), which scientists had previously thought could be doomed because of the effects of climate change.

The unexpectedly fast rate of the rising earth may markedly increase the stability of the ice sheet against catastrophic collapse due to ice loss, scientists say.

Moreover, the rapid rise of the earth in this area also affects gravity measurements, which implies that up to 10 percent more ice has disappeared in this part of Antarctica than previously assumed.

Researchers led by scientists at The Ohio State University used a series of six GPS stations (part of the POLENET-ANET array) attached to bedrock around the Amundsen Sea Embayment to measure its rise in response to thinning ice.

The "uplift rate" was measured at up to 41 millimeters (1.6 inches) a year, said Terry Wilson, one of the leaders of the study and a professor emeritus of earth sciences at Ohio State.

In contrast, places like Iceland and Alaska, which have what are considered rapid uplift rates, generally are measured rising 20 to 30 millimeters a year.
"The rate of uplift we found is unusual and very surprising. It's a game changer," Wilson said.

And it is only going to get faster. The researchers estimate that in 100 years, uplift rates at the GPS sites will be 2.5 to 3.5 times more rapid than currently observed.

While modeling studies have shown that bedrock uplift could theoretically protect WAIS from collapse, it was believed that the process would take too long to have practical effects.

"We previously thought uplift would occur over thousands of years at a very slow rate, not enough to have a stabilizing effect on the ice sheet. Our results suggest the stabilizing effect may only take decades," Wilson said.

Wilson said the rapid rise of the bedrock in this part of Antarctica suggests that the geology underneath Antarctica is different from what scientists had previously believed.

Some scientists suggest that WAIS may have passed a tipping point in which ice loss can no longer be stopped, which could be catastrophic, Wilson said. The glaciers there contain enough water to raise global sea levels up to four feet.

The problem is that much of this area of Antarctica is below sea level. Relatively warm ocean water has flowed in underneath the bottom of the ice sheet, causing thinning and moving the grounding line—where the water, ice and solid earth meet—further inland.

The process seemed unstoppable, Wilson said. "But we found feedbacks that could slow or even stop the process."

One important feedback involves "pinning points—elevated features of the earth rising from the surface below the grounding line that pin the ice sheet to solid earth. These pinning points are going up in response to the uplift of the earth and could prevent further retreat of the ice sheet.

Another feedback is lowering sea levels. Massive ice sheets along the ocean have their own gravitational pull and raise the sea level near them. But as the ice thins and retreats, the gravitational pull lessens and the sea level near the coast goes down.

"The lowering of the sea level, the rising of pinning points and the decrease of the inland slope due to the uplift of the bedrock are all feedbacks that can stabilize the ice sheet," Wilson said.

Other researchers had estimated how much the earth would have to rise to protect WAIS given a range of future climate warming scenarios.

Results of this study estimate that the bedrock at the Pine Island Glacier grounding line (which is part of WAIS) will have risen about 8 meters in 100 years. That is about three times higher than values shown by others to reduce run-away retreat in this area.

"Under many realistic climate models, this should be enough to stabilize the ice sheet," Wilson said.

She said while this study delivers some potentially good news for the Amundsen Sea Embayment, that doesn't mean all is well in Antarctica.

"The physical geography of Antarctica is very complex. We found some potentially positive feedbacks in this area, but other areas could be different and have negative feedbacks instead," she said. Regardless of feedbacks, models suggest that the WAIS will collapse if future global warming is large."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on June 21, 2018, 10:03:31 PM
Regardless of ice models, Barletta(2018) is good news. In all cases, faster uplift is a stabilizing force. So i do not agree with the statement that:

"However, if one assumes radiative forcing scenarios close to BAU for the next two decades and projections from Pollard & DeConto's recent work, then Barletta et al (2018)'s finding are actually bad news regarding the potential collapse of the WAIS this century."

Barletta's work shows that bedrock in the Amundsen sea is rising at two to three times the previously estimated rate, and will rise even faster in future. I quote from the paper:

"The extremely low upper mantle viscosity that we constrain supports the possibility of increased stability of the WAIS with respect to previous studies (16, 17). Lower mantle viscosity leads to faster bedrock uplift in response to ice mass loss. Rapidly rising bedrock shallows the ocean at the grounding line and reduces the buoyancy forces experienced by the edge of the ice sheet while reducing the slope of the bed beneath the ice sheet (fig. S3)"

"In 100 years, uplift rates at the GPS sites will be between 2.5 and 3.5 times larger than currently observed (Fig. 3B), and the bedrock at the Pine Island Glacier grounding line will have risen by about 8 m compared to the present (Fig. 3, C and D). This is about three times higher than values shown to reduce runaway ice surface velocities within 100 years (15). The time required to build sufficient deformation to trigger the stabilization effect is much shorter (27) than in (16). Under low and medium climate forcing, with the onset of the stabilization feedback about two times faster (27), the condition for ice-sheet stability and its possible readvance can reasonably be expected to occur much earlier than predicted in previous studies (16, 17). Based on our estimates, it might produce a deformation large enough and early enough in the deglaciation phase to prevent the complete collapse of the WAIS even under strong climate forcing."

The bad news in Barlettta's work is that because of the revised GIA, it turns out that actual ice mass loss over the last few decades is larger than previously thought.

"We thus contend that published GRACE-derived ice mass loss estimates for ASE, for example, ~108 Gt/year (1) (drainage basins of Pine Island and Thwaites and Smith glaciers), are systematically underestimated by between 10.0 and 13.9 Gt/year, which is more than 10% of the total ice mass loss estimate for the ASE."

i attach fig S3.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 21, 2018, 11:39:49 PM
Regardless of ice models, Barletta(2018) is good news. In all cases, faster uplift is a stabilizing force. So i do not agree with the statement that:

"However, if one assumes radiative forcing scenarios close to BAU for the next two decades and projections from Pollard & DeConto's recent work, then Barletta et al (2018)'s finding are actually bad news regarding the potential collapse of the WAIS this century."

Everyone is entitled to their own opinions; and while Barletta et al (2018) can believe that their findings will help to pin Thwaites, their Figure S3 (see first image), looks a rather similar to Rignot et al (2017) for the Thwaites gateway (see second & third images), and I believe that marine cliff failures (see the fourth image from Wise et al (2017), will mean that the suspected pinning point will not be able to stop DeConto & Pollard (2016)'s ice cliff and hydrofracturing from occurring within the next twenty to thirty years:

Yu, H., Rignot, E., Morlighem, M., & Seroussi, H. (2017). Iceberg calving of Thwaites Glacier, West Antarctica: full-Stokes modeling combined with linear elastic fracture mechanics. The Cryosphere, 11(3), 1283, doi:10.5194/tc-11-1283-2017

https://www.the-cryosphere.net/11/1283/2017/tc-11-1283-2017.pdf
https://www.the-cryosphere.net/11/1283/2017/tc-11-1283-2017-assets.html
&
Wise et al. (2017), "Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks", Nature 550, 506-510, doi:10.1038/nature24458

https://www.nature.com/articles/nature24458
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on June 22, 2018, 12:00:52 AM
The associated summary by Langin (doi: 10.1126/science.360.6395.1283 ) in the same issue of Science lays out your both point and mine:

Some extracts from that article:

--
“It may just buy the world a few extra decades,” says Rick Aster

“It’s not a get out of jail free card,” says Ted Scambos, a glaciologist at the National Snow and Ice Data Center in Boulder, Colorado. “It’s more of a refinement on the pace of [ice sheet] collapse,” he says, especially if we continue “stomping on the climate gas pedal.” Ingo Sasgen, a geophysicist at the Alfred Wegener Institute in Bremerhaven, Germany, agrees. “It’s still a rather slow process compared to melting,” he says. “If you have a very strong warming from the ocean, the ice sheet will disintegrate whatever the solid earth does.”
--

I take the Barletta results as good news, since this is the one of the few results that suppress WAIS mass loss rather than enchance it. So the situation is slightly better than I thought.

That summary also references an article in Nature by Kingslake et al. on which i commented earlier:

https://forum.arctic-sea-ice.net/index.php/topic,622.msg159185.html#msg159185

That article looks at GIA as well. But in light of Barletta results, I think they need to revisit their calculations in the Amundsen sector, since the crust beneath is more labile than they assumed. That may explain the lack of skill in that sector.

sidd

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 22, 2018, 03:57:39 AM
I take the Barletta results as good news, since this is the one of the few results that suppress WAIS mass loss rather than enchance it. So the situation is slightly better than I thought.

sidd,

All of your points are well taken, however considerations that might make the situation slight worse than you might (or might not) have been thinking include:

a) The low viscousity of the magma almost certainly means that it is convecting heat upward from the Earth's core faster than previously thought by consensus scientists; which means that the geothermal heat flux through the bedrock is greater, which means that both basal ice melting is higher and that the stiffness of the basal ice is lower.  Both of these factors should increase conventional ice flow.
b) The local Earth's crust is rising because more rock mass is moving into this area from surrounding areas.  This means that as ice mass is lost, the local sea level will not fall as fast as it would have with more viscous magma; which means that there will be more buoyant force on the marine glacier which means it will be less stable.
c) More local Earth movement means more seismic and volcanic activity, both of which reduce ice stability.

Ice sheet models will need to improve considerably before anyone can conclude that we are all safer than consensus scientists thought before this research was available.

Best regards,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Sebastian Jones on June 22, 2018, 05:57:28 AM
Gaia is even more amazing than I thought.  :o
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on June 22, 2018, 06:03:28 PM



sidd,

All of your points are well taken, however considerations that might make the situation slight worse than you might (or might not) have been thinking include:

a) The low viscousity of the magma almost certainly means that it is convecting heat upward from the Earth's core faster than previously thought by consensus scientists; which means that the geothermal heat flux through the bedrock is greater, which means that both basal ice melting is higher and that the stiffness of the basal ice is lower.  Both of these factors should increase conventional ice flow.


This is the asthenosphere, the top part of the mantle where the solidus and the geothermal gradient converge. There isn't necessarily any partial melt (magma), but the viscosity is lower than the upper mantle and the lithosphere (the brittle part of the top of the mantle and the crust). The asthenosphere does flow, and that is where the compensation mechanism for PGR is thought to originate. The ductile flow that is thought to happen as the mechanism for isostatic compensation will not affect mantle convection or necessarily increase or decrease the temperature at the base of the lithosphere. Even if it did the timescales for this change are much greater than the time for ice melt.

Thinning or thickening of the lithosphere can effect the geothermal gradient (e.g. you get volcanic activity at rifts). Melting ice effectively thins the lithosphere, and you get pressure release, but also you change the temperature at the crust/ice boundary. I'm not sure how that would effect the solidus/geothermal gradient, but if you do increase partial melt, again, that will take a long time to effect the surface unless you already have existing magma chambers at high levels in the crust.




Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 23, 2018, 12:03:07 AM
This is the asthenosphere, the top part of the mantle where the solidus and the geothermal gradient converge. There isn't necessarily any partial melt (magma), but the viscosity is lower than the upper mantle and the lithosphere (the brittle part of the top of the mantle and the crust). The asthenosphere does flow, and that is where the compensation mechanism for PGR is thought to originate. The ductile flow that is thought to happen as the mechanism for isostatic compensation will not affect mantle convection or necessarily increase or decrease the temperature at the base of the lithosphere. Even if it did the timescales for this change are much greater than the time for ice melt.

Thinning or thickening of the lithosphere can effect the geothermal gradient (e.g. you get volcanic activity at rifts). Melting ice effectively thins the lithosphere, and you get pressure release, but also you change the temperature at the crust/ice boundary. I'm not sure how that would effect the solidus/geothermal gradient, but if you do increase partial melt, again, that will take a long time to effect the surface unless you already have existing magma chambers at high levels in the crust.

Rox,

Please review the linked pdf, and see if you are interested in revising any of your statements.

Best,
ASLR

Begeman, C. B., Tulaczyk, S. M., & Fisher, A. T. (2017). Spatially variable geothermal heat flux in West Antarctica: Evidence and implications. Geophysical Research Letters, 44. https://doi.org/10.1002/2017GL075579

https://websites.pmc.ucsc.edu/~afisher/CVpubs/pubs/Begeman2017_GRL_AntWGZ-HF.pdf

Abstract Geothermal heat flux (GHF) is an important part of the basal heat budget of continental ice sheets. The difficulty of measuring GHF below ice sheets has directly hindered progress in the understanding of ice sheet dynamics. We present a new GHF measurement from below the West Antarctic Ice Sheet, made in subglacial sediment near the grounding zone of the Whillans Ice Stream. The measured GHF is 88 ± 7 mW m_2, a relatively high value compared to other continental settings and to other GHF measurements along the eastern Ross Sea of 55 mW m_2 and 69 ± 21 mW m_2 but within the range of regional values indicated by geophysical estimates. The new GHF measurement was made ~100 km from the only other direct GHF measurement below the ice sheet, which was considerably higher at 285 ± 80mWm_2, suggesting spatial variability that could be explained by shallow magmatic intrusions or the advection of heat by crustal fluids. Analytical calculations suggest that spatial variability in GHF exceeds spatial variability in the conductive heat flux through ice along the Siple Coast. Accurate GHF measurements and high-resolution GHF models may be necessary to reliably predict ice sheet evolution, including responses to ongoing and future climate change.

Extract: "Current geophysical GHF models underestimate the observed magnitude and spatial variability of GHF, which may be enhanced by magmatism or advection of crustal fluids."

Caption for the first image: "Figure 2. (a) GHF measurements and estimates for West Antarctica (Engelhardt, 2004a; Fisher et al., 2015; Foster, 1978; Fudge et al., 2013) and the western Ross Sea region (Morin et al., 2010, and references therein; Schröder et al., 2011) overlain on ice velocity (Rignot et al., 2011). Grounding line outlined black (Bindschadler et al., 2015). Profile line (A-A0) shown in black. Extent of GHF estimates below Thwaites glacier (THW, dashed line) (Schroeder et al., 2014). (b) Estimates of spatial variability in heat conduction and production along the profile line shown in Figure 2a, as difference from mean conductive heat flux along that profile (79mWm_2). (c) Shear heat flux estimates calculated from ice velocity and associated errors. GHF measurements and estimates close to the profile line are plotted (mean ±1 SE, SLW value lies off axis)."

Caption for the second image: "Figure 3. (a) Analytical model for GHF based on Fox Maule et al. (2005) (black and gray lines) compared with GHF measurements and estimates (blue) as a function of magnetic crustal thickness. The SLW value lies well above the plot. Dotted lines show the envelope of ±15% variation in crustal thermal conductivity from 2.8 W m_1 °C_1. (b) GHF anomaly due to modeled magmatic intrusions with cubic geometry. Intrusion depths are the distance from the surface of the crust to the top of the intrusion. GHF values are the maximum achieved at the surface over the center of the intrusion. Black contours represent mean ±1 SE bounds on GHF at SLW. Gray contours mark the time since emplacement at which the maximum GHF values plotted are achieved. (c) Probability density functions of GHF models for West Antarctica (An=An et al., 2015; FM=Fox Maule et al., 2005; SR=Shapiro & Ritzwoller, 2004) and GHF measurements in the Basin and Range Province, USA, 16% of which exceed 300 mW m_2 (National Geothermal Data System). In Figures 3a and 3c, GHF measurements and estimates for West Antarctica are plotted as mean ±1 SE, where available (references in Figure 2). GHF estimates below Thwaites glacier (THW), shown in Figure 3a, plotted as mean, ±1 SD (solid line), and the full range of THW values (dotted line) which extend off axis to 375 mW m_2 (Schroeder et al., 2014)."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 23, 2018, 12:18:38 AM
With regards to a more specific near-term cryosphere prediction, I predict that in less than 2.5-years, the PIIS and the SW Tributary Ice Shelf will experience a concurrent major calving event (along the intersecting cracks shown in the attached Sentinel-1 image from Nov 28 2017) that will temporarily cause the ice velocities in the SW Tributary Glacier to accelerate.

The attached Sentinel-1 image from June 21, 2018, indicates that the SW Tributary Ice Shelf has already experienced a major calving event, and we will see whether the PIIS experiences a major calving event in the same vicinity within the next year.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on June 23, 2018, 08:00:32 PM

Rox,

Please review the linked pdf, and see if you are interested in revising any of your statements.

Best,
ASLR


To paraphrase the paper "There's magmatic activity in the rift under the ice sheets; it shows up as concentrated hot spots under the ice; it looks like modern rift regimes; models underestimate the special variation and intensity; but we don't have a lot of data; it might be important"

What I wrote was really to correct your first paragraph. Low viscosity magma does not conduct heat from the earths core. Heat is transported from the core by mantle convection, and that is certainly not magma;  It also takes a LONG time, it's about 2500km and it convection is thought to move at 20mm a year. Changes to it are not likely to effect the ice regime in the next 10000 years. I probably should have been more direct and not got into where magma actually forms and how pressure/temperature changes could produce more magma.


Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: FishOutofWater on June 23, 2018, 10:03:26 PM
This paper finds an extremely high heat flow and low viscosity that is best explained by partial melting in the upper mantle. The heat flow is higher than the basin and range which has a low velocity zone and ongoing volcanism. If there's a rapid ice mass loss there will be decompression melting. This could increase volcanic activity as the ice melts as happened during the late Pleistocene in Alaska and Iceland.

This rapid isostatic adjustment is only good news if we stop emitting GHGs. Perhaps, then, the ice would find a new grounding line. If we keep the heat on with GHG emissions this will only add to the melting which we now know is already worse than we thought.

This isostatic adjustment rates found in the study are stunning, but the will not be fast enough to compensate for accelerated melting if we keep our feet on the gas pedal.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 24, 2018, 02:10:27 AM

Rox,

Please review the linked pdf, and see if you are interested in revising any of your statements.

Best,
ASLR


To paraphrase the paper "There's magmatic activity in the rift under the ice sheets; it shows up as concentrated hot spots under the ice; it looks like modern rift regimes; models underestimate the special variation and intensity; but we don't have a lot of data; it might be important"

What I wrote was really to correct your first paragraph. Low viscosity magma does not conduct heat from the earths core. Heat is transported from the core by mantle convection, and that is certainly not magma;  It also takes a LONG time, it's about 2500km and it convection is thought to move at 20mm a year. Changes to it are not likely to effect the ice regime in the next 10000 years. I probably should have been more direct and not got into where magma actually forms and how pressure/temperature changes could produce more magma.

Thank you for the clarifications.  I concur that the main points of concur are the numerous pre-existing concentrated hotspots under the ice, and I also concur with FishOutofWater that if we continue BAU emissions for much longer, the isostatic adjustment rates will not be fast enough to compensate for the other consequences of ice mass loss.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 25, 2018, 09:13:07 PM
After many tens of millions of years of repeated ice sheet collapse, it is not surprising that many of the pre-existing hotspots beneath the WAIS are located in critical areas like underneath the PIG:

Title: "Researchers discover volcanic heat source under major Antarctic glacier"

https://phys.org/news/2018-06-volcanic-source-major-antarctic-glacier.html

Extract: " A researcher from the University of Rhode Island's Graduate School of Oceanography and five other scientists have discovered an active volcanic heat source beneath the Pine Island Glacier in Antarctica.

The scientists conclude by writing: "The magnitude and the variations in the rate of the volcanic heat supplied to the Pine Island Glacier, either by internal magma migration, or by an increase in volcanism as a consequence of ice sheet thinning, may impact the future dynamics of the Pine Island Glacier, during the contemporary period of climate-driven glacial retreat.""

See also:

Brice Loose et al. Evidence of an active volcanic heat source beneath the Pine Island Glacier, Nature Communications (2018). DOI: 10.1038/s41467-018-04421-3

http://www.nature.com/articles/s41467-018-04421-3

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: steve s on June 25, 2018, 11:06:31 PM
Makes me wonder more about what's happening under the Thwaites. Sea ice concentration is much lower near its outflow than by the PIG. From NSIDC  for June 24th:

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: steve s on June 28, 2018, 10:24:37 PM
The Thwaites outflow seems to be increasing, and to be warm! (https://seaice.uni-bremen.de/data/amsr2/today/Antarctic_AMSR2_nic.png), much of the near glacier waters are shown to be ice free - see the close up below.

Given ASLR's latest post, 2 above, perhaps the focus of the research should have been on the Thwaites, not the PIG.

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on June 28, 2018, 10:38:06 PM
The Thwaites outflow seems to be increasing, and to be warm! (https://seaice.uni-bremen.de/data/amsr2/today/Antarctic_AMSR2_nic.png), much of the near glacier waters are shown to be ice free - see the close up below.

Given ASLR's latest post, 2 above, perhaps the focus of the research should have been on the Thwaites, not the PIG.

Per the attached image from Reply #27, the zone of low sea ice concentration that you are referring to may be associated with warm ocean water advecting from the Dotson Ice Shelf.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: steve s on June 28, 2018, 11:39:34 PM
ASLR,

1) The current pattern of melting does not match the heat pattern in the computer generated image of post 27; and
2) I do not remember a similar mid-winter sea ice pattern -- maybe a polynya -- in the past.

But i'm merely an interested amateur, finding it a disturbing coincidence when the nearby land seems to be rising faster than the ice above is melting.   
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Pmt111500 on June 29, 2018, 04:18:38 PM
The Thwaites outflow seems to be increasing, and to be warm! (https://seaice.uni-bremen.de/data/amsr2/today/Antarctic_AMSR2_nic.png), much of the near glacier waters are shown to be ice free - see the close up below.

Given ASLR's latest post, 2 above, perhaps the focus of the research should have been on the Thwaites, not the PIG.



Isn't that the same area than last year? My guess was then it's an upwelling area for northern mid-level waters, and I see no reason to change my highly subjective opinion. Pacification of Ross Sea, or whatever antarctic loop that area was part of. The waters that might have gone Arctic producing BOE.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: steve s on June 29, 2018, 06:44:22 PM
Pmt, I don't have a shot from last year, but I'd like to see one -- or better, a time series. The outflow seems to be more akin to a glacial belch. I've attached a June 3rd close up of the same area -- which shows a full sea ice coverage with the beginning of the melt out starting near the glacier.
 
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: oren on June 29, 2018, 06:57:00 PM
Humanity needs to throw maximum monitoring resources at these two glaciers - buoys, boreholes, under-ice submersibles, and whatever else is physically possible. This is ground zero of abrupt sea level rise. (Apologies to ASLR for plagiarizing the username  ;))
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: solartim27 on June 30, 2018, 05:15:01 PM
I've noticed that iceberg b22a has been moving recently, sort of surprising for the middle of winter.
From the Icebergs thread
My focus is more on West-Antarctica particularly B22a (44X24 nm) which blocks Thwaites Glacier from the open sea. If this beast becomes loose all the icebergs behind can drift out as well.

Here's a recent shot from Polar View, the computer I used to make gifs crashed, and I haven't figured out a good alternate yet.
https://www.polarview.aq/images/105_S1jpgfull/S1B_IW_GRDH_1SSH_20180629T095911_82DD_S_1.final.jpg  (55 Mb)
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on July 30, 2018, 04:44:54 AM
While each individual needs to learn on his/her own how to accept the truth about climate change; nevertheless, presenting the truth about climate trends in Bayesian terms is the most honest way for the media to convey a truth that they only partially understand/accept themselves:

Title: "How Did the End of the World Become Old News?"

http://nymag.com/daily/intelligencer/amp/2018/07/climate-change-wildfires-heatwave-media-old-news-end-of-the-world.html

Extract: "Over the last few days, there has been a flurry of chatter among climate writers and climate scientists, and the climate-curious who follow them, about this failure. In perhaps the most widely parsed and debated Twitter exchange, MSNBC’s Chris Hayes — whose show, All In, has distinguished itself with the seriousness of its climate coverage — described the dilemma facing every well-intentioned person in his spot: the transformation of the planet and the degradation may be the biggest and most important story of our time, indeed of all time, but on television, at least, it has nevertheless proven, so far, a “palpable ratings killer.” All of which raises a very dispiriting possibility, considering the scale of the climate crisis: Has the end of the world as we know it become, already, old news?"
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: VeliAlbertKallio on August 01, 2018, 12:03:12 AM
I have cited sections of this thread in the UK Houses of Parliament evidence on Section "4. The John Mercer Effect: the ‘Forbidden Line’ on Sea Level Rise". Unfortunately, due to the Parliament rules, I could not represent whole text as such but had to abbreviate and leave out few points. I am also rather sad because this was thought by many at one good solution for climate change. :'(

Our Changing Climate in Action: the Risk of Global Warming and the Environmental Damage from the Rising Ocean Water Table | Sustainable Seas Enquiry | Written evidence submitted by Veli Albert Kallio, FRGS (SSI0121) | Ordered to be published 23 May 2018 by the House of Commons.

Abstract:

Recently NATURE published a discussion on construction of sills in attempt to prevent or slow melting glaciers that are discharging ice into the ice fjords. Several further papers promptly followed publication of this essentially erroneous article in a respected NATURE magazine. Here it is pointed out that there is a discrepancy of several magnitudes thus excluding a long-term viability to manage the edges of ice fjords or continental ice shelves/sheets due to a phenomenon known as the mega-erratics. These are blocks of hard rocks that are several kilometres in size that have been dislocated by a warmed and wet edges of glacier/ice sheet/ice shelf. This Parliament evidence points out the error that was not apparent to the peer-reviewers at the time and in subsequent papers that followed. The Parliament was shown evidence that large enough obstacles cannot be possibly made to prevent ice discharges due to a progression of melting, that softens and lubricates glaciers, ice caps and ice sheets. The forces unleashed by the ice front exceeds several magnitudes from the conceived objects that sills were proposed. The only, and very only effect is temporary and limited to prevention of warm water incursion where these methods will work for a while in a cold, dry, and relatively stable ice formations.

Long-term projections suggested to prevent warmed and water-infested glaciers from discharging ice into the ocean cannot be made as the forces of ice exceed many magnitudes of the sills and levies that can be made of concrete blocks, aggregates or other materials. Thus the prevention of sea level rise by this method for centuries or millennia is not functional one and thus the mitigation and prevention of rubbish gyros in ocean, the supply of housing, nuclear and food production security must be looked at as solution by the ocean littoral states. Several examples of various types of risk to the sustainability of oceans have been presented in addition to the above exposed misconception. This comes with much regret as it appears that one 'hoped-for-solution' to manage the future climate change impacts has largely foundered on the issue that the sills cannot be made strong enough to contain most important, warmed glaciers or edges of unstable ice shelves. However, for a short-term this may offer small-scale solutions provided that costs remain sufficiently small. Aggressively melting ice formations with darkened surfaces, wide spread melt water ponds, or water filled crevasses it does not offer much, if any, prolonged ice stability. (The document is best viewed as a .pdf file due to the lay-out of graph and legends.)

https://www.academia.edu/37157851/Our_Changing_Climate_in_Action_the_Risk_of_Global_Warming_and_the_Environmental_Damage_from_the_Rising_Ocean_Water_Table_Sustainable_Seas_Enquiry_Written_evidence_submitted_by_Veli_Albert_Kallio_FRGS_SSI0121_Ordered_to_be_published_23_May_2018_by_the_House_of_Commons

Stopping the Flood: Could We Use Targeted Geoengineering to Mitigate Sea Level Rise?
Michael J. Wolovick1 and John C. Moore2,3
1Atmosphere and Ocean Sciences Program, Department of Geosciences, Princeton University, GFDL, 201 Forrestal Road,
Princeton, NJ 08540, USA
2College of Global Change and Earth System Science, Beijing Normal University, Beijing, China
3Arctic Centre, University of Lapland, Finland
Correspondence: M.J. Wolovick (wolovick@princeton.edu)

Abstract. The Marine Ice Sheet Instability (MISI) is a dynamic feedback that can cause an ice sheet to enter a runaway collapse. Thwaites Glacier, West Antarctica, is the largest individual source of future sea level rise and may have already entered the MISI. Here, we use a suite of coupled ice–ocean flowband simulations to explore whether targeted geoengineering using an artificial sill or artificial ice rises could counter a collapse. Successful interventions occur when the floating ice shelf regrounds 5 on the pinning points, increasing buttressing and reducing ice flux across the grounding line. Regrounding is more likely with a continuous sill that is able to block warm water transport to the grounding line. The smallest design we consider is comparable in scale to existing civil engineering projects but has only a 30% success rate, while larger designs are more effective. There are multiple possible routes forward to improve upon the designs that we considered, and with decades or more to research designs it is plausible that the scientific community could come up with a plan that was both effective and achievable. While 10 reducing emissions remains the short-term priority for minimizing the effects of climate change, in the long run humanity may need to develop contingency plans to deal with an ice sheet collapse.

--

http://data.parliament.uk/writtenevidence/committeeevidence.svc/evidencedocument/environmental-audit-committee/sustainable-seas/written/83150.pdf
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 15, 2018, 06:20:03 PM
The linked reference indicates that the projected increase (with continued global warming) of more frequent strong El Nino events combined with the projected increase in positive SAM, will significantly increase ice mass loss from the ASE, which will increase the risk of a collapse of the WAIS:

Deb, P., A. Orr, D. H. Bromwich, J. P. Nicolas, J. Turner, and J. S. Hosking, 2018: Summer drivers of atmospheric variability affecting ice shelf thinning in the Amundsen Sea Embayment, West Antarctica. Geophy. Res. Lett., 45. doi: 10.1029/2018GL077092.

http://polarmet.osu.edu/PMG_publications/deb_bromwich_grl_2018.pdf

Abstract:  "Satellite data and a 35-year hindcast of the Amundsen Sea Embayment summer climate using the Weather Research and Forecasting model are used to understand how regional and large-scale atmospheric variability affects thinning of ice shelves in this sector of West Antarctica by melting from above and below (linked to intrusions of warm water caused by anomalous westerlies over the continental shelf edge). El Niño episodes are associated with an increase in surface melt but do not have a statistically significant impact on westerly winds over the continental shelf edge. The location of the Amundsen Sea Low and the polarity of the Southern Annular Mode (SAM) have negligible impact on surface melting, although a positive SAM and eastward shift of the Amundsen Sea Low cause anomalous westerlies over the continental shelf edge. The projected future increase in El Niño episodes and positive SAM could therefore increase the risk of disintegration of West Antarctic ice shelves."

Extract: "Our study suggests that ASE ice shelves could experience an intensification of melt in the future from both above and below as a result of both regional and large-scale atmospheric changes, potentially increasing the risk of their disintegration, which in turn could potentially trigger a collapse of the West Antarctic ice sheet (DeConto & Pollard, 2016). To better understand this threat will require further detailed investigation of the impacts of ENSO, the polarity of the SAM, and the depth/location of the ASL on ASE ice shelves. Also necessary is improving the reliability of future projections, such as ENSO and its teleconnections, as well as the response of the SAM to recovery of the Antarctic ozone hole and increased greenhouse gas emissions (Polvani, Waugh, et al., 2011)."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 23, 2018, 03:30:27 PM
The linked articles confirm that not only are the Earth's rotation poles wandering rapidly, but so are its magnetic poles:

Title: "Shifting Ice Caps - Magnetic Poles and Ice Caps move in Tandem"

https://planet-earth-2017.com/wandering-poles/

Extract: "“The rate of the magnetic pole’s movement has increased in the last  century compared with fairly steady movement in the previous four centuries”, said Joseph Stoner and the Oregon researchers."

See also:

Title: "Magnetic north pole drifting fast"

http://news.bbc.co.uk/2/hi/science/nature/4520982.stm

Extract: " The Earth's north magnetic pole is drifting away from North America so fast that it could end up in Siberia within 50 years, scientists have said."

The linked reference provides paleo evidence that the Earth has experienced geomagnetic pole reversals in as little as a century, and that we are overdue for our next geomagnetic pole reversal:

Yu-Min Chou, Xiuyang Jiang, Qingsong Liu, Hsun-Ming Hu, Chung-Che Wu, Jianxing Liu, Zhaoxia Jiang, Teh-Quei Lee, Chun-Chieh Wang, Yen-Fang Song, Cheng-Cheng Chiang, Liangcheng Tan, Mahjoor A. Lone, Yongxin Pan, Rixiang Zhu, Yaoqi He, Yu-Chen Chou, An-Hung Tan, Andrew P. Roberts, Xiang Zhao, and Chuan-Chou Shen (August 20, 2018), "Multidecadally resolved polarity oscillations during a geomagnetic excursion", PNAS, 201720404; https://doi.org/10.1073/pnas.1720404115

http://www.pnas.org/content/early/2018/08/14/1720404115

Abstract: "Polarity reversals of the geomagnetic field have occurred through billions of years of Earth history and were first revealed in the early 20th century. Almost a century later, details of transitional field behavior during geomagnetic reversals and excursions remain poorly known. Here, we present a multidecadally resolved geomagnetic excursion record from a radioisotopically dated Chinese stalagmite at 107–91 thousand years before present with age precision of several decades. The duration of geomagnetic directional oscillations ranged from several centuries at 106–103 thousand years before present to millennia at 98–92 thousand years before present, with one abrupt reversal transition occurring in one to two centuries when the field was weakest. These features indicate prolonged geodynamo instability. Repeated asymmetrical interhemispheric polarity drifts associated with weak dipole fields likely originated in Earth’s deep interior. If such rapid polarity changes occurred in future, they could severely affect satellites and human society."

See also:
Title: "We Have The Most Precise Reading Yet on How Fast Earth's Magnetic Poles Could Flip"

https://www.sciencealert.com/earth-geomagnetic-polarity-excursion-rapid-reversal-ancient-past

Extract: "An analysis of a stalagmite from the depths of a cave in China has unveiled clues about an event in Earth's history when its magnetic field flipped back and forth in a geological blink.

The stalagmite was cut into more than 190 samples and analysed using a high-resolution cryogenic magnetometer, providing a century-scale resolution of Earth's magnetic field direction and strength 100 thousand years ago.

Among several smaller drifts in polarity they spotted a flicker of a reversal some 98,000 years ago that stayed in place for a century or two before slipping back again.

On a geological time scale, this excursion is shockingly brief, and could suggest any significant changes to our protective shell won't come with much warning."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Tor Bejnar on August 23, 2018, 06:08:26 PM
Quote
The linked reference provides paleo evidence that the Earth has experienced geomagnetic pole reversals in as little as a century, and that we are overdue for our next geomagnetic pole reversal:
The Earth may be statistically overdue for a reversal, but it is not a train-on-a-set-schedule sort of thing.  From Wikipedia (https://en.wikipedia.org/wiki/Geomagnetic_reversal)
Quote
The time spans of chrons are randomly distributed with most being between 0.1 and 1 million years[citation needed] with an average of 450,000 years. Most reversals are estimated to take between 1,000 and 10,000 years. The latest one, the Brunhes–Matuyama reversal, occurred 780,000 years ago, and may have happened very quickly, within a human lifetime.[1] In August 2018, researchers reported a reversal lasting only 200 years.[2]

A brief complete reversal, known as the Laschamp event, occurred only 41,000 years ago during the last glacial period. That reversal lasted only about 440 years with the actual change of polarity lasting around 250 years.
...
So that 'overdue-ness' is only if you ignore the Laschamp event.  Of course, Earth may be in the labor-pains of a reversal since about 400 years ago.  Some things just take time!

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 24, 2018, 12:50:27 AM
The Earth may be statistically overdue for a reversal, but it is not a train-on-a-set-schedule sort of thing.

Your statement is most certainly correct; however, those who might be concerned that an abrupt collapse of the WAIS (induced by following a BAU pathway for a few more decades) might trigger such a geomagnetic pole reversal might want to re-read Replies #103, #113, #115, #116 and #117.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on August 24, 2018, 01:07:11 AM
As I have said before, I am doubtful that icesheet collapse will trigger mag pole reversal. I am unaware of evidence that WAIS collapse in the Eemian ror in Holsteinian did any such thing.

Mechanism that generated the mag field is very poorly understood, and mechanism of pole reversal is even less understood. Present state of knowledge makes speculation of pole reversal due to WAIS collapse the equivalent of haruspicy.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 24, 2018, 08:43:10 PM
If one is looking for proof beyond a reasonable doubt (that abrupt ice mass losses could influence geomagnetic migrations), one might never that the precautions required to protect modern electronic systems from such a possibly abrupt geomagnetic flip (see the first image).

The title of the second attached image is "Approximate chronology of Heinrich events vs Dansgaard-Oeschger events and Antarctic Isotope Maxima", & it indicates that the magnetic field weakening between 105,000 and 103,000 years ago might line-up with the Heinrich event HS-10.

Title: "Earth's Magnetic Field Could Flip Much Faster Than Previously Thought"

https://www.forbes.com/sites/davidbressan/2018/08/23/earths-magnetic-field-could-flip-much-faster-than-previously-thought/#3ad0357f438c


Extract: "Modern geomagnetic measurements have shown that Earth's magnetic field is rapidly fading, by almost 16 percent since the year 1840.

… the scientists discovered two phases with a weaker magnetic field, between 105,000 and 103,000 and 98,000 to 92,000 years ago. During the more recent phase, the Magnetic North Pole "moved" from Alaska to a spot in the Antarctic Ocean. What surprised the scientist was the speed of this almost complete reversal, apparently just 144 years, with some decades as margin of error of the used radiometric dating technique. Thereafter the magnetic field switched back into the "normal", modern polarity.

… as the paper suggests, if significant magnetic disturbances really can happen in just a century, this poses new challenges to our civilization, as technology should be ready to deal with such changes."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 24, 2018, 08:48:26 PM
As I have said before, I am doubtful that icesheet collapse will trigger mag pole reversal. I am unaware of evidence that WAIS collapse in the Eemian ror in Holsteinian did any such thing.

Mechanism that generated the mag field is very poorly understood, and mechanism of pole reversal is even less understood. Present state of knowledge makes speculation of pole reversal due to WAIS collapse the equivalent of haruspicy.

sidd

As I have stated previously:

Regarding correlating true polar wander (shifting of the Earth's rotational axis) and magnetic field reversals and mass redistribution around the Earth; I provide the first linked reference that provides paleo evidence that during periods of little polar wander the is reduced activity of magnetic pole flipping; while the second linked article makes it clear that polar wander is associated with all mass (ice, sea level, groundwater, isostatic rebound) redistribution.

Courtillot V & Besse J. (1987 Sep 4), "Magnetic field reversals, polar wander, and core-mantle coupling", Science vol 237, issue (4819), pp 1140-7, DOI:10.1126/science.237.4819.1140

http://science.sciencemag.org/content/237/4819/1140

Abstract: "True polar wander, the shifting of the entire mantle relative to the earth's spin axis, has been reanalyzed. Over the last 200 million years, true polar wander has been fast (approximately 5 centimeters per year) most of the time, except for a remarkable standstill from 170 to 110 million years ago. This standstill correlates with a decrease in the reversal frequency of the geomagnetic field and episodes of continental breakup. Conversely, true polar wander is high when reversal frequency increases. It is proposed that intermittent convection modulates the thickness of a thermal boundary layer at the base of the mantle and consequently the core-to-mantle heat flux. Emission of hot thermals from the boundary layer leads to increases in mantle convection and true polar wander. In conjunction, cold thermals released from a boundary layer at the top of the liquid core eventually lead to reversals. Changes in the locations of subduction zones may also affect true polar wander. Exceptional volcanism and mass extinctions at the Cretaceous-Tertiary and Permo-Triassic boundaries may be related to thermals released after two unusually long periods with no magnetic reversals. These environmental catastrophes may therefore be a consequence of thermal and chemical couplings in the earth's multilayer heat engine rather than have an extraterrestrial cause."

&

Title: "Climate Change Is Moving the North Pole"

https://news.nationalgeographic.com/2016/04/160408-climate-change-shifts-earth-poles-water-loss/

Extract: "As ice melts and aquifers are drained, Earth's distribution of mass is changing—and with it the position of the planet's spin axis."


Also, see the following reference which indicates that about 66% of the polar wander over the indicated period was due to rapid changes in ice mass loss:

Surendra Adhikari and Erik R. Ivins (08 Apr 2016), "Climate-driven polar motion: 2003–2015", Science Advances, Vol. 2, no. 4, e1501693, DOI: 10.1126/sciadv.1501693

http://advances.sciencemag.org/content/2/4/e1501693

Abstract: "Earth’s spin axis has been wandering along the Greenwich meridian since about 2000, representing a 75° eastward shift from its long-term drift direction. The past 115 years have seen unequivocal evidence for a quasi-decadal periodicity, and these motions persist throughout the recent record of pole position, in spite of the new drift direction. We analyze space geodetic and satellite gravimetric data for the period 2003–2015 to show that all of the main features of polar motion are explained by global-scale continent-ocean mass transport. The changes in terrestrial water storage (TWS) and global cryosphere together explain nearly the entire amplitude (83 ± 23%) and mean directional shift (within 5.9° ± 7.6°) of the observed motion. We also find that the TWS variability fully explains the decadal-like changes in polar motion observed during the study period, thus offering a clue to resolving the long-standing quest for determining the origins of decadal oscillations. This newly discovered link between polar motion and global-scale TWS variability has broad implications for the study of past and future climate."

Also here are some other background references:

1. Adam C. Maloof Galen P. Halverson Joseph L. Kirschvink Daniel P. Schrag Benjamin P. Weiss Paul F. Hoffman (2006), "Combined paleomagnetic, isotopic, and stratigraphic evidence for true polar wander from the Neoproterozoic Akademikerbreen Group, Svalbard, Norway",  GSA Bulletin, 118 (9-10): 1099-1124, DOI: https://doi.org/10.1130/B25892.1

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/118/9-10/1099/125331/combined-paleomagnetic-isotopic-and-stratigraphic?redirectedFrom=fulltext

Abstract: "We present new paleomagnetic data from three Middle Neoproterozoic carbonate units of East Svalbard, Norway. The paleomagnetic record is gleaned from 50 to 650 m of continuous, platformal carbonate sediment, is reproduced at three locations distributed over >100 km on a single craton, and scores a 5–6 (out of 7) on the Van der Voo (1990) reliability scale. Two >50° shifts in paleomagnetic direction are coincident with equally abrupt shifts in δ13C and transient changes in relative sea level. We explore four possible explanations for these coincidental changes: rapid plate tectonic rotation during depositional hiatus, magnetic excursions, nongeocentric axial-dipole fields, and true polar wander. We conclude that the observations are explained most readily by rapid shifts in paleogeography associated with a pair of true polar wander events. Future work in sediments of equivalent age from other basins can test directly the true polar wander hypothesis because this type of event would affect every continent in a predictable manner, depending on the continent's changing position relative to Earth's spin axis."

2. J. R. Creveling, J. X. Mitrovica, N.-H. Chan, K. Latychev & I. Matsuyama (08 November 2012), "Mechanisms for oscillatory true polar wander", Nature, volume 491, pages 244–248,
doi:10.1038/nature11571

http://www.nature.com/articles/nature11571

Abstract: "Palaeomagnetic studies of Palaeoproterozoic to Cretaceous rocks propose a suite of large and relatively rapid (tens of degrees over 10 to 100 million years) excursions of the rotation pole relative to the surface geography, or true polar wander (TPW). These excursions may be linked in an oscillatory, approximately coaxial succession about the centre of the contemporaneous supercontinent. Within the framework of a standard rotational theory, in which a delayed viscous adjustment of the rotational bulge acts to stabilize the rotation axis, geodynamic models for oscillatory TPW generally appeal to consecutive, opposite loading phases of comparable magnitude. Here we extend a nonlinear rotational stability theory to incorporate the stabilizing effect of TPW-induced elastic stresses in the lithosphere. We demonstrate that convectively driven inertia perturbations acting on a nearly prolate, non-hydrostatic Earth with an effective elastic lithospheric thickness of about 10 kilometres yield oscillatory TPW paths consistent with palaeomagnetic inferences. This estimate of elastic thickness can be reduced, even to zero, if the rotation axis is stabilized by long-term excess ellipticity in the plane of the TPW. We speculate that these sources of stabilization, acting on TPW driven by a time-varying mantle flow field, provide a mechanism for linking the distinct, oscillatory TPW events of the past few billion years."

3. To learn how much the North Pole has shifted in the recent decades due to rapid ice mass loss, see Chen, J..L., C.R. Wilson, J.C. Ries, B.D. Tapley, Rapid ice melting drives Earth's pole to the east, Geophys. Res. Lett., Vol. 40, 1-6, DOI: 10.1002/grl.50552, 2013; which can be found at the prime author's website at the University of Texas, where you can download a preprint (made available by the author):

http://www.csr.utexas.edu/personal/chen/publication.html

and here is a link directly to the preprint pdf:

ftp://ftp.csr.utexas.edu/pub/ggfc/papers/2013GL056164_preprint.pdf

"
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 27, 2018, 03:15:41 AM
The linked reference indicates that Arctic Amplification is more sensitive to heat influx from the North Pacific than from the North Atlantic.  Here I note that a collapse of the WAIS would lead to a very large heat flux from the North Pacific into the Artic Ocean:

Summer Praetorius  et al. (2018), "Global and Arctic climate sensitivity enhanced by changes in North Pacific heat flux", Nature Communications, volume 9, Article number: 3124, DOI: https://doi.org/10.1038/s41467-018-05337-8

http://www.nature.com/articles/s41467-018-05337-8

Abstract: "Arctic amplification is a consequence of surface albedo, cloud, and temperature feedbacks, as well as poleward oceanic and atmospheric heat transport. However, the relative impact of changes in sea surface temperature (SST) patterns and ocean heat flux sourced from different regions on Arctic temperatures are not well constrained. We modify ocean-to-atmosphere heat fluxes in the North Pacific and North Atlantic in a climate model to determine the sensitivity of Arctic temperatures to zonal heterogeneities in northern hemisphere SST patterns. Both positive and negative ocean heat flux perturbations from the North Pacific result in greater global and Arctic surface air temperature anomalies than equivalent magnitude perturbations from the North Atlantic; a response we primarily attribute to greater moisture flux from the subpolar extratropics to Arctic. Enhanced poleward latent heat and moisture transport drive sea-ice retreat and low-cloud formation in the Arctic, amplifying Arctic surface warming through the ice-albedo feedback and infrared warming effect of low clouds. Our results imply that global climate sensitivity may be dependent on patterns of ocean heat flux in the northern hemisphere."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on August 27, 2018, 08:03:58 PM

On Polar wander and reversals


It seems that there is a correlation between polar wander and reversals. And it seems that rapid ice melt correlates with polar wander. Note that these correlations are on vastly different timescales.

The first paper speculates that there is a causative mechanism that is due to changes in mantle/core boundary conditions, the dynamic convection changes in the mantle altering the shape of the earth and causing polar wander, and correlating with magnetic pole reversals from thermal changes at the core mantle boundary. The paper discussing convective changes backs up the fact that you get polar reversals when the convective pattern of the mantle changes.

Perhaps Ice unloading will change the shape of the Earth and shift the axis of rotation enough to change mantle convection, but it's unlikely; there is a lot more mantle than ice, it would be analogous to a small rock hitting a car and changing it's direction (mantle mass 4×10^27g, total ice mass, 2.4x10^22g). The mantle will eventually adjust to take into account the new shape of the earth after ice melt, but it's more than likely going to be down to Asthenospheric mantle compensation as is modeled in PGR, and that alone will take 1000's of years.

My guess is the polar wander caused by ice melt is just noise in the ancient signal.


Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 27, 2018, 08:43:45 PM
My guess is the polar wander caused by ice melt is just noise in the ancient signal.

RoxTheGeologist,

Thank you for your thoughtful comments, and you may well be correct that ice mass redistribution from an abrupt collapse of the WAIS to the oceans of the world, might not be a sufficient trigger to accelerate the current ongoing weakening of the global geomagnetic fields.  Nevertheless, have you considered the distinctive geomagnetic field lines in the Southern Hemisphere (shown in the last image of Reply #115) and the rather unique geology beneath the WAIS as indicated by the following information which comes from the 'Antarctic Tectonics' thread with the first two images in this post coming from:

http://www.largeigneousprovinces.org/apr13

"The links between large igneous provinces, and continental break-up: evidence reviewed from Antarctica" by: Bryan C Storey,  Alan P M Vaughan and Teal R Riley; April 2013
Gateway Antarctica, Private Bag 4800, University of Canterbury, Christchurch, New Zealand; bryan.storey@canterbury.ac.nz

The first attached image shows:  Middle Jurassic Gondwana reconstruction showing three large igneous provinces (after Storey & Kyle 1997); Ferrar, Karoo and Chon Aike, and the location of the Weddell Sea Triple Junction (WSTJ) after Elliot & Fleming 2000.  DML, Dronning Maud Land; FI, Falkland Islands

The second attached image shows:  Antarctic map showing the Transantarctic Mountains as the rift shoulder of the West Antarctic Rift System (WARS), the related Cenozoic alkaline magmatic province (WARS volcanoes), the outline of the Middle Jurassic Ferrar magmatic province and the outline of the mid Cretaceous alkaline magmatism in Marie Byrd Land.

The third image shows a map of Antarctica with the relief of the crust thickness below it's ice as indicated by seismic data. Abbreviations: DML, Dronning Maud Land; GSM, Gamburtsev Subglacial Mountains.  CREDIT: Baranov, A., Morelli, A., The Moho depth map of the Antarctica region, Tectonophysics (2013).

The fourth image shows the modeled internal structure of the lithosphere in West Antarctica, showing a major source of heat from the upper mantle.

Best regards,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 27, 2018, 10:10:24 PM
RoxTheGeologist,

For convenience I provide the image from Reply #115 showing the correlation between the global magnetic field lines off the coast of South Africa and off the coast of West Antarctica.

Best,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: steve s on August 28, 2018, 01:00:02 AM
ASLR,

I'm not quite sure what light the magnetic field diagram is supposed to bring to the discussion. It seems to me the magnitude of the folds in the lines would be considerably less if the projection were less distorting; that the changes in the magnetic field might be an interesting note to your argument, but cannot be inferred from the diagram; and that the fold might cause the equivalent of Jupiter's Great Red Spot under different atmospheric conditions. However, I think RTG has a strong argument in the absence of a good theory -- correlations don't do much by themselves.

So, please elucidate a theoretical connection that will explain how the minor mass shift might be causal rather than coincident.
 
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 28, 2018, 02:17:38 AM
ASLR,

I'm not quite sure what light the magnetic field diagram is supposed to bring to the discussion. It seems to me the magnitude of the folds in the lines would be considerably less if the projection were less distorting; that the changes in the magnetic field might be an interesting note to your argument, but cannot be inferred from the diagram; and that the fold might cause the equivalent of Jupiter's Great Red Spot under different atmospheric conditions. However, I think RTG has a strong argument in the absence of a good theory -- correlations don't do much by themselves.

So, please elucidate a theoretical connection that will explain how the minor mass shift might be causal rather than coincident.
 

The following is a copy of my Reply #113 (which suggests that the trigger for a magnetic pole reversal may be associated with the South Atlantic Anomaly):

The first image shows the southern supercontinent Gondwana about 183million year ago at the point of the initial breakup of the supercontinent.  The second image highlights the Euler geometry of hexagons and pentagons bounded by the supercontinent rupture lines that define the lines of minimum energy required to break apart the supercontinent.  These two images illustrate the origins of the area known as the South Atlantic Anomaly – an expanse of the field currently stretching from Chile to Zimbabwe, as discussed in the reference linked (and the last two images) below.  The Hare et al. (2018) linked open access reference indicates that this region is likely a key area of the Earth core-mantle boundary that is likely in the process of triggering a flip in the Earth's magnetic poles.

Vincent J. Hare et al. (15 February 2018), "New Archeomagnetic Directional Records From Iron Age Southern Africa (ca. 425–1550 CE) and Implications for the South Atlantic Anomaly", GRL, DOI: 10.1002/2017GL076007

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076007/full

Abstract: "The paucity of Southern Hemisphere archeomagnetic data limits the resolution of paleosecular variation models. At the same time, important changes in the modern and historical field, including the recent dipole decay, appear to originate in this region. Here a new directional record from southern Africa is presented from analysis of Iron Age (ca. 425–1550 CE) archeological materials, which extends the regional secular variation curve back to the first millennium. Previous studies have identified a period of rapid directional change between 1225 and ∼1550 CE. The new data allow us to identify an earlier period of relatively rapid change between the sixth and seventh centuries CE. Implications for models of recurrent flux expulsion at the core-mantle boundary are discussed. In addition, we identify a possible relationship of changes recorded in these African data with archeomagnetic jerks."

See also:

Title: "A Mysterious Anomaly Under Africa Is Radically Weakening Earth's Magnetic Field"

https://www.sciencealert.com/something-mysterious-under-southern-africa-dramatically-weakening-earth-s-magnetic-field-south-atlantic-anomaly

Extract: "This could be precursor to Earth's poles swapping places.

The region that concerns scientists the most at the moment is called the South Atlantic Anomaly – a huge expanse of the field stretching from Chile to Zimbabwe. The field is so weak within the anomaly that it's hazardous for Earth's satellites to enter it, because the additional radiation it's letting through could disrupt their electronics.

… the artefacts revealed that the weakening in the South Atlantic Anomaly isn't a standalone phenomenon of history.

Similar fluctuations occurred in the years 400-450 CE, 700-750 CE, and 1225-1550 CE – and the fact that there's a pattern tells us that the position of the South Atlantic Anomaly isn't a geographic fluke.

"We're getting stronger evidence that there's something unusual about the core-mantel boundary under Africa that could be having an important impact on the global magnetic field," Tarduno says.

The current weakening in Earth's magnetic field – which has been taking place for the last 160 years or so – is thought to be caused by a vast reservoir of dense rock called the African Large Low Shear Velocity Province, which sits about 2,900 kilometres (1,800 miles) below the African continent.

"It is a profound feature that must be tens of millions of years old," the researchers explained in The Conversation last year.

"While thousands of kilometres across, its boundaries are sharp."

This dense region, existing in between the hot liquid iron of Earth's outer core and the stiffer, cooler mantle, is suggested to somehow be disturbing the iron that helps generate Earth's magnetic field.

There's a lot more research to do before we know more about what's going on here.

As the researchers explain, the conventional idea of pole reversals is that they can start anywhere in the core – but the latest findings suggest what happens in the magnetic field above us is tied to phenomena at special places in the core-mantle boundary."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: steve s on August 28, 2018, 06:35:06 AM
So where does loss of Antarctic ice come into play?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 28, 2018, 05:33:45 PM
So where does loss of Antarctic ice come into play?

It would help this exchange if you would review the earlier posts in this thread; as it seems unreasonable that I should re-post all of the related information.  Nevertheless, my Replay #115 ties ice mass loss to magma flow which is related to geomagnetic fields (see the first & second images) & states:

"While glaciovolcanism (defined as “the interactions of magma with ice in all its forms, including snow, firn and any meltwater”), may still be in its infancy; nevertheless, I provide the following links to relevant information (& two images about geomagnetism), and I note that there is more information in the 'Antarctic Tectonics' thread in the Antarctic folder; for those who are interested in learning more about this topic:

J.L. Smellie (2018), "Chapter 10 – Glaciovolcanism: A 21st Century Proxy for Palaeo-Ice",
Past Glacial Environments (Second Edition), Pages 335–375, https://doi.org/10.1016/B978-0-08-100524-8.00010-5

https://www.sciencedirect.com/science/article/pii/B9780081005248000105

Abstract: "Glaciovolcanism is a young science that has undergone a major transformation during the last 15 years. It is important for a variety of reasons but it is set to play a major role in deriving critical parameters of past ice sheets and thus greatly improve the accuracy of their reconstruction. Glaciovolcanic studies can deduce a wider range of parameters than any other methodology currently existing, including: establishing the presence of ice, its age, ice thickness, ice surface elevation, and basal thermal regime. These attributes can be acquired routinely for many glaciovolcanic sequences and, uniquely, several are quantifiable. Most glaciovolcanic terrains provide punctuated rather than continuous records of the coeval ice sheet, i.e., with numerous time gaps. Despite the gaps, glaciovolcanic studies of ice sheets have been completed successfully in the three major glaciovolcanic regions of the Earth: mainly Antarctica, but also Iceland and British Columbia (Canada). Future studies in these and other glaciovolcanic regions will considerably improve our knowledge of Earth’s water inventory and contribute to a better understanding of past ice dynamics and the impact of the cryosphere on global climate."

&

Title: "Antarctic Glaciovolcanism:

https://www2.le.ac.uk/departments/geology/people/smellie-jl/personal/ant-glaciovolc
"
However glaciovolcanism is only part of the scenario as in this thread we assume the worst case WAIS collapse which produces almost 5m of average sea level rise around the world (see the third image).  This much change in mean sea level would increase both seismic and volcanic activity around the would and likely would accelerate some local continental drift.

Furthermore, the combination of sea level rise and ice mass loss is already causing polar wander (see the fourth image), which RTG acknowledges relates to magnetic pole reversals as the alignment of the Earths faults and rifts change w.r.t. rotational forces when the rotational axis shifts.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 28, 2018, 06:02:01 PM
steve s,

You may (or may not) wish to also review the various posts (particularly my posts) in the thread entitled 'Earthquakes and climate change' in the Science folder at the following link.

https://forum.arctic-sea-ice.net/index.php/topic,283.msg139205.html#msg139205

My Reply #8 states:

"I like the following quote from Bill McGuire's book:

"Twenty thousand years ago, Iceland was entirely covered by a layer of ice that averaged close to a kilometer in thickness.  Around 15-16,000 year ago, planetary warming triggered rapid melting of the glaciers, reducing the load acting on the volcanoes beneath and on the underlying asthenosphere.  By 12,000 years ago unloading was sufficiently advanced to trigger a spectacular response.  Over a period of 1500 years or so, the volcanic eruption rate jumped by between 30 and 50 times, before falling back to today's level.  This volcanic rejuvenation was in part a reflection of the release of magma held ready and waiting, within and beneath the volcanoes themselves, but mainly testament to a huge increase in the supply of fresh magma from deeper within the Earth.  Such was the load reduction due to the rapid loss of ice mass, that the depressed lithosphere quickly bounced back by as much as half a kilometer, dramatically reducing the pressures in the asthenosphere and triggering a 30-fold jump in magma production."

If such behavior were to occur in the West Antarctic Ice Sheet, WAIS, (where there are numerous volcanoes and faults and a very thin crust), then the world would experience a significant increase in the rate of SLR."

My Reply #51 in that thread points out that due to the fingerprint effect a collapse of the WAIS would result in a non-uniform change in sea level around the world (see the first attached image); which would put additional differential stresses on global faults/rifts which would cause additional tectonic plate movement:

Furthermore, my Reply #62 in that thread discusses the significant amount of glacial isostatic rebound that would (& is now beginning to) occur with WAIS ice mass loss.  The second attached image indicates that with a complete WAIS collapse this rebound in several areas of the Byrd Subglacial Basin, BSB, would be several hundred meters.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on August 28, 2018, 07:58:52 PM
Yes, the unloading of the ice sheet in the WAIS could produce increased volcanic activity over a geologically short period of time, and I fear that there is the possibility it might have a catastrophic affect within our life times. Every km of ice depth is replaced by 300 or so M of rock from isostatic rebound and, perhaps, by thick lava flows.

Note, though, that the tectonic's are very different to Iceland. The West Antarctic rift is a very slowly growing rift, and therefore the store of magma is probably low because the lithiosphere hasn't been thinning quickly. The WAR is spreading at about 2mm a year. Iceland sits on a hotspot that's also on a MOR that's spreading at an average rate 25mm a year (the fastest measured spreading on land is probably Greece, at 70+mm a year, in the oceans the EPR, spreads at 150mm a year). We didn't see a change in magnetism due to changes in the icesheet in Iceland, despite the unloading of ice and the massive increase in volcanism. I doubt very much we will see it in the Antarctic.



Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 28, 2018, 08:54:23 PM
RoxTheGeologists,

Thank you for your valid comments, and I most certainty do not think that the evidence that I have presented proves beyond a reasonable doubt that there will be a change in magnetism due to a collapse of the WAIS (this century).  That said, I believe that the Earth System models used to investigate such a possible occurrence are so crude that they certainly cannot disprove such a possible change in magnetism, especially since a collapse of the WAIS would induce not only relatively local tectonic changes but would also induce global tectonic changes.

Thanks again for your comments (& I acknowledge that it would be nice if you are correct, but I am concerned that the modern electronic-based society will be caught unprepared if you are incorrect).

Best,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: steve s on August 28, 2018, 09:18:38 PM
ASLR,

I understand the tectonics involved and think that the Thwaites Glacier is likely to have its melt accelerated by vulcanism, but I see no obvious case for more than a trivial direct influence of ice loss on magnetic reversal (at most). So I agree with RTG.

 
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 28, 2018, 10:10:46 PM
ASLR,

I understand the tectonics involved and think that the Thwaites Glacier is likely to have its melt accelerated by vulcanism, but I see no obvious case for more than a trivial direct influence of ice loss on magnetic reversal (at most). So I agree with RTG.
steve s,

I sincerely hope that both yourself and RTG are correct.  However, if the cascade of tipping points hypothesized in this thread actually occur, we may find out as soon as 2040 whether, or not, you are both incorrect.

Regards,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 28, 2018, 11:45:16 PM
In order to provide readers with a feel for how extreme true polar wander and change the angle of the Earth's rotational axis, I provide the following linked reference:

Bernhard Steinberger & Trond H. Torsvik (03 April 2008), "Absolute plate motions and true polar wander in the absence of hotspot tracks", Nature volume 452, pages 620–623, DOI: https://doi.org/10.1038/nature06824

http://www.nature.com/articles/nature06824

Abstract: "The motion of continents relative to the Earth’s spin axis may be due either to rotation of the entire Earth relative to its spin axis—true polar wander—or to the motion of individual plates. In order to distinguish between these over the past 320 Myr (since the formation of the Pangaea supercontinent), we present here computations of the global average of continental motion and rotation through time in a palaeomagnetic reference frame. Two components are identified: a steady northward motion and, during certain time intervals, clockwise and anticlockwise rotations, interpreted as evidence for true polar wander. We find ∼18° anticlockwise rotation about 250-220 Myr ago and the same amount of clockwise rotation about 195-145 Myr ago. In both cases the rotation axis is located at about 10-20° W, 0° N, near the site that became the North American–South American–African triple junction at the break-up of Pangaea. This was followed by ∼10° clockwise rotation about 145-135 Myr ago, followed again by the same amount of anticlockwise rotation about 110-100 Myr ago, with a rotation axis in both cases ∼25-50° E in the reconstructed area of North Africa and Arabia. These rotation axes mark the maxima of the degree-two non-hydrostatic geoid during those time intervals, and the fact that the overall net rotation since 320 Myr ago is nearly zero is an indication of long-term stability of the degree-two geoid and related mantle structure. We propose a new reference frame, based on palaeomagnetism, but corrected for the true polar wander identified in this study, appropriate for relating surface to deep mantle processes from 320 Myr ago until hotspot tracks can be used (about 130 Myr ago)."

Edit: To add more relevant data about recent changes in the Earth's rotational tilt see (& the associated image):

"Ocean circulation and climate at the Eemian and last glacial inception" by Andreas Born
Dissertation for the degree of Philosophiae Doctor (PhD), Geophysical Institute,

http://bora.uib.no/bitstream/handle/1956/4436/Dr.thesis_Andreas%20Born.pdf?sequence=1&isAllowed=y

Extract: "The tilt (obliquity) of the Earth’s rotational axis relative to the plane of rotation around the sun varies between 22.1◦and 24.5◦on a 41,000 year cycle."

Edit: For ease of reference regarding sea level rise change during the Eemian, I provide the second image.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: prokaryotes on August 30, 2018, 03:24:11 AM
While the linked research, indicating more rapid bedrock uplift in Amundsen Sea Embayment, seems like good news, if one refers to projections from ice sheet models that do not include Pollard's & DeConto's ice cliff and hydrofacturing mechanism and which assume radiative forcing scenarios of RCP 4.5 or less.  However, if one assumes radiative forcing scenarios close to BAU for the next two decades and projections from Pollard & DeConto's recent work, then Barletta et al (2018)'s finding are actually bad news regarding the potential collapse of the WAIS this century.

V.R. Barletta el al. (22 Jun 2018), "Observed rapid bedrock uplift in Amundsen Sea Embayment promotes ice-sheet stability," Science,:
Vol. 360, Issue 6395, pp. 1335-1339, DOI: 10.1126/science.aao1447.

http://science.sciencemag.org/content/360/6395/1335
Because there is a volcano beneath Pine Island Glacier, and because

Evidence of an active volcanic heat source beneath the Pine Island Glacier https://www.nature.com/articles/s41467-018-04421-3 and because there was a recent eruption

A recent volcanic eruption beneath the West Antarctic ice sheet https://www.nature.com/articles/ngeo106 Ancient Antarctic eruption noted http://news.bbc.co.uk/2/hi/science/nature/7194579.stm the uplift may mean that the heat source also advances. 


Quote
The localization of mantle helium to glacial meltwater reveals that volcanic heat induces melt beneath the grounded glacier and feeds the subglacial hydrological network crossing the grounding line. The observed transport of mantle helium out of the Ice Shelf cavity indicates that volcanic heat is supplied to the grounded glacier at a rate of ~ 2500 ± 1700 MW, which is ca. half as large as the active Grimsvötn volcano on Iceland. Our finding of a substantial volcanic heat source beneath a major WAIS glacier highlights the need to understand subglacial volcanism, its hydrologic interaction with the marine margins, and its potential role in the future stability of the WAIS.

ps. can someone suggest a good open study on Marine ice cliff instability?
Here https://www.sciencedirect.com/science/article/pii/S0012821X14007961
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 30, 2018, 03:41:25 AM
ps. can someone suggest a good open study on Marine ice cliff instability?
From a Google search:

Daniel F Martin1, Brent M Minchew2, Stephen F Price3 and Esmond G Ng1, (2018), "Modeling Marine Ice Cliff Instability: Higher resolution leads to lower impact", (1)Lawrence Berkeley National Laboratory, Berkeley, CA, United States, (2)Organization Not Listed, Washington, DC, United States, (3)Los Alamos National Laboratory, Los Alamos, NM, United States

https://agu.confex.com/agu/fm18/preliminaryview.cgi/Paper435681.html

&

Jeremy N Bassis1, Doug Benn2 and Brandon Robert Berg1, (2018), "Anatomy of the Marine Ice Cliff Instability", (1)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (2)University of St Andrews, Dept. of Geography and Sustainable Development, St Andrews, United Kingdom

https://agu.confex.com/agu/fm18/preliminaryview.cgi/Paper436995.html

&

Frank Pattyn (2018), "The paradigm shift in Antarctic ice sheet modelling", Nature Communications, volume 9, Article number: 2728, DOI: https://doi.org/10.1038/s41467-018-05003-z


https://www.nature.com/articles/s41467-018-05003-z
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on August 30, 2018, 03:41:25 AM
2500 MW melts about 1/4 Gtonne ice per year (Check my math, always)
Amundsen sea glaciers are losing about  100Gtonne/yr.

So still down in the noise.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: prokaryotes on August 30, 2018, 03:58:23 AM
2500 MW melts about 1/2 Gtonne ice per year (Check my math, always)
Amundsen sea glaciers are losing about  100Gtonne/yr.

So still down in the noise.

sidd

Quote
All the datasets illustrate the previously documented accelerating mass loss of Antarctica (Rignot et al., 2011a, b; Velicogna, 2009). In 2005–2010, the ice sheet experienced ice mass loss driven by an increase in mass loss in the Amundsen Sea sector of West Antarctica (Mouginot et al., 2014). The following years showed a reduced increase in mass loss, as colder ocean conditions prevailed in the Amundsen Sea embayment sector of West Antarctica in 2012–2013 which reduced the melting of the ice shelves

The large interannual variability in mass balance in 2005– 2015, characteristic of Antarctica, nearly masks out the trend in mass loss, which is more apparent in the longer time series than in short time series. The longer record highlights the pronounced decadal variability in ice sheet mass balance in Antarctica, demonstrating the need for multidecadal time series in Antarctica, which have been obtained only by IOM and altimetry. The interannual variability in mass balance is driven almost entirely by surface mass balance processes. The mass loss of Antarctica, about 200 Gt yr−1 in recent years, is only about 10 % of its annual turnover of mass (2200 Gt yr−1 ), in contrast with Greenland where the mass loss has been growing rapidly to nearly 100 % of the annual turnover of mass.

The annual turnover of mass of Antarctica is about 2200 Gt yr−1 (over 6 mm yr−1 of SLE), 5 times larger than in Greenland (Wessem et al., 2017). In contrast to Greenland, ice and snow melt have a negligible influence on Antarctica’s mass balance, which is therefore completely controlled by the balance between snowfall accumulation in the drainage basins and ice discharge along the periphery.

200 Gt from entire continent, i would think most from the WAIS. https://www.earth-syst-sci-data.net/10/1551/2018/essd-10-1551-2018.pdf
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: prokaryotes on August 30, 2018, 04:01:48 AM
From a Google search:
Thanks.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 30, 2018, 04:07:09 AM
From a Google search:
Thanks.

The following link provides interactive diagrams of ice mass loss from various regions of the Antarctic thru August 16, 2016:

https://data1.geo.tu-dresden.de/ais_gmb/
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: prokaryotes on August 30, 2018, 02:45:41 PM
..
Is there a topic discussing Marine Ice Sheet Instability?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 30, 2018, 05:01:51 PM
..
Is there a topic discussing Marine Ice Sheet Instability?

There is currently no individual thread devoted to Marine Ice Sheet Instability.  However, the are numerous threads in the Antarctic folder (including those linked below) that contain numerous posts on this complex topic:

https://forum.arctic-sea-ice.net/index.php/topic,85.0.html
https://forum.arctic-sea-ice.net/index.php/topic,21.0.html
https://forum.arctic-sea-ice.net/index.php/topic,72.0.html
https://forum.arctic-sea-ice.net/index.php/topic,130.0.html

Part of the problem is that models of Marine Ice Sheet Instability are so immature that it is difficult to comment on them without writing a PhD Dissertation each and every time.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 30, 2018, 10:22:44 PM
The linked reference indicates that the Beaufort Gyre halocline has been 'archiving' ocean heat for the past three decades.  When this warm water is eventually released, it will melt significant amounts of Arctic sea ice.

Mary-Louise Timmermans, John Toole and Richard Krishfield (29 Aug 2018), "Warming of the interior Arctic Ocean linked to sea ice losses at the basin margins", Science Advances , Vol. 4, no. 8, eaat6773, DOI: 10.1126/sciadv.aat6773

http://advances.sciencemag.org/content/4/8/eaat6773

Abstract: "Arctic Ocean measurements reveal a near doubling of ocean heat content relative to the freezing temperature in the Beaufort Gyre halocline over the past three decades (1987–2017). This warming is linked to anomalous solar heating of surface waters in the northern Chukchi Sea, a main entryway for halocline waters to join the interior Beaufort Gyre. Summer solar heat absorption by the surface waters has increased fivefold over the same time period, chiefly because of reduced sea ice coverage. It is shown that the solar heating, considered together with subduction rates of surface water in this region, is sufficient to account for the observed halocline warming. Heat absorption at the basin margins and its subsequent accumulation in the ocean interior, therefore, have consequences for Beaufort Gyre sea ice beyond the summer season."

See also:

Title: "‘Archived’ heat has reached deep into the Arctic interior, researchers say"

https://news.yale.edu/2018/08/29/archived-heat-has-reached-deep-arctic-interior-researchers-say

Extract: "“We document a striking ocean warming in one of the main basins of the interior Arctic Ocean, the Canadian Basin,” said lead author Mary-Louise Timmermans, a professor of geology and geophysics at Yale University.

The upper ocean in the Canadian Basin has seen a two-fold increase in heat content over the past 30 years, the researchers said. They traced the source to waters hundreds of miles to the south, where reduced sea ice has left the surface ocean more exposed to summer solar warming. In turn, Arctic winds are driving the warmer water north, but below the surface waters."

&

Title: "'Ticking Time Bomb' of Heated Ocean Discovered Hidden Under The Arctic"

https://www.sciencealert.com/ticking-time-bomb-hidden-heated-ocean-water-under-arctic-canada-basin-chukchi-sea

Extract: "New research has uncovered evidence of a vast reservoir of heated water building up underneath the Arctic Ocean and penetrating deep into the heart of the polar region, where it threatens to melt the ice frozen on top. And maybe a lot of it.

"We document a striking ocean warming in one of the main basins of the interior Arctic Ocean, the Canadian Basin," explains oceanographer Mary-Louise Timmermans from Yale University.
Timmermans and her team analysed temperature data on the Canada Basin taken over the last 30 years, and found that the amount of heat in the warmest part of the water had effectively doubled in the period 1987 to 2017."

Edit: See Reply #75 for other discussion about the Beaufort Gyre.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on August 30, 2018, 11:27:12 PM

It takes 4.186x10^6 Joules to raise a cubic meter of water 1°C - so at 4.4x10^8 Joules per m2, there is enough energy to raise 100m about 1°C. Looking at their graphs, 50-150m is approximately the depth they used between the 31 and 33psu salinity boundaries.

If we have an extra 2.2x10^8 Joules per m2

That's enough heat to melt an extra ~0.6m of ice.

The density change of going from -1.3°C to 0°C at 31 psu doesn't make a huge density difference (about 0.1 g per liter), but the density difference as compared to the surface water drops by around 4% possible indicating decreased resistance to mixing; the surface waters, at 1.25°C, 28psu, are about 2.40g per liter less dense.

One can only assume that the heating will accelerate with the current state of the Arctic, and that at some point the heat loss by conduction through the surface mixed layer will be able to keep up with the extra heat input .. that or it will reach the adiabatic threshold and start mixing.


Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 31, 2018, 01:01:48 AM
One can only assume that the heating will accelerate with the current state of the Arctic, and that at some point the heat loss by conduction through the surface mixed layer will be able to keep up with the extra heat input .. that or it will reach the adiabatic threshold and start mixing.

The one consideration that you are ignoring is that per the research that I reference in Reply #75, the relatively freshwater layer immediately above the deeper warm layer of water, is unstable.  So it is not that the deeper and denser warm water will magically float up through less dense cooler water, but rather that the upper cooler/fresher lay may well some day flow laterally away (into the North Atlantic) which would then leave the warm water closer to the surface.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on August 31, 2018, 10:22:47 PM

Less dense layers are, by definition, unstable when surrounded by higher density fluids. They are constantly under pressure to move laterally, just like oil spreading over water (but with mixing at the boundaries). The low density lens of fresher water in the Arctic has to be continually replenished by Arctic River drainage and/or by the freeze/melt cycle, otherwise, as you say, it will just disappear. The low density upper Arctic layer flows out of the Arctic through the Fram strait and the CAA; if it didn't then the Arctic surface would become fresher and fresher, rather like the Baltic.

I don't think that the lower layers are going to become vertically unstable and overturn, however, there will be less resistance to mixing between layers as the density difference between those layers lessens.

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on August 31, 2018, 10:50:59 PM
Your description of the behavior of the Beaufort Gyre, and how it accumulates and disperses relatively freshwater is overly simplified; which results in incorrect conclusions.  The first linked article (cited in Reply #75), makes it clear that in recent decades the Beaufort Gyre has been accumulating an atypically large amount of freshwater, possibly due the mechanism cited by Proshutinsky et al (2015).  If the feedback mechanism cited by Proshutinsky et al (2015) were to be disrupted some year in the future, one would expect an atypically large outflow of relatively freshwater from the Beaufort Gyre and consequently an atypically large up-flow of relatively warm deep water that is currently beneath the relatively freshwater cap in the Beaufort Gyre:

Title: "How a Wayward Arctic Current Could Cool the Climate in Europe"

http://e360.yale.edu/features/how-a-wayward-arctic-current-could-cool-the-climate-in-europe

Extract: "The Beaufort Gyre, a key Arctic Ocean current, is acting strangely. Scientists say it may be on the verge of discharging a huge amount of ice and cold freshwater that could kick off a period of lower temperatures in northern Europe.

…something is amiss with this vital plumbing system in the Arctic, a region warming faster than any other on the planet. Thanks in part to rising air temperatures, steadily disappearing sea ice, and the annual melting of 270 billion tons of ice from Greenland’s ice cap, the gyre is no longer functioning as it has predictably done for more than a half century. And now, scientists are anticipating that a sudden change in the Beaufort Gyre could set in motion events that — in a steadily warming world — would actually lead to a temporary but significant cooling of the North Atlantic region.

During the second half of the 20th century — and, most likely, earlier — the gyre adhered to a cyclical pattern in which it would shift gears every five to seven years and temporarily spin in a counter-clockwise direction, expelling ice and freshwater into the eastern Arctic Ocean and the North Atlantic. But for more than a dozen years, this carousel of ice and, increasingly, freshwater has been spinning faster in its usual clockwise direction, all the while collecting more and more freshwater from three sources: melting sea ice, huge volumes of runoff flowing into the Arctic Ocean from Russian and North American rivers, and the relatively fresh water streaming in from the Bering Sea….

The gyre’s strange behavior is likely linked, at least in part, to the profound warming of the Arctic, and it demonstrates how disruptions in one rapidly changing region of the world can affect ecosystems hundreds, even thousands, of miles away. In a recent paper, Krishfield, Proshutinsky, and other scientists suggest that frigid freshwater pouring into the north Atlantic Ocean from the rapidly melting Greenland ice sheet is forming a cap on the North Atlantic that results in stratification that prevents storm-triggering heat from the northern end of the Gulf Stream from rising to the surface. The scientists say this may be inhibiting the formation of cyclones that would cause the motion of the gyre to weaken or temporarily reverse.

If that is the case, it may mean the gyre will continue to grow and spin clockwise for years to come."

See also:

Andrey Proshutinsky, Dmitry Dukhovskoy, Mary-Louise Timmermans, Richard Krishfield, Jonathan L. Bamber (2015), "Arctic circulation regimes", Philosophical Transactions of the Royal Society A, DOI: 10.1098/rsta.2014.0160

http://rsta.royalsocietypublishing.org/content/373/2052/20140160

Abstract: "Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on September 01, 2018, 04:03:55 PM
One can only assume that the heating will accelerate with the current state of the Arctic, and that at some point the heat loss by conduction through the surface mixed layer will be able to keep up with the extra heat input .. that or it will reach the adiabatic threshold and start mixing.

The one consideration that you are ignoring is that per the research that I reference in Reply #75, the relatively freshwater layer immediately above the deeper warm layer of water, is unstable.  So it is not that the deeper and denser warm water will magically float up through less dense cooler water, but rather that the upper cooler/fresher lay may well some day flow laterally away (into the North Atlantic) which would then leave the warm water closer to the surface.

I was answering your point: One of the most important fundamental driving force for freshwater drainage out of the Arctic ocean is lateral density difference. Low salinity water is continually flowing out of the Arctic. It's not something I would ignore. I attempted to simplify my answer to get the idea across. Clearly i failed.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on September 01, 2018, 04:28:48 PM
I was answering your point: One of the most important fundamental driving force for freshwater drainage out of the Arctic ocean is lateral density difference. Low salinity water is continually flowing out of the Arctic. It's not something I would ignore. I attempted to simplify my answer to get the idea across. Clearly i failed.

While it is true that low salinity water is continually flowing out of the Arctic, the key issue to understand is that the volume of low salinity water discharging from the Beaufort Gyre fluctuates, and that since 1997 the gyre has been accumulating an atypically large volume of low salinity water, which will most likely be discharged in a future pulse rather than in a uniform flow.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: vox_mundi on September 20, 2018, 04:50:54 PM
More supporting evidence that Climate Change is impacting polar drift

Scientists ID Three Causes of Earth's Spin Axis Drift (https://phys.org/news/2018-09-scientists-id-earth-axis-drift.html)
https://phys.org/news/2018-09-scientists-id-earth-axis-drift.html

(https://geology.com/18/spin-axis-drift.jpg)
The observed direction of polar motion, shown as a light blue line, compared with the sum (pink line) of the influence of Greenland ice loss (blue), postglacial rebound (yellow) and deep mantle convection (red). The contribution of mantle convection is highly uncertain.

Using observational and model-based data spanning the entire 20th century, NASA scientists have for the first time identified three broadly-categorized processes responsible for this drift—contemporary mass loss primarily in Greenland, glacial rebound, and mantle convection.

"The traditional explanation is that one process, glacial rebound, is responsible for this motion of Earth's spin axis. But recently, many researchers have speculated that other processes could have potentially large effects on it as well," said first author Surendra Adhikari of NASA's Jet Propulsion Laboratory in Pasadena, California. "We assembled models for a suite of processes that are thought to be important for driving the motion of the spin axis. We identified not one but three sets of processes that are crucial—and melting of the global cryosphere (especially Greenland) over the course of the 20th century is one of them."

While ice melt is occurring in other places (like Antarctica), Greenland's location makes it a more significant contributor to polar motion.

"There is a geometrical effect that if you have a mass that is 45 degrees from the North Pole—which Greenland is—or from the South Pole (like Patagonian glaciers), it will have a bigger impact on shifting Earth's spin axis than a mass that is right near the Pole," said coauthor Eric Ivins, also of JPL.


The results suggest that tracking polar shifts can serve as a check on current estimates of ice loss, says Erik Ivins, a geophysicist at NASA’s Jet Propulsion Laboratory in Pasadena, California. When mass is lost in one part of a spinning sphere, its spin axis will tilt directly towards the position of the loss, he says — exactly as Chen’s team observed for Greenland. “It’s a unique indicator of the point where the mass is lost,” says Ivins.

Scientists can locate the north and south poles to within 0.03 milliarcseconds by using Global Positioning System measurements to determine the angle of Earth’s spin. Knowing the motion of the poles constrains estimates of ice loss made by other methods, Chen says

With these three broad contributors identified, scientists can distinguish mass changes and polar motion caused by long-term Earth processes over which we have little control from those caused by climate change. They now know that if Greenland's ice loss accelerates, polar motion likely will, too.

JPL Interactive Polar Motion Simulator: https://vesl.jpl.nasa.gov/sea-level/polar-motion/

What drives 20th century polar motion? (https://www.sciencedirect.com/science/article/pii/S0012821X18305314?via%3Dihub)

https://www.sciencedirect.com/science/article/pii/S0012821X18305314

Quote
Abstract

Astrometric and geodetic measurements show that the mean position of Earth's spin axis drifted through the solid crust toward Labrador, Canada at an average speed of  cm/yr during the 20th century. Understanding the origins of this secular polar motion (SPM) has significance for modeling the global climate, as it provides a link to ice mass balance and sea-level rise. A perplexing issue, however, is that while glacial isostatic adjustment (GIA) models satisfactorily explain the direction of SPM, the associated prediction of the amplitude is insufficient. Our Bayesian GIA analysis, with constraints from relative sea-level and vertical land motion data, reveals that this process only accounts for % of the observed SPM amplitude. This shortfall motivates a more broadly scoped reassessment of SPM drivers. To address this, we assemble a complete reconstruction of Earth's surface mass transport derived from recent advancements in modeling the global 20th century cryospheric, hydrologic, oceanic, and seismogenic mass exchange. The summed signals, nonetheless, cannot fully reconcile the observed SPM, even when considering the error statistics of each driver. We investigate an additional excitation source: changes in Earth's inertia tensor caused by mantle convection. Sophisticated models have recently been advanced in tectonic plate reconstructions, in conjunction with geoid and seismic tomographic models. Here we use these models to compute new estimates of SPM. While the convection-driven SPM has considerable uncertainty, the average direction of 283 recent models aligns with the residual SPM (within 2.7 +/- 14.8 ), significantly reducing the gap between observation and prediction. We assert that one key mechanism for driving 20th century SPM is long-term mass movement due to mantle convection.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on October 03, 2018, 11:49:16 PM
As continued global warming should increase the frequency with which atmospheric rivers reach Greenland, we may be in for some rude surprises in the coming decades (w.r.t. increasing rates of ice mass loss from the Greenland Ice Sheet):

William Neff (2018), "Atmospheric rivers melt Greenland", Nature Climate Change 8, 857-858, DOI: https://doi.org/10.1038/s41558-018-0297-4

http://www.nature.com/articles/s41558-018-0297-4

Abstract: "Recent years have seen increased melting of the Greenland Ice Sheet, contributing to accelerated rates of sea-level rise.  New research suggests that this melting due to an increased frequency of atmospheric rivers, narrow filaments of moist air moving polewards."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on October 25, 2018, 02:44:44 PM
It might help to understand the linked article by Hansen (October 15, 2018) if one considers that the ENSO phenomenon behaves as a chaotic strange attractor, and the mathematics of Chaos Theory indicates that such strange attractors are better characterized by their nodes (La Nina events) rather than the intervening excited states (El Nino events).  Thus in the attached image from Hansen (October 15, 2018) the fact that the trend lines for La Nina events are becoming steeper faster than either the average trend line of the trend line for El Nino events; means that the Earth's climate state is likely shifting into one more dominated by more active ENSO behavior; which most climate models indicate will have a higher Equilibrium Climate Sensitivity, ECS, than we have been recently experiencing.  Indeed, a warming rate of 0.38C per decade is much faster than most consensus climate scientists acknowledge, and is consistent with Hansen's ice-climate feedback mechanism:

Title: "Global Warming Acceleration Plus Miscellaneous"

http://www.columbia.edu/~jeh1/mailings/2018/20181015_GlobalWarmingAcceleration.pdf

Extract: "Global temperature minima associated with La Ninas are more uniform in depth than El Nino maxima. This provides an opportunity to check whether the global warming rate is accelerating.


La Nina minima probably provide a better estimate, and they provide more recent rates. As the figure shows, the most recent two La Ninas imply a warming rate of 0.38°C per decade, at least double the longer term rate! Such acceleration is predicted by climate models for continued high fossil fuel emissions as a result of amplifying climate feedbacks and is a cause for concern. We expect global temperature rise in the next few months to confirm our analysis."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Klondike Kat on October 25, 2018, 04:55:53 PM
The only problem with that graph is that the minimum may not have occurred yet.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Lennart van der Linde on October 25, 2018, 08:22:59 PM
Except that Hansen notes a minimum has likely been reached as El Nino conditions have started.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on October 26, 2018, 09:57:48 AM
Except that Hansen notes a minimum has likely been reached as El Nino conditions have started.

The two linked ENSO websites by the U.S. – NOAA, and the Australian – BoM, indicate that we have been in a Modoki-type of El Nino condition since the end of September 2018, and that there is approximately a 70% chance that an official El Nino event will be called for the 2018-19 season:

Title: "Weekly SST data"

http://www.cpc.ncep.noaa.gov/data/indices/wksst8110.for


                     Nino1+2      Nino3         Nino34        Nino4
 Week           SST SSTA    SST SSTA   SST SSTA    SST SSTA
 12SEP2018     20.5 0.2     25.2 0.4     27.0 0.3     29.1 0.4
 19SEP2018     20.3-0.1     25.0 0.2     27.0 0.3     29.1 0.4
 26SEP2018     20.2-0.3     25.5 0.6     27.3 0.6     29.3 0.6
 03OCT2018     21.3 0.7     25.6 0.7     27.4 0.7     29.5 0.8
 10OCT2018     21.1 0.4     25.6 0.7     27.3 0.6     29.5 0.9
 17OCT2018     21.1 0.3     25.9 1.0     27.6 0.9     29.6 0.9

&

Title: "ENSO Wrap-Up - Current state of the Pacific and Indian oceans - 23 October 2018"

http://www.bom.gov.au/climate/enso/

Extract: "The Bureau's ENSO Outlook remains at El Niño ALERT, indicating there is approximately a 70% chance of El Niño occurring in 2018—around triple the normal likelihood."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on October 26, 2018, 06:00:41 PM
As continued global warming should increase the frequency with which atmospheric rivers reach Greenland, we may be in for some rude surprises in the coming decades (w.r.t. increasing rates of ice mass loss from the Greenland Ice Sheet):

William Neff (2018), "Atmospheric rivers melt Greenland", Nature Climate Change 8, 857-858, DOI: https://doi.org/10.1038/s41558-018-0297-4

http://www.nature.com/articles/s41558-018-0297-4

Abstract: "Recent years have seen increased melting of the Greenland Ice Sheet, contributing to accelerated rates of sea-level rise.  New research suggests that this melting due to an increased frequency of atmospheric rivers, narrow filaments of moist air moving polewards."

It worries me that we have this huge gravitationally unstable mass of ice on top of Greenland that is gradually warming, getting wet and having more snow piled on top of it, causing more pressure melting at it's base. The only thing keeping it up is the friction along it's base and its mechanical integrity. Once it loses mechanical integrity all bets are off. Whats to stop the whole damn thing sliding into the ocean in chunks?

An underlying principle in geology is that "The present is the key to the past". Unfortunately that doesn't really help us understand events that might happen once every 100,000 years.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Hefaistos on October 27, 2018, 07:28:28 AM

It worries me that we have this huge gravitationally unstable mass of ice on top of Greenland that is gradually warming, getting wet and having more snow piled on top of it, causing more pressure melting at it's base. The only thing keeping it up is the friction along it's base and its mechanical integrity. Once it loses mechanical integrity all bets are off. Whats to stop the whole damn thing sliding into the ocean in chunks?
...

I don't think it's "gravitationally unstable", especially as compared to parts of Antarctic's ice.
It's got to be a very slow process warming the glaciers up, especially as it seems that Greenland is about to replace the Arctic sea as the north cold pole, once ASI is gone.

Even if there are 'rain rivers' coming in, the quantity of rain water is negligible compared to the thousands of meters of glacier ice.
"Whats to stop the whole damn thing sliding into the ocean in chunks?" - I wouldn't worry about this particular scenario.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Sleepy on October 27, 2018, 08:02:11 AM
Are you sure about that Hefaistos?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: magnamentis on October 27, 2018, 06:52:00 PM
just in case that someone's understanding is otherwise, sea ice does NOT add to weight of the region, it will displace the amount of weight in water equivalent. only land-ice would add weight, hence in case that greenland keeps it's approximate ice-volume for another while not much (nothing ) will change and in case greenland would loose a lot of it's ice-shield the balance should improve because a lot of weight (mass) that's not centered by now would disappear while in the centers, south and north there won't be much of a mass-shift.


antarctic ice-shield is sufficiently centered over the pole and the north pole i mentioned above.

only should greenland significantly gain ice volume would things be different while i'm sure, in that case so would other regions and neutralize some (most) of the effect.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on October 27, 2018, 11:02:36 PM
just in case that someone's understanding is otherwise, sea ice does NOT add to weight of the region, it will displace the amount of weight in water equivalent. only land-ice would add weight, hence in case that greenland keeps it's approximate ice-volume for another while not much (nothing ) will change and in case greenland would loose a lot of it's ice-shield the balance should improve because a lot of weight (mass) that's not centered by now would disappear while in the centers, south and north there won't be much of a mass-shift.


antarctic ice-shield is sufficiently centered over the pole and the north pole i mentioned above.

only should greenland significantly gain ice volume would things be different while i'm sure, in that case so would other regions and neutralize some (most) of the effect.

In order to further help avoid confusion, the weight of sea ice is opposed by the opposite force of buoyancy, meaning that it is essentially free floating; however, the great majority of the Greenland Ice Sheet, GIS, consists of marine-terminating glaciers that have a very large component of something called Volume above Floatation.  This means that marine glaciers and marine-terminating glaciers rest on the seafloor, and the weight of the volume above floatation holds these glaciers down from floating.  Thus all portions of the volume above floatation for the GIS (and the EAIS and WAIS) would contribute to sea-level-raise if they were to either melt, and/or move/slide/calve into water depths so deep that they float.

Edit, see also:

Title: "Calculating glacier ice volumes and sea level equivalents"

http://www.antarcticglaciers.org/glaciers-and-climate/estimating-glacier-contribution-to-sea-level-rise/

Extract:

Table 1. Sea level equivalent (SLE) from various land ice sources. From IPCC AR5 (Vaughan et al, 2013).

Ice on land                                   Sea level equivalent (m)
Antarctic Ice Sheet                                           58.3
Greenland Ice Sheet                                         7.36
Glaciers and ice caps                                        0.41
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Hefaistos on October 30, 2018, 07:06:19 AM
Are you sure about that Hefaistos?

Yeah. In comparison to e.g. WAIS we shouldn't worry too much about GIS.

GIS rests in a 'cradle' of mountain chains. Sure, there are some weak spots, but with Greenland becoming the new Northern cold pole, I suppose dramatic melt due to 'rain rivers' will be restrained.

+Historical evidence from Eemian:

"Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling (‘NEEM’) ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 ± 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 ± 250 metres, reaching surface elevations 122,000 years ago of 130 ± 300 metres lower than the present."

https://www.nature.com/articles/nature11789
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Sleepy on October 30, 2018, 07:37:22 AM
Are you sure about that Hefaistos?

Yeah. In comparison to e.g. WAIS we shouldn't worry too much about GIS.
Of course, because Greenland melt will end up in the the southern hemisphere and Antarctic melt will end up here. As for the rest, I wouldn't be sure or suppose anything with current warming rates.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on October 30, 2018, 10:08:58 PM
It seems to me that the behavior of the NEGIS during the Holocene Optimum ~7.8 – 1.2 ka, provides a point of concern as to how much ice mass loss may occur for this key marine terminating ice stream in the coming decades:

Nicolaj K. Larsen et al. (14 May 2018), "Instability of the Northeast Greenland Ice Stream over the last 45,000 years", Nature Communications, Volume 9, Article number: 1872, doi:10.1038/s41467-018-04312-7

http://www.nature.com/articles/s41467-018-04312-7

Abstract: "The sensitivity of the Northeast Greenland Ice Stream (NEGIS) to prolonged warm periods is largely unknown and geological records documenting such long-term changes are needed to place current observations in perspective. Here we use cosmogenic surface exposure and radiocarbon ages to determine the magnitude of NEGIS margin fluctuations over the last 45 kyr (thousand years). We find that the NEGIS experienced slow early Holocene ice-margin retreat of 30–40 m a−1, likely as a result of the buttressing effect of sea-ice or shelf-ice. The NEGIS was ~20–70 km behind its present ice-extent ~41–26 ka and ~7.8–1.2 ka; both periods of high orbital precession index and/or summer temperatures within the projected warming for the end of this century. We show that the NEGIS was smaller than present for approximately half of the last ~45 kyr and is susceptible to subtle changes in climate, which has implications for future stability of this ice stream."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: litesong on October 31, 2018, 01:03:24 AM
I don't think it's "gravitationally unstable", especially as compared to parts of Antarctic's ice......  Even if there are 'rain rivers' coming in, the quantity of rain water is negligible compared to the thousands of meters of glacier ice.
First, comparing Greenland to Antarctica can't be done for many reasons, one being that West Antarctica is nearly a set of above sea level islands & underwater grounding rock islands. Second, already the center core of Greenland is in uplift. Third, those 'rain rivers' aren't considered "iffy", since Greenland is losing sea ice, as much as 400+ cubic kilometers per year, even tho total solar irradiation has been low for 12 years. When the Pineapple Express pours on our Cascade Mountains in Washington state, the rain rivers, not only pour into our valleys, but melt the snows & glaciers, which also exit with the rains. Some of our glaciers are gone & the majority on in recession. When the sun upgrades to normal, will Hefaistos consider Greenland 'rain rivers' iffy, when Greenland ice loss hits 1000 cubic kilometers per year, or 5000 per year, or 10,000 per year? 
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Sleepy on October 31, 2018, 01:15:37 PM
We’ve entered some profoundly unfamiliar planetary territory.
https://mashable.com/article/climate-change-carbon-pollution-15-million-years/ (https://mashable.com/article/climate-change-carbon-pollution-15-million-years/)
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Hefaistos on October 31, 2018, 03:04:35 PM
I don't think it's "gravitationally unstable", especially as compared to parts of Antarctic's ice......  Even if there are 'rain rivers' coming in, the quantity of rain water is negligible compared to the thousands of meters of glacier ice.
First, comparing Greenland to Antarctica can't be done for many reasons, one being that West Antarctica is nearly a set of above sea level islands & underwater grounding rock islands. Second, already the center core of Greenland is in uplift. Third, those 'rain rivers' aren't considered "iffy", since Greenland is losing sea ice, as much as 400+ cubic kilometers per year, even tho total solar irradiation has been low for 12 years. When the Pineapple Express pours on our Cascade Mountains in Washington state, the rain rivers, not only pour into our valleys, but melt the snows & glaciers, which also exit with the rains. Some of our glaciers are gone & the majority on in recession. When the sun upgrades to normal, will Hefaistos consider Greenland 'rain rivers' iffy, when Greenland ice loss hits 1000 cubic kilometers per year, or 5000 per year, or 10,000 per year?
Sorry, but when you quoted me, you omitted an important part of the argument. Here is what I wrote: "I don't think it's "gravitationally unstable", especially as compared to parts of Antarctic's ice.
It's got to be a very slow process warming the glaciers up, especially as it seems that Greenland is about to replace the Arctic sea as the north cold pole, once ASI is gone.
Even if there are 'rain rivers' coming in, the quantity of rain water is negligible compared to the thousands of meters of glacier ice."

GIS is on high altitudes, it's freezing temperatures most of the year. Rain rivers will eat the ice sheet away on the edges, at lower altitudes, but higher up, where most of GIS is, 'rain rivers' will be 'snow cannons', and the snow that falls will eventually be compressed to form new ice.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on October 31, 2018, 04:41:50 PM
While certainly the WAIS is more susceptible to rapid collapse from hydrofacturing of ice shelves followed by cliff failures of the subsequently exposed marine glacier ice cliffs; nevertheless, the GIS has a significant number of marine terminating glacier that are subject to accelerating rates of cliff failures (with continued global warming) as indicated by the linked reference and associated image:

Tanja Schlemm and Anders Levermann (2018), "A simple stress-based cliff-calving law", The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-205

https://www.the-cryosphere-discuss.net/tc-2018-205/tc-2018-205.pdf

Abstract. Over large coastal regions in Greenland and Antarctica the ice sheet calves directly into the ocean. In contrast to ice-shelf calving, an increase in cliff calving directly contributes to sea-level rise and a monotonously increasing calving rate with ice thickness can constitute a self-amplifying ice loss mechanism that may significantly alter sea-level projections both of Greenland and Antarctica. Here we seek to derive a minimalistic stress-based parameterization for cliff calving. To this end we compute the stress field for a glacier with a simplified two-dimensional geometry from the two-dimensional Stokes equation. First we assume a constant yield stress to derive the failure region at the glacier front from the stress field within the ice sheet. Secondly, we assume a constant response time of ice failure due to exceedance of the yield stress. With this strongly constraining but very simple set of assumption we propose a cliff-calving law where the calving rate follows a power-law dependence on the freeboard of the ice with exponents between 2 and 3 depending on the relative water depth at the calving front. The critical freeboard below which the ice front is stable decreases with increasing relative water depth of the calving front. For a dry water front it is, for example, 75m. The purpose of this study is not to provide a comprehensive calving law, but to derive a particularly simple equation with a transparent and minimalistic set of assumptions.

Edit: At risk of stating the obvious, as the calving face retreats down a negatively slope into a marine basin such as either the Byrd Subglacial Basin, BSB (in West Antarctica), or the central basin beneath the Greenland Ice Sheet, both the relative water depth and the freeboard of the associated ice cliff increase which leads to a positive feedback on the rate of acceleration of calving.  Furthermore, the keel draft of the associated calved icebergs are always shallower than the associated water depth, and thus the associated icebergs may float out of the glacier gateway into the open ocean, and/or contribute immediately to sea level rise by floating above the submerged basin floor and pushing associate water out the glacier gateway into the open ocean.

Edit2: Of course it is also true that if the calving face of marine glacier retreats into a submerged basin (like BSB or the central Greenland Basin) that the calved icebergs might (or might not) form a sufficiently dense ice mélange that could buttress and thus inhibit further ice cliff failures until the ice mélange disperses.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on October 31, 2018, 06:05:09 PM
Pretty scary news (that CaCO3 is currently being dissolved from the seafloor) even for Halloween, in that this happened during the PETM, and it took Earth over 100,000 years to recover from that event:

Olivier Sulpis, Bernard P. Boudreau, Alfonso Mucci, Chris Jenkins, David S. Trossman, Brian K. Arbic, and Robert M. Key (published ahead of print October 29, 2018), "Current CaCO3 dissolution at the seafloor caused by anthropogenic CO2", PNAS, https://doi.org/10.1073/pnas.1804250115

http://www.pnas.org/content/early/2018/10/23/1804250115

Significance

The geological record contains numerous examples of “greenhouse periods” and ocean acidification episodes, where the spreading of corrosive (CO2-enriched) bottom waters enhances the dissolution of CaCO3 minerals delivered to the seafloor or contained within deep-sea sediments. The dissolution of sedimentary CaCO3 neutralizes excess CO2, thus preventing runaway acidification, and acts as a negative-feedback mechanism in regulating atmospheric CO2 levels over timescales of centuries to millennia. We report an observation-based indication and quantification of significant CaCO3 dissolution at the seafloor caused by man-made CO2. This dissolution is already occurring at various locations in the deep ocean, particularly in the northern Atlantic and near the Southern Ocean, where the bottom waters are young and rich in anthropogenic CO2.

Abstract

Oceanic uptake of anthropogenic CO2 leads to decreased pH, carbonate ion concentration, and saturation state with respect to CaCO3 minerals, causing increased dissolution of these minerals at the deep seafloor. This additional dissolution will figure prominently in the neutralization of man-made CO2. However, there has been no concerted assessment of the current extent of anthropogenic CaCO3 dissolution at the deep seafloor. Here, recent databases of bottom-water chemistry, benthic currents, and CaCO3 content of deep-sea sediments are combined with a rate model to derive the global distribution of benthic calcite dissolution rates and obtain primary confirmation of an anthropogenic component. By comparing preindustrial with present-day rates, we determine that significant anthropogenic dissolution now occurs in the western North Atlantic, amounting to 40–100% of the total seafloor dissolution at its most intense locations. At these locations, the calcite compensation depth has risen ∼300 m. Increased benthic dissolution was also revealed at various hot spots in the southern extent of the Atlantic, Indian, and Pacific Oceans. Our findings place constraints on future predictions of ocean acidification, are consequential to the fate of benthic calcifiers, and indicate that a by-product of human activities is currently altering the geological record of the deep sea.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: litesong on October 31, 2018, 06:12:47 PM
Rain rivers will eat the ice sheet away on the edges, at lower altitudes, but higher up, where most of GIS is, 'rain rivers' will be 'snow cannons', and the snow that falls will eventually be compressed to form new ice.
With AGW warming the planet, some warmer snows which used to "be compressed to form new ice" aren't forming new ices. Also, any rain that is falling is warmer rain, that melts more snow & ice. Classic examples are lower latitude mountains which are now losing their glaciers. Our Washington state Cascade Mountains are losing glaciers rapidly, even on Mt. Rainier. Many of our late summer rivers into early fall have decreased their mass flow rates due to no longer existing glaciers which used to supply river & creek waters in the last times before fall rains & snows began. Increasing AGW effects as at the low latitude conditions, are already nibbling at the fringes of Greenland (& yes, at Antarctica too) & surprisingly at higher Greenland elevations.
 Yeah, the Greenland Ice Sheet is not stable.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: litesong on October 31, 2018, 06:29:16 PM
We’ve entered some profoundly unfamiliar planetary territory.
https://mashable.com/article/climate-change-carbon-pollution-15-million-years/ (https://mashable.com/article/climate-change-carbon-pollution-15-million-years/)
First, it was less than 600,000 years ago, then 600,000 years ago, then 800,000 years ago. Now scientists are saying CO2 is higher than 15 million years ago? This here AGW stuff.... its a time machine.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Sleepy on October 31, 2018, 09:24:55 PM
Unfortunately litesong, no-one has invented a time machine that can take us back.
It's the speed that's the big issue here, followed by the speed and then in third place, the speed.

Using the Eeemian as an analogy, with Greenland as the new "cold pole" doesn't really work. First, we now know that the year-to-year variability in SMB can be high and is highly dependent on the weather. Second, the ice on Greenland covers "only" ~1,700,000 km², the Arctic Ocean ~14,000,000 km². Third, during the Eemian it was warmer summers that melted the ice thanks to different orbital parameters. Fourth, CO2 levels during the Eemian peaked around 280ppm.

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=1021.0;attach=110515;image)

Hopefully GRACE-FO starts producing soon. It won't help us mitigate though.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 01, 2018, 03:54:43 PM
The linked research indicates that: a) the oceans have absorbed 60% heat than assumed by AR5; b) The carbon budget assumed by AR5 must be decreased by at least 25%; and c) the range of climate sensitivity is higher than assumed by AR5:

Title: "Earth's oceans have absorbed 60 percent more heat than previously thought"

https://m.phys.org/news/2018-10-earth-oceans-absorbed-percent-previously.html

Extract: "First author Laure Resplandy, an assistant professor of geosciences and the Princeton Environmental Institute, said that her and her co-authors' estimate is more than 60 percent higher than the figure in the 2014 Fifth Assessment Report on climate change from the United Nations Intergovernmental Panel on Climate Change (IPCC).

Scientists know that the ocean takes up roughly 90 percent of all the excess energy produced as the Earth warms, so knowing the actual amount of energy makes it possible to estimate the surface warming we can expect, said co-author Ralph Keeling, a Scripps Oceanography geophysicist and Resplandy's former postdoctoral adviser.

"The result significantly increases the confidence we can place in estimates of ocean warming and therefore helps reduce uncertainty in the climate sensitivity, particularly closing off the possibility of very low climate sensitivity," Keeling said.

The researchers' findings suggest that if society is to prevent temperatures from rising above that mark, emissions of carbon dioxide, the chief greenhouse gas produced by human activities, must be reduced by 25 percent compared to what was previously estimated, Resplandy said."

See also:
 
Resplandy et al. (Oct 31 2018), "Quantification of ocean heat uptake from changes in atmospheric O₂ and CO₂ composition", Nature 563, 105-108, doi: https://doi.org/10.1038/s41586-018-0651-8

http://www.nature.com/articles/s41586-018-0651-8

Finally, I note that Resplandy's calculation that the carbon budget should be reduced by 25% is essentially the same thing as saying that TCR is 25% larger than estimated by AR5.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 05, 2018, 11:44:56 PM
The linked reference indicates that 128 kya, the bipolar seesaw contributed significantly to the warming of the Antarctic and Southern Ocean temperatures, due ice melting in the Northern Hemisphere.  This supports Hanson's ice-climate feedback mechanism and further indicates that ice mass loss from Greenland will accelerated ice mass loss from Antarctica:

Max D. Holloway et al. (23 October 2018), "Simulating the 128‐ka Antarctic Climate Response to Northern Hemisphere Ice Sheet Melting Using the Isotope‐Enabled HadCM3", Geophysical Research Letters, https://doi.org/10.1029/2018GL079647

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL079647

Abstract
Warmer than present Antarctic and Southern Ocean temperatures during the last interglacial, approximately 128,000 years ago, have been attributed to changes in north‐south ocean heat transport, causing opposing hemispheric temperature anomalies. We investigate the magnitude of Antarctic warming and Antarctic ice core isotopic enrichment in response to Northern Hemisphere meltwater input during the early last interglacial. A 1,600‐year HadCM3 simulation driven by 0.25 Sv of meltwater input reproduces 50–60% of the peak Southern Ocean summer sea surface temperature anomaly, sea ice retreat, and ice core isotope enrichment. We also find a robust increase in the proportion of cold season precipitation during the last interglacial, leading to lower isotopic values at the Antarctic ice core sites. These results suggest that a HadCM3 simulation including 0.25 Sv for 3,000–4,000 years would reconcile the last interglacial observations, providing a potential solution for the last interglacial missing heat problem.

Plain Language Summary
The Antarctic isotope and temperature maximum, which occurred approximately 128,000 years Before Present (yBP) during the warmer than present last interglacial period, is hypothesized to have resulted from a slowdown in northward ocean heat transport due to ice sheet melting into the North Atlantic—a mechanism known as the bipolar seesaw. We test this hypothesis by running and analyzing long, fully coupled, isotope‐enabled climate model simulations, which include meltwater entering the North Atlantic, for this critical period 128,000 yBP. Results are evaluated against ocean and ice core data. After 1,600 years, we simulate 55% of the peak Southern Ocean summer sea surface temperature anomaly, 50% of the estimated winter sea ice retreat, and 60% of the ice core isotope enrichment reconstructed during the early last interglacial Antarctic climate optimum.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Sleepy on November 08, 2018, 07:11:23 AM
Hopefully GRACE-FO starts producing soon. It won't help us mitigate though.
I'm a bit sleepy but amazing timing by NASA and GFZ.  ;D

News | November 1, 2018
GRACE-FO Resumes Data Collection
https://www.jpl.nasa.gov/news/news.php?feature=7276
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 21, 2018, 09:14:40 PM
While in other threads I have stated that I would no longer post in the ASIF, I have decided that as the risk of abrupt sea level rise, SLR, this century is so much higher than many decisionmakers appreciate; I will periodically post in this one ASIF thread.  In this regard, I make a few posts illustrating how decisionmakers are confused about the topic of abrupt SLR, and I begin by providing the first linked reference by Pattyn (2018), which points out that many (most) current consensus ice-sheet model projections of Antarctic Ice Sheet, AIS, contribution to SLR used inappropriate equilibrium initial states for their models; while dynamical initial states are necessary for short-term projections on the order of decades.  Furthermore, Pattyn (2018) notes that such dynamical initial conditions need to properly account for not only Marine Ice Sheet Instability, MISI, but also for Marine Ice Cliff Instability, MICI, and for hydro-fracturing mechanisms (see the first attached image).

Frank Pattyn (2018 Jul 16), "The paradigm shift in Antarctic ice sheet modelling", Nat Commun. 2018; 9: 2728; doi:  10.1038/s41467-018-05003-z

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6048022/

Abstract: "The Antarctic ice sheet is one of the largest potential contributors to future sea level rise. Predicting its future behaviour using physically-based ice sheet models has been a bottleneck for the past decades, but major advances are ongoing."

Extract: "A key aspect of projecting future Antarctic mass loss with dynamical ice sheet models is related to the initial state of the model. Since ice sheet models were initially applied for palaeo-climatic studies on long time scales, initialisation was generally obtained from a long spin-up time leading to a steady-state ice sheet (both in terms of geometry and thermodynamics). However, for predictions on shorter time scales (decades to centuries), a stable spin-up generally leads to an ice sheet geometry far different from the one currently observed, which is one of the reasons why such ice sheet models may respond differently than observations suggest. Moreover, using a steady-state for initialising the ice sheet prevents models from properly accounting for the dynamical mass losses observed over the last decade, as the present-day ice sheet is not in steady state. Motivated by the increasing ice sheet imbalance of the ASE glaciers over the last 20 years, and supported by the recent boom in satellite data availability, data-assimilation methods are progressively used to evaluate unknown fields using time-evolving states accounting for the transient nature of observations and the model dynamics."

Next I note that, Bronselaer et al (2018) used an AIS model that does not account for MICI nor hydro-fracturing (which are not likely to be significant before 2040) to show that by 2040 upwelling of relatively warm circumpolar deep water, CDW, around Antarctic will shift the potential ice melting temperature difference upward from below 1,000 m depth to roughly 750 m depth, and will increasingly advect this warm CDW towards the grounding line (see the second attached image) for key marine glaciers such as the Pine Island Glacier, PIG (see the third image wrt the water depth of the grounding line) and the Thwaites Glacier (see the fourth image).  What is critical to note wrt Bronselaer et al (2018) is that by 2040 the temperature of the Southern Ocean would be thousands of years from full equilibrium, but for key AIS marine glaciers both the top and bottom ice surfaces exposed to air and water respectively will experience ice mass loss sufficient to trigger localized MICI and hydro-fracturing mechanisms (if they had been included in Bronselaer et al (2018)'s model.

Bronselaer, B. et al. (2018) Change in future climate due to Antarctic meltwater, Nature, doi:s41586-018-0712-z

https://www.nature.com/articles/s41586-018-0712-z

Abstract: "Meltwater from the Antarctic Ice Sheet is projected to cause up to one metre of sea-level rise by 2100 under the highest greenhouse gas concentration trajectory (RCP8.5) considered by the Intergovernmental Panel on Climate Change (IPCC). However, the effects of meltwater from the ice sheets and ice shelves of Antarctica are not included in the widely used CMIP5 climate models, which introduces bias into IPCC climate projections. Here we assess a large ensemble simulation of the CMIP5 model ‘GFDL ESM2M’ that accounts for RCP8.5-projected Antarctic Ice Sheet meltwater. We find that, relative to the standard RCP8.5 scenario, accounting for meltwater delays the exceedance of the maximum global-mean atmospheric warming targets of 1.5 and 2 degrees Celsius by more than a decade, enhances drying of the Southern Hemisphere and reduces drying of the Northern Hemisphere, increases the formation of Antarctic sea ice (consistent with recent observations of increasing Antarctic sea-ice area) and warms the subsurface ocean around the Antarctic coast. Moreover, the meltwater-induced subsurface ocean warming could lead to further ice-sheet and ice-shelf melting through a positive feedback mechanism, highlighting the importance of including meltwater effects in simulations of future climate."

Caption for the second attached image: "Fig. 5 | Mechanism for ocean warming. a, Hovmoller diagram of the meltwater-induced ocean temperature anomaly, averaged along the Antarctic coast, as a function of time. The black dotted line indicates the maximum warming in a given year. b, c, Schematic of the meltwater-induced Southern Ocean subsurface warming, shown as a zonal-mean cross-section. In the pre-industrial state (b), isopycnals (black lines) are tilted towards the ocean surface by westerly winds (black circles, directed out of the page), away from the continental shelf, with an upward heat flux transporting heat from the warm CDW (orange water) towards the cooler surface (blue water), as shown by the red arrow. In the perturbed state (c), meltwater from the Antarctic Ice Sheet freshens the surface (blue), depressing isopycnals (solid to dashed black lines) so that isopycnal mixing transports heat towards the continent rather than towards the ocean surface (red arrow), leading to coastal warming at depth around the shelf and cooling at the surface."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 21, 2018, 09:16:29 PM
As a follow-on to my last post I note that, Pollard, DeConto & Alley (2018) use their Antarctic Ice Sheet, AIS, model with ice-cliff and hydrofracturing failure mechanisms together with ice mélange back pressures calibrated to that currently observed for the Jakobshavn marine terminating glacier in Greenland.  Pollard et al (2018) then assumed the abrupt imposition of warm mid-Pliocene climate conditions (which roughly have a GMSTA above pre-industrial of over 1.5C and ocean water temperatures beneath the ice of key AIS marine glaciers comparable to those found by Bronselaer et al (2018) after 2040).  Assuming these approximations Antarctica could look like the illustrations shown in column 'b' in the first image, and may contributed about 3 m to SLR, by roughly 2090, per panel 'a' of the second attached image.  Furthermore, the third attached image (from Hansen (2018)) show that currently GMSTA is about 1.05C and that the most recent two La Ninas imply a warming rate of 0.38°C per decade; which indicates that by 2040 GMSTA may be over 1.8C (which would match Mid-Pliocene conditions).  Finally, the last attached image (from Hansen et al (2016)) shows gold colored curves for abrupt ice sheet mass loss beginning circa 2040, that show such an ice mass loss would temporarily cool GMSTA, but would also temporarily increase the global energy imbalance, which implies an abrupt & temporary increase in climate sensitivity that would wreak severe storm activity around the planet:

David Pollard, Robert M. DeConto, Richard B. Alley (13 March 2018), "A continuum model of ice mélange and its role during retreat of the Antarctic Ice Sheet", Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2018-28

https://www.geosci-model-dev-discuss.net/gmd-2018-28/gmd-2018-28.pdf

Abstract: "Rapidly retreating thick ice fronts can generate large amounts of mélange (floating ice debris), which may affect episodes of rapid retreat of Antarctic marine ice. In modern Greenland fjords, mélange provides substantial back pressure on calving ice faces, which slows ice-front velocities and calving rates. On the much larger scales of West Antarctica, it is unknown if mélange could clog seaways and provide enough back pressure to act as a negative feedback slowing retreat.  Here we describe a new mélange model, using a continuum mechanical formulation that is computationally feasible for long-term continental Antarctic applications. It is tested in an idealized rectangular channel and calibrated very basically using observed modern conditions in Jakobshavn fjord, West Greenland. The model is then applied to drastic retreat of Antarctic ice in response to warm mid-Pliocene climate. With mélange parameter values that yield reasonable modern Jakobshavn results, Antarctic marine ice still retreats drastically in the Pliocene simulations, with little slowdown despite the huge amounts of mélange generated. This holds both for the rapid early collapse of West Antarctica, and later retreat into major East Antarctic basins. If parameter values are changed to make the mélange much more resistive to flow, far outside the range for reasonable Jakobshavn results, West Antarctica still collapses and retreat is slowed or prevented only in a few East Antarctic basins."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Sleepy on November 21, 2018, 09:25:29 PM
Welcome back ASLR.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 21, 2018, 09:34:18 PM
As I said that I would make a few posts (which I take to mean three posts today), I provide the following like to an article that cites research that confirms that current ice mass loss is contributing (see blue line in the attached image) to the drift of the Earth's rotational axis about the poles:

Scientists Identified Three Reasons Responsible for Earth’s Spin Axis Drift

http://www.geologyin.com/2018/09/scientists-identified-three-reasons.html

Extract: "A typical desk globe is designed to be a geometric sphere and to rotate smoothly when you spin it. Our actual planet is far less perfect—in both shape and in rotation.

Earth is not a perfect sphere. When it rotates on its spin axis—an imaginary line that passes through the North and South Poles—it drifts and wobbles. These spin-axis movements are scientifically referred to as "polar motion." Measurements for the 20th century show that the spin axis drifted about 4 inches (10 centimeters) per year. Over the course of a century, that becomes more than 11 yards (10 meters).

Using observational and model-based data spanning the entire 20th century, NASA scientists have for the first time identified three broadly-categorized processes responsible for this drift—contemporary mass loss primarily in Greenland, glacial rebound, and mantle convection.

"The traditional explanation is that one process, glacial rebound, is responsible for this motion of Earth's spin axis. But recently, many researchers have speculated that other processes could have potentially large effects on it as well," said first author Surendra Adhikari of NASA's Jet Propulsion Laboratory in Pasadena, California."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 21, 2018, 09:35:20 PM
Welcome back ASLR.

With a limited bandwidth ;)

Thanks,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: oren on November 22, 2018, 04:09:24 AM
Great to see you back ASLR, even if on a limited fashion. Your scientific contributions are sorely missed. Hopefully they will increase again as time goes by, as there are many subjects you have been covering that have been suffering as a result of your absence.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Lennart van der Linde on November 22, 2018, 08:09:50 AM
Good to see you back, ASLR!
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Stephan on November 22, 2018, 06:40:51 PM
Thank you for having you back. We have missed your contributions.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 24, 2018, 02:07:49 AM
Thank you all.

&

As stated in the first linked article, when Hansen et al. (2016) clearly presented their case/scenarios for abrupt SLR and associated coming superstorms in the coming decades; it "… met with skepticism from a number of other climate scientists."  However, this first linked article and the associated reference by Alessandro Silvano et al (18 Apr 2018), provides some concrete evidence that at least portions of Hansen's ice-climate feedback mechanism (e.g. reduced global overturning circulation) are already being activated. 

Title: "One of the most worrisome predictions about climate change may be coming true"

http://www.columbia.edu/~jeh1/mailings/2018/Mooney.2018.WorrisomePredictionsMayComeTrue.WP.pdf

Extract: "Two years ago, former NASA climate scientist James Hansen and a number of colleagues laid out a dire scenario in which gigantic pulses of fresh water from melting glaciers could upend the circulation of the oceans, leading to a world of fast-rising seas and even superstorms.

Hansen’s scenario was based on a computer simulation, not hard data from the real world, and met with skepticism from a number of other climate scientists. But now, a new oceanographic study appears to have confirmed one aspect of this picture — in its early stages, at least.

The new research, based on ocean measurements off the coast of East Antarctica, shows that melting Antarctic glaciers are indeed freshening the ocean around them. And this, in turn, is blocking a process in which cold and salty ocean water sinks below the sea surface in winter, forming “the densest water on the Earth,” in the words of study lead author Alessandro Silvano, a researcher with the University of Tasmania in Hobart."

&

Alessandro Silvano et al (18 Apr 2018), "Freshening by glacial meltwater enhances melting of ice shelves and reduces formation of Antarctic Bottom Water", Science Advances, Vol. 4, no. 4, eaap9467, DOI: 10.1126/sciadv.aap9467

http://advances.sciencemag.org/content/4/4/eaap9467

Abstract: "Strong heat loss and brine release during sea ice formation in coastal polynyas act to cool and salinify waters on the Antarctic continental shelf. Polynya activity thus both limits the ocean heat flux to the Antarctic Ice Sheet and promotes formation of Dense Shelf Water (DSW), the precursor to Antarctic Bottom Water. However, despite the presence of strong polynyas, DSW is not formed on the Sabrina Coast in East Antarctica and in the Amundsen Sea in West Antarctica. Using a simple ocean model driven by observed forcing, we show that freshwater input from basal melt of ice shelves partially offsets the salt flux by sea ice formation in polynyas found in both regions, preventing full-depth convection and formation of DSW. In the absence of deep convection, warm water that reaches the continental shelf in the bottom layer does not lose much heat to the atmosphere and is thus available to drive the rapid basal melt observed at the Totten Ice Shelf on the Sabrina Coast and at the Dotson and Getz ice shelves in the Amundsen Sea. Our results suggest that increased glacial meltwater input in a warming climate will both reduce Antarctic Bottom Water formation and trigger increased mass loss from the Antarctic Ice Sheet, with consequences for the global overturning circulation and sea level rise."

Indeed, the second reference Caesar et al. (2018) (and the associated linked RealClimate article), provide further proof that the AMOC is slowing as projected by Hansen et al (2016).

Caesar et al. (April 12, 2018) "Observed fingerprint of a weakening Atlantic Ocean overturning circulation", Nature, Vol 556, http://doi.org/10.1038/s41586-018-0006-5

https://www.nature.com/articles/s41586-018-0006-5.epdf?author_access_token=d9GwXXnkYQw6itiGny0ZW9RgN0jAjWel9jnR3ZoTv0OdzeJ18XkImxSDnyYEEsE8cCDHkcmVSlMgRd2VzekBpzVfe728uOBU7B1e8unrLGpKyeWhlTvQKe6JHGdYV8iLm4nND7KgW4aTVEUH8xo0AA%3D%3D

Abstract: "The Atlantic meridional overturning circulation (AMOC)—a system of ocean currents in the North Atlantic—has a major impact on climate, yet its evolution during the industrial era is poorly known owing to a lack of direct current measurements. Here we provide evidence for a weakening of the AMOC by about 3 ± 1 sverdrups (around 15 per cent) since the mid-twentieth century. This weakening is revealed by a characteristic spatial and seasonal sea-surface temperature ‘fingerprint’—consisting of a pattern of cooling in the subpolar Atlantic Ocean and warming in the Gulf Stream region—and is calibrated through an ensemble of model simulations from the CMIP5 project. We find this fingerprint both in a high-resolution climate model in response to increasing atmospheric carbon dioxide concentrations, and in the temperature trends observed since the late nineteenth century. The pattern can be explained by a slowdown in the AMOC and reduced northward heat transport, as well as an associated northward shift of the Gulf Stream. Comparisons with recent direct measurements from the RAPID project and several other studies provide a consistent depiction of record-low AMOC values in recent years."

See also:

Title: "If you doubt that the AMOC has weakened, read this"

http://www.realclimate.org/index.php/archives/2018/05/if-you-doubt-that-the-amoc-has-weakened-read-this/

Furthermore, the third linked reference (Pedro et al. (2018)) demonstrates that the bipolar seesaw (associated with changes in the global overturning circulation) is indeed part of a larger 'interhemispheric coupling' that is a bigger part of Hansen's ice-climate feedback mechanism.  However, while Pedro et al (2018) focus on calibrating their computer model for 'interhemispheric coupling' first triggered by ice mass loss from the Greenland Ice Sheet, GIS; the associated first image clearly shows paleo-evidence that 'interhemispheric coupling' triggered by ice mass loss from the Antarctic Ice Sheet, AIS, leads to an abrupt warming of the GIS.  This indicates that if my various posts in this thread are correct that the AIS may contribute multiple meters to SLR in the coming decades, then this will likely trigger a rapid warming of the GIS in the subsequent decades; which would then drive further abrupt SLR & more superstorms.

Joel B. Pedro , Markus Jochum, Christo Buizert, Feng He, Stephen Barker & Sune O. Rasmussen (15 July 2018), "Beyond the bipolar seesaw: Toward a process understanding of interhemispheric coupling", Quaternary Science Reviews, Volume 192, , Pages 27-46, https://doi.org/10.1016/j.quascirev.2018.05.005

https://www.sciencedirect.com/science/article/pii/S0277379117310351

Abstract: "The thermal bipolar ocean seesaw hypothesis was advanced by Stocker and Johnsen (2003) as the ‘simplest possible thermodynamic model’ to explain the time relationship between Dansgaard–Oeschger (DO) and Antarctic Isotope Maxima (AIM) events. In this review we combine palaeoclimate observations, theory and general circulation model experiments to advance from the conceptual model toward a process understanding of interhemispheric coupling and the forcing of AIM events. We present four main results: (1) Changes in Atlantic heat transport invoked by the thermal seesaw are partially compensated by opposing changes in heat transport by the global atmosphere and Pacific Ocean. This compensation is an integral part of interhemispheric coupling, with a major influence on the global pattern of climate anomalies. (2) We support the role of a heat reservoir in interhemispheric coupling but argue that its location is the global interior ocean to the north of the Antarctic Circumpolar Current (ACC), not the commonly assumed Southern Ocean. (3) Energy budget analysis indicates that the process driving Antarctic warming during AIM events is an increase in poleward atmospheric heat and moisture transport following sea ice retreat and surface warming over the Southern Ocean. (4) The Antarctic sea ice retreat is itself driven by eddy-heat fluxes across the ACC, amplified by sea-ice–albedo feedbacks. The lag of Antarctic warming after AMOC collapse reflects the time required for heat to accumulate in the ocean interior north of the ACC (predominantly the upper 1500 m), before it can be mixed across this dynamic barrier by eddies."

Finally for this post, the second attached image from the Sentinel satellite for Nov 23 2018, shows that the Southwest Tributary Ice Shelf is no longer blocked by the Pine Island Ice Shelf; which means that the ice flow velocity of the Southwest Tributary Glacier is currently accelerating; which in turn means that the east shear margin of the Thwaites Glacier (see the third image) well progressively offer less stabilization to the Thwaites Glacier; which in turn may well trigger the abrupt collapse of major portions of the Byrd Subglacial Basin within the next one to two decades (when considering concurrent influences from the ENSO & ASL interactions).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RealityCheck on November 24, 2018, 02:32:13 PM
Good to see your postings here again, ASLR. Welcome back from me too. I long ago concluded that this is this single most important thread on the forum. So thanks for your renewed contributions, if only here...
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: John_The_Elder on November 24, 2018, 03:42:51 PM
Great to see you back. You are one of the best! :)
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 24, 2018, 08:57:49 PM
Great to see you back ASLR, even if on a limited fashion. Your scientific contributions are sorely missed. Hopefully they will increase again as time goes by, as there are many subjects you have been covering that have been suffering as a result of your absence.

oren,

You (& others who are so inclined) should feel free to re-post any information that I provide in this thread to other threads where you feel that contrarians (and/or those who err on the side of least drama) are putting their collective thumbs on the scales.

For example, in the 'Hansen e al paper: 3+ meters SLR by 2100' thread, Reply #713 indicated that the findings of Polyak et al. (2018) that "Altogether, the data show that the MIS-5e highstand began by 126.6  ± 0.4 ka and ended no earlier than 116.0  ± 0.8 ka, representing 10.5 kyr of remarkable Western Mediterranean RSL stability between 1.4 and 2.9 m.a.p.s.l.", induced sidd to state:

"I find this striking because part of my concern for WAIS stability stems from the evidence for late Eemina sea level rise. If that did not actually happen, my concern is (slightly) diminished."

https://forum.arctic-sea-ice.net/index.php/topic,1327.700.html

In this regard, I note that the correct interpretation of paleo-SLR data is notoriously challenging and includes many uncertainties that could easily change Polyak et al. (2018)'s conclusions such as is illustrated by their own Fig. 3 (see the first attached image), including:

1. They show that their calculated RSL values (ranging from +1.4m to well over +14m) depend significantly on what GIA model and GIA assumptions that they utilize.
2. Their simplified GIA assumptions do not effectively consider phased ice mass loss scenarios from the NH and the SH.

See also:

Title: "Scientists find stable sea levels during last interglacial"

https://www.sciencedaily.com/releases/2018/09/180910111314.htm

Extract: ""This is the most accurate, best resolved sea level record for MIS-5e of the last interglacial period," said Polyak. "It provides exceptionally accurate timing of the sea level history during the above mentioned period and shows that it rose to 6 meters above present sea level ~127,000 years ago, it would have gradually fell to 2 meters by 122,000 years ago, and would have stayed at that elevation for the remainder of the sea level highstand to 116,000 years ago," says Onac. "The results suggest that if the pre-industrial temperature will be surpassed by 1.5 to 2°C, sea level will respond and rise 2 to 6 meters (7 to 20 feet) above present sea level.""

& see:

Victor J. Polyak, Bogdan P. Onac, Joan J. Fornós, Carling Hay, Yemane Asmerom, Jeffrey A. Dorale, Joaquín Ginés, Paola Tuccimei, Angel Ginés. A highly resolved record of relative sea level in the western Mediterranean Sea during the last interglacial period. Nature Geoscience, 2018; DOI: 10.1038/s41561-018-0222-5

https://www.nature.com/articles/s41561-018-0222-5

Abstract: "The magnitude and trajectory of sea-level change during marine isotope stage (MIS) 5e of the last interglacial period is uncertain. In general, sea level may have been 6–9 m above present sea level, with one or more oscillations of up to several metres superimposed. Here we present a well-dated relative sea-level record from the island of Mallorca in the western Mediterranean Sea for MIS-5e, based on the occurrence of phreatic overgrowths on speleothems forming near sea level. We find that relative sea-level in this region was within a range of 2.15 ±  0.75 m above present levels between 126,600 ±  400 and 116,000 ±  800 years ago, although centennial-scale excursions cannot be excluded due to some gaps in the speleothem record. We corrected our relative sea-level record for glacio-isostatic adjustment using nine different glacial isostatic models. Together, these models suggest that ice-equivalent sea-level in Mallorca peaked at the start of MIS-5e then gradually decreased and stabilized by 122,000 years ago, until the highstand termination 116,000 years ago. Our sea-level record does not support the hypothesis of rapid sea-level fluctuations within MIS-5e. Instead, we suggest that melting of the polar ice sheets occurred early in the interglacial period, followed by gradual ice-sheet growth."

Additional information Supplementary information is available for this paper at https://doi.org/10.1038/ s41561-018-0222-5.


As further evidence that Polyak et al. (2018) may be erring on the side of least drama, Stocchi et al. (2018) find that: "Evidences of two MIS 5e RSL stands are found in Mallorca, northern Tyrrhenian coast of Italy, southeastern Sardinia and Tunisia."; which directly contradicts Polyak et al. (2018)'s conclusion.

See:

Stocchi et al. (2018), "MIS 5e relative sea-level changes in the Mediterranean Sea: Contribution of isostatic disequilibrium", Quaternary Science Reviews 185, 122-134, https://doi.org/10.1016/j.quascirev.2018.01.004

http://www.staff.science.uu.nl/~boer0160/docs/Stocchi_etal_QSR_2018.pdf

Abstract: "Sea-level indicators dated to the Last Interglacial, or Marine Isotope Stage (MIS) 5e, have a twofold value. First, they can be used to constrain the melting of Greenland and Antarctic Ice Sheets in response to global warming scenarios. Second, they can be used to calculate the vertical crustal rates at active margins. For both applications, the contribution of glacio- and hydro-isostatic adjustment (GIA) to vertical displacement of sea-level indicators must be calculated. In this paper, we re-assess MIS 5e sea-level indicators at 11 Mediterranean sites that have been generally considered tectonically stable or affected by mild tectonics. These are found within a range of elevations of 2–10 m above modern mean sea level. Four sites are characterized by two separate sea-level stands, which suggest a two-step sea-level highstand during MIS 5e. Comparing field data with numerical modeling we show that (i) GIA is an important contributor to the spatial and temporal variability of the sea-level highstand during MIS 5e, (ii) the isostatic imbalance from the melting of the MIS 6 ice sheet can produce a >2.0 m sea-level highstand, and (iii) a two-step melting phase for the Greenland and Antarctic Ice Sheets reduces the differences between observations and predictions. Our results show that assumptions of tectonic stability on the basis of the MIS 5e records carry intrinsically large uncertainties, stemming either from uncertainties in field data and GIA models. The latter are propagated to either Holocene or Pleistocene sea-level reconstructions if tectonic rates are considered linear through time."

Extract: "Conclusions
1. The observed range of MIS 5e RSL highstand from 11 tectonically stable sites in the Mediterranean is comprised between 2 and 10m above present msl.  The observed highstands are not necessarily coeval.  Evidences of two MIS 5e RSL stands are found in Mallorca, northern Tyrrhenian coast of Italy, southeastern Sardinia and Tunisia.
2. The GIA-induced RSL changes across the Mediterranean are characterized by significant regional variability throughout the MIS 5e.  The Earth is in isostatic imbalance and a generalized RSL above present sea level is predicted. …
3. According to GIA, the MIS 5e RSL highstand occurs at different times as a function of the geographical location in the Mediterranean.
4. To precisely quantify the GrIS and AIS retreat during MIS5e on the basis on RSL data, requires that the maximum extent, thickness and retreat of the MIS 6 ice sheets, and in particular of Fennoscandia, are constrained.
5. A two-step melting chronology where the GrIS and AIS retreat is out of phase is capable of reconciling predictions and observation provided that the GIA processes are included.
6. Neglecting the uncertainties that are related to RSL indicators and GIA may lead to over or underestimations of local crustal motions even at sites that are considered tectonically stable.  As a consequence, we suggest that caution should be exercised when extrapolating long-term tectonic rates from MIS 5e shorelines."

Furthermore Barlow et al. (2018) find no evidence that RSL fell (note that it takes longer to form new ice sheets and it can take for them to collapse) significantly from the circa 127kya peak (see the second attached image) during the MIS 5e (Eemian).

Barlow NLM, McClymont EL, Whitehouse PL, Stokes CR, Jamieson SSR, Woodroffe SA, Bentley MJ, Callard SL, Ó Cofaigh C, Evans DJA, Horrocks JR, Lloyd JM, Long AJ, Margold M, Roberts DH & Sanchez-Montes ML (2018), "Lack of evidence for a substantial sea-level fluctuation within the Last Interglacial", Nature Geoscience, vol. 11, 627–634, https://doi.org/10.1038/s41561-018-0195-4

https://www.nature.com/articles/s41561-018-0195-4

Abstract: "During the Last Interglacial, global mean sea level reached approximately 6 to 9 m above the present level. This period of high sea level may have been punctuated by a fall of more than 4 m, but a cause for such a widespread sea-level fall has been elusive. Reconstructions of global mean sea level account for solid Earth processes and so the rapid growth and decay of ice sheets is the most obvious explanation for the sea-level fluctuation. Here, we synthesize published geomorphological and stratigraphic indicators from the Last Interglacial, and find no evidence for ice-sheet regrowth within the warm interglacial climate. We also identify uncertainties in the interpretation of local relative sea-level data that underpin the reconstructions of global mean sea level. Given this uncertainty, and taking into account our inability to identify any plausible processes that would cause global sea level to fall by 4 m during warm climate conditions, we question the occurrence of a rapid sea-level fluctuation within the Last Interglacial. We therefore recommend caution in interpreting the high rates of global mean sea-level rise in excess of 3 to 7 m per 1,000 years that have been proposed for the period following the Last Interglacial sea-level lowstand."

Extract: "In conclusion, reconstructions of GMSL during the LIG4,5 have raised the intriguing possibility that fluctuations in ice-sheet volume occurred within the interglacial, that is, ice sheets regrew and then decayed. We have considered several possible driving mechanisms, acting alone or in combination, for multimetre changes in GMSL during the LIG. We find that the current understanding of ice-sheet histories during MIS 6 is not adequate enough to rule out the possibility that limitations in the modelling of the solid Earth response could be contributing to the appearance of a GMSL fall during the LIG3,11. However, if the GMSL fall was driven by changes in ice-sheet mass balance, it would require 1.15–3.45 million km3 of ice to form in less than 1,000 years; we found little geomorphological or sedimentary evidence for such substantial ice-sheet regrowth during the LIG. It is also clear that large uncertainties associated with the interpretation of some local RSL data that underpin the reconstructed GMSL curve remain. Taken together, our analysis leads us to question the occurrence of a rapid GMSL fall within the LIG, which also raises important questions about the very high reconstructed rates of GMSL rise following the lowstand; reported to be approximately 3 to 7 m kyr–1 (ref. 5).

We conclude that it is critical that future reconstructions of GMSL during the LIG include a range of realistic ice-sheet scenarios from the preceding glacial (MIS 6); take into account the impact of dynamic topography on the reconstructed elevations of former RSLs; and assemble a geographically and temporally widespread dataset of local RSL, with careful interpretation of fossil sea-level indicators with respect to tidal datums and accurate chronologies. Until these issues are better resolved, we would urge caution in using rates of GMSL rise from the LIG to project future sea-level changes.

5. Kopp, R. E., Simons, F. J., Mitrovica, J. X., Maloof, A. C. & Oppenheimer, M. A probabilistic assessment of sea level variations within the last interglacial stage. Geophys. J. Int. 193, 711–716 (2013)."


Finally, the third attached image from Austermann et al. (2017) indicates that correctly paleo-SLR data to account for dynamic topography (DT) can increase calculated estimates of paleo-SLR by about a meter in the Western Mediterranean during MIS 5e (Eemian);

Austermann J, Mitrovica JX, Huybers P and Rovere A (2017), "Detection of a dynamic topography signal in last interglacial sea-level records", Science Advances, vol. 3(7), e1700457, https://doi.org/10.1126/sciadv.1700457

http://advances.sciencemag.org/content/3/7/e1700457

Abstract: "Estimating minimum ice volume during the last interglacial based on local sea-level indicators requires that these indicators are corrected for processes that alter local sea level relative to the global average. Although glacial isostatic adjustment is generally accounted for, global scale dynamic changes in topography driven by convective mantle flow are generally not considered. We use numerical models of mantle flow to quantify vertical deflections caused by dynamic topography and compare predictions at passive margins to a globally distributed set of last interglacial sea-level markers. The deflections predicted as a result of dynamic topography are significantly correlated with marker elevations (>95% probability) and are consistent with construction and preservation attributes across marker types. We conclude that a dynamic topography signal is present in the elevation of last interglacial sea-level records and that the signal must be accounted for in any effort to determine peak global mean sea level during the last interglacial to within an accuracy of several meters."

Extract: "A complication in all these studies is that various geodynamic processes contribute to the present elevation of paleo sea level records (8). A notable example of these processes is tectonic uplift or subsidence at active plate boundaries [for example, see Zazo et al. (9)], which often leads to the exclusion of these sites in reconstructions of past GMSL. Another important deformational process is the response of the Earth system to changes in ice and ocean loading during ice age cycles (10, 11), or glacial isostatic adjustment (GIA), a process first studied in the context of the LIG by Lambeck and Nakada (12). The accuracy of model-derived corrections for this global process is subject to uncertainties in ice history and mantle viscoelastic structure [for example, see Lambeck et al. (13)]. Additionally, the redistribution of sediment can lead to sea level changes through the buildup of topography and loading-induced deformation of the solid Earth and gravity field (14, 15).

Earth’s surface is further deflected by viscous stresses associated with buoyancy variations and flow within Earth’s convective mantle that can alter the elevation of sea-level markers subsequent to their formation (16–22). Effects of this so-called dynamic topography (DT) on the current elevation of sea-level markers dating to the mid-Pliocene (~3 million years ago) have been documented (23–25) and imply meter-scale displacements for LIG sea-level markers (24). Kopp et al. (4) incorporated uncertainties due to vertical land movement and applied nonzero rates in several passive margin regions. Although this correction may implicitly include the DT process, effects of DT are generally not addressed in sea level studies of Pleistocene interglacials and have not previously been shown to be detectable during the LIG. Here, we quantify and analyze the effects of DT on globally distributed markers of local peak sea level during the LIG."

Best,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Shared Humanity on November 24, 2018, 09:21:24 PM
AbruptSLR...just wanted to say that I am happy to see you still posting here.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Alison on November 25, 2018, 03:08:49 AM
Missed ya ASLR.  :)
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 25, 2018, 05:05:29 PM
Thanks again for all of the well wishes.

Additionally, to be clear past interglacial periods do not service as analogues for projecting future modern-day climate change; for which state-the-art Earth System Models, ESMs, (with ice-cliff and hydrofracturing mechanisms included) are the best tool for projecting coming climate change.  That said, paleo-information from past glacial and interglacial periods can be helpful in calibrating ESM projections.  In this regard the first linked reference (& associated article) by Rehfeld et al (2018) demonstrates that: "… AWI researchers have now demonstrated that, though climate change has decreased around the globe from glacial to interglacial periods, the difference is by no means as pronounced as previously assumed."  This of course means that climate sensitivity (which is positively correlated with climate variability) is currently higher than consensus scientists previously assumed:

Kira Rehfeld et al, Global patterns of declining temperature variability from the Last Glacial Maximum to the Holocene, Nature (2018). DOI: 10.1038/nature25454

https://www.nature.com/articles/nature25454

Abstract: "Changes in climate variability are as important for society to address as are changes in mean climate1. Contrasting temperature variability during the Last Glacial Maximum and the Holocene can provide insights into the relationship between the mean state of the climate and its variability. However, although glacial–interglacial changes in variability have been quantified for Greenland, a global view remains elusive. Here we use a network of marine and terrestrial temperature proxies to show that temperature variability decreased globally by a factor of four as the climate warmed by 3–8 degrees Celsius from the Last Glacial Maximum (around 21,000 years ago) to the Holocene epoch (the past 11,500 years). This decrease had a clear zonal pattern, with little change in the tropics (by a factor of only 1.6–2.8) and greater change in the mid-latitudes of both hemispheres (by a factor of 3.3–14). By contrast, Greenland ice-core records show a reduction in temperature variability by a factor of 73, suggesting influences beyond local temperature or a decoupling of atmospheric and global surface temperature variability for Greenland. The overall pattern of reduced variability can be explained by changes in the meridional temperature gradient, a mechanism that points to further decreases in temperature variability in a warmer future."

See also:
Title: "Researchers compare global temperature variability in glacial and interglacial periods"

https://phys.org/news/2018-02-global-temperature-variability-glacial-interglacial.html

Extract: "On the basis of a unique global comparison of data from core samples extracted from the ocean floor and the polar ice sheets, AWI researchers have now demonstrated that, though climate change has decreased around the globe from glacial to interglacial periods, the difference is by no means as pronounced as previously assumed."

To better quantify the implications of Rehfeld et al (2018)'s finding, the following linked reference by Dessler & Forster (2018) clearly demonstrate that the likely range for ECS in the period from 2000 to 2017 was 2.4 to 4.6C (with a mode and a mean of 2.9 and 3.3C, respectively) as opposed to AR5's cited likely range of 1.5 to 4.5C.

Furthermore, it is important to remember that ECS is not a fixed value but rather is projected to increase with continued global warming, this century:

A. E. Dessler and P.M. Forster (07 August 2018), "An estimate of equilibrium climate sensitivity from interannual variability', Journal of Geophysical Research Atmospheres, https://doi.org/10.1029/2018JD028481

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JD028481?campaign=wolacceptedarticle

Abstract
Estimating the equilibrium climate sensitivity (ECS; the equilibrium warming in response to a doubling of CO2) from observations is one of the big problems in climate science. Using observations of interannual climate variations covering the period 2000 to 2017 and a model‐derived relationship between interannual variations and forced climate change, we estimate ECS is likely 2.4‐4.6 K (17‐83% confidence interval), with a mode and median value of 2.9 and 3.3 K, respectively. This analysis provides no support for low values of ECS (below 2 K) suggested by other analyses. The main uncertainty in our estimate is not observational uncertainty, but rather uncertainty in converting observations of short‐term, mainly unforced climate variability to an estimate of the response of the climate system to long‐term forced warming.

Plain language summary
Equilibrium climate sensitivity (ECS) is the amount of warming resulting from doubling carbon dioxide. It is one of the important metrics in climate science because it is a primary determinant of how much warming we will experience in the future. Despite decades of work, this quantity remains uncertain: the last IPCC report stated a range for ECS of 1.5‐4.5 deg. Celsius. Using observations of interannual climate variations covering the period 2000 to 2017, we estimate ECS is likely 2.4‐4.6 K. Thus, our analysis provides no support for the bottom of the IPCC's range."

You can obtain a copy of the paper here:

https://drive.google.com/file/d/1nt4YEMLc0AwWEAHtHAcwDEVzHkyKj1G-/view

Finally, Dessler & Forster (2018)'s findings combined with those of Brown & Caldeira 2017 https://www.nature.com/articles/nature24672 and Caldwell 2018 https://journals.ametsoc.org/doi/10.1175/JCLI-D-17-0631.1 should place best estimates of the current value of ECS at 3.5 or greater.  This is important in that it increases the probability of abrupt ice mass loss from the WAIS within the next couple of decades.  Also, Rehfeld et al (2018)'s findings confirm Hansen's projections about the coming of superstorms when the ice mass loss from the WAIS cools the surface of the Southern Ocean, and warms the tropical oceans, thus increasing the atmospheric thermal gradient from the tropics to the poles.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2018, 04:46:32 PM
From Replies #219 & #220 there is a strong case to be made that key portions of the Antarctic Ice Sheet may be initially subject to cliff-failures and hydrofracturing by about 2040 when GMSTA may be between 1.5 and 1.8C above pre-industrial.  Furthermore, the first linked reference Zhuan et al. (2018) demonstrates that climate sensitivity [aka climate model response (M) combined with internal climate variability (V)] dominates the rate of increase of GMSTA vs GHG emissions in this timeframe.  Unfortunately, contrarians (and/or those who prefer to err on the side of least drama) like to point at incomplete and biased definitions of climate sensitivity that give low estimates ECS, and TCR, which decision makers are all too willing to use in their policies.  Therefore, in this post I provide some more insight as to why the true ECS values (over the next 20 years) is higher that the ~3C value recommended by IPCC.

Meijia Zhuan et al. (12 November 2018), "A method for investigating the relative importance of three components in overall uncertainty of climate projections", International Journal of Climatology, https://doi.org/10.1002/joc.5920

https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.5920

Abstract: "Climate model response (M) and greenhouse gas emissions (S) uncertainties are consistently estimated as spreads of multi‐model and multi‐scenario climate change projections. There has been less agreement in estimating internal climate variability (V). In recent years, an initial condition ensemble (ICE) of a climate model has been developed to study V. ICE is simulated by running a climate model using an identical climate forcing but different initial conditions. Inter‐member differences of an ICE manifestly represent V. However, ICE has been barely used to investigate relative importance of climate change uncertainties. Accordingly, this study proposes a method of using ICEs, without assuming V as constant, for investigating the relative importance of climate change uncertainties and its temporal‐spatial variation. Prior to investigating temporal‐spatial variation in China, V estimated using ICE was compared to that using multi‐model individual time series at national scale. Results show that V using ICE is qualitatively similar to that using multi‐model individual time series for temperature. However, V is not constant for average and extreme precipitations. V and M dominate before 2050s especially for precipitation. S is dominant in the late 21st century especially for temperature. Mean temperature change is projected to be 30%‐70% greater than its uncertainty until 2050s, while uncertainty becomes 10%‐40% greater than the change in the late 21st century. Precipitation change uncertainty overwhelms its change by 70%‐150% throughout 21st century. Cold regions (e.g. northern China, Qinghai‐Tibetan Plateau) tend to have greater temperature change uncertainties. In dry regions (e.g. northwest China), all three uncertainties tend to be great for changes in average and extreme precipitations. This study emphasizes the importance of considering climate change uncertainty in impact studies, especially taking into account that V is irreducible in the future. Using ICEs without assuming V as constant is an appropriate approach to study climate change uncertainty."
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First, Skeie et al. (2018) demonstrate that: "Sensitivity analysis performed by merging the upper (0–700m) and the deep-ocean OHC or using only one OHC dataset (instead of four in the main analysis) both give an enhancement of the mean ECSinf by about 50% from our best estimate."  Thus considering increases in ocean heat content considerable increases estimates of effective ECS above those currently used by policymakers and indeed that used by Hansen et al. (2016).  Furthermore, we all need to remember that the ocean has been warming from pre-industrial conditions for nearly 270 years, and unlike previous interglacial warming periods, the oceans had the entire Holocene to absorb heat, which, is important when evaluating the stability of subsea methane hydrates (particularly in the Arctic Ocean).

Skeie, R. B., Berntsen, T., Aldrin, M., Holden, M., and Myhre, G.: Climate sensitivity estimates – sensitivity to radiative forcing time series and observational data, Earth Syst. Dynam., 9, 879-894, https://doi.org/10.5194/esd-9-879-2018, 2018.

https://www.earth-syst-dynam.net/9/879/2018/
https://www.earth-syst-dynam.net/9/879/2018/esd-9-879-2018.pdf

Abstract: "Inferred effective climate sensitivity (ECSinf) is estimated using a method combining radiative forcing (RF) time series and several series of observed ocean heat content (OHC) and near-surface temperature change in a Bayesian framework using a simple energy balance model and a stochastic model. The model is updated compared to our previous analysis by using recent forcing estimates from IPCC, including OHC data for the deep ocean, and extending the time series to 2014. In our main analysis, the mean value of the estimated ECSinf is 2.0°C, with a median value of 1.9°C and a 90% credible interval (CI) of 1.2–3.1°C. The mean estimate has recently been shown to be consistent with the higher values for the equilibrium climate sensitivity estimated by climate models. The transient climate response (TCR) is estimated to have a mean value of 1.4°C (90% CI 0.9–2.0°C), and in our main analysis the posterior aerosol effective radiative forcing is similar to the range provided by the IPCC. We show a strong sensitivity of the estimated ECSinf to the choice of a priori RF time series, excluding pre-1950 data and the treatment of OHC data. Sensitivity analysis performed by merging the upper (0–700m) and the deep-ocean OHC or using only one OHC dataset (instead of four in the main analysis) both give an enhancement of the mean ECSinf by about 50% from our best estimate."
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Second, not only do we need to consider heat absorbed by the oceans, but Sallee (2018) notes that: "Since 2006, an estimated 60%–90% of global ocean heat content change associated with global warming is based in the Southern Ocean."  Thus most of this recent increase in ocean heat content is available to destabilize key Antarctic marine glaciers (see the first attached image & associated caption below).

Sallée, J.-B. (2018), "Southern Ocean warming", Oceanography 31(2), https://doi.org/10.5670/oceanog.2018.215.

https://tos.org/oceanography/article/southern-ocean-warming
https://tos.org/oceanography/assets/docs/31-2_sallee.pdf

Abstract: "The Southern Ocean plays a fundamental role in global climate. With no continental barriers, it distributes climate signals among the Pacific, Atlantic, and Indian Oceans through its fast-flowing, energetic, and deep-reaching dominant current, the Antarctic Circumpolar Current. The unusual dynamics of this current, in conjunction with energetic atmospheric and ice conditions, make the Southern Ocean a key region for connecting the surface ocean with the world ocean’s deep seas. Recent examinations of global ocean temperature show that the Southern Ocean plays a major role in global ocean heat uptake and storage. Since 2006, an estimated 60%–90% of global ocean heat content change associated with global warming is based in the Southern Ocean. But the warming of its water masses is inhomogeneous. While the upper 1,000 m of the Southern Ocean within and north of the Antarctic Circumpolar Current are warming rapidly, at a rate of 0.1°–0.2°C per decade, the surface subpolar seas south of this region are not warming or are slightly cooling. However, subpolar abyssal waters are warming at a substantial rate of ~0.05°C per decade due to the formation of bottom waters on the Antarctic continental shelves. Although the processes at play in this warming and their regional distribution are beginning to become clear, the specific mechanisms associated with wind change, eddy activity, and ocean-ice interaction remain areas of active research, and substantial challenges persist to representing them accurately in climate models."

Caption for first image: "FIGURE 1. Schematic showing temperature trends in different layers of the Southern Ocean. The layers are defined as main water masses of the Southern Ocean: Subtropical Water (TW), Mode Water (MW), Intermediate Water (IW), Circumpolar Deep Water (CDW), and Bottom Water (BW). Black arrows show the main overturning pathways in the basin, and the dashed black contours show a vertical slice of the deep-reaching Antarctic Circumpolar Current circulating clockwise around the Antarctic continent. The red arrows and associated numbers represent processes at play in the warming of the Southern Ocean and are discussed in the text: 1 increased surface stratification and shallowing of CDW layer, 2 increased heat uptake in the subpolar basins, 3 increased northward heat transport associated with increased subpolar heat uptake, 4 reduced eddy- mediated southward heat transport across the Antarctic Circumpolar Current, 5 intrusion of CDW onto the continental shelves, and 6 warming of the bottom water ventilating the abyssal ocean."

Second, Purkey & Johnson show that the increase in the Antarctic Westerly wind velocities associated with the Antarctic ozone hole has advected the warm CDW southward when it can more easily destabilize key marine glaciers.  As shown in the second accompanying image figure 4a the warm CDW has surged from the north into the Weddell-Enderby Basin at depths shallower than 1000m (depths that can feed directly into the Filchner Trough leading beneath the FRIS. 

Sarah G. Purkey and Gregory C. Johnson (2012), "Global Contraction of Antarctic Bottom Water between the 1980s and 2000s", Journal of Climate, https://doi.org/10.1175/JCLI-D-11-00612.1

https://journals.ametsoc.org/doi/10.1175/JCLI-D-11-00612.1

Abstract: "A statistically significant reduction in Antarctic Bottom Water (AABW) volume is quantified between the 1980s and 2000s within the Southern Ocean and along the bottom-most, southern branches of the meridional overturning circulation (MOC). AABW has warmed globally during that time, contributing roughly 10% of the recent total ocean heat uptake. This warming implies a global-scale contraction of AABW. Rates of change in AABW-related circulation are estimated in most of the world’s deep-ocean basins by finding average rates of volume loss or gain below cold, deep potential temperature (θ) surfaces using all available repeated hydrographic sections. The Southern Ocean is losing water below θ = 0°C at a rate of −8.2 (±2.6) × 106 m3 s−1. This bottom water contraction causes a descent of potential isotherms throughout much of the water column until a near-surface recovery, apparently through a southward surge of Circumpolar Deep Water from the north. To the north, smaller losses of bottom waters are seen along three of the four main northward outflow routes of AABW. Volume and heat budgets below deep, cold θ surfaces within the Brazil and Pacific basins are not in steady state. The observed changes in volume and heat of the coldest waters within these basins could be accounted for by small decreases to the volume transport or small increases to θ of their inflows, or fractional increases in deep mixing. The budget calculations and global contraction pattern are consistent with a global-scale slowdown of the bottom, southern limb of the MOC."

Caption: "FIG. 4. (a)–(c) Total rates of volume change for select basins (legends) below each potential isotherm (DV curves, solid lines) with 95% confidence intervals (shading) along three of the four northward pathways for AABW out of the Southern Ocean from south to north (orange through green to purple). Minimum u values spreading from the orange to the green basins (lower horizontal black lines) and the green to the purple basins (upper horizontal black lines) are estimated from a climatology (Gouretski and Koltermann 2004). Color-coded numbers along the right axis indicate mean depths of selected us for the corresponding basin."
&
Third, Hansen has warned that changing ENSO patterns (due to global warming) are disproportionately working to destabilize Antarctic marine glaciers, and as noted by Cha et al (2018), all the changes in the ENSO pattern that Hansen warned about are coming true now (i.e. more frequent El Nino events, less frequent La Nina events, and more frequent warming of the Nino 3 region that is primarily responsible for advecting tropical Pacific Ocean heat energy to West Antarctica via atmospheric Rossby waves)

Sang‐Chul Cha et al. (05 November 2018), "A Recent Shift Toward an El Niño‐Like Ocean State in the Tropical Pacific and the Resumption of Ocean Warming", Geophysical Research Letters, https://doi.org/10.1029/2018GL080651

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL080651

Abstract
Since approximately 2011, the tropical Pacific has been sharply shifting toward an opposite phase to that observed in the previous decade. This shift has coincided with a recent resumption of global warming after a hiatus in the 2000s. Based on a model‐data analysis using an ensemble empirical mode decomposition, we identified a distinct low‐frequency mode of the sea level in the tropical Pacific and showed its connection to global ocean warming and the suppression of global warming during the early 2000s, as well as the resumption of warming during recent years. Hindcast and model experiments conducted to illustrate the physical mechanism linking the decadal mode to the Pacific Decadal Oscillation‐related trade winds, which regulate the strength of the Equatorial Undercurrent and the surface temperature of the tropical Pacific Ocean, revealed an El Niño‐like state for the last several years.

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Fourth, I noted that freshwater hosing of the North Atlantic from both ice mass loss from Greenland [see Bondzio et al. (2018) and Ying et al. (2018)] and from a likely pulse of low salinity water released from the Beaufort Sea Gyre (likely sometime in the next two decades); would further slow the global overturning current [see Buarque et al (2018)]; which via the bipolar seesaw mechanism will both further destabilize Antarctic marine glaciers and will increase tropical ocean surface temperatures.

Johannes H. Bondzio et al. (15 November 2018), "Control of ocean temperature on Jakobshavn Isbræ's present and future mass loss", Geophysical Research Letters, https://doi.org/10.1029/2018GL079827

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL079827

Abstract

Large uncertainties in model parameterizations and input datasets make projections of future sea level rise contributions of outlet glaciers challenging. Here, we introduce a novel technique for weighing large ensemble model simulations that uses information of key observables. The approach is robust to input errors and yields calibrated means and error estimates of a glacier's mass balance. We apply the technique to Jakobshavn Isbræ, using a model that includes a dynamic calving law, and closely reproduce the observed behavior from 1985 until 2018 by forcing the model with ocean temperatures only. Our calibrated projection suggests that the glacier will continue to retreat and contribute about 5.1 mm to eustatic sea level rise by 2100 under present‐day climatic forcing. Our analysis shows that the glacier's future evolution will strongly depend on the ambient oceanic setting.

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Jun Ying et al. (2018), "Inter-model uncertainty in the change of ENSO’s amplitude under global warming: Role of the response of atmospheric circulation to SST anomalies", Journal of Climate, https://doi.org/10.1175/JCLI-D-18-0456.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0456.1

Abstract: "This study investigates the mechanism of the large inter-model uncertainty in the change of ENSO’s amplitude under global warming, based on 31 CMIP5 models. We find that the uncertainty in ENSO’s amplitude is significantly correlated to that of the change in the response of atmospheric circulation to SST anomalies (SSTAs) in the eastern equatorial Pacific Niño3 region. This effect of the atmospheric response to SSTAs mainly influences the uncertainty in ENSO’s amplitude during El Niño (EN) phases, but not during La Niña (LN) phases, showing pronounced nonlinearity. The effect of the relative SST warming and the present-day response of atmospheric circulation to SSTAs are the two major contributors to the inter-model spread of the change in the atmospheric response to SSTAs, of which the latter is more important. On the one hand, models with a stronger (weaker) mean-state SST warming in the eastern equatorial Pacific, relative to the tropical-mean warming, favor a larger (smaller) increase in the change in the response of atmospheric circulation to SSTAs in the eastern equatorial Pacific during EN. On the other hand, models with a weaker (stronger) present-day response of atmospheric circulation to SSTAs during EN tend to exhibit a larger (smaller) increase in the change under global warming. The result implies that an improved simulation of the present-day response of atmospheric circulation to SSTAs could be effective in lowering the uncertainty in ENSO’s amplitude change under global warming."

&

Ramos Buarque, S. and Salas y Melia, D.: Link between the North Atlantic Oscillation and the surface mass balance components of the Greenland Ice Sheet under preindustrial and last interglacial climates: a study with a coupled global circulation model, Clim. Past, 14, 1707-1725, https://doi.org/10.5194/cp-14-1707-2018, 2018.

https://www.clim-past.net/14/1707/2018/

Abstract. The relationship between the surface mass balance (SMB) components (accumulation and melting) of the Greenland Ice Sheet (GrIS) and the North Atlantic Oscillation (NAO) is examined from numerical simulations performed with a new atmospheric stretched grid configuration of the Centre National de Recherches Météorologiques Coupled Model (CNRM-CM) version 5.2 under three periods: preindustrial climate, a warm phase (early Eemian, 130kaBP) and a cool phase (late Eemian, 115kaBP) of the last interglacial. The horizontal grid of the atmospheric component of CNRM-CM5.2 is stretched from the tilted pole on Baffin Bay (72°N, 65°W) in order to obtain a higher spatial resolution on Greenland. The correlation between simulated SMB anomalies averaged over Greenland and the NAO index is weak in winter and significant in summer (about 0.6 for the three periods). In summer, spatial correlations between the NAO index and SMB components display different patterns from one period to another. These differences are analyzed in terms of the respective influence of the positive and negative phases of the NAO on accumulation and melting. Accumulation in south Greenland is significantly correlated with the positive (negative) phase of the NAO in a warm (cold) climate. Under preindustrial and 115kaBP climates, melting along the margins is more correlated with the positive phase of the NAO than with its negative phase, whereas at 130kaBP it is more correlated with the negative phase of the NAO in north and northeast Greenland.

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2018, 04:59:07 PM
As my last post was limited by the 2000 word limit per post, I continue here:

Fifth, Chen et al (2018) illustrates the risk of increasing atmospheric methane emissions from hydrates as the Arctic Ocean warms and its current patterns change.

Leifer, I., Chen, F. R., McClimans, T., Muller Karger, F., and Yurganov, L.: Satellite ice extent, sea surface temperature, and atmospheric methane trends in the Barents and Kara Seas, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-237, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2018-237/

Abstract. Over a decade (2003–2015) of satellite data of sea-ice extent, sea surface temperature (SST), and methane (CH4) concentrations in lower troposphere over 10 focus areas within the Barents and Kara Seas (BKS) were analyzed for anomalies and trends relative to the Barents Sea. Large positive CH4 anomalies were discovered around Franz Josef Land (FJL) and offshore west Novaya Zemlya in early fall. Far smaller CH4 enhancement was found around Svalbard, downstream and north of known seabed seepage. SST increased in all focus areas at rates from 0.0018 to 0.15°Cyr−1, CH4 growth spanned 3.06 to 3.49ppbyr−1.
The strongest SST increase was observed each year in the southeast Barents Sea in June due to strengthening of the warm Murman Current (MC), and in the south Kara Sea in September. The southeast Barents Sea, the south Kara Sea and coastal areas around FJL exhibited the strongest CH4 growth over the observation period. Likely sources are CH4 seepage from subsea permafrost and hydrate thawing and the petroleum reservoirs underlying the central and east Barents Sea and the Kara Sea. The spatial pattern was poorly related to seabed depth. However, the increase in CH4 emissions over time may be explained by a process of shoaling of strengthening warm ocean currents that would also advect the CH4 to areas where seasonal deepening of the surface ocean mixed layer depth leads to ventilation of these water masses. Continued strengthening of the MC will further increase heat transfer to the BKS, with the Barents Sea ice-free in ~15 years. We thus expect marine CH4 flux to the atmosphere from this region to continue increasing.
&

Sixth, Zamanian et al. (2018) shows that CO₂ emission from soil inorganic carbon into the atmosphere with continued warming has been likely underestimated.

Kazem Zamanian et al. (08 October 2018), "Contribution of soil inorganic carbon to atmospheric CO2: More important than previously thought", Global Change Biology, https://doi.org/10.1111/gcb.14463

https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14463

Extract: "We conclude that, considering the factors mentioned by Datta and Mandal (2018), our estimation (Zamanian et al., 2018) of CO2 fluxes from carbonates by N fertilization (7.5 × 1012 g C year−1) and from liming of acidic soils (273 × 1012 g C year−1) as accurate as it can be done to date is possibly an underestimation."

&

Seventh, the next two articles show that the size of the Antarctic ozone hole (which increases the Westerly wind velocity over the Southern Ocean & thus shift the warm CDW shoreward) is still significant and will remain significant until well after the 2040 timeframe considered in this post.

Title: "Antarctic ozone hole grows, but not by much"

https://cosmosmagazine.com/geoscience/antarctic-ozone-hole-grows-but-not-by-much

Extract: "The hole, which peaks every year at the end of the southern winter, topped out at about 22.9 million square kilometres – almost three times the area of the continental US – and was the thirteenth largest out of the past 40.
And while that’s not exactly cause for unrestrained celebration, it is, say scientists at NASA's Goddard Space Flight Centre in Maryland, which monitors the phenomenon, testament to the tentative success of the 1987 Montreal Protocol, which led to the phasing out of man-made ozone-depleting substances.
“Chlorine levels in the Antarctic stratosphere have fallen about 11% from the peak year in 2000.
"This year’s colder temperatures would have given us a much larger ozone hole if chlorine was still at levels we saw back in the year 2000.”
The size of the ozone hole is directly affected by annual temperatures, with warmer weather restricting its growth. Warm averages in 2016 led to a hole 19.7 million kilometres in area, but it increased in 2018 on the back of the coldest run of temperatures since 1979."

&

Title: "Hole in Earth's Ozone Layer Could Be Closed in 2060s, UN Report Says"

https://weather.com/news/news/2018-11-07-ozone-hole-healing/

Extract: "The ozone hole over the Antarctic is expected to be closed in the 2060s, the report said. Other areas in the atmosphere could recover even earlier if all goes as planned."
&

Eight, while not related to climate sensitivity, the following article and Velders et al. (2015), illustrate that if the Kigali Amendment to the Montreal Protocol prove ineffective, radiative forcing from HFCs could increase significantly in the coming decades [see the attached image from Velders et al. (2015)]

Title: "Fast-Rising Demand for Air Conditioning Is Adding to Global Warming. The Numbers Are Striking."

https://insideclimatenews.org/news/11112018/climate-change-home-air-conditioning-half-degree-global-warming-by-2100

Extract: "With window units set to more than triple by 2050, home air conditioning is on pace to add half a degree Celsius to global warming this century, a new report says."

&

Guus J.M.Velders et al. (2015), "Future atmospheric abundances and climate forcings from scenarios of global and regional hydrofluorocarbon (HFC) emissions", Atmospheric Environment, Volume 123, Part A, December 2015, Pages 200-209, https://doi.org/10.1016/j.atmosenv.2015.10.071

https://www.sciencedirect.com/science/article/pii/S135223101530488X
https://ac.els-cdn.com/S135223101530488X/1-s2.0-S135223101530488X-main.pdf?_tid=16e884ef-7981-4c7b-b1a0-f211d675a9bd&acdnat=1543182231_4fac32e869522e2e888d45a5a2229aeb

Abstract: "Hydrofluorocarbons (HFCs) are manufactured for use as substitutes for ozone-depleting substances that are being phased out globally under Montreal Protocol regulations. While HFCs do not deplete ozone, many are potent greenhouse gases that contribute to climate change. Here, new global scenarios show that baseline emissions of HFCs could reach 4.0–5.3 GtCO2-eq yr−1 in 2050. The new baseline (or business-as-usual) scenarios are formulated for 10 HFC compounds, 11 geographic regions, and 13 use categories. The scenarios rely on detailed data reported by countries to the United Nations; projections of gross domestic product and population; and recent observations of HFC atmospheric abundances. In the baseline scenarios, by 2050 China (31%), India and the rest of Asia (23%), the Middle East and northern Africa (11%), and the USA (10%) are the principal source regions for global HFC emissions; and refrigeration (40–58%) and stationary air conditioning (21–40%) are the major use sectors. The corresponding radiative forcing could reach 0.22–0.25 W m−2 in 2050, which would be 12–24% of the increase from business-as-usual CO2 emissions from 2015 to 2050. National regulations to limit HFC use have already been adopted in the European Union, Japan and USA, and proposals have been submitted to amend the Montreal Protocol to substantially reduce growth in HFC use. Calculated baseline emissions are reduced by 90% in 2050 by implementing the North America Montreal Protocol amendment proposal. Global adoption of technologies required to meet national regulations would be sufficient to reduce 2050 baseline HFC consumption by more than 50% of that achieved with the North America proposal for most developed and developing countries."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2018, 05:35:30 PM
As this is the Ice Apocalypse thread, we cannot neglect to consider the fact that the current high rate of anthropogenic radiative forcing (at least 100 times faster than during the PETM) increases the risk that a cascade (domino effect) of activated positive feedback mechanisms could drive the Earth irreversibly towards a 'hothouse' condition, if we allow the Earth to temporarily reach Mid-Pliocene conditions (which will cause abrupt ice mass loss from Antarctica), as shown in Steffen et al. (2018) & the three associated images, and the associated article.

Will Steffen, Johan Rockström, Katherine Richardson, Timothy M. Lenton, Carl Folke, Diana Liverman, Colin P. Summerhayes, Anthony D. Barnosky, Sarah E. Cornell, Michel Crucifix, Jonathan F. Donges, Ingo Fetzer, Steven J. Lade, Marten Scheffer, Ricarda Winkelmann, Hans Joachim Schellnhuber (2018), "Trajectories of the Earth System in the Anthropocene", Proc. Nat. Acad. Sci., https://doi.org/10.1073/pnas.1810141115

http://www.pnas.org/content/115/33/8252

Abstract: "We explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced. Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene. We examine the evidence that such a threshold might exist and where it might be. If the threshold is crossed, the resulting trajectory would likely cause serious disruptions to ecosystems, society, and economies. Collective human action is required to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state. Such action entails stewardship of the entire Earth System—biosphere, climate, and societies—and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values."
&
Title: "Climate Change Could Have a Domino Effect"

https://www.chemistryviews.org/details/news/1023141/Climate_Change_Could_Have_a_Domino_Effect.html

Extract: "The initial domino stones could form the tipping points, which already react to a relatively small increase in global temperatures, such as the melting of the West Antarctic and Greenland Ice Sheet and the Arctic sea ice. As this continues to fuel warming through positive feedback loops, it could then be "swept" by tipping points with slightly higher thresholds, such as the Gulf Stream ocean current or the Southern Ocean's buffering of global CO2. Once such a cascade is triggered, it might cause a runaway effect that could catapult Earth's climate out of its stable phase even as human emissions are reduced. The earth could be 4–5 °C warmer than pre-industrial temperatures and have sea levels 10–60 m higher than today."
&

Furthermore, Fischer et al. (2018) (& the associated article) supports the concern that if we allow the world to reach Mid-Pliocene conditions we could lock-in a cascade of positive feedbacks that could effectively double the current value of climate sensitivity.

Fischer et al. (2018), "Palaeoclimate constraints on the impact of 2 °C anthropogenic warming and beyond", Nature Geoscience, vol. 11, 474–485, https://doi.org/10.1038/s41561-018-0146-0

https://www.nature.com/articles/s41561-018-0146-0

Abstract: "Over the past 3.5 million years, there have been several intervals when climate conditions were warmer than during the preindustrial Holocene. Although past intervals of warming were forced differently than future anthropogenic change, such periods can provide insights into potential future climate impacts and ecosystem feedbacks, especially over centennial-to-millennial timescales that are often not covered by climate model simulations. Our observation-based synthesis of the understanding of past intervals with temperatures within the range of projected future warming suggests that there is a low risk of runaway greenhouse gas feedbacks for global warming of no more than 2 °C. However, substantial regional environmental impacts can occur. A global average warming of 1–2 °C with strong polar amplification has, in the past, been accompanied by significant shifts in climate zones and the spatial distribution of land and ocean ecosystems. Sustained warming at this level has also led to substantial reductions of the Greenland and Antarctic ice sheets, with sea-level increases of at least several metres on millennial timescales. Comparison of palaeo observations with climate model results suggests that, due to the lack of certain feedback processes, model-based climate projections may underestimate long-term warming in response to future radiative forcing by as much as a factor of two, and thus may also underestimate centennial-to-millennial-scale sea-level rise."

&

Title: "Global warming may be twice what climate models predict"

https://phys.org/news/2018-07-global-climate.html

Extract: "Observations of past warming periods suggest that a number of amplifying mechanisms, which are poorly represented in climate models, increase long-term warming beyond climate model projections," said lead author, Prof Hubertus Fischer of the University of Bern.

"This suggests the carbon budget to avoid 2°C of global warming may be far smaller than estimated, leaving very little margin for error to meet the Paris targets."

To get their results, the researchers looked at three of the best-documented warm periods, the Holocene thermal maximum (5000-9000 years ago), the last interglacial (129,000-116,000 years ago) and the mid-Pliocene warm period (3.3-3 million years ago).

The warming of the first two periods was caused by predictable changes in the Earth's orbit, while the mid-Pliocene event was the result of atmospheric carbon dioxide concentrations that were 350-450ppm – much the same as today."
&

Furthermore, Liu et al. (2018) confirms that a sufficient perturbance of the AMOC into the Arctic Ocean (say due to abrupt ice mass loss from Antarctic beginning in 2040) could lead "… to a rapid Arctic sea ice retreat within 5 years after the perturbations are activated."  Such possible activation of the positive Arctic ice-albedo mechanism, could then trigger other positive feedback mechanisms.

Wei Liu et al. (2018), "The mechanisms of the Atlantic Meridional Overturning Circulation slowdown induced by Arctic sea ice decline", Journal of Climate, https://doi.org/10.1175/JCLI-D-18-0231.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0231.1

Abstract: "We explore the mechanisms by which Arctic sea ice decline affects the Atlantic Meridional Overturning Circulation (AMOC) in a suite of numerical experiments perturbing Arctic sea ice radiative budget within a fully coupled climate model. The imposed perturbations act to increase the amount of heat available to melt ice, leading to a rapid Arctic sea ice retreat within 5 years after the perturbations are activated. In response, the AMOC gradually weakens over the next ∼100 years. The AMOC changes can be explained by the accumulation in the Arctic and subsequent downstream propagation to the North Atlantic of buoyancy anomalies controlled by temperature and salinity. Initially, during the first decade or so, the Arctic sea ice loss results in anomalous positive heat and salinity fluxes in the subpolar North Atlantic, inducing positive temperature and salinity anomalies over the regions of oceanic deep convection. At first, these anomalies largely compensate one another, leading to a minimal change in upper ocean density and deep convection in the North Atlantic. Over the following years, however, more anomalous warm water accumulates in the Arctic and spreads to the North Atlantic. At the same time, freshwater that accumulates from seasonal sea ice melting over most of the upper Arctic Ocean also spreads southward, reaching as far as south of Iceland. These warm and fresh anomalies reduce upper ocean density and suppress oceanic deep convection. The thermal and haline contributions to these bouyancy anomalies, and therefore to the AMOC slowdown during this period, are found to have similar magnitudes. We also find that the related changes in horizontal wind-driven circulation could potentially push freshwater away from the deep convection areas and hence strengthen the AMOC, but this effect is overwhelmed by mean advection."

Edit: To help convey how close we currently are to reaching Mid-Pliocene conditions, I attach the fourth image of Fischer et al. (2018) Figure 1.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2018, 07:47:25 PM
 I re-post the following from the Potential Collapse Scenario for the WAIS" thread

"Based on my interpretation of the two linked references, I suspect that local ice cliff failures near the base of the Thwaites Ice Tongue (see the four images) will begin sometime 2025 and 2033, and will be initiated due to influences from Super El Nino events in that timeframe:

Yu, H., Rignot, E., Morlighem, M., & Seroussi, H. (2017). Iceberg calving of Thwaites Glacier, West Antarctica: full-Stokes modeling combined with linear elastic fracture mechanics. The Cryosphere, 11(3), 1283, doi:10.5194/tc-11-1283-2017

https://www.the-cryosphere.net/11/1283/2017/tc-11-1283-2017.pdf
https://www.the-cryosphere.net/11/1283/2017/tc-11-1283-2017-assets.html

Abstract. "Thwaites Glacier (TG), West Antarctica, has been losing mass and retreating rapidly in the past few decades.  Here, we present a study of its calving dynamics combining a two-dimensional flow-band full-Stokes (FS) model of its viscous flow with linear elastic fracture mechanics (LEFM) theory to model crevasse propagation and ice fracturing.  We compare the results with those obtained with the higher-order (HO) and the shallow-shelf approximation (SSA) models coupled with LEFM. We find that FS/LEFM produces surface and bottom crevasses that are consistent with the distribution of depth and width of surface and bottom crevasses observed by NASA’s Operation IceBridge radar depth sounder and laser altimeter, whereas HO/LEFM and SSA/LEFM do not generate crevasses that are consistent with observations.  We attribute the difference to the nonhydrostatic condition of ice near the grounding line, which facilitates crevasse formation and is accounted for by the FS model but not by the HO or SSA models. We find that calving is enhanced when pre-existing surface crevasses are present, when the ice shelf is shortened or when the ice shelf front is undercut. The role of undercutting depends on the timescale of calving events. It is more prominent for glaciers with rapid calving rates than for glaciers with slow calving rates. Glaciers extending into a shorter ice shelf are more vulnerable to calving than glaciers developing a long ice shelf, especially as the ice front retreats close to the grounding line region, which leads to a positive feedback to calving events. We conclude that the FS/LEFM combination yields substantial improvements in capturing the stress field near the grounding line of a glacier for constraining crevasse formation and iceberg calving."

Extract: "In our simulations, we find that crevasses propagate significantly faster near the ice front when the ice shelf is shortened.

The reason for the propagation of crevasses is the existence of a nonhydrostatic condition of ice immediately downstream of the grounding line, which is not accounted for in simplified models that assume hydrostatic equilibrium everywhere on the ice shelf.  We also find that calving is enhanced in the presence of pre-existing surface crevasses or shorter ice shelves or when the ice front is undercut.  We conclude that it is important to consider the full stress regime of ice in the grounding line region to replicate the conditions conducive to calving events, especially the nonhydrostatic condition that is critical to propagate the crevasses."

&

The second linked reference confirms that the ENSO is directly associated with surface air temperatures across the interior of West Antarctica, and I note that the frequency of extreme El Nino events is projected to double when the global mean surface temp. anom. gets to 1.5C:

Kyle R. Clem, James A. Renwick, and James McGregor (2017), "Large-Scale Forcing of the Amundsen Sea Low and its Influence on Sea Ice and West Antarctic Temperature", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0891.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0891.1?utm_content=buffer2e94d&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Using empirical orthogonal function (EOF) analysis and atmospheric reanalyses, we examine the principal patterns of seasonal West Antarctic surface air temperature (SAT) and their connection to sea ice and the Amundsen Sea Low (ASL). During austral summer, the leading EOF (EOF1) explains 35% of West Antarctic SAT variability and consists of a widespread SAT anomaly over the continent linked to persistent sea ice concentration anomalies over the Ross and Amundsen Seas from the previous spring. Outside of summer, EOF1 (explaining ~40-50% of the variability) consists of an east-west dipole over the continent with SAT anomalies over the Antarctic Peninsula opposite those over western West Antarctica. The dipole is tied to variability in the Southern Annular Mode (SAM) and in-phase El Niño-Southern Oscillation (ENSO) / SAM combinations that influence the depth of the ASL over the central Amundsen Sea (near 105°W). The second EOF (EOF2) during autumn, winter, and spring (explaining ~15-20% of the variability) consists of a dipole shifted approximately 30 degrees west of EOF1 with a widespread SAT anomaly over the continent. During winter and spring, EOF2 is closely tied to variability in ENSO and a tropically-forced wavetrain that influences the ASL in the western Amundsen / eastern Ross Seas (near 135°W) with an opposite sign circulation anomaly over the Weddell Sea; the ENSO-related circulation brings anomalous thermal advection deep onto the continent. We conclude the ENSO-only circulation pattern is associated with SAT variability across interior West Antarctica, especially during winter and spring, while the SAM circulation pattern is associated with an SAT dipole over the continent.""
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 26, 2018, 07:52:40 PM
As a follow-on to my last post, the first  image shows the deepwater changes across the Amundsen Sea continental shelf through which the warm CDW flows towards the grounding lines of key marine glaciers.

The second image shows a computer simulation of the pattern of warm CDW flow in the Amundsen Sea continental shelf area; which indicates how warm CDW can flow from the PIG to the Thwaites grounding line.

The third image shows that the submerged ridge seaward of Thwaites can help direct the warm CDW come from the PIG towards the 'trough' that crosses the Thwaites ice plug.

Bertler, N.A., Naish, T.T., Mayewski, P.A. and Barrett, P.J., (2006), "Opposing oceanic and atmospheric ENSO influences on the Ross Sea Region, Antarctica", Advances in Geosciences, 6, pp 83-88, SRef-ID: 1680-7359/adgeo/2006-6-83.

Next, the second linked reference indicates that from January to June the ASL typically moves from about 110 degrees W (where it is in position to help direct warm CDW into the ASE) to about 150 degrees W (where it does not help to direct warm CDW into the ASE).  I note also that:

(a) As the SAM has become more positive, due to global warming, the ASL has become more intensity and has tended to drift more to the west than previously; and

(b) El Nino events do not typically occur in the January to June timeframe but rather in the October to Dec timeframe, which helps to explain way more warm CDW flows into the ASE during El Nino events

Turner, J., Phillips, T., Hosking, J. S., Marshall, G. J. and Orr, A. (2013), The Amundsen Sea low. Int. J. Climatol., 33: 1818–1829. doi: 10.1002/joc.3558

http://onlinelibrary.wiley.com/doi/10.1002/joc.3558/abstract

Abstract: "We develop a climatology of the Amundsen Sea low (ASL) covering the period 1979–2008 using ECMWF operational and reanalysis fields. The depth of the ASL is strongly influenced by the phase of the Southern annular mode (SAM) with positive (negative) mean sea level pressure anomalies when the SAM is negative (positive). The zonal location of the ASL is linked to the phase of the mid-tropospheric planetary waves and the low moves west from close to 110°W in January to near 150°W in June as planetary waves 1 to 3 amplify and their phases shift westwards. The ASL is deeper by a small, but significant amount, during the La Niña phase of El Niño-Southern Oscillation (ENSO) compared to El Niño. The difference in depth of the low between the two states of ENSO is greatest in winter. There is no statistically significant difference in the zonal location of the ASL between the different phases of ENSO. Over 1979–2008 the low has deepened in January by 1.7 hPa dec−1 as the SAM has become more positive. It has also deepened in spring and autumn as the semi-annual oscillation has increase in amplitude over the last 30 years. An increase in central pressure and eastward shift in March has occurred as a result of a cooling of tropical Pacific SSTs that altered the strength of the polar front jet."


Finally, the third linked 2017 reference confirms that the ENSO is directly associated with surface air temperatures across the interior of West Antarctica, and I note that the frequency of Super El Nino events is projected to double when the global mean surface temp. anom. gets to 1.5C:

Kyle R. Clem, James A. Renwick, and James McGregor (2017), "Large-Scale Forcing of the Amundsen Sea Low and its Influence on Sea Ice and West Antarctic Temperature", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0891.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0891.1?utm_content=buffer2e94d&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Using empirical orthogonal function (EOF) analysis and atmospheric reanalyses, we examine the principal patterns of seasonal West Antarctic surface air temperature (SAT) and their connection to sea ice and the Amundsen Sea Low (ASL). During austral summer, the leading EOF (EOF1) explains 35% of West Antarctic SAT variability and consists of a widespread SAT anomaly over the continent linked to persistent sea ice concentration anomalies over the Ross and Amundsen Seas from the previous spring. Outside of summer, EOF1 (explaining ~40-50% of the variability) consists of an east-west dipole over the continent with SAT anomalies over the Antarctic Peninsula opposite those over western West Antarctica. The dipole is tied to variability in the Southern Annular Mode (SAM) and in-phase El Niño-Southern Oscillation (ENSO) / SAM combinations that influence the depth of the ASL over the central Amundsen Sea (near 105°W). The second EOF (EOF2) during autumn, winter, and spring (explaining ~15-20% of the variability) consists of a dipole shifted approximately 30 degrees west of EOF1 with a widespread SAT anomaly over the continent. During winter and spring, EOF2 is closely tied to variability in ENSO and a tropically-forced wavetrain that influences the ASL in the western Amundsen / eastern Ross Seas (near 135°W) with an opposite sign circulation anomaly over the Weddell Sea; the ENSO-related circulation brings anomalous thermal advection deep onto the continent. We conclude the ENSO-only circulation pattern is associated with SAT variability across interior West Antarctica, especially during winter and spring, while the SAM circulation pattern is associated with an SAT dipole over the continent."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 27, 2018, 12:38:41 AM
The linked article & associated reference provide evidence that during the Holocene the sea line on the Texas coastline rose by several meters within a period of decades, almost certainly due to collapsing glaciers:

Title: "Oceans Can Rise in Sudden Bursts"

https://www.scientificamerican.com/article/oceans-can-rise-in-sudden-bursts/

Extract: "Fossilized corals off Texas show that in the past, sea level rose several meters in just decades, probably due to collapsing glaciers"

&

Pankaj Khanna, André W. Droxler, Jeffrey A. Nittrouer, John W. Tunnell Jr & Thomas C. Shirley (2017), "Coralgal reef morphology records punctuated sea-level rise during the last deglaciation", Nature Communications, https://doi.org/10.1038/s41467-017-00966-x

https://www.nature.com/articles/s41467-017-00966-x

Abstract: "Coralgal reefs preserve the signatures of sea-level fluctuations over Earth’s history, in particular since the Last Glacial Maximum 20,000 years ago, and are used in this study to indicate that punctuated sea-level rise events are more common than previously observed during the last deglaciation. Recognizing the nature of past sea-level rises (i.e., gradual or stepwise) during deglaciation is critical for informing models that predict future vertical behavior of global oceans. Here we present high-resolution bathymetric and seismic sonar data sets of 10 morphologically similar drowned reefs that grew during the last deglaciation and spread 120km apart along the south Texas shelf edge. Herein, six commonly observed terrace levels are interpreted to be generated by several punctuated sea-level rise events forcing the reefs to shrink and backstep through time. These systematic and common terraces are interpreted to record punctuated sea-level rise events over timescales of decades to centuries during the last deglaciation, previously recognized only during the late Holocene."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wili on November 27, 2018, 03:52:55 AM
Sorry not to say this sooner--good to have you back, bro! Your posts are always deeply appreciated, and were sorely missed in your absence!
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 27, 2018, 04:48:17 PM
Sorry not to say this sooner--good to have you back, bro! Your posts are always deeply appreciated, and were sorely missed in your absence!

wili,

Thank you.

Also, as an official El Nino for the 2018-2019 ENSO season will almost certainly be declared in either December or January, I provide the linked article and associated linked reference that provides statistical evidence that El Nino events significantly accelerate ice mass loss from the ice shelves in the Amundsen Sea Embayment; which further destabilizes the key marine glaciers in this region:

Title: "El Nino's long reach to Antarctic ice"

https://www.bbc.com/news/science-environment-42614412

Extract: "ENSO is recognised to have global influence, altering patterns of rainfall and drought, for example. And in the southern polar region, it appears to influence atmospheric pressure fields.

One in particular, referred to as the Amundsen Sea Low, governs both regional winds and ocean circulation.

During an El Niño, this fosters higher snowfall rates on shelves, raising their height, but it also pulls more warm water up from the deep which can get under the shelves and melt them.

The combined effect leads to a loss in mass of the shelves. In a big El Niño phase, like the one in 1997/98, this reduction can be equivalent in scale to that stemming from the ongoing, long-term negative thinning trend.

"That means for a short period of time you are adding the two together. And that's key information to put into computer models if you want to properly represent the dynamics of these systems," explained Dr Paolo, who has now moved to the US space agency.

In La Niña years, the reverse happens: less snowfall, but also less melting on the shelves' undersides. This works briefly to slow the ongoing, long-term negative trend. "


See also:

Paolo, F. S., Padman, L., Fricker, H. A., Adusumilli, S., Howard, S., & Siegfried, M. R. (2018). Response of Pacific-sector Antarctic ice shelves to the El Niño/Southern Oscillation. Nature Geoscience, 11(2), 121–126. doi:10.1038/s41561-017-0033-0

https://www.nature.com/articles/s41561-017-0033-0

&

Title: "Strong chance of a new El Niño forming by early 2019"

https://www.bbc.com/news/science-environment-46347451

Best,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 28, 2018, 12:24:51 AM
In September 2012 the Thwaites Ice Tongue flow rate surged and continued flowing at a high rate through the end of 2012 (and this high flow rate can be associated with the surface elevation depression shown in the first image)

In this regards, the linked reference studies a subglacial draining event beneath Thwaites Glacier from June 2013 to January 2014 (see the last three attached images):

Smith et. al. (2017), "Connected subglacial lake drainage beneath Thwaites Glacier, West Antarctica", The Cryosphere, 11, 451–467, doi:10.5194/tc-11-451-2017

http://www.the-cryosphere.net/11/451/2017/tc-11-451-2017.pdf

Abstract. We present conventional and swath altimetry data from CryoSat-2, revealing a system of subglacial lakes that drained between June 2013 and January 2014 under the central part of Thwaites Glacier, West Antarctica (TWG). Much of the drainage happened in less than 6 months, with an apparent connection between three lakes spanning more than 130 km. Hydro-potential analysis of the glacier bed shows a large number of small closed basins that should trap water produced by subglacial melt, although the observed largescale motion of water suggests that water can sometimes locally move against the apparent potential gradient, at least during lake-drainage events. This shows that there are important limitations in the ability of hydro-potential maps to predict subglacial water flow. An interpretation based on a map of the melt rate suggests that lake drainages of this type should take place every 20–80 years, depending on the connectivity of the water flow at the bed. Although we observed an acceleration in the downstream part of TWG immediately before the start of the lake drainage, there is no clear connection between the drainage and any speed change of the glacier."

There is more information on the June 2013 to Jan 2014 drainage of four subglacial lakes beneath the Thwaites Glacier.  The article is entitled: "Hidden lakes drain below West Antarctica’s Thwaites Glacier".

http://www.washington.edu/news/2017/02/08/hidden-lakes-drained-under-west-antarcticas-thwaites-glacier/

Extract: "Researchers at the University of Washington and the University of Edinburgh used data from the European Space Agency’s CryoSat-2 to identify a sudden drainage of large pools below Thwaites Glacier, one of two fast-moving glaciers at the edge of the ice sheet. The study published Feb. 8 in The Cryosphere finds four interconnected lakes drained in the eight months from June 2013 and January 2014. The glacier sped up by about 10 percent during that time, showing that the glacier’s long-term movement is fairly oblivious to trickles at its underside.

Melting at the ice sheet base would refill the lakes in 20 to 80 years, Smith said. Over time meltwater gradually collects in depressions in the bedrock. When the water reaches a certain level it breaches a weak point, then flows through channels in the ice. As Thwaites Glacier thins near the coast, its surface will become steeper, Smith said, and the difference in ice pressure between inland regions and the coast may push water coastward and cause more lakes to drain."

Obviously, when these subglacial lakes have refilled by the basal meltwater drainage system, in the coming decades, Thwaites will be primed for another surge.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 28, 2018, 12:28:16 AM
In regards to my last post, the linked reference (see also the first attached image and associated caption below, and the second image that shows the basal meltwater drainage system beneath Thwaites) provides more evidence of high geothermal flux and associated basal melt water beneath the Thwaites Glacier, both of which will threaten its future stability, and they both work to refill the recently drainage subglacial lakes beneath Thwaites:

Dustin M. Schroeder, Donald D. Blankenship, Duncan A. Young, and Enrica Quartini, (2014), "Evidence for elevated and spatially variable geothermal flux beneath the West Antarctic Ice Sheet", PNAS, doi: 10.1073/pnas.1405184111

http://www.pnas.org/content/early/2014/06/04/1405184111.abstract

http://www.pnas.org/content/suppl/2014/06/04/1405184111.DCSupplemental

Also see:
http://www.utexas.edu/news/2014/06/10/antarctic-glacier-melting/

Caption: "This map shows the locations of geothermal flow underneath Thwaites Glacier in West Antarctica that were identified with airborne ice-penetrating radar. The dark magenta triangles show where geothermal flow exceeds 150 milliwatts per square meter, and the light magenta triangles show where flow exceeds 200 milliwatts per square meter. Letters C, D and E denote high melt areas: in the western-most tributary, C; adjacent to the Crary mountains, D; and in the upper portion of the central tributaries, E. Credit: University of Texas Institute Geophysics"
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2018, 03:29:01 AM
Calculation of the remaining carbon budget has been made using unsafe assumptions, including: use of TCR instead of ECS, use of too low of a value of TCR, use of incomplete model projections, use of models that do not consider chaos theory even though the climate is chaotic, use of out-of-date data, using unsafe assumptions about the negative radiative forcing from aerosols, incorporation of too much faith in world leaders to limit carbon emissions, no consideration of freshwater hosing, radiative forcing scenarios are too low, assumed losses of carbon sinks are too optimistic, assuming that geoengineering is feasible.  In consideration of this the US DOE initially started a program called Accelerated Climate Modeling for Energy, ACME; which has subsequently been renamed Energy-Exascale-Earth System Model, E3SM, in an attempt to better understand the actual nature of our collective situation w.r.t. coming climate change.  E3SM models/hardware are expected be continuously updated for several decades; nevertheless, the version of the E3SM model extant at the end of 2017 is currently being used in the CMIP6 program which will heavily influence the coming AR6 findings.  As E3SM is currently the most advanced (but still imperfect) climate model, I provide the following discussion and links related to this matter.

As indicated in the first linked article, preliminary runs of the 2017 version of the E3SM model project that the current value of ECS might have a mean value of about 5.2C (& this high value is likely attributable to the state-of-the-art way that E3SM models aerosols and cloud feedback mechanisms).

While some consensus scientists (like Bjorn Stevens) have said that it is difficult to determine whether the 2017 version of E3SM CMIP6 projections will be any more relevant than other models in the CMIP6 program; I believe that these findings from the world's most advanced ESM warrant the adoptions of the Precautionary Principle, particularly as the 2017 version of E3SM only partially addresses Hansen's ice-climate feedback mechanism:

Title: "DOE’s maverick climate model is about to get its first test"
doi:10.1126/science.aau0578

http://www.sciencemag.org/news/2018/05/does-maverick-climate-model-about-get-its-first-test

Extract: "In 2017, after President Donald Trump took office and pulled the nation out of the Paris climate accords, DOE dropped "climate" from the project name. The new name, the Energy Exascale Earth System Model (E3SM), better reflects the model's focus on the entire Earth system, says project leader David Bader of Lawrence Livermore National Laboratory in California.
..
One preliminary result, on the climate's sensitivity to carbon dioxide (CO2), will "raise some eyebrows," Bader says. Most models estimate that, for a doubling of CO2 above preindustrial levels, average global temperatures will rise between 1.5°C and 4.5°C. The E3SM predicts a strikingly high rise of 5.2°C, which Leung suspects is due to the way the model handles aerosols and clouds. And like many models, the E3SM produces two bands of rainfall in the tropics, rather than the one seen in nature near the equator.

The first test of the E3SM will be its performance in CMIP6. Nearly three dozen modeling groups, including newcomers from South Korea, India, Brazil, and South Africa, are expected to submit results to the intercomparison between now and 2020."

Furthermore, the second linked pdf and associated videos, present some of the findings from the 2017 runs (prior to the CMIP6 runs), including the first attached image comparing hindcastes by the 2017 version of the E3SM model versions other 2017 runs by other advanced ESM models.  While the E3SM (2017) runs may not be sufficiently calibrated to matches its greater-than-normal degree of nonlinear responses, nevertheless the first attached image indicates that E3SM (2017) projected that higher than consensus negative forcing from anthropogenic radiative forcing has masked most of the consequences of the calculated 5.2C value of ECS up to the 2016-17 timeframe.  Even if E3SM (2017) is too responsive to radiative forcing, its projection highlight the potential extreme risks that humanity is taking by assuming that the recent potential high values of negative aerosol forcing are not masking current high values of ECS.  One disturbing possible conclusion from this E3SM (2017) projection might be that since ECS is dependent on the rate of forcing, the sharp global decline in global anthropogenic aerosol negative forcing after the 1990's may have triggered higher values of ECS.  Furthermore, if the E3SM (2017) projection indeed to demonstrate that ECS is very sensitive to the rate of radiative forcing, this would diminish the relevance of paleo-determined values for ECS as the rate of forcing in the past was from hundreds to many thousands of times slower that in modern times.

Title: "E3SM v1 Water Cycle Model for DECK and CMIP6 Submissions by Chris Golaz (of January 25, 2018)":

https://e3sm.org/wp-content/uploads/2018/10/2018-01-25_AllHands_Golaz_opt.pdf
https://www.youtube.com/watch?v=t9AJzu0--pE
&
See also:

E3SM All-Hands Presentations
https://e3sm.org/about/events/all-hands-presentations/
&
Energy Exascale Earth System Model
https://esgf-node.llnl.gov/projects/e3sm/
&

The following the linked references present findings from E3SM model runs from near the end of 2017, or early 2018, which illustrate that: a) Atmospheric module EAMv1 of E3SM still does not fully simulate cloud feedback mechanisms [see Xie et al. (2018)]; b) Land Ice module of E3SM does not include either the ice-cliff nor the hydrofracturing failure mechanisms [see the second attached image & Hoffman et al. (2018)]; and c) the E3SM module for projecting the potential loss of the Thwaites Ice Shelf is still relatively primitive.

Shaocheng Xie et al. (04 October 2018), "Understanding Cloud and Convective Characteristics in Version 1 of the E3SM Atmosphere Model", JAMES, https://doi.org/10.1029/2018MS001350

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018MS001350

Abstract: "This study provides comprehensive insight into the notable differences in clouds and precipitation simulated by the Energy Exascale Earth System Model Atmosphere Model version 0 and version 1 (EAMv1). Several sensitivity experiments are conducted to isolate the impact of changes in model physics, resolution, and parameter choices on these differences. The overall improvement in EAMv1 clouds and precipitation is primarily attributed to the introduction of a simplified third‐order turbulence parameterization Cloud Layers Unified By Binormals (along with the companion changes) for a unified treatment of boundary layer turbulence, shallow convection, and cloud macrophysics, though it also leads to a reduction in subtropical coastal stratocumulus clouds. This lack of stratocumulus clouds is considerably improved by increasing vertical resolution from 30 to 72 layers, but the gain is unfortunately subsequently offset by other retuning to reach the top‐of‐atmosphere energy balance. Increasing vertical resolution also results in a considerable underestimation of high clouds over the tropical warm pool, primarily due to the selection for numerical stability of a higher air parcel launch level in the deep convection scheme. Increasing horizontal resolution from 1° to 0.25° without retuning leads to considerable degradation in cloud and precipitation fields, with much weaker tropical and subtropical short‐ and longwave cloud radiative forcing and much stronger precipitation in the intertropical convergence zone, indicating poor scale awareness of the cloud parameterizations. To avoid this degradation, significantly different parameter settings for the low‐resolution (1°) and high‐resolution (0.25°) were required to achieve optimal performance in EAMv1."

Plain Language Summary
The Energy Exascale Earth System Model (E3SM) is a new and ongoing U.S. Department of Energy (DOE) climate modeling effort to develop a high‐resolution Earth system model specifically targeting next‐generation DOE supercomputers to meet the science needs of the nation and the mission needs of DOE. The increase of model resolution along with improvements in representing cloud and convective processes in the E3SM atmosphere model version 1 has led to quite significant model behavior changes from its earlier version, particularly in simulated clouds and precipitation. To understand what causes the model behavior changes, this study conducts sensitivity experiments to isolate the impact of changes in model physics, resolution, and parameter choices on these changes. Results from these sensitivity tests and discussions on the underlying physical processes provide substantial insight into the model errors and guidance for future E3SM development.
&

Matthew J. Hoffman et al . (2018), MPAS-Albany Land Ice (MALI): a variable-resolution ice sheet model for Earth system modeling using Voronoi grids", Geosci. Model Dev., 11, 3747–3780, https://doi.org/10.5194/gmd-11-3747-2018

https://www.geosci-model-dev.net/11/3747/2018/gmd-11-3747-2018.pdf

Abstract. We introduce MPAS-Albany Land Ice (MALI) v6.0, a new variable-resolution land ice model that uses unstructured Voronoi grids on a plane or sphere. MALI is built using the Model for Prediction Across Scales (MPAS) framework for developing variable-resolution Earth system model components and the Albany multi-physics code base for the solution of coupled systems of partial differential equations, which itself makes use of Trilinos solver libraries. MALI includes a three-dimensional first-order momentum balance solver (Blatter–Pattyn) by linking to the Albany-LI ice sheet velocity solver and an explicit shallow ice velocity solver. The evolution of ice geometry and tracers is handled through an explicit first-order horizontal advection scheme with vertical remapping. The evolution of ice temperature is treated using operator splitting of vertical diffusion and horizontal advection and can be configured to use either a temperature or enthalpy formulation. MALI includes a mass-conserving subglacial hydrology model that supports distributed and/or channelized drainage and can optionally be coupled to ice dynamics. Options for calving include “eigencalving”, which assumes that the calving rate is proportional to extensional strain rates. MALI is evaluated against commonly used exact solutions and community benchmark experiments and shows the expected accuracy. Results for the MISMIP3d benchmark experiments with MALI’s Blatter–Pattyn solver fall between published results from Stokes and L1L2 models as expected. We use the model to simulate a semi-realistic Antarctic ice sheet problem following the initMIP protocol and using 2 km resolution in marine ice sheet regions. MALI is the glacier component of the Energy Exascale Earth System Model (E3SM) version 1, and we describe current and planned coupling to other E3SM components.
&

Hoffman, M., J. Fyke, S. Price, X. Asay-Davis, and M. Perego (in prep.): Effects of ice shelf melt variability on the evolution of Thwaites Glacier, West Antarctica. Geophys. Res. Lett

https://www.colorado.edu/lab/icesheetclimate/publications

Therefore, if my prior estimates are correct that Pollard, DeConto and Alley (2018) projected Antarctic ice mass losses for Mid-Pliocene conditions may begin circa 2040; then E3SM projections may well prove to be unsafe.

The discussion at the linked Pik-Postdam website considers the probability that tipping cascades of significantly interlinked positive feedback mechanisms might potentially leading to abrupt climate change, particularly if perturbated by a collapse of key Antarctic marine glaciers:

Title: "DominoES project    Domino Effects in the Earth System: Can Antarctica tip climate policy?"

https://www.pik-potsdam.de/research/projects/activities/dominoes

Extract: "Tipping elements are components of the Earth system that could be pushed into qualitatively different states by small external perturbations, with profound environmental impacts possibly endangering the livelihoods of millions of people. There are indications for significant interlinkages between climate tipping elements and even the potential for tipping cascades or domino effects from the climate to the social sphere. We will assess these effects for a highly relevant tipping chain connecting climatic tipping elements like Antarctica and Greenland with potential social tipping processes in public opinion formation and climate policy changes, and their societal implications.

DominoES is a joint project by the Potsdam Institute for Climate Impact Research (PIK) and the Leibniz Institute for the Social Sciences (GESIS) funded by the Leibniz Association (2017 - 2020)."

For those who do not understand dynamical sensitivity, I note that it is related to the influence of climate attractors (from chaos theory), which can capture energy from radiative forcing and progressively ratchet-up climate states (see the last two attached images).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2018, 02:25:17 PM
The Last Glacial Termination, LGT, occurred from 18,000 to 11,650 kya, and the following reference, reconstructs the dynamic response of the Antarctic ice sheets to warming in this period in order to better evaluate Hansen's ice-climate feedback mechanisms.  The abstract from the second linked reference concludes: "Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections.  With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise."

Fogwill, et. al. (2017), "Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the last Glacial Termination", Scientific Reports 7, Article number 39979, doi:10.1038/srep39979

https://www.nature.com/articles/srep39979


Also a rain-dominated Arctic would be affected by Hansen's ice-climate feedback mechanism driven by a WAIS collapse beginning circa 2040 (which almost all ESM projections currently ignore), and or pulses of methane emission from thermokarst lakes.   Also the second linked reference assumes that ECS is only around 3C.

Richard Bintanja and Olivier Andry (2017), “Towards a rain-dominated Arctic”, Geophysical Research Abstracts Vol. 19, EGU2017-4402

http://meetingorganizer.copernicus.org/EGU2017/EGU2017-4402.pdf

Abstract: “Current climate models project a strong increase in Arctic precipitation over the coming century, which has been attributed primarily to enhanced surface evaporation associated with sea-ice retreat. Since the Arctic is still quite cold, especially in winter, it is often (implicitly) assumed that the additional precipitation will fall mostly as snow. However, very little is known about future changes in rain/snow distribution in the Arctic, notwithstanding the importance for hydrology and biology. Here we use 37 state-of-the-art climate models in standardised twenty-first century (2006–2100) simulations to show that 70◦ – 90◦N average annual Arctic snowfall will actually decrease, despite the strong increase in precipitation, and that most of the additional precipitation in the future (2091– 2100) will fall as rain. In fact, rain is even projected to become the dominant form of precipitation in the Arctic region. This is because Arctic atmospheric warming causes a greater fraction of snowfall to melt before it reaches the surface, in particular over the North Atlantic and the Barents Sea. The reduction in Arctic snowfall is most pronounced during summer and autumn when temperatures are close to the melting point, but also winter rainfall is found to intensify considerably. Projected (seasonal) trends in rain/snowfall will heavily impact Arctic hydrology (e.g. river discharge, permafrost melt), climatology (e.g. snow, sea ice albedo and melt) and ecology (e.g. water and food availability).”

See also the following linked reference:

R. Bintanja et al. Towards a rain-dominated Arctic, Nature Climate Change (2017). DOI: 10.1038/nclimate3240

http://www.nature.com/nclimate/journal/v7/n4/full/nclimate3240.html

Extract: "Rain causes more (extensive) permafrost melt [Refs. 7,26], which most likely leads to enhanced emissions of terrestrial methane [Ref. 27] (a powerful greenhouse gas), more direct runoff (a smaller seasonal delay) and concurrent freshening of the Arctic Ocean [Ref 18]. Rainfall also diminishes snow cover extent and considerably lowers the surface albedo of seasonal snow, ice sheets and sea ice [Ref. 9] , reinforcing surface warming and amplifying the retreat of ice and snow; in fact, enhanced rainfall will most likely accelerate sea-ice retreat by lowering its albedo (compared with that of fresh snowfall) "
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2018, 02:29:17 PM
For those interested in an overview of atmospheric bridges, oceanic tunnels and global climatic telecommunications, I offer the following linked 2007 open access reference.  However, I warn that it only provides a low level overview and does not explicitly address issues such as ice-climate feedback (ala Hansen et al 2016) nor issues like the role of Agulhus Leakage in the bipolar seesaw mechanism:

Zhengyu Liu & Mike Alexander (23 June 2007), "Atmospheric bridge, oceanic tunnel, and global climatic teleconnections', Reviews of Geophysics; DOI: 10.1029/2005RG000172

http://onlinelibrary.wiley.com/doi/10.1029/2005RG000172/full

Abstract: "We review teleconnections within the atmosphere and ocean, their dynamics and their role in coupled climate variability. We concentrate on teleconnections in the latitudinal direction, notably tropical-extratropical and interhemispheric interactions, and discuss the timescales of several teleconnection processes. The tropical impact on extratropical climate is accomplished mainly through the atmosphere. In particular, tropical Pacific sea surface temperature anomalies impact extratropical climate variability through stationary atmospheric waves and their interactions with midlatitude storm tracks. Changes in the extratropics can also impact the tropical climate through upper ocean subtropical cells at decadal and longer timescales. On the global scale the tropics and subtropics interact through the atmospheric Hadley circulation and the oceanic subtropical cell. The thermohaline circulation can provide an effective oceanic teleconnection for interhemispheric climate interactions."

The first attached image shows an oceanic Rossby Wave Train that can propagate from the Equatorial Pacific to West Antarctica in a timeframe of months.

The second image shows that during a paleo (45 kya) North Atlantic hosing (D-O) event, warm Gulf Stream water flowed under the less saline (but colder) surface water in order to warm the Norwegian Sea.  Also, the third image shows that under extant conditions with both cool North Pacific and North Atlantic ocean temperatures, atmospheric Rossby waves can still telecommunicate heat from the tropical oceans directly to Arctic regions (as indicated).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 29, 2018, 03:32:05 PM
The linked reference points out that per their 1D models the Arctic continental shelf methane hydrate stability zone (HSZ) can take ~ 10 to 20 kyrs to respond to changes in initial temperature conditions associated with the end of the last ice age.  However, while it is pleasant to think of middle of the 10 to 20 kya range, as the attached image indicates the Holocene began about 11 kya and thus we should now start to see portions of the HSZ becoming unstable due to the global temperature increase leading to the beginning of the Holocene.  This emphasizes that modelers need to get their initial conditions correct:

Valentina V. Malakhova & Alexey V. Eliseev (2017), "The role of heat transfer time scale in the evolution of the subsea permafrost and associated methane hydrates stability zone during glacial cycles", Global and Planetary Change, https://doi.org/10.1016/j.gloplacha.2017.08.007

http://www.sciencedirect.com/science/article/pii/S0921818117301273

Abstract: "Climate warming may lead to degradation of the subsea permafrost developed during Pleistocene glaciations and release methane from the hydrates, which are stored in this permafrost. It is important to quantify time scales at which this release is plausible. While, in principle, such time scale might be inferred from paleoarchives, this is hampered by considerable uncertainty associated with paleodata. In the present paper, to reduce such uncertainty, one–dimensional simulations with a model for thermal state of subsea sediments forced by the data obtained from the ice core reconstructions are performed. It is shown that heat propagates in the sediments with a time scale of ∼ 10-20 kyr. This time scale is longer than the present interglacial and is determined by the time needed for heat penetration in the unfrozen part of thick sediments. We highlight also that timings of shelf exposure during oceanic regressions and flooding during transgressions are important for simulating thermal state of the sediments and methane hydrates stability zone (HSZ). These timings should be resolved with respect to the contemporary shelf depth (SD). During glacial cycles, the temperature at the top of the sediments is a major driver for moving the HSZ vertical boundaries irrespective of SD. In turn, pressure due to oceanic water is additionally important for SD ≥ 50 m. Thus, oceanic transgressions and regressions do not instantly determine onset s of HSZ and/or its disappearance. Finally, impact of initial conditions in the subsea sediments is lost after ∼ 100 kyr. Our results are moderately sensitive to intensity of geothermal heat flux."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2018, 05:09:41 PM
While this thread goes well beyond Hansen's ice-climate feedback mechanisms; nevertheless, Hansen's basic position on this matter lies at the heart of this thread.  Therefore, I note that it is a clear example of scientific reticence that consensus climate science has not highly cited Hansen et al. (2016), " Ice Melt, Sea Level Rise, and Superstorms", as discussed in the first linked documents (also see the attached image showing Hansen's illustration of both the ocean stratification and precipitation feedback mechanisms):

James Hansen (October 26, 2017), "Scientific Reticence: a DRAFT Discussion" and "Scientific Reticence and the Fate of Humanity"

http://www.columbia.edu/~jeh1/mailings/2017/20171026_ScientificReticence.pdf
https://unfccc.int/event/abibimman-foundation-james-hansen-scientific-reticence-a-threat-to-humanity-and-nature

Extract: "Frank Dentener, an editor of Atmospheric Chemistry and Physics, in a recent note to me observed that Ice Melt, Sea Level Rise, and Superstorms, hereafter Ice Melt, was not highly cited or mainstream in climate impact discussions. He was concerned because he thought it important for peer-reviewed extreme scenarios to be included in the upcoming IPCC AR6 cycle."
&

Furthermore, the second linked reference indicates that consensus climate science has been largely ignoring Hansen's warnings about fat-tail climate risks since well before 2007, and I note that the longer we wait to take effective action the worse our climate situation becomes:

Hansen (2007), "Scientific Reticence and Sea Level Rise", Environmental Research Letters, Volume 2, Number 2, doi:10.1088/1748-9326/2/2/024002

http://iopscience.iop.org/article/10.1088/1748-9326/2/2/024002
https://arxiv.org/abs/physics/0703220

Abstract: "I suggest that a "scientific reticence" is inhibiting communication of a threat of potentially large sea level rise. Delay is dangerous because of system inertias that could create a situation with future sea level changes out of our control. I argue for calling together a panel of scientific leaders to hear evidence and issue a prompt plain-written report on current understanding of the sea level change issue."

Finally for this post, I note that no matter how much reticence that consensus climate scientists have (or have not) exhibited; I believe that climate science has presented adequate information (even considering the associated uncertainties) for global decision makers to take far greater measures to fight climate change then what they currently have planned.  Until decision makers are willing to open their collective eyes (or become replaced by decision makers who are willing to open their eyes) and take the large number of fat-tailed risks that we face serious; the only out-come that I can see for the path that we are currently taking is socio-economic collapse sometime before 2060.

Title: "A Failure of Imagination on Climate Risks"

http://www.resilience.org/stories/2017-07-26/a-failure-of-imagination-on-climate-risks/

Extract: "Climate change is an existential risk that could abruptly end human civilisation because of a catastrophic “failure of imagination” by global leaders to understand and act on the science and  evidence before them.

At the London School of Economics in 2008, Queen Elizabeth questioned: “Why did no one foresee the timing, extent and severity of the Global Financial Crisis?” The British Academy answered a year later: “A psychology of denial gripped the financial and corporate world… [it was] the failure of the collective imagination of many bright people… to understand the risks to the system as a whole”.

A “failure of imagination” has also been identified as one of the reasons for the breakdown in US intelligence around the 9/11 attacks in 2001.

A similar failure is occurring with climate change today.

The problem is widespread at the senior levels of government and global corporations. A 2016 report, Thinking the unthinkable, based on interviews with top leaders around the world, found that:

“A proliferation of ‘unthinkable’ events… has revealed a new fragility at the highest levels of corporate and public service leaderships. Their ability to spot, identify and handle unexpected, non-normative events is… perilously inadequate at critical moments… Remarkably, there remains a deep reluctance, or what might be called ‘executive myopia’, to see and contemplate even the possibility that ‘unthinkables’ might happen, let alone how to handle them."

Such failures are manifested in two ways in climate policy. At the political, bureaucratic and business level in underplaying the high-end risks and in failing to recognise that the existential risk of climate change is totally different from other risk categories. And at the research level in underestimating the rate of climate change impact and costs, along with an under-emphasis on, and poor communication of, those high-end risks."

In my next several posts I plan on citing several significant potential sources of fat-tailed risks that could contribute to a cascade (domino effect) of tipping points potentially driving the Earth Systems into progressively high states of activation (with higher climate attractors and higher climate sensitivities), if mankind doesn't get off our current BAU pathway immediately (which most likely will not happen).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2018, 05:20:15 PM
As one example of a fat-tailed risk that could contribute to a cascade of tipping point feedback and forcing mechanisms, the linked article is entitled: "Draining huge African peatland a threat to climate: study", this significant GHG source is missing from AR5.  A collapse of the WAIS beginning in 2040 could activate this huge source of possible GHG emissions well before the end of this century:

https://www.yahoo.com/news/draining-huge-african-peatland-threat-climate-study-195730012.html

Extract: "A swampy forest in central Africa the size of England covers previously unknown carbon stocks equivalent to three years' worth of global CO2 emissions, scientists revealed Wednesday.
Draining these peatlands for agriculture, or reduced rainfall due to climate change, would release massive amounts of planet-warming greenhouse gases, they warned in a study published in Nature magazine.

"We found 30 billion tonnes of carbon that nobody knew was there," said Simon Lewis, co-lead author of the study and a professor at the University of Leeds.

"If the Congo Basin peatlands were to be destroyed, it would release billions of tonnes of CO2 into the atmosphere," he told AFP."

Edit, see also the following linked article that indicates that the Congo Basin peatlands formed during the Holocene and thus this fat-tailed risk is not accounted for in models of paleo interglacial periods:

Title: "Guest post: A plan to solve the mysteries of Congo’s vast tropical peatland"

https://www.carbonbrief.org/guest-post-a-plan-to-solve-mysteries-of-congos-vast-tropical-peatland

Extract: "Radiocarbon dating at the base of the peat – up to five metres below the surface – has revealed that the peatland began to form about 10,000 years ago – when central Africa became warmer and wetter as the Earth emerged from the last ice age.

Critically, our initial discovery of the peatland included no data from the DRC, which we believe houses two-thirds of the peatland area and its associated carbon stocks. Our new work will test this hypothesis and provide the first data-driven maps of the peatlands in the DRC.

Peatlands are important not just in terms of removing carbon from the atmosphere: the waterlogged conditions means these wetlands also release large quantities of the greenhouse gas methane."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2018, 11:13:55 PM
The linked reference indicates that the collapse of an ice sheet can result in the abrupt reorganization of the associated jet stream:

Juan M. Lora, Jonathan L. Mitchell & Aradhna E. Tripati (22 November 2016), "Abrupt reorganization of North Pacific and western North American climate during the last deglaciation", Geophysical Research Letters, DOI: 10.1002/2016GL071244

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071244/full

Abstract: "Dramatic hydroclimate shifts occurred in western North America during the last deglaciation, but the timing and mechanisms driving these changes are uncertain and debated, and previous modeling has largely relied on linear interpolations between equilibrium snapshot simulations. Using a published transient climate simulation and a range of proxy records, we analyze the region's climate evolution in order to identify the mechanisms governing hydroclimate shifts. A rapid loss of ice around 14,000 years ago causes an abrupt reorganization of the circulation, which precipitates drying and moistening of southwestern and northwestern North America, respectively. The atmospheric circulation transitions between two states on a timescale of decades to centuries, during which time the westerly jet shifts north by about 7°. In contrast to previous studies, we find that changes in the water budget of western North America prior to this event are not attributable to variations in the position of the jet, but rather to the intensity of moisture transport into the continent."

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on November 30, 2018, 11:15:49 PM
The linked reference evaluates the implications of more accurately considering a 3-D viscoelastic Earth models as opposed to the less accurate assumption of elastic response on the sea-level fingerprint implications of an abrupt collapse of the WAIS.  Their findings conclude that "… when viscous effects are included, the peak sea-level fall predicted in the vicinity of WAIS during a melt event will increase by ~25% and ~50%, relative to the elastic case, for events of duration 25 years and 100 years, respectively."  This is important w.r.t. global sea level rise as the further the local sea-level drops around West Antarctica, the higher sea level will raise at distance away from West Antarctica.

Carling C. Hay, Harriet C. P. Lau, Natalya Gomez, Jacqueline Austermann, Evelyn Powell, Jerry X. Mitrovica, Konstantin Latychev, and Douglas A. Wiens (2016), "Sea-level fingerprints in a region of complex Earth structure: The case of WAIS", Journal of Climate, DOI: http://dx.doi.org/10.1175/JCLI-D-16-0388.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0388.1

Abstract: "Sea-level fingerprints associated with rapid melting of the West Antarctic Ice Sheet (WAIS) have generally been computed under the assumption of a purely elastic response of the solid Earth. We investigate the impact of viscous effects on these fingerprints by computing gravitationally self-consistent sea-level changes that adopt a 3-D viscoelastic Earth model in the Antarctic region consistent with available geological and geophysical constraints. In West Antarctica, the model is characterized by a thin (~65 km) elastic lithosphere and sub-lithospheric viscosities that span three orders of magnitude, reaching values as low as ~4 × 1018 Pa s beneath WAIS. Our calculations indicate that sea-level predictions in the near field of WAIS will depart significantly from elastic fingerprints in as little as a few decades. For example, when viscous effects are included, the peak sea-level fall predicted in the vicinity of WAIS during a melt event will increase by ~25% and ~50%, relative to the elastic case, for events of duration 25 years and 100 years, respectively. Our results have implications for studies of sea-level change due to both ongoing mass loss from WAIS over the next century and future, large scale collapse of WAIS on century-to-millennial time scales."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 03:58:56 PM
It is important to note here that the best ESMs cannot match the climate response during MIS 11c (the Holsteinian Peak), where MIS 11 extents from 424,000 to 374,000 years ago (see the first linked reference).  This means that the best CMIP5 models are currently underestimating the degree of nonlinear global warming that we are likely to experience with continued anthropogenic radiative forcing:

The Mid-Brunhes Event (MBE) coincides with MIS 11 (the Holsteinian) about 400,000 to 350,000 years ago, and marks a major transition to subsequent enhanced Arctic Amplification as discussed in the open access linked reference (see the first three attached images while the fourth image from another source help to clarify that after the MBE interglacial peak global mean peak temperatures have been higher).  Furthermore, the reference associates this change with the bipolar seesaw and episodic collapses of the WAIS.  This research clearly associates the bipolar seesaw mechanism with Hansen's ice-climate feedback and with Arctic Amplification.  This also implies that if the WAIS collapses this century, that warm Atlantic water will penetrate deep into the Arctic Ocean Basin, where it would likely have an impact on any shallow methane hydrates:

Cronin et al (2017), "Enhanced Arctic Amplification Began at the Mid-Brunhes Event ~400,000 years ago", Scientific Reports 7, Article No. 14475, doi: 10.1038/s41598-017-13821-2

https://www.nature.com/articles/s41598-017-13821-2

Extract: "Enhanced Arctic amplification at the MBE suggests a major climate threshold was reached at ~400 ka involving Atlantic Meridional Overturning Circulation (AMOC), inflowing warm Atlantic Layer water, ice sheet, sea-ice and ice-shelf feedbacks, and sensitivity to higher post-MBE interglacial CO₂ concentrations.

Southern Hemisphere ocean-atmosphere-sea ice processes are critical for understanding the MBE, specifically the idea that there is a bipolar seesaw operating between Northern and Southern Hemispheres on millennial timescales explain warmer interglacial condition in the Southern Hemisphere.  Barker et al. (2011) demonstrated that abrupt millennial-scale AMOC variability characterized the last 800 ka, albeit without the large amplitude shift seen in our Arctic records.  Holden et al. proposed a role for decreased stability of the West Antarctic Ice Sheet following the MBE, leading to AMOC slowdown during deglacials.  Thus, it is possible that ice sheet/ice shelf instability characterized both hemispheres providing the necessary non-linear dynamics to explain large amplitude temperature events in the Arctic Ocean.  However establishing the relationship between bottom temperature, sea ice and productivity during stadial and interstadial periods – require better sediment core resolution in the Arctic.  Nonetheless, the large shift in Arctic land ice, ice shelves and sea ice at the MBE, suggests an amplification of Arctic climate sensitivity related to higher interglacial CO₂ concentrations and associated feedbacks involving ice shelves and ice sheets, Heinrich-like events, AMOC-forcing Arctic Ocean temperature oscillations, and deeper submergence of Atlantic water in the central Arctic Basin."
&

Furthermore, the linked reference studies the paleo decay of the Cordilleran ice sheet and finds that it lost most of its ice mass earlier than consensus science previously thought, and it lost much of its ice mass over a relatively short period.  CMIP5 models were not calibrated with such information which indicates that dry land ice sheets may be less stable during global warming periods.  Personally, I am concerned about the impact of rainfall at increasingly high latitudes (with warming) on both the Greenland Ice Sheet, on Arctic permafrost, and on the WAIS:

B. Menounos et al (10 Nov 2017), "Cordilleran Ice Sheet mass loss preceded climate reversals near the Pleistocene Termination", Science, Vol. 358, Issue 6364, pp. 781-784, DOI: 10.1126/science.aan3001

http://science.sciencemag.org/content/358/6364/781

Abstract: "The Cordilleran Ice Sheet (CIS) once covered an area comparable to that of Greenland. Previous geologic evidence and numerical models indicate that the ice sheet covered much of westernmost Canada as late as 12.5 thousand years ago (ka). New data indicate that substantial areas throughout westernmost Canada were ice free prior to 12.5 ka and some as early as 14.0 ka, with implications for climate dynamics and the timing of meltwater discharge to the Pacific and Arctic oceans. Early Bølling-Allerød warmth halved the mass of the CIS in as little as 500 years, causing 2.5 to 3.0 meters of sea-level rise. Dozens of cirque and valley glaciers, along with the southern margin of the CIS, advanced into recently deglaciated regions during the Bølling-Allerød and Younger Dryas."

Extract: "Disappearance of an ice sheet
The Cordilleran Ice Sheet is thought to have covered westernmost Canada until about 13,000 years ago, even though the warming and sea level rise of the last deglaciation had begun more than a thousand years earlier. This out-of-phase behavior has puzzled glaciologists because it is not clear what mechanisms could account for it. Menounos et al. report measurements of the ages of cirque and valley glaciers that show that much of western Canada was ice-free as early as 14,000 years ago—a finding that better agrees with the record of global ice volume (see the Perspective by Marcott and Shakun). Previous reconstructions seem not to have adequately reflected the complexity of ice sheet decay."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 04:04:50 PM
The linked reference indicates that the PIIS is calving further upstream (thru 2015) than in the past due to various oceanic driven factors including intensified melting with basal crevasses.  This means that the  calving face of the PIIS is likely to continue to retreat, even before GMSTA warms sufficiently for hydrofracturing to become a significant failure mechanism for the PIIS.

Seongsu Jeong, Ian M. Howat & Jeremy N. Bassis (28 November 2016), "Accelerated ice shelf rifting and retreat at Pine Island Glacier, West Antarctica", Geophysical Research Letters, DOI: 10.1002/2016GL071360

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071360/full

Abstract: "Pine Island Glacier has undergone several major iceberg calving events over the past decades. These typically occurred when a rift at the heavily fractured shear margin propagated across the width of the ice shelf. This type of calving is common on polar ice shelves, with no clear connection to ocean-ice dynamic forcing. In contrast, we report on the recent development of multiple rifts initiating from basal crevasses in the center of the ice shelf, resulted in calving further upglacier than previously observed. Coincident with rift formation was the sudden disintegration of the ice mélange that filled the northern shear margin, resulting in ice sheet detachment from this margin. Examination of ice velocity suggests that this internal rifting resulted from the combination of a change in ice shelf stress regime caused by disintegration of the mélange and intensified melting within basal crevasses, both of which may be linked to ocean forcing."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 04:06:30 PM
Most climate models do not include wind-albedo interaction that is currently inducing surface melting in portions of East Antarctica, but the linked reference documents field evidence for this mechanism that could contribute to a faster rate of AIS destabilization with global warming then currently projected:

J. T. M. Lenaerts, et. al.  (2016), "Meltwater produced by wind–albedo interaction stored in an East Antarctic ice shelf", Nature Climate Change, doi:10.1038/nclimate3180

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3180.html

Abstract: "Surface melt and subsequent firn air depletion can ultimately lead to disintegration of Antarctic ice shelves causing grounded glaciers to accelerate and sea level to rise. In the Antarctic Peninsula, foehn winds enhance melting near the grounding line, which in the recent past has led to the disintegration of the most northerly ice shelves. Here, we provide observational and model evidence that this process also occurs over an East Antarctic ice shelf, where meltwater-induced firn air depletion is found in the grounding zone. Unlike the Antarctic Peninsula, where foehn events originate from episodic interaction of the circumpolar westerlies with the topography, in coastal East Antarctica high temperatures are caused by persistent katabatic winds originating from the ice sheet’s interior. Katabatic winds warm and mix the air as it flows downward and cause widespread snow erosion, explaining >3 K higher near-surface temperatures in summer and surface melt doubling in the grounding zone compared with its surroundings. Additionally, these winds expose blue ice and firn with lower surface albedo, further enhancing melt. The in situ observation of supraglacial flow and englacial storage of meltwater suggests that ice-shelf grounding zones in East Antarctica, like their Antarctic Peninsula counterparts, are vulnerable to hydrofracturing."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 04:10:28 PM
The linked reference provides field evidence supporting Hansen's ice-climate interaction mechanism.

Pepijn Bakker et al, Centennial-scale Holocene climate variations amplified by Antarctic Ice Sheet discharge, Nature (2016). DOI: 10.1038/nature20582

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature20582.html

Abstract: "Proxy-based indicators of past climate change show that current global climate models systematically underestimate Holocene-epoch climate variability on centennial to multi-millennial timescales, with the mismatch increasing for longer periods. Proposed explanations for the discrepancy include ocean–atmosphere coupling that is too weak in models, insufficient energy cascades from smaller to larger spatial and temporal scales, or that global climate models do not consider slow climate feedbacks related to the carbon cycle or interactions between ice sheets and climate. Such interactions, however, are known to have strongly affected centennial- to orbital-scale climate variability during past glaciations, and are likely to be important in future climate change. Here we show that fluctuations in Antarctic Ice Sheet discharge caused by relatively small changes in subsurface ocean temperature can amplify multi-centennial climate variability regionally and globally, suggesting that a dynamic Antarctic Ice Sheet may have driven climate fluctuations during the Holocene. We analysed high-temporal-resolution records of iceberg-rafted debris derived from the Antarctic Ice Sheet, and performed both high-spatial-resolution ice-sheet modelling of the Antarctic Ice Sheet and multi-millennial global climate model simulations. Ice-sheet responses to decadal-scale ocean forcing appear to be less important, possibly indicating that the future response of the Antarctic Ice Sheet will be governed more by long-term anthropogenic warming combined with multi-centennial natural variability than by annual or decadal climate oscillations."

See also the linked article entitled: "Antarctic Ice Sheet study reveals 8,000-year record of climate change".

http://phys.org/news/2016-12-antarctic-ice-sheet-reveals-year.html

Extract: "An international team of researchers has found that the Antarctic Ice Sheet plays a major role in regional and global climate variability - a discovery that may also help explain why sea ice in the Southern Hemisphere has been increasing despite the warming of the rest of the Earth.


Global climate models that look at the last several thousand years have failed to account for the amount of climate variability captured in the paleoclimate record, according to lead author Pepijn Bakker, a climate modeller from the MARUM Center for Marine Environmental Studies at the University of Bremen in Germany.

The researchers first turned their attention to the Scotia Sea. "Most icebergs calving off the Antarctic Ice Sheet travel through this region because of the atmospheric and oceanic circulation," explained Weber. "The icebergs contain gravel that drop into the sediment on the ocean floor - and analysis and dating of such deposits shows that for the last 8,000 years, there were centuries with more gravel and those with less."

The research team's hypothesis is that climate modellers have historically overlooked one crucial element in the overall climate system. They discovered that the centuries-long phases of enhanced and reduced Antarctic ice mass loss documented over the past 8,000 years have had a cascading effect on the entire climate system.

Using sophisticated computer modelling, the researchers traced the variability in iceberg calving (ice that breaks away from glaciers) to small changes in ocean temperatures."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 04:13:03 PM
With continued global warming one can expect more Agulhas leakage; which per the linked reference means that one can expect the AMOC to continue slowing; which should work synergistically with Hansen's ice-climate feedback, particularly if the WAIS collapses in coming decades:

Kathryn A. Kelly, Kyla Drushka, LuAnne Thompson, Dewi Le Bars & Elaine L. McDonagh (25 July 2016), "Impact of slowdown of Atlantic overturning circulation on heat and freshwater transports", Geophysical Research Letters, DOI: 10.1002/2016GL069789

http://onlinelibrary.wiley.com/doi/10.1002/2016GL069789/abstract

Abstract: "Recent measurements of the strength of the Atlantic overturning circulation at 26°N show a 1 year drop and partial recovery amid a gradual weakening. To examine the extent and impact of the slowdown on basin wide heat and freshwater transports for 2004–2012, a box model that assimilates hydrographic and satellite observations is used to estimate heat transport and freshwater convergence as residuals of the heat and freshwater budgets. Using an independent transport estimate, convergences are converted to transports, which show a high level of spatial coherence. The similarity between Atlantic heat transport and the Agulhas Leakage suggests that it is the source of the surface heat transport anomalies. The freshwater budget in the North Atlantic is dominated by a decrease in freshwater flux. The increasing salinity during the slowdown supports modeling studies that show that heat, not freshwater, drives trends in the overturning circulation in a warming climate."

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 04:30:50 PM
Per the linked Gavin Schmidt tweeter thread, for a 20yr loess trend line Gavin is predicting that the GMSTA in 2019 will be 1.2+/-0.15C (see the first attached image) or 1.23C for a 15yr loess trend line (see the extract below).  I note that this prediction is in line with Hansen's prediction that I cited in Reply #220 and as is indicated by the second attached image.

https://twitter.com/ClimateOfGavin/status/1068336654887337984

Extract: "ENSO forecast for DJF here: https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/ … (I used 1±0.6 (95% CI)). Note there is also some dependence on the smoothing; predictions for 2019 would be 1.23 or 1.17 using a 15yr or 30yr loess smooth....1.2±0.15 ºC above the late 19th C. A warmer yr than 2018 (which will #4), almost certain >1ºC yr, and 1 in 3 chance of a new record."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 04:39:21 PM
The findings of the linked reference highlight the risk that with continued global warming this century the tropical rainforests could collapse; which, would increase realized temperatures above those projected this century by CMIP5.  Such a collapse of the tropical rainforests would not only mean the loss of a major carbon sink but would also increase carbon emissions from both the decaying dead forests & the associated peatlands:

Isabel P. Montañez, Jennifer C. McElwain, Christopher J. Poulsen Joseph D. White, William A. DiMichele, Jonathan P. Wilson, Galen Griggs & Michael T. Hren (2016), "Climate, pCO2 and terrestrial carbon cycle linkages during late Palaeozoic glacial–interglacial cycles, Nature Geoscience", nature.com/articles/doi:10.1038/ngeo2822


http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2822.html

Abstract: "Earth’s last icehouse, 300 million years ago, is considered the longest-lived and most acute of the past half-billion years, characterized by expansive continental ice sheets and possibly tropical low-elevation glaciation. This atypical climate has long been attributed to anomalous radiative forcing promoted by a 3% lower incident solar luminosity and sustained low atmospheric pCO2 (≤300 ppm). Climate models, however, indicate a CO2 sensitivity of ice-sheet distribution and sea-level response that questions this long-standing climate paradigm by revealing major discrepancy between hypothesized ice distribution, pCO2, and geologic records of glacioeustasy. Here we present a high-resolution record of atmospheric pCO2 for 16 million years of the late Palaeozoic, developed using soil carbonate-based and fossil leaf-based proxies, that resolves the climate conundrum. Palaeo-fluctuations on the 105-yr scale occur within the CO2 range predicted for anthropogenic change and co-vary with substantial change in sea level and ice volume. We further document coincidence between pCO2 changes and repeated restructuring of Euramerican tropical forests that, in conjunction with modelled vegetation shifts, indicate a more dynamic carbon sequestration history than previously considered and a major role for terrestrial vegetation–CO2 feedbacks in driving eccentricity-scale climate cycles of the late Palaeozoic icehouse."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 08:57:21 PM
I provide the following to linked references to indicate that correctly accounting for dynamical climate sensitivity in the coming decades require the use of very sophisticated climate models that can account for bipolar seesaw mechanisms correctly and which correctly apply paleo-lessons-learned (including the impacts of freshwater hosing) to our current dynamic conditions:


Joel Pedro, Markus Jochum, Christo Buizert, Sune Rasmussen, and Feng He (2017), "The Bipolar Seesaw and Its Discontents", Geophysical Research Abstracts, Vol. 19, EGU2017-11688

http://meetingorganizer.copernicus.org/EGU2017/EGU2017-11688.pdf

Abstract: "The thermal bipolar ocean seesaw hypothesis is the prevailing explanation for the out-of-phase changes in northern and southern high-latitude climate during the Dansgaard-Oeschger (D-O) events of the last glacial period and deglaciation (Stocker and Johnsen, 2003). However the seesaw hypothesis has been challenged on several grounds: it neglects the much larger transport of heat in the atmosphere compared to ocean, and it does not specify the modes and time scales of signal propagation in the coupled ocean-atmosphere system. The purpose of this presentation is to critically review the seesaw hypothesis and address these critiques.

We use transient simulations with a coupled ocean-atmosphere-sea-ice global climate model (GCM) to trace the ocean and atmospheric heat-transport changes and pathways of inter-hemispheric signal propagation during a simulated collapse and a simulated strengthening of the Atlantic Meridional Overturning Circulation (AMOC). While the simulated AMOC perturbations result in climate variations in close agreement with palaeoclimate observations, changes to the heat budget and their propagation throughout the globe differ from the ideas of Stocker and Johnsen (2003). The key differences are as follows. (1) Changes in ocean heat transport in the Atlantic in response to AMOC perturbations are partially compensated by changes in northward heat transport in the global atmosphere and in the Pacific Ocean. (2) There is little ocean transmission of temperature anomalies between the South Atlantic and high latitude Southern Ocean, because the lack of zonal boundaries and the steeply outcropping isopycnals of the Antarctic Circumpolar Current (ACC) act as a barrier to signal propagation. (3) On the multi-centennial timescale of the simulations the heat content of the Southern Ocean to the south of the ACC is insensitive to AMOC changes, and South Atlantic temperature anomalies, rather than crossing the ACC spread at intermediate depths into the Indian and Pacific oceans. (4) The global intermediate-depth ocean to the north of the ACC thus better fits the description of being a ’heat reservoir’ for changes in the AMOC than the Southern Ocean. (5) In the simulations, signal propagation to latitudes south of the ACC (including Antarctica) is dominated by teleconnections between the Hadley Circulation, the mid-latitude westerlies and Southern Ocean sea ice extent.

We conclude with an inter-hemispheric coupling hypothesis that recognises the coupled nature of (interbasin) ocean and atmosphere heat transport, the difficulty of propagating ocean anomalies across the ACC and the role of wind-stress, sea ice and associated surface heat flux changes on temperature variations at high latitudes.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 10:21:58 PM
The linked reference models the influence of surface melt lakes on the Larsen C Ice Shelf, and finds that not only do such melt lakes increase the risk of abrupt hydrofracturing failure of the ice shelf, but also: a) decreases surface albedo which increases surface ice melting and b) softens the ice associated with crevasses in the ice.  Such feedback mechanisms may soon become applicable to more southerly ice shelves around Antarctica in the coming decades:

Buzzard, S., Feltham, D., and Flocco, D.: Modelling the fate of surface melt on the Larsen C Ice Shelf, The Cryosphere, 12, 3565-3575, https://doi.org/10.5194/tc-12-3565-2018, 2018.

https://www.the-cryosphere.net/12/3565/2018/
https://www.the-cryosphere.net/12/3565/2018/tc-12-3565-2018.pdf

Abstract: "Surface melt lakes lower the albedo of ice shelves, leading to additional surface melting. This can substantially alter the surface energy balance and internal temperature and density profiles of the ice shelf. Evidence suggests that melt lakes also played a pivotal role in the sudden collapse of the Larsen B Ice Shelf in 2002.

Here a recently developed, high-physical-fidelity model accounting for the development cycle of melt lakes is applied to the Larsen C Ice Shelf, Antarctica's most northern ice shelf and one where melt lakes have been observed. We simulate current conditions on the ice shelf using weather station and reanalysis data and investigate the impacts of potential future increases in precipitation and air temperature on melt lake formation, for which concurrent increases lead to an increase in lake depth.

Finally, we assess the viability in future crevasse propagation through the ice shelf due to surface meltwater accumulation."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 01, 2018, 10:45:22 PM
The linked reference indicates that 'Arctic Browning' is currently reducing the Arctic's ability to absorb CO₂.

Rachael Treharne et al. (25 November 2018), "Arctic browning: Impacts of extreme climatic events on heathland ecosystem CO2 fluxes", Global Change Biology, https://doi.org/10.1111/gcb.14500

https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14500

Abstract: "Extreme climatic events are among the drivers of recent declines in plant biomass and productivity observed across Arctic ecosystems, known as “Arctic browning.” These events can cause landscape‐scale vegetation damage and so are likely to have major impacts on ecosystem CO2 balance. However, there is little understanding of the impacts on CO2 fluxes, especially across the growing season. Furthermore, while widespread shoot mortality is commonly observed with browning events, recent observations show that shoot stress responses are also common, and manifest as high levels of persistent anthocyanin pigmentation. Whether or how this response impacts ecosystem CO2 fluxes is not known. To address these research needs, a growing season assessment of browning impacts following frost drought and extreme winter warming (both extreme climatic events) on the key ecosystem CO2 fluxes Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP), ecosystem respiration (Reco) and soil respiration (Rsoil) was carried out in widespread sub‐Arctic dwarf shrub heathland, incorporating both mortality and stress responses. Browning (mortality and stress responses combined) caused considerable site‐level reductions in GPP and NEE (of up to 44%), with greatest impacts occurring at early and late season. Furthermore, impacts on CO2 fluxes associated with stress often equalled or exceeded those resulting from vegetation mortality. This demonstrates that extreme events can have major impacts on ecosystem CO2 balance, considerably reducing the carbon sink capacity of the ecosystem, even where vegetation is not killed. Structural Equation Modelling and additional measurements, including decomposition rates and leaf respiration, provided further insight into mechanisms underlying impacts of mortality and stress on CO2 fluxes. The scale of reductions in ecosystem CO2 uptake highlights the need for a process‐based understanding of Arctic browning in order to predict how vegetation and CO2 balance will respond to continuing climate change."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 02, 2018, 04:59:23 PM
The first linked reference determines the paleoclimate sensitivity during the Middle Eocene at a latitude of 64 degrees 48 minutes in Canada (see the first image), and finds a regional climate sensitivity of about 13C.  The second image illustrates that these findings indicate exceptionally high values of Arctic Amplification during this period as the atmospheric carbon dioxide concentrations were found to be only about 490 ppm.  While the mean global surface temperature was warmer during the Middle Eocene than today, we are warming at a much faster rate and C02e is already above 530 ppm.  This does not bode well for our collective future:

Alexander P. Wolfe, Alberto V. Reyes, Dana L. Royer, David R. Greenwood, Gabriela Doria, Mary H. Gagen, Peter A. Siver and John A. Westgate (May 2017), "Middle Eocene CO2 and climate reconstructed from the sediment fill of a subarctic kimberlite maar", GEOLOGY, July 2017; v. 45; no. 7; p. 619–622, doi:10.1130/G39002.1


https://gsw.silverchair-cdn.com/gsw/Content_public/Journal/geology/45/7/10.1130_G39002.1/1/619.pdf?Expires=1502222555&Signature=bqBU8Y3KgwV619Rh98~HEPqPp~aWdJ3w9x893T75q0T5Bn70XB~7Xvjub8K7QrFGN5OhK1RYvai3Aw5yfCYLSjKnKMt7KIMCoZnbo8drd9wtDSqrfEqLJJYFd6X7WWR~nBW9BCmhI0t2QOV2QqS7xkvQPDLc~saDe8e9-V8rrwXRI~WR-KsTvbGe2wz~XUmEU3c-lt~TD1TLajAj4Cb5EVeLNGjtF~0pt2fdKtvHMbl8C9~r5TimyGysbu5vExwPrbZvpLvfjxzipB-l5fiD7QH9qCslsthuwWOPIGGCUquL0tI6lMHQZXugcX5ix1ge4Uj7Ed6RQVvB07liZCi7mA__&Key-Pair-Id=APKAIUCZBIA4LVPAVW3Q
&
http://www.geosociety.org/datarepository/2017/2017202.pdf

Abstract: "Eocene paleoclimate reconstructions are rarely accompanied by parallel estimates of CO2 from the same locality, complicating assessment of the equilibrium climate response to elevated CO2. We reconstruct temperature, precipitation, and CO2 from latest middle Eocene (ca. 38 Ma) terrestrial sediments in the post eruptive sediment fill of the Giraffe kimberlite in subarctic Canada. Mutual climatic range and oxygen isotope analyses of botanical fossils reveal a humid temperate forest ecosystem with mean annual temperatures (MATs) more than 17 °C warmer than present and mean annual precipitation ~4× present. Metasequoia stomatal indices and gas-exchange modeling produce median CO2 concentrations of ~630 and ~430 ppm, respectively, with a combined median estimate of ~490 ppm. Reconstructed MATs are more than 6 °C warmer than those produced by Eocene climate models forced at 560 ppm CO2. Estimates of regional climate sensitivity, expressed as ΔMAT per CO2 doubling above preindustrial levels, converge on a value of ~13 °C, underscoring the capacity for exceptional polar amplification of warming and hydrological intensification under modest CO2 concentrations once both fast and slow feedbacks become expressed."

As a follow-on about Arctic Amplification, the second linked reference indicates that freshwater hosing events in the North Atlantic can result in warming of the Nordic Seas (see the third image); which can accelerate Arctic Amplification & which is another example of dynamical climate sensitivity:

Mélanie Wary et. al. (2017), "Regional seesaw between North Atlantic and Nordic Seas
during the last glacial abrupt climate events", Clim. Past Discuss., doi:10.5194/cp-2017-14

http://www.clim-past-discuss.net/cp-2017-14/cp-2017-14.pdf

Abstract. Dansgaard-Oeschger oscillations constitute one of the most enigmatic features of the last glacial cycle.  Their cold atmospheric phases have been commonly associated with cold sea-surface temperatures and expansion of sea ice in the North Atlantic and adjacent seas. Here, based on dinocyst analyses from the 48-30 ka BP interval of four sediment cores from the northern Northeast Atlantic and southern Norwegian Sea, we provide direct and quantitative evidence of a regional paradoxical seesaw pattern: cold Greenland and North Atlantic phases coincide with warmer sea-surface conditions and shorter seasonal sea-ice cover durations in the Norwegian Sea as compared to warm phases. Combined with additional paleorecords and multi-model hosing simulations, our results suggest that during cold Greenland phases, reduced Atlantic meridional overturning circulation and cold North Atlantic sea-surface conditions were accompanied by the subsurface propagation of warm Atlantic waters that re-emerged in the Nordic Seas and provided moisture towards Greenland summit.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 02, 2018, 05:02:44 PM
The first linked article entitled: "SkS Analogy 4 - Ocean Time Lag" illustrates how consensus based 'scientific' call to action can greatly underplay the risks associated with regard to dynamical climate sensitivity as illustrated by the second linked reference associated with the influences that the IPO as short-term GMSTA.  The first attached image is from the first reference & indicates that due to a 30-year lag we will not reach 2C warming until 2035 + 30 – 2065.  However, the second & third images, from the second reference, indicate respectively that we appear to have entered a warm IPO period (which may well last until ~2035); which indicates that we could reach +1.8C by 2034 (when considering the confidence range).

https://www.skepticalscience.com/SkS_Analogy_04_Ocean_Time_Lag.html

Extract: "Greenhouse gases (GHG) determine amount of warming, but oceans delay the warming.

This figure therefore shows the temperature anomaly starting in 1970, the year when the temperature increase due to greenhouse gases began to emerge from the background noise. This figure indicates 3 things: (1) the time lag between emitting greenhouse gases and when we see the principle effect is about 30 years, due mostly to the time required to heat the oceans, (2) the rate of temperature increase predicted by a climate sensitivity of 3°C tracks well with the observed rate of temperature increase, and (3) we have already locked in more than 1.5°C warming. As of 2017 we have reached 406 ppm CO2. At the current increase of 2 ppm CO2/yr., this implies that we will reach 440 ppm and lock in 2°C warming by 2035 … if we don’t act now."

The second reference is:

Henley, B. J and King, A. D. (2017) Trajectories toward the 1.5C Paris target: Modulation by the Interdecadal Pacific Oscillation, Geophysical Research Letters, doi:10.1002/2017GL073480

http://onlinelibrary.wiley.com/doi/10.1002/2017GL073480/abstract

Abstract: "Global temperature is rapidly approaching the 1.5°C Paris target. In the absence of external cooling influences, such as volcanic eruptions, temperature projections are centered on a breaching of the 1.5°C target, relative to 1850–1900, before 2029. The phase of the Interdecadal Pacific Oscillation (IPO) will regulate the rate at which mean temperature approaches the 1.5°C level. A transition to the positive phase of the IPO would lead to a projected exceedance of the target centered around 2026. If the Pacific Ocean remains in its negative decadal phase, the target will be reached around 5 years later, in 2031. Given the temporary slowdown in global warming between 2000 and 2014, and recent initialized decadal predictions suggestive of a turnaround in the IPO, a sustained period of rapid temperature rise might be underway. In that case, the world will reach the 1.5°C level of warming several years sooner than if the negative IPO phase persists."

Plain Language Summary
Global temperature is rapidly approaching the 1.5°C Paris target. In this study, we find that in the absence of external cooling influences, such as volcanic eruptions, the midpoint of the spread of temperature projections exceeds the 1.5°C target before 2029, based on temperatures relative to 1850–1900. We find that the phase of the Interdecadal Pacific Oscillation (IPO), a slow-moving natural oscillation in the climate system, will regulate the rate at which global temperature approaches the 1.5°C level. A transition to the positive phase of the IPO would lead to a projected exceedance of the target centered around 2026. If the Pacific Ocean remains in its negative phase, however, the projections are centered on reaching the target around 5 years later, in 2031. Given the temporary slowdown in global warming between 2000 and 2014, and recent climate model predictions suggestive of a turnaround in the IPO, a sustained period of rapid temperature rise might be underway. In that case, the world will reach the 1.5°C level of warming several years sooner than if the negative IPO phase persists.


See also the associated following article entitled: "Pacific Ocean shift could see 1.5C limit breached within a decade":

https://www.carbonbrief.org/pacific-ocean-shift-could-see-1point5-limit-breached-within-decade

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 02, 2018, 05:18:53 PM
Under the new Shared Socioeconomic Pathways, SSP, scenarios (see the first two summary images) RCP 8.5 roughly corresponds to the SSP5 baseline.  Thus I provide a link to a reference that describes SSP5, from which I took the third attached image of SSP5's assumed world population (peaking at about 8.5 billion circa 2060), GDP, Energy Demand and Food Demand.  The fourth attached image shows the UN's 2017 world population projections that indicate a 50/50 chance of reaching a world population of over 10 billion by 2060 (which SSP3 assumes).  Thus either we had better get off our current BAU pathway immediately, or the world population will become unsustainable long before 2060:

Kriegler et al. (2017), "Fossil-fueled development (SSP5): An energy and resource intensive scenario for the 21st century", Global Environmental Change, Volume 42, January 2017, Pages 297-315, https://doi.org/10.1016/j.gloenvcha.2016.05.015

http://www.sciencedirect.com/science/article/pii/S0959378016300711?via%3Dihub

Abstract: "This paper presents a set of energy and resource intensive scenarios based on the concept of Shared Socio-Economic Pathways (SSPs). The scenario family is characterized by rapid and fossil-fueled development with high socio-economic challenges to mitigation and low socio-economic challenges to adaptation (SSP5). A special focus is placed on the SSP5 marker scenario developed by the REMIND-MAgPIE integrated assessment modeling framework. The SSP5 baseline scenarios exhibit very high levels of fossil fuel use, up to a doubling of global food demand, and up to a tripling of energy demand and greenhouse gas emissions over the course of the century, marking the upper end of the scenario literature in several dimensions. These scenarios are currently the only SSP scenarios that result in a radiative forcing pathway as high as the highest Representative Concentration Pathway (RCP8.5). This paper further investigates the direct impact of mitigation policies on the SSP5 energy, land and emissions dynamics confirming high socio-economic challenges to mitigation in SSP5. Nonetheless, mitigation policies reaching climate forcing levels as low as in the lowest Representative Concentration Pathway (RCP2.6) are accessible in SSP5. The SSP5 scenarios presented in this paper aim to provide useful reference points for future climate change, climate impact, adaption and mitigation analysis, and broader questions of sustainable development."

For SSP population information see:

http://www.sciencedirect.com/science/article/pii/S0959378014001095

For a SSP Poster see:

https://unfccc.int/files/science/workstreams/research/application/pdf/part1_iiasa_rogelj_ssp_poster.pdf

For Current SSP information see the website entitled: "SSP Database (Shared Socioeconomic Pathways) - Version 1.1"

https://tntcat.iiasa.ac.at/SspDb/dsd?Action=htmlpage&page=about
&

See also:

2018 World Population Data Sheet With Focus on Changing Age Structures
https://www.prb.org/2018-world-population-data-sheet-with-focus-on-changing-age-structures/
The world population will reach 9.9 billion by 2050, up 2.3 billion or 29 percent from an estimated 7.6 billion people now, according to projections by Population Reference Bureau (PRB) included in the 2018 World Population Data Sheet.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 03, 2018, 04:48:02 PM
The following reference provides direct terrestrial paleo-evidence from Antarctica supporting Hansen's ice-climate feedback mechanism during the Antarctic Cold Reversal (ACR; 14,600-12,700 years ago). including cooling of the surface of the Southern Ocean, slowing of the Overturning Current and accelerated ice mass loss from marine glaciers around Antarctica as warm CDW was directed towards the grounding line for these marine glaciers (see the attached image):

Fogwill et. al. (2017), "Antarctic Ice Sheet Discharge Driven by Atmospheric-Ocean Feedbacks at the Last Glacial Termination", Scientific Reports, 7, Article No. 39979, doi: 10.1038/srep39979.

http://www.nature.com/articles/srep39979

Abstract: "Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000–11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved ‘horizontal ice core’ from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600–12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise."

Extract: "Supported by marine geological evidence of enhanced iceberg calving, and independent ice-sheet and Earth system modelling experiments, the Patriot Hills BIA provides the first direct terrestrial evidence that the Antarctic ice sheet was highly responsive to global ice-ocean-atmosphere feedbacks during the LGT. Modelling suggests this pattern could be Antarctic wide, sustained by ice-ocean feedbacks amplified by the delivery of CDW onto the Antarctic Continental Shelf. The counterintuitive finding of sustained ice-sheet mass loss across this sector of the AIS during a period of atmospheric cooling suggests that Southern Ocean AIS feedbacks were likely modulated by global atmospheric teleconnections during a period of asynchronous hemispheric climate change. Defining the details of these atmosphere-ocean-ice feedbacks is crucial to reducing uncertainty in sea level projections, and understanding the implications of observed high-latitude Southern Hemisphere environmental changes today, which may conspire to amplify future Antarctic ice mass loss."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 03, 2018, 04:58:27 PM
The linked reference finds limited ice-stream bed erosion beneath the PIG.  To me this is clear evidence supporting the belief that most of the paleo-ice mass loss from the PIG occurred due to Marine Ice Cliff Instability (MICI), as indicated by Pollard, DeConto and Alley (2018):

Davies, D., Bingham, R. G., King, E. C., Smith, A. M., Brisbourne, A. M., Spagnolo, M., Graham, A. G. C., Hogg, A. E., and Vaughan, D. G.: How dynamic are ice-stream beds?, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-214, in review, 2017.

https://www.the-cryosphere-discuss.net/tc-2017-214/

Abstract. Projections of sea-level rise contributions from West Antarctica's dynamically thinning ice streams contain high uncertainty because some of the key processes involved are extremely challenging to observe. An especially poorly observed parameter is sub-decadal stability of ice-stream beds. Only two previous studies have made repeated geophysical measurements of ice-stream beds at the same locations in different years, but both studies were limited in spatial extent. Here, we present the results from repeat radar measurements of the bed of Pine Island Glacier, West Antarctica, conducted 3–6 years apart, along a cumulative ~ 60 km of profiles. Analysis of the correlation of bed picks between repeat surveys show that 90 % of the ice-stream bed displays no significant change despite the glacier increasing in speed by up to 40 % over the last decade. We attribute the negligible detection of morphological change at the bed of Pine Island Glacier to the ubiquitous presence of a deforming till layer, wherein sediment transport is in steady state, such that sediment is transported along the basal interface without inducing morphological change to the radar-sounded bed. Significant change was only detected in one 500 m section of the bed where a change in bed morphology occurs with a difference in vertical amplitude of 3–5 m. Given the precision of our measurements, the maximum possible erosion rate that could go undetected along our profiles is 500 mm a-1, far exceeding erosion rates reported for glacial settings from proglacial sediment yields, but substantially below subglacial erosion rates of 1000 mm a-1 previously reported from repeat geophysical surveys in West Antarctica.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 03, 2018, 05:00:26 PM
The linked reference presents new findings that the retreat of the Barents Sea Ice Sheet at the end of the last ice age resulted in the explosive release of methane from Arctic seafloor hydrates as overpressure from the ice sheet disappeared.  The researchers find that this serves as a good past analogy of what may likely happen in the near-term future if the WAIS were to collapse, and/or if marine terminating glaciers in Greenland were to retreat rapidly.  As methane has a GWP100 of about 35 such explosive releases of methane could have a significant impact on global warming this century.  Such short-term methane forcings would be superimposed on top of Hansen's ice-climate feedback mechanism.

K. Andreassen, A. Hubbard, M. Winsborrow, H. Patton, S. Vadakkepuliyambatta, A. Plaza-Faverola, E. Gudlaugsson, P. Serov, A. Deryabin, R. Mattingsdal, J. Mienert & S. Bünz (02 Jun 2017), "Massive blow-out craters formed by hydrate-controlled methane expulsion from the Arctic seafloor", Science, Vol. 356, Issue 6341, pp. 948-953
DOI: 10.1126/science.aal4500

http://science.sciencemag.org/content/356/6341/948

Abstract: "Widespread methane release from thawing Arctic gas hydrates is a major concern, yet the processes, sources, and fluxes involved remain unconstrained. We present geophysical data documenting a cluster of kilometer-wide craters and mounds from the Barents Sea floor associated with large-scale methane expulsion. Combined with ice sheet/gas hydrate modeling, our results indicate that during glaciation, natural gas migrated from underlying hydrocarbon reservoirs and was sequestered extensively as subglacial gas hydrates. Upon ice sheet retreat, methane from this hydrate reservoir concentrated in massive mounds before being abruptly released to form craters.  We propose that these processes were likely widespread across past glaciated petroleum provinces and that they also provide an analog for the potential future destabilization of subglacial gas hydrate reservoirs beneath contemporary ice sheets."

We should not forget that the only contemporary ice sheet comparable to the paleo marine ice sheet in the Barents Sea basis, that is at risk of being destabilized this century is the WAIS; which could make a significant contribution to methane emissions into the atmosphere give a sufficient abrupt collapse scenario.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 03, 2018, 08:16:40 PM
Most people do not want to consider the 'Deep Uncertainty' associated with the potential collapse of the WAIS; which in my opinion puts pressure on ice sheet modelers to only evaluate lower bound dynamic ice collapse cases such as yellow curve marked '+ WAIS, DP16' in the first attached image from the first linked reference Bakker et al. (2017); which forced those authors to estimate the upper bound curve marked '+ WAIS, worst case' based on expert opinion (see the extract below from Bakker et al., 2017).  While I concur with Bakker et al. (2017)'s upper bound curve, I believe that it is difficult for non-experts to appreciate what 'Deep' uncertainties are consider by the upper bound curve that are not considered by the lower bound curve; therefore, I provide the following partial list of considerations:

1. If ECS is dominated by warming of the Tropical Pacific as indicated by the central panel of the second image (from Andrew Ringberg 2015) then the accumulating heat from the future Tropical Pacific will telecommunicate that heat (both through the atmosphere and through the ocean) to the WAIS much quicker than assumed by researchers with dynamic ice models such as Pollard, DeConto and Alley; which could lead to hydrofracturing and cliff failures decades earlier than their 2016, 2017 and 2018 model projections consider.

2. Pollard, DeConto and Alley's regional climate model does not adequately account for Hansen's ice-climate feedback mechanism, and also their model mesh resolution is not adequate to account for fine interactions.

3. Both the PIIS and the Thwaites Ice Shelf, are deteriorating earlier than assumed by any published dynamic ice model that I have seen.

4. No dynamic ice model that I have seen adequately accounts for the 3D nature of the likely ice cliff faces for the Thwaites Glacier.

Bakker, A. M. R., Wong, T. E., Ruckert, K. L., & Keller, K. (2017). Sea-level projections representing the deeply uncertain contribution of the West Antarctic ice sheet. Scientific Reports, 7(1). doi:10.1038/s41598-017-04134-5

https://www.nature.com/articles/s41598-017-04134-5
or
https://arxiv.org/abs/1609.07119

Abstract: "Future sea-level rise poses nontrivial risks for many coastal communities. Managing these risks often relies on consensus projections like those provided by the IPCC. Yet, there is a growing awareness that the surrounding uncertainties may be much larger than typically perceived. Recently published sea-level projections appear widely divergent and highly sensitive to non-trivial model choices and the West Antarctic Ice Sheet (WAIS) may be much less stable than previously believed, enabling a rapid disintegration. In response, some agencies have already announced to update their projections accordingly. Here, we present a set of probabilistic sea-level projections that approximate deeply uncertain WAIS contributions. The projections aim to inform robust decisions by clarifying the sensitivity to non-trivial or controversial assumptions. We show that the deeply uncertain WAIS contribution can dominate other uncertainties within decades. These deep uncertainties call for the development of robust adaptive strategies. These decision-making needs, in turn, require mission-oriented basic science, for example about potential signposts and the maximum rate of WAIS induced sea-level changes.

Extract: "It is important to note that we do not intend to assign an implicit probability distribution to these deeply uncertain projections. We simply want to characterize and communicate key aspects of the deeply uncertain WAIS contribution to sea-level rise."
&

Future Fate of the Polar Ice Sheets: Rob DeConto - March 30
https://www.youtube.com/watch?v=aqVPlBf4ydo

See also the second linked reference Kopp et al. (2017) that provides additional discussion of 'Deep; uncertainties with regard to future ice mass loss from Antarctica:

Robert E. Kopp et al (2017), "Evolving understanding of Antarctic ice-sheet physics and ambiguity in probabilistic sea-level projections", arXiv:1704.05597v2

https://arxiv.org/pdf/1704.05597.pdf

Abstract: "Mechanisms such as ice-shelf hydrofracturing and ice-cliff collapse may rapidly increase discharge from marine-based ice sheets. Here, we link a probabilistic framework for sea-level projections to a small ensemble of Antarctic ice-sheet (AIS) simulations incorporating these physical processes to explore their influence on global-mean sea-level (GMSL) and relative sea-level (RSL). We compare the new projections to past results using expert assessment and structured expert elicitation about AIS changes. Under high greenhouse gas emissions (Representative Concentration Pathway [RCP] 8.5), median projected 21st century GMSL rise increases from 79 to 146 cm. Without protective measures, revised median RSL projections would by 2100 submerge land currently home to 153 million people, an increase of 44 million. The use of a physical model, rather than simple parameterizations assuming constant acceleration of ice loss, increases forcing sensitivity: overlap between the central 90% of simulations for 2100 for RCP 8.5 (93–243 cm) and RCP 2.6 (26–98 cm) is minimal. By 2300, the gap between median GMSL estimates for RCP 8.5 and RCP 2.6 reaches > 10 m, with median RSL projections for RCP 8.5 jeopardizing land now occupied by 950 million people (vs. 167 million for RCP 2.6). The minimal correlation between the contribution of AIS to GMSL by 2050 and that in 2100 and beyond implies current sea-level observations cannot exclude future extreme outcomes. The sensitivity of post-2050 projections to deeply uncertain physics highlights the need for robust decision and adaptive management frameworks."
&

Finally the third linked reference (Wong & Keller, 2017) provides a worked example of how the concept of 'Deep Uncertainty' can be applied to coastal flood risk projections for New Orleans (see the third attached image):

Tony E. Wong and Klaus Keller (2017), "Deep Uncertainty Surrounding Coastal Flood Risk Projections: A Case Study for New Orleans", Earth’s Future, 5, 1015–1026, https://doi.org/10.1002/2017EF000607

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017EF000607
or
https://arxiv.org/ftp/arxiv/papers/1705/1705.07722.pdf

Abstract: "Future sea-level rise drives severe risks for many coastal communities. Strategies to manage these risks hinge on a sound characterization of the uncertainties. For example, recent studies suggest that large fractions of the Antarctic ice sheet (AIS) may rapidly disintegrate in response to rising global temperatures, leading to potentially several meters of sea-level rise during the next few centuries. It is deeply uncertain, for example, whether such an AIS disintegration will be triggered, how much this would increase sea-level rise, whether extreme storm surges intensify in a warming climate, or which emissions pathway future societies will choose. Here, we assess the impacts of these deep uncertainties on projected flooding probabilities for a levee ring in New Orleans, Louisiana. We use 18 scenarios, presenting probabilistic projections within each one, to sample key deeply uncertain future projections of sea-level rise, radiative forcing pathways, storm surge characterization, and contributions from rapid AIS mass loss. The implications of these deep uncertainties for projected flood risk are thus characterized by a set of 18 probability distribution functions. We use a global sensitivity analysis to assess which mechanisms contribute to uncertainty in projected flood risk over the course of a 50-year design life. In line with previous work, we find that the uncertain storm surge drives the most substantial risk, followed by general AIS dynamics, in our simple model for future flood risk for New Orleans."

Edit, for those who do not know, or cannot remember how heat energy is telecommunicated from the Tropical Pacific to West Antarctica see the fourth image from Fogwill et al (2011), that shows that the atmospheric Rossby wavetrain pattern depends on the ENSO and SAM conditons.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on December 03, 2018, 08:53:25 PM
Re: Davies on stability of PIG bed doi:10.5194/tc-12-1615-2018

"clear evidence supporting the belief that most of the paleo-ice mass loss from the PIG occurred due to Marine Ice Cliff Instability "

I don't see anything in this paper about MICI. Perhaps you mean a different paper ?
 
sidd


Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 03, 2018, 10:13:50 PM
Re: Davies on stability of PIG bed doi:10.5194/tc-12-1615-2018

"clear evidence supporting the belief that most of the paleo-ice mass loss from the PIG occurred due to Marine Ice Cliff Instability "

I don't see anything in this paper about MICI. Perhaps you mean a different paper ?
 
sidd

While it is true that Davies et al (2017) do not discuss MICI, the 'clear evidence' that I was referring to is the rough nature of the stream bed shown in their radar images (e.g. see the first attached image); which to me indicates that in paleo times there has been a limited amount of dynamic basal shear wearing down such rough stream bed features.  To make my point clearer I provide the second image from Frank Pattyn (2018 Jul 16), that shows that even with a relatively level stream bed (as is currently the case for the PIG) MICI calving can occur without a large amount of basal sliding to wear down the stream bed roughness.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 03, 2018, 10:43:53 PM
The linked reference discusses how the Southern Ocean may be an unreliable sink for carbon dioxide (see the attached image).  We will eventually learn whether the Southern Ocean continues as a sink for carbon dioxide if La Nina events become less frequent with continued global warming:

Jeff Tollefson (2016) "How much longer can Antarctica's hostile ocean delay global warming?", Nature, Vol 539, Issue 7629

http://www.nature.com/news/how-much-longer-can-antarctica-s-hostile-ocean-delay-global-warming-1.20978#graphic

Extract: "If that trend were to continue, atmospheric CO2 levels would rise even faster in the future. However, a study in Science last year found that the carbon sink started to strengthen in the early 2000s (see ‘The unreliable sink’)."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 03, 2018, 11:43:05 PM
The linked video of a May 28, 2008 calving event of Ilulissat Glacier (also called Jakobshavn Glacier) gives some idea of the dynamic nature of cliff failures.  As noted below the height of the ice cliff face (above water) for Ilulissat/Jakobshavn is 300 to 400-ft; while the height of the ice cliff face for Thwaites could be many times this height if/when the grounding line retreats down the retrograde stream bed:

Title: "Chasing Ice"

https://www.youtube.com/watch?v=hC3VTgIPoGU

Extract: " This rare footage has gone on record as the largest glacier calving event ever captured on film, by the 2016 Guiness Book of World Records.

On May 28, 2008, Adam LeWinter and Director Jeff Orlowski filmed a historic breakup at the Ilulissat Glacier in Western Greenland. The calving event lasted for 75 minutes and the glacier retreated a full mile across a calving face three miles wide. The height of the ice is about 3,000 feet, 300-400 feet above water and the rest below water."

P.S. While many have already seen this video, its dynamic nature never fails to impress me.

Edit: For those who are not familiar with the profile (elevations in kilometers) of the Thwaites Glacier, I provide the attached representative image.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 12:17:30 AM
Seawater percolation into below sea level layers of the firn in Antarctic ice shelves is not a good thing, and is more widespread than previously assumed (as indicated by the linked reference):

Cook, S., Galton-Fenzi, B. K., Ligtenberg, S. R. M., and Coleman, R.: Brief Communication: Widespread potential for seawater infiltration on Antarctic ice shelves, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-146, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2018-146/

Abstract. Antarctica's future contribution to sea level change depends on the fate of its fringing ice shelves. One variable which may affect the rates of iceberg calving from ice shelves is the presence of liquid water, including the percolation of seawater into permeable firn layers. Here, we present evidence that most ice shelves around Antarctica have regions where permeable firn exists below sea level. The findings indicate that seawater infiltration onto ice shelves may be much more widespread in Antarctica than previously recognised. Our results present the most likely locations for seawater infiltration to occur, and may be used as an indicator of where future radar studies might be focussed.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wdmn on December 04, 2018, 07:06:14 AM
Thanks for all your work ASLR.

I find it strange that these top scientists in their field have not "adequately account[ed] for Hansen's ice-climate feedback mechanism."

How could they not get called out for such an oversight?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Pmt111500 on December 04, 2018, 07:25:35 AM
Thanks for all your work ASLR.

I find it strange that these top scientists in their field have not "adequately account[ed] for Hansen's ice-climate feedback mechanism."

How could they not get called out for such an oversight?
Attributing the mechanism to Hansen is not correct though he's the most famous and vocal advocate of this. Can't recall who was the first to do a paper on this sensible and probably true mechanism, but it's been around for only maybe 10? years (at least there was some talk of this early in 2010s), so oversights before that cannot be 'called out'.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wdmn on December 04, 2018, 07:48:04 AM
The model projections in question are from 2016, 2017, and 2018.

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Pmt111500 on December 04, 2018, 08:02:52 AM
The model projections in question are from 2016, 2017, and 2018.
Ah ok, didn't read further up, then it might have been possible to insert the calculus describing the mechanism somehow to the models.
The fully coupled models are though very complex so they'd have to make sure runaways (quadratic or log-linear) on other variables wouldn't happen.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Lennart van der Linde on December 04, 2018, 08:16:27 AM
Thanks for the Rob DeConto presentation of March 30th 2018, ASLR.
From 56m-66m I find particularly interesting, where he talks about (quite arbitrary) speed limits for cliff failure in his model, and stretching these limits in newer versions, as yet unpublished, if I understand correctly. Also atmospheric modelling would seem to slow melt in the first decades (compared to an earlier version), but cliff failure could speed it up more later, it seems from what he says here.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 05:46:45 PM
Thanks for the Rob DeConto presentation of March 30th 2018, ASLR.
From 56m-66m I find particularly interesting, where he talks about (quite arbitrary) speed limits for cliff failure in his model, and stretching these limits in newer versions, as yet unpublished, if I understand correctly. Also atmospheric modelling would seem to slow melt in the first decades (compared to an earlier version), but cliff failure could speed it up more later, it seems from what he says here.

Lennart,

I didn't have the heart to mention the seemingly arbitrary limitation that you raised from the video about DeConto's dynamic ice projections, as the most telling quote from the video for me is where he states that his life has been ruined since his 2015 paper with Pollard & Alley about ice cliff failures and hydrofracturing.

We should all ask ourselves why any of us might think that consensus climate science deals well with 'Deep Uncertainty'.  I very much appreciate the work of DeConto, Pollard and Alley, but none of us should expect that their projections and confidence levels adequately address 'Deep Uncertainty'; but rather we should work to better appreciates the multiple caveats buried in their presentations, that particularly cause their finding to project delayed dates for initiating the potential collapse phase of particularly the WAIS.

W.r.t. delayed dates for initiating cliff failures for particularly both the PIG and Thwaites, I list the following three considerations of the many 'Deep Uncertainty' issues that I hope will be better addressed in AR6:

1. The first from Nature Geoscience 2012, DOI: 10.1038/NGEO1671, shows in good detail the areas of the Antarctic subject to the indicated number of days of surface ice melting in January 2005.  This image indicates that both the PIG/Thwaite drainage basins and the Ross Sea Embayment areas are subject to a substantial risk of episodic surface ice melting in the future (as per Pollard's concern).  Also the second image show episodic surface ice meltwater on PIIS circa January 2005, and I note that hydrofacturing of an entire ice shelf can occur in as little as a day, once appropriate crevassing and surface meltwater conditions have occurred.

2. The third image from Orsi et al. 2012 reports temperature measurements from a station at the WAIS Divide which indicates that for the 50-year period from 1957 to 2007 the surface temperature at the WAIS Divide increased at a mean rate of 0.231 C/decade; however for the 20-year period that mean rate of surface temperature was 0.804 C/decade.  This means that the WAIS is currently one of the fastest warming locations on Earth, which means that after 2040 surface melting of the ice sheet will be come more frequently a factor that affects both ice sheet  and ice shelf (as occurred in the Antarctic Peninsula for the Larsen B ice shelf) stability.  Futhermore, strong El Nino events can temporarily raise surface temperatures well above the decade trend line for periods of month, thus increasing the risk of high episodic ice mass loss during future strong El Nino events (& we appear to be entering a period of more frequent El Nino events).

3. The linked reference discusses state of the surface temperature at the West Antarctic Divide for the past ~ 40,000 years (fourth image bottom panel).  Findings indicate that current climate models are challenged to hind cast the observed findings and that models with low climate sensitivities can be eliminated from consideration.  Furthermore, they find that an Antarctic Amplification of 2 to 3 time GMSTA.  These findings do not bode well for the stability of the WAIS with continued global warming:

Kurt M. Cuffey, Gary D. Clow, Eric J. Steig, Christo Buizert, T. J. Fudge, Michelle Koutnik, Edwin D. Waddington, Richard B. Alley, and Jeffrey P. Severinghaus (2016), "Deglacial temperature history of West Antarctica", PNAS, vol. 113 no. 50, 14249–14254, doi: 10.1073/pnas.1609132113

http://www.pnas.org/content/113/50/14249

Abstract: "The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth’s climate responds to various forcings, including a rise in atmospheric CO2. This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes’ sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was 11.3±1.8 ∘  11.3±1.8∘ C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted."

Extract: "Of greatest immediate interest, however, is our demonstration that the global deglacial temperature change was amplified by a factor of 2–3 in the Antarctic, that Antarctic warming was largely achieved by 15 ka in coherence with records from Southern Hemisphere mountain ranges, and that climate models of the deglaciation perform well on average, but that the ones with lowest sensitivity can be discounted. The early warming of the Southern Hemisphere, which our study helps to quantify, arose from combined effects of reduced northward oceanic heat transport, increased insolation, and increasing atmospheric CO2. Quantitative simulation of this phenomenon could provide an illuminating challenge for model studies."

Best,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 05:56:19 PM
It is also unclear to me why anyone would think that mankind will get off a BAU pathway before 2040, when I believe that cliff failures and hydrofracturing is reasonably likely to initiate in the WAIS (e.g. see the linked article, and I note that the Keeling Curve shows that Mauna Loa CO2 concentrations are currently 2.93ppm above where they were a year ago):

Title: "Carbon emissions from advanced economies rise for 1st time in 5 years"

https://www.axios.com/carbon-emissions-advanced-economies-rise-globally-07b2f169-f184-42f0-b724-88026b843475.html

Extract: "The International Energy Agency said Tuesday that combined carbon dioxide emissions from the world's advanced economies are set to rise 0.5% in 2018, ending a 5-year declining trend."

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 06:05:41 PM
The model projections in question are from 2016, 2017, and 2018.
Ah ok, didn't read further up, then it might have been possible to insert the calculus describing the mechanism somehow to the models.
The fully coupled models are though very complex so they'd have to make sure runaways (quadratic or log-linear) on other variables wouldn't happen.

To re-emphasize my point from Reply #219, Bronselaer et al (2018) used an AIS model that does not account for MICI nor hydro-fracturing (which are not likely to be significant before 2040, and thus there is no concern for runaways) to show that by 2040 upwelling of relatively warm circumpolar deep water, CDW, around Antarctic will shift the potential ice melting temperature difference upward from below 1,000 m depth to roughly 750 m depth, and will increasingly advect this warm CDW towards the grounding line (see the attached image) for key marine glaciers such as the Pine Island Glacier, PIG and the Thwaites Glacier. What is critical to note wrt Bronselaer et al (2018) is that by 2040 the temperature of the Southern Ocean would be thousands of years from full equilibrium, but for key AIS marine glaciers both the top and bottom ice surfaces exposed to air and water respectively will experience ice mass loss sufficient to trigger localized MICI and hydro-fracturing mechanisms [if they had been included in Bronselaer et al (2018)'s] model.  In summary, this shows that the ice-climate feedback mechanism is already significant w.r.t. to potentially triggering significant ice cliff failures in the WAIS circa 2040.

Bronselaer, B. et al. (2018) Change in future climate due to Antarctic meltwater, Nature, doi:s41586-018-0712-z

https://www.nature.com/articles/s41586-018-0712-z

Abstract: "Meltwater from the Antarctic Ice Sheet is projected to cause up to one metre of sea-level rise by 2100 under the highest greenhouse gas concentration trajectory (RCP8.5) considered by the Intergovernmental Panel on Climate Change (IPCC). However, the effects of meltwater from the ice sheets and ice shelves of Antarctica are not included in the widely used CMIP5 climate models, which introduces bias into IPCC climate projections. Here we assess a large ensemble simulation of the CMIP5 model ‘GFDL ESM2M’ that accounts for RCP8.5-projected Antarctic Ice Sheet meltwater. We find that, relative to the standard RCP8.5 scenario, accounting for meltwater delays the exceedance of the maximum global-mean atmospheric warming targets of 1.5 and 2 degrees Celsius by more than a decade, enhances drying of the Southern Hemisphere and reduces drying of the Northern Hemisphere, increases the formation of Antarctic sea ice (consistent with recent observations of increasing Antarctic sea-ice area) and warms the subsurface ocean around the Antarctic coast. Moreover, the meltwater-induced subsurface ocean warming could lead to further ice-sheet and ice-shelf melting through a positive feedback mechanism, highlighting the importance of including meltwater effects in simulations of future climate."

Caption for the second attached image: "Fig. 5 | Mechanism for ocean warming. a, Hovmoller diagram of the meltwater-induced ocean temperature anomaly, averaged along the Antarctic coast, as a function of time. The black dotted line indicates the maximum warming in a given year. b, c, Schematic of the meltwater-induced Southern Ocean subsurface warming, shown as a zonal-mean cross-section. In the pre-industrial state (b), isopycnals (black lines) are tilted towards the ocean surface by westerly winds (black circles, directed out of the page), away from the continental shelf, with an upward heat flux transporting heat from the warm CDW (orange water) towards the cooler surface (blue water), as shown by the red arrow. In the perturbed state (c), meltwater from the Antarctic Ice Sheet freshens the surface (blue), depressing isopycnals (solid to dashed black lines) so that isopycnal mixing transports heat towards the continent rather than towards the ocean surface (red arrow), leading to coastal warming at depth around the shelf and cooling at the surface."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 09:16:54 PM
In my last post (& in Reply #219) regarding Bronselaer et al (2018), I focused on the implications for the PIG and Thwaites Glacier of the ice-climate feedback raising the depth of the warm CDW up to about El-500m depth circa 2040 (or before).  So, in this post, I note that the lip of the entrance to the Filchner Trough has a sill depth of about El-650m, which could accommodate a large volume of warm CDW beneath the FRIS (Filchner Ronne Ice Shelf) circa 2040, see the first image.  The second image shows a large array of instrumentation currently monitoring the circulation patterns beneath the FRIS (see also the first linked reference); which is currently observing that seasonally modified CDW finds its way beneath the FRIS.  The third image show the locations of two subglacial basins with very smooth seafloors that can sustain rapid groundling line retreat (for both the Moller and Institute Ice Streams) once the warm CDW has melted the ice providing buttressing support at the lip of the basins.  The fourth image comes from the second reference and shows recently measure bathymetry beneath the FRIS in this critical area.

Hellmer, H. , Hattermann, T. , Ryan, S. , Janout, M. and Schröder, M. (2018): The Filchner Trough / Filchner Ice Shelf cavity system , 27th International Polar Conference, Rostock, Germany, 25 March 2018 - 29 March 2018 .

http://epic.awi.de/46889/

Abstract: "Since austral summer 2013/14 AWI maintains a mooring array on the eastern slope of Filchner Trough at 76°S to monitor any flow of warm waters of open ocean origin towards the Filchner Ice Shelf (FIS) cavity. During the austral summers 2015/16 and 2016/17, seven oceanographic moorings were deployed beneath FIS through hot-water-drilled access holes to investigate and monitor the processes controlling the supply of ocean heat to the ice shelf base. This data, transferred to AWI via satellite link, shows that two ‘regimes’ exist beneath FIS. Dense High Salinity Shelf Water (HSSW), formed in front of the Ronne Ice Shelf, dominates the southern cavity and exits as Ice Shelf Water (ISW) the cavity along the western flank of the Filchner Trough. Less dense HSSW with a local origin in front of FIS enters the cavity on the eastern side of the Filchner Trough during parts of the year but seems to be trapped at depth, interacting laterally with derivatives of the Ronne-sourced HSSW. No evidence exists that it penetrates to the deep southern FIS grounding line. At 76°S, the flow of warm waters towards FIS is seasonal, limited to late summer/early winter, being replaced by ISW for the rest of the year. The link of the two sub-ice shelf circulation regimes to different regions of dense water formation on the continental shelf, and its sensitivity to the inflow of warm waters need to be investigated further to reduce the uncertainty of estimates on the FIS mass balance for today and the future."
&

S. H. R. Rosier et al. ( 08 June 2018), "A New Bathymetry for the Southeastern Filchner‐Ronne Ice Shelf: Implications for Modern Oceanographic Processes and Glacial History", JGR Oceans, https://doi.org/10.1029/2018JC013982

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JC013982

Abstract
The Filchner‐Ronne Ice Shelf, the ocean cavity beneath it, and the Weddell Sea that bounds it, form an important part of the global climate system by modulating ice discharge from the Antarctic Ice Sheet and producing cold dense water masses that feed the global thermohaline circulation. A prerequisite for modeling the ice sheet and oceanographic processes within the cavity is an accurate knowledge of the sub‐ice sheet bedrock elevation, but beneath the ice shelf where airborne radar cannot penetrate, bathymetric data are sparse. This paper presents new seismic point measurements of cavity geometry from a particularly poorly sampled region south of Berkner Island that connects the Filchner and Ronne ice shelves. An updated bathymetric grid formed by combining the new data with existing data sets reveals several new features. In particular, a sill running between Berkner Island and the mainland could alter ocean circulation within the cavity and change our understanding of paleo‐ice stream flow in the region. Also revealed are deep troughs near the grounding lines of Foundation and Support Force ice streams, which provide access for seawater with melting potential. Running an ocean tidal model with the new bathymetry reveals large differences in tidal current velocities, both within the new gridded region and further afield, potentially affecting sub‐ice shelf melt rates.

Plain Language Summary
The Filchner‐Ronne Ice Shelf in Antarctica is the largest body of floating ice in the world and plays an important role in the global climate system through its interactions with the ocean and Antarctic Ice Sheet. Due to its thickness and remoteness, the shape of the large ocean cavity beneath this floating ice shelf is poorly understood, yet this information is crucial for ice and ocean models of the region. In this study we present recent measurements of the thickness of this ocean cavity and, in combination with previous measurements, produce a new map of the area. A number of new features are revealed in this map, and we discuss the implications for ocean currents within the cavity, as well as past and future ice sheet flow.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 09:24:03 PM
Seawater percolation into below sea level layers of the firn in Antarctic ice shelves is not a good thing, and is more widespread than previously assumed (as indicated by the linked reference):
...

For those who do not understand why meltwater in the firn of Antarctic ice shelves is a concern I provide the attached image with a title from the article which reads: "Conceptual illustration of firn air depletion and its consequences for ice-shelf hydrology and stability. (a) An ice shelf covered by a firn layer containing sufficient air. The inset shows meltwater being stored in the pore space of the firn. (b) An ice shelf with a depleted firn layer. Due to the absence of pore space, meltwater forms ponds that drain into fractures. Alternatively, water is routed to the fractures efficiently as shown in the leftmost fractures. Courtesy: Journal of Glaciology and Kuipers et al":

"Firn air depletion as a precursor of Antarctic ice-shelf Collapse" Peter Kuipers Munneke, Stefan R.M. Ligtenberg, Michiel van den Broeke, David G. Vaughan, Journal of Glaciology, 60 (220), (2014). DOI: 10.3189/2014JoG13J183.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 09:33:25 PM
I estimate that by 2040 that the calving face of RIS should have retreated at least 35km (using the current rate of retreat), and I postulate that this retreat of the ice shelf face will cause the Ross Gyre current (see the first & second attached images) to follow the retreating face until the gyre current is directed at the shallow trough leading to the base of the Byrd Glacier (see the third image).  Also, by 2040 I believe that that the Antarctic Bottom Water (AABW) production in this region will be sufficiently reduced (by both changing atmospheric patterns and the strengthening of the CDW volume & temperature) so that the cold AABW entrained in the Ross Gyre will not be able to adequately dilute the CDW entained in the Ross Gyre (assuming also that the ice melt from the Getz Ice Shelf has slowed sufficiently to reduce the dilution of the CDW crossing the continental shelf with meltwater).  Therefore, I postulate that a warm tongue of CDW may make its way to the grounding line for the Byrd Glacier, which will help to trigger a positive feedback cycle (including a "saline pump" advection action working with the Byrd Glacier) that will alternate the circulation patterns in the Ross Sea Embayment so as to direct the warm CDW tongue water from the Byrd Glacier southward along the grounding lines of the Siple Coast ice streams (note that there is a pre-existing shallow trough leading from the Byrd Glacier to the Siple Coast;  As the RIS is already thinner than the FRIS, and the CDW will be warmer by then, I postulate that a large portion of the RIS will be subject to a melt-pond collapse mechanism between 2050 & 2060; which, will reduce the buttressing of the RIS on the Siple Coast ice streams.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 09:39:36 PM
My Reply #279 provides images of episodic surface ice melting event in the WAIS during January 2005; and just to reinforce the consideration that such episodic surface melting events will likely increase in frequency, extent and duration with continued global warming I provide the attached image showing the episodic surface ice melting event from January 2016 (which was more intense than the 2005 event).  Such episodic event increase the risk of associated hydrofracture calving events for key WAIS ice shelves, within the next couple of decades.

Edit, I decided to add the second image that show changes in yearly surface temperature around Antarctica between 1981 and 2007, that clearly indicates the trend that the surface temperature of the WAIS is warming more rapidly than the EAIS.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 10:06:40 PM
I provide the attached image showing current annual Antarctic snowfall in order to emphasize that:

1. Current snowfall on for the FRIS and the RIS (Ross Ice Shelf) is relatively low, and thus it is not likely that snow cover on these two ice shelfs would reduce the risk of hydrofracturing circa 2040.
&
2. Current snowfall on the Byrd Subglacial Basin catchment is relatively high; which may result in steeper surface gradients on the Amundsen Sea Embayment, ASE, marine glaciers circa 2040; which in turn would increase the likelihood of associated ice cliff failures in this area in that timeframe.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 11:12:08 PM
I provide the attached image of DeConto et al. (2016) Figure 4c in order to make two different points:

1. The ice-climate feedback as described by Hansen (and others) is a very complex feedback mechanism which many/most researchers fail to fully replicate in their models, include those by Pollard and DeConto, even though the attached image has a red dotted curve that indicates that they think that they have accounted for this feedback.  However, they clearly have only accounted for a small portion of the full feedback mechanism as they do not show any significant impact from this feedback mechanism until circa 2100, while Bronselaer et al (2018) clearly demonstrate that this feedback is already moderately changing the nature of the CDW today and that by 2040 the ice-climate feedback on the CDW will be significant enough possibly induce ice cliff failures in some key ASE marine glacier.
&
2. This image shows the Totten Glacier (T) beginning to collapse circa 2080, however, the following two linked references indicate that wind induced upwelling of warm CDW is already accelerating ice mass loss from the Totten Ice Shelf (and grounding line).  Therefore, if Pollard and DeConto's model(s) were refined to account for the ice-climate feedback identified by Bronselaer et al. (2018) then their projections of ice mass loss from Totten may well be accelerated.

P.S.: A full modeling of the ice-climate feedback mechanism would need to account for many different sub-mechanisms including: a. ENSO interactions, b. Ocean Overturning Current interactions; c. Arctic & Antarctic sea ice interactions; d. the Bipolar Seesaw mechanism; e. associated Cloud feedback interactions; e. associated changes in Arctic and Antarctic snow/rain fall patterns; f. associated changings in CDW circulation patterns; g. associated changes in both atmospheric and oceanic telecommunication patterns; h. associated regional changes in both SSTA and land surface temperatures; etc.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 04, 2018, 11:55:59 PM
The linked UN article about the IPCC's Special Report: Global Warming of 1.5C; indicates that GMSTA cannot be kept below 1.5C without action on short-lived climate pollutants (SLCPs) like methane; however, the attached image shows the Mauna Loa atmospheric methane concentration thru Dec 4, 2018; which indicates that there is currently no slowdown in the current trend in methane emissions.  Therefore, it is difficult for me to see how GMSTA is going to say well below Pliocene levels [see Pollard, DeConto & Alley (2018) & Reply #220] in the coming decades:

Title: "Keeping warming to 1.5˚C impossible without reducing Short-lived Climate Pollutants"

https://www.unenvironment.org/news-and-stories/press-release/keeping-warming-15c-impossible-without-reducing-short-lived-climate

Extract: "Our best chance to avoid runaway warming is to act right away to reduce highly potent but short-lived climate pollutants (SLCPs) like methane, tropospheric ozone, hydrofluorocarbons (HFCs) and black carbon. This must go hand-in-hand with deep and persistent cuts in long-lived greenhouse gases like carbon dioxide (CO2).

Fast and immediate action on SLCPs can avoid over half a degree of warming by 2050. It will also avoid over 50% of the predicted warming in the Arctic by 2050, thereby significantly decreasing the chances of triggering dangerous climate tipping points, like the irreversible release of carbon dioxide and methane from thawing Arctic permafrost.

Drew Shindell, Professor of Climate Sciences at Duke University and a lead author on the IPCC report, said no scenario exists where the world can get to 1.5 degrees without reducing these highly potent, but short-lived climate forcers alongside CO2."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 05, 2018, 12:21:44 AM
Per the linked reference, '… carbon dioxide outgassing from rivers is estimated to be equivalent to one-fifth of combined emissions from fossil fuel combustion and cement production …"; however, Allen & Pavelsky (2018) estimate that the surface area of rivers and streams has been underestimated by about 44%.  This is not good news especially when considering methane emissions from lakes, reservoirs, rivers and streams.

George H. Allen &Tamlin M. Pavelsky (10 Aug 2018), "Global extent of rivers and streams", Science, Vol. 361, Issue 6402, pp. 585-588, DOI: 10.1126/science.aat0636

http://science.sciencemag.org/content/361/6402/585

Extract: "Expanding the role of rivers
The surfaces of rivers and streams are interfaces for a host of chemical exchanges with the atmosphere and biosphere. For instance, carbon dioxide outgassing from rivers is estimated to be equivalent to one-fifth of combined emissions from fossil fuel combustion and cement production. Allen and Pavelsky used satellite imagery to estimate the surface area of rivers and streams (see the Perspective by Palmer and Ruhi). The stunning map that they generated results in an upward revision, by about one-third, to the total surface area of rivers and streams on Earth."
&
Abstract: "The turbulent surfaces of rivers and streams are natural hotspots of biogeochemical exchange with the atmosphere. At the global scale, the total river-atmosphere flux of trace gasses such as carbon dioxide depends on the proportion of Earth’s surface that is covered by the fluvial network, yet the total surface area of rivers and streams is poorly constrained. We used a global database of planform river hydromorphology and a statistical approach to show that global river and stream surface area at mean annual discharge is 773,000 ± 79,000 square kilometers (0.58 ± 0.06%) of Earth’s nonglaciated land surface, an area 44 ± 15% larger than previous spatial estimates. We found that rivers and streams likely play a greater role in controlling land-atmosphere fluxes than is currently represented in global carbon budgets."

Also, the following reference indicates the carbon emissions from the soil are increasing with global warming:

Bond-Lamberty, B., Bailey, V. L., Chen, M., Gough, C. M., & Vargas, R. (2018). Globally rising soil heterotrophic respiration over recent decades. Nature, 560(7716), 80–83. doi:10.1038/s41586-018-0358-x; https://doi.org/10.1038/s41586-018-0358-x

https://www.nature.com/articles/s41586-018-0358-x

Abstract: "Global soils store at least twice as much carbon as Earth’s atmosphere. The global soil-to-atmosphere (or total soil respiration, RS) carbon dioxide (CO2) flux is increasing, but the degree to which climate change will stimulate carbon losses from soils as a result of heterotrophic respiration (RH) remains highly uncertain5–8. Here we use an updated global soil respiration database to show that the observed soil surface RH:RS ratio increased significantly, from 0.54 to 0.63, between 1990 and 2014 (P = 0.009). Three additional lines of evidence provide support for this finding. By analysing two separate global gross primary production datasets, we find that the ratios of both RH and RS to gross primary production have increased over time. Similarly, significant increases in RH are observed against the longest available solar-induced chlorophyll fluorescence global dataset, as well as gross primary production computed by an ensemble of global land models. We also show that the ratio of night-time net ecosystem exchange to gross primary production is rising across the FLUXNET2015 dataset. All trends are robust to sampling variability in ecosystem type, disturbance, methodology, CO2 fertilization effects and mean climate. Taken together, our findings provide observational evidence that global RH is rising, probably in response to environmental changes, consistent with metaanalyses and long-term experiments. This suggests that climate-driven losses of soil carbon are currently occurring across many ecosystems, with a detectable and sustained trend emerging at the global scale."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 05, 2018, 07:34:50 PM
The first image is from Hansen et al (2016), showing the ocean stratification and precipitation portions of the ice-climate feedback mechanism.  I repost this image to remind readers that this mechanism proposes: a cooling of the sea surface temperature, SST, an increase in sea ice extent, SIE, and a reduction of sea surface salinity, SSS, not only due to ice melt but also due to precipitation (and its difference with evaporation).  The first two linked references confirm these trends (see the second and third images); however, as most consensus climate models ignore the ice-climate feedback mechanism, they both discuss possible alternate mechanisms.  Nevertheless, since ~1980, this SST, SIE and SSS data is fully consistent with the ice-climate mechanism, and I also note that the associated change in SST tends to mask the full strength of climate sensitivity when measured by GMSTA:

Zhang, L., Delworth, T. L., Cooke, W., & Yang, X. (2018). Natural variability of Southern Ocean convection as a driver of observed climate trends. Nature Climate Change. doi:10.1038/s41558-018-0350-3, https://doi.org/10.1038/s41558-018-0350-3

https://www.nature.com/articles/s41558-018-0350-3

Abstract: "Observed Southern Ocean surface cooling and sea-ice expansion over the past several decades are inconsistent with many historical simulations from climate models. Here we show that natural multidecadal variability involving Southern Ocean convection may have contributed strongly to the observed temperature and sea-ice trends. These observed trends are consistent with a particular phase of natural variability of the Southern Ocean as derived from climate model simulations. Ensembles of simulations are conducted starting from differing phases of this variability. The observed spatial pattern of trends is reproduced in simulations that start from an active phase of Southern Ocean convection. Simulations starting from a neutral phase do not reproduce the observed changes, similarly to the multimodel mean results of CMIP5 models. The long timescales associated with this natural variability show potential for skillful decadal prediction."

Extract: "However, we cannot conclude that internally generated SO deep convection is the only driver, even in recent observations. The SO deep-convection change could work together with various other mechanisms identified in earlier studies3–16, such as wind-driven ice transport and cold/warm-temperature advection, and anthropogenic surface freshening due to an amplified hydrological cycle and ice-sheet melting. As mentioned above, the surface wind trend favours warm SST and decreasing sea ice over the Antarctic Peninsula through warm advection and over the Amundsen– Bellingshausen seas through enhanced vertical mixing caused by anomalous negative wind stress curl. Our model also shows that the long-lasting westerly winds over the SO induce upwelling and a spin-up of the AABW cell, which in turn generates the warm SST.  The surface freshwater changes due to shifted storm tracks and melting ice sheet in future may slow down the SO MOC15, which also cannot be excluded. It is also possible that melting of land-based ice sheets, a process usually not included in climate models, could cause surface freshening and the subsequent suppressed convection and SST cooling."
&

Purich, A., England, M. H., Cai, W., Sullivan, A., & Durack, P. J. (2018). Impacts of Broad-Scale Surface Freshening of the Southern Ocean in a Coupled Climate Model. Journal of Climate, 31(7), 2613–2632. doi:10.1175/jcli-d-17-0092.1, https://doi.org/10.1175/JCLI-D-17-0092.1

https://journals.ametsoc.org/doi/10.1175/JCLI-D-17-0092.1

Abstract: "The Southern Ocean surface has freshened in recent decades, increasing water column stability and reducing upwelling of warmer subsurface waters. The majority of CMIP5 models underestimate or fail to capture this historical surface freshening, yet little is known about the impact of this model bias on regional ocean circulation and hydrography. Here experiments are performed using a global coupled climate model with additional freshwater applied to the Southern Ocean to assess the influence of recent surface freshening. The simulations explore the impact of persistent and long-term broad-scale freshening as a result of processes including precipitation minus evaporation changes. Thus, unlike previous studies, the freshening is applied as far north as 55°S, beyond the Antarctic ice margin. It is found that imposing a large-scale surface freshening causes a surface cooling and sea ice increase under preindustrial conditions, because of a reduction in ocean convection and weakened entrainment of warm subsurface waters into the surface ocean. This is consistent with intermodel relationships between CMIP5 models and the simulations, suggesting that models with larger surface freshening also exhibit stronger surface cooling and increased sea ice. Additional experiments are conducted with surface salinity restoration applied to capture observed regional salinity trends. Remarkably, without any mechanical wind trend forcing, these simulations accurately represent the spatial pattern of observed surface temperature and sea ice trends around Antarctica. This study highlights the importance of accurately simulating changes in Southern Ocean salinity to capture changes in ocean circulation, sea surface temperature, and sea ice."

Caption for the third attached image: "FIG. 1. Trends over 1950–2000. (a) Observed SSS trends from Durack and Wijffels (2010); (b) zonal-mean SSS trends for observations (Durack and Wijffels 2010) and CMIP5 models; (c) zonal-mean precipitation trends for observations (ERA-Interim, COREv2, GPCPv2.2, CMAP standard, CMAP enhanced) and CMIP5 models; and (d) zonal-mean P–E trends for observations (ERA-Interim, COREv2) and CMIP5 models. In (a), stippling indicates significance at the 95% level. In (b) observations are shown in dashed black. In (c)–(d) observations are shown in colors, and vary in the time periods they cover (refer to the data and methods section). In (b)–(d) CMIP5 models are shown in grey, and the ACCESS1.0 CMIP5 run is shown in dark blue."

Note: Sea Surface Salinity, SSS, can be measured remotely in units of PSU, see the extract for the linked website:

http://www.salinityremotesensing.ifremer.fr/sea-surface-salinity/definition-and-units

Extract: "Ocean salinity is generally defined as the salt concentration (e.g., Sodium and Chloride) in sea water. It is measured in unit of PSU (Practical Salinity Unit), which is a unit based on the properties of sea water conductivity. It is equivalent to per thousand or (o/00) or to g/kg."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 05, 2018, 08:55:26 PM
The first attached image, indicates a flattening of the influence of increasing values of ECS on GMSTA; thus implying that increases in atmospheric GHG concentrations may be more impactful on future global warming.  However, the oceans and land vegetation currently sequester about one half of all current anthropogenic emissions; thus if these carbon sinks are compromised with future global warming then mankind's ability to limit future increases in atmospheric GHG concentrations would also be compromised.  In this frame of mind, the first linked reference is entitled "Doubling Down on Our Faustian Bargain" and it indicates that temporary radiative forcing masking factors (such as: both anthropogenic & natural aerosols, and temporary increases in CO₂ absorption by plants) have allowed mankind to accumulate large accumulations of carbon in the atmosphere, land and ocean; that could actively contribute to future radiative forcing once the temporary masking factors have been eliminated. 

The second, third & fourth linked references cite research on forests, as an illustration of how sensitive such carbon sinks can be to future climate disruption (such as :wet-dry cycles, pests, fires, etc) especially as our current rate of increase of radiative forcing is much higher than at any time since the PETM; and thus vegetation (both on land & in the ocean) will not have adequate time to adapt to such rapidly changing climate conditions:


James Hansen, Pushker Kharecha, Makiko Sato (2013), "Doubling Down on Our Faustian Bargain", Environmental Research Letters.

http://iopscience.iop.org/article/10.1088/1748-9326/8/1/011006/meta
&
http://www.columbia.edu/~jeh1/mailings/2013/20130329_FaustianBargain.pdf

Abstract: "Rahmstorf et al 's (2012) conclusion that observed climate change is comparable to projections, and in some cases exceeds projections, allows further inferences if we can quantify changing climate forcings and compare those with projections. The largest climate forcing is caused by well-mixed long-lived greenhouse gases. Here we illustrate trends of these gases and their climate forcings, and we discuss implications. We focus on quantities that are accurately measured, and we include comparison with fixed scenarios, which helps reduce common misimpressions about how climate forcings are changing.
Annual fossil fuel CO2 emissions have shot up in the past decade at about 3% yr-1, double the rate of the prior three decades (figure 1). The growth rate falls above the range of the IPCC (2001) 'Marker' scenarios, although emissions are still within the entire range considered by the IPCC SRES (2000). The surge in emissions is due to increased coal use (blue curve in figure 1), which now accounts for more than 40% of fossil fuel CO2 emissions."

The second linked article is entitled: "Forests 'held their breath' during global warming hiatus, research shows".  This illustrates Hansen's Faustian Bargain.

https://phys.org/news/2017-01-forests-held-global-hiatus.html

Extract: "The study shows that, during extended period of slower warming, worldwide forests 'breathe in' carbon dioxide through photosynthesis, but reduced the rate at which they 'breathe out'—or release the gas back to the atmosphere."


The third linked reference indicates that forests play a more important role in keeping the planet cool than was previously appreciated.  Thus if one assumes that they are entitled to make self-serving assumptions one could assume that decision makers will not only preserve forests but will expand them in the future.  However, the reality is that we are currently losing forests at a rate appropriate for a BAU scenario; and which could accelerate in the future.  Thus if we keep losing forest, our AR5 projections may err on the side of least drama:

Ryan M. Bright et al. Local temperature response to land cover and management change driven by non-radiative processes, Nature Climate Change (2017). DOI: 10.1038/nclimate3250

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3250.html

Abstract: "Following a land cover and land management change (LCMC), local surface temperature responds to both a change in available energy and a change in the way energy is redistributed by various non-radiative mechanisms. However, the extent to which non-radiative mechanisms contribute to the local direct temperature response for different types of LCMC across the world remains uncertain. Here, we combine extensive records of remote sensing and in situ observation to show that non-radiative mechanisms dominate the local response in most regions for eight of nine common LCMC perturbations. We find that forest cover gains lead to an annual cooling in all regions south of the upper conterminous United States, northern Europe, and Siberia—reinforcing the attractiveness of re-/afforestation as a local mitigation and adaptation measure in these regions. Our results affirm the importance of accounting for non-radiative mechanisms when evaluating local land-based mitigation or adaptation policies."

The fourth reference (see also the second attached image) indicates a two-fold increase of carbon cycle sensitivity to tropical temperature variations:

Wang, X., Piao, S., Ciais, P., Friedlingstein, P., Myneni, R.B., Cox, P., Heimann, M., Miller, J., Peng, S.P., Wang, T., Yang, H. and Chen, A., (2014), "A two-fold increase of carbon cycle sensitivity to tropical temperature variations", Nature, 2014; DOI: 10.1038/nature12915.

http://www.nature.com/nature/journal/v506/n7487/full/nature12915.html#extended-data

http://sites.bu.edu/cliveg/files/2014/01/wang-nature-2014.pdf

Abstract: "Earth system models project that the tropical land carbon sink will decrease in size in response to an increase in warming and drought during this century, probably causing a positive climate feedback. But available data are too limited at present to test the predicted changes in the tropical carbon balance in response to climate change. Long-term atmospheric carbon dioxide data provide a global record that integrates the interannual variability of the global carbon balance. Multiple lines of evidence demonstrate that most of this variability originates in the terrestrial biosphere. In particular, the year-to-year variations in the atmospheric carbon dioxide growth rate (CGR) are thought to be the result of fluctuations in the carbon fluxes of tropical land areas. Recently, the response of CGR to tropical climate interannual variability was used to put a constraint on the sensitivity of tropical land carbon to climate change. Here we use the long-term CGR record from Mauna Loa and the South Pole to show that the sensitivity of CGR to tropical temperature interannual variability has increased by a factor of 1.9 ± 0.3 in the past five decades. We find that this sensitivity was greater when tropical land regions experienced drier conditions. This suggests that the sensitivity of CGR to interannual temperature variations is regulated by moisture conditions, even though the direct correlation between CGR and tropical precipitation is weak. We also find that present terrestrial carbon cycle models do not capture the observed enhancement in CGR sensitivity in the past five decades. More realistic model predictions of future carbon cycle and climate feedbacks require a better understanding of the processes driving the response of tropical ecosystems to drought and warming."

Caption for the second attached image: " Figure 1 | Change in detrended anomalies in CGR and tropical MAT, in dCGR/dMAT and in ªintCGR over the past five decades. a, Change in detrended CGR anomalies at Mauna Loa Observatory (black) and in detrended tropical MAT anomalies (red) derived from the CRU data set16. Tropical MAT is calculated as the spatial average over vegetated tropical lands (23uN to 23u S).  The highest correlations between detrended CGR and detrended tropicalMAT are obtained when no time lags are applied (R50.53, P,0.01). b, Change in dCGR/dMAT during the past five decades. c, Change in cintCGR during the past five decades. In b and c, different colours showdCGR/dMATor cint CGR estimated with moving time windows of different lengths (20 yr and 25 yr). Years on the horizontal axis indicate the central year of the moving time window used to derive dCGR/dMAT or cintCGR (for example, 1970 represents period 1960–1979 in the 20-yr time window). The shaded areas show the confidence interval of dCGR/dMATand cintCGR, as appropriate, derived using 20-yr or 25-yr moving windows in 500 bootstrap estimates."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 05, 2018, 11:09:50 PM
Just a quick note to remind readers that positive feedback mechanisms reinforce each other, which increases ECS with continued warming.  For example, the linked reference provides evidence that Arctic Amplification over the past 30-years has caused shrubs to grow taller throughout the tundra; which in turn causes more Arctic Amplification via both decreased albedo, and insulation of the ground that leads to accelerated permafrost degradation, etc.

Title: 'Taller plants moving into Arctic because of climate change"

https://www.sciencedaily.com/releases/2018/09/180926140816.htm

Extract: "While the Arctic is usually thought of as a vast, desolate landscape of ice, it is in fact home to hundreds of species of low-lying shrubs, grasses and other plants that play a critical role in carbon cycling and energy balance.

Now, Arctic experts have discovered that the effects of climate change are behind an increase in plant height across the tundra over the past 30 years.

"Taller plants trap more snow, which insulates the underlying soil and prevents it from freezing as quickly in winter.

"An increase in taller plants could speed up the thawing of this frozen carbon bank, and lead to an increase in the release of greenhouse gases.

"We found that the increase in height didn't happen in just a few sites, it was nearly everywhere across the tundra."

See also:

Bjorkman et al. (2018), "Plant functional trait change across a warming tundra biome", Nature, DOI: 10.1038/s41586-018-0563-7

https://www.nature.com/articles/s41586-018-0563-7

Abstract: "The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 05, 2018, 11:43:41 PM
As almost no CMIP5 models included ice-climate feedback mechanisms, the linked Wikipedia article on climate change feedbacks does not even mention it.  That appears to be the consensus way to deal with 'Deep Uncertainty', i.e. 'Out of sight, out of mind':

Title: "Climate change feedback"

https://en.wikipedia.org/wiki/Climate_change_feedback

Edit:
Also, the linked Wikipedia article on runaway climate change does not explicitly discuss ice-climate feedback mechanisms; but at least it cites Hansen et al (2013):

Title: " Runaway climate change"

https://en.wikipedia.org/wiki/Runaway_climate_change

Extract: "Hansen et al. 2013 suggests that the Earth could become in large parts uninhabitable and note that this may not even require burning of all fossil fuels, because of higher climate sensitivity (3–4 °C or 5.4–7.2 °F) based on a 550 ppm scenario."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 06, 2018, 12:20:55 AM
The linked reference presents findings that can be used to help calibrate Hansen's ice-climate feedback mechanism:

Pepijn Bakker & Matthias Prange (03 August 2018), "Response of the Intertropical Convergence Zone to Antarctic Ice Sheet Melt", Geophysical Research Letters, https://doi.org/10.1029/2018GL078659

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL078659

"Abstract
Past cooling events in the Northern Hemisphere have been shown to impact the location of the intertropical convergence zone (ITCZ) and therewith induce a southward shift of tropical precipitation. Here we use high resolution coupled ocean‐atmosphere simulations to show that reasonable past melt rates of the Antarctic Ice Sheet can similarly have led to shifts of the ITCZ, albeit in opposite direction, through large‐scale surface air temperature changes over the Southern Ocean. Through sensitivity experiments employing slightly negative to large positive meltwater fluxes, we deduce that meridional shifts of the Hadley cell and therewith the ITCZ are, to a first order, a linear response to Southern Hemisphere high‐latitude surface air temperature changes and Antarctic Ice Sheet melt rates. This highlights the possibility to use past episodes of anomalous melt rates to better constrain a possible future response of low latitude precipitation to continued global warming and a shrinking Antarctic Ice Sheet.

Plain Language Summary
Changes in high‐latitude climate can impact the tropical regions through so‐called atmospheric and oceanic teleconnections. Research has mostly focused on past southward shifts in the band of heavy tropical precipitation, called the intertropical convergence zone (ITCZ), linked to large‐scale cooling in the Northern Hemisphere resulting from large‐scale continental ice sheet buildup or a slowdown of the large‐scale Atlantic meridional ocean circulation. Here we use high resolution climate simulations to show that melting of the Antarctic Ice Sheet can similarly lead to northward shifts of the ITCZ and the displacement of the accompanying rain belt. Future melt rates of the Antarctic Ice Sheet are highly uncertain, but our work shows that it might have a nonnegligible impact on the tropical climate. Moreover, we find that because of the apparent linearity of the system under consideration, studying episodes of past changes in the size of the Antarctic Ice Sheet can help us constrain the possible changes in the low latitude hydroclimate."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on December 06, 2018, 05:29:39 AM
Wikipedia is open editing, unless there is a lock on the article, so i would suggest correcting errors. I have  done so myself.

ITCZ shifts north in response to antarctic ice melt seems to be a robust response. I have seen this now in a buncha papers. I wonder if Held has ever blogged about it.

sidd
 
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 06, 2018, 04:29:26 PM
In some of my past posts I have identified the relatively poor past capability of consensus scientists (e.g.: AR4 & AR5) and of extant policy makers (e.g.: the Paris Accord) to deal effectively with 'Deep Uncertainty', as a major obstacle to first acknowledging and then addressing the risks that the numerous ice-climate feedback mechanisms may follow one of several possible pathways to abrupt climate change and abrupt sea level rise.  Therefore, I provide the first following link to the website for the 'Society for Decision Making Under Deep Uncertainty' (DMDU); which, provides numerous publications related to: Robust Decision Making in the face of Deep Uncertainty in Climate Change, including the four linked articles:

http://www.deepuncertainty.org/category/recent-publications/

1. For interactive monitoring for adaptive response systems, see:
http://www.deepuncertainty.org/2018/09/03/designing-a-monitoring-system-to-detect-signals-to-adapt-to-uncertain-climate-change/

Extract: "Adaptive plans aim to anticipate uncertain future changes by combining low-regret short-term actions with long-term options to adapt, if necessary. Monitoring and timely detection of relevant changes, and critical transitions or tipping points is crucial to ensure successful and timely implementation and reassessment of the plan."

2. For robustness in many-objective climate action, see:
http://www.deepuncertainty.org/2018/08/31/including-robustness-considerations-in-the-search-phase-of-many-objective-robust-decision-making-2018/

Extract: "Many-Objective Robust Decision Making (MORDM) is a prominent model-based approach for dealing with deep uncertainty. MORDM has four phases: a systems analytical problem formulation, a search phase to generate candidate solutions, a trade-off analysis where different strategies are compared across many objectives, and a scenario discovery phase to identify the vulnerabilities."

3. For an example of robust management of resources, see
http://www.deepuncertainty.org/2018/08/07/real%e2%80%90options-water-supply-planning-multistage-scenario-trees-for-adaptive-and-flexible-capacity-expansion-under-probabilistic-climate-change-uncertainty-2018/

Extract: "Planning water supply infrastructure includes identifying interventions that cost‐effectively secure an acceptably reliable water supply. Climate change is a source of uncertainty for water supply developments as its impact on source yields is uncertain. Adaptability to changing future conditions is increasingly viewed as a valuable design principle of strategic water planning. Because present decisions impact a system’s ability to adapt to future needs, flexibility in activating, delaying and replacing engineering projects should be considered in least‐cost water supply intervention scheduling. This is a principle of Real Option Analysis (ROA) which this paper applies to least‐cost capacity expansion scheduling via multistage stochastic mathematical programming."

4. For discussion of adaptive pathways to manage sea level rise, see:
http://www.deepuncertainty.org/2018/08/07/strategic-adaptation-pathway-planning-to-manage-sea-level-rise-and-changing-coastal-flood-risk-2018/

Extract: "Communities around the world are already committed to future sea-level rise. Long-term adaptation planning to manage associated coastal flood impacts is, however, challenged by uncertainty and contested stakeholder priorities. This study provides a proof of concept for a combined robust decision making (RDM) and dynamic adaptive policy pathways (DAPP) approach in coastal flood risk management. The concept uses model-based support and largely open source tools to help local government plan coastal adaptation pathways. Key steps in the method are illustrated using a hypothetical case study in Australia. The study shows how scenario discovery can provide multi-dimensional descriptions of adaptation tipping points which may inform the development of technical signpost indicators. Transient scenarios uncovered limitations in seemingly robust adaptation policies, where historical path dependencies may constrain the rate of adaptation and the extent to which future coastal flood impacts can be successfully managed. Lived values have the potential to offer insights about non-material social trade-offs that residents may need to accept for the benefit of reduced flood risk, and could form a basis for defining socially-oriented signpost indicators. However, the nuances and subjectivity of lived values means that ongoing engagement with residents is essential as part of a combined RDM and DAPP approach to preserve the communities’ way of life. The learnings from this hypothetical case study suggest that testing in a real world participatory setting could be valuable in further developing a combined RDM and DAPP approach to plan adaptation pathways and manage future coastal flood risk."

With regard to the last linked article's comment that '... historical path dependencies may constrain the rate of adaptation ...'; I have encountered this situation in Louisiana and I note that our global modern world is built on many historical dependencies that will likely severely limit mankind's ability to respond appropriately to abrupt climate change beginning circa 2040.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 06, 2018, 05:34:31 PM
We should all recognize that the timing and impact of hydrofracturing can be accelerated from that assumed by Pollard and DeConto by such mechanisms as the formation of basal channels in ice shelves where: "These channels also result in ice surface deformation, which diverts supraglacial rivers into the transverse fractures."  Thus, it may take less atmospheric warming and less associated ice shelf surface melting to cause hydrofracturing to collapse Antarctic ice shelves than Pollard and DeConto are assuming (which might support the projection of abrupt sea level rise some years before 2040:

Christine F. Dow et al. (13 Jun 2018), "Basal channels drive active surface hydrology and transverse ice shelf fracture", Science Advances, Vol. 4, no. 6, eaao7212, DOI: 10.1126/sciadv.aao7212

http://advances.sciencemag.org/content/4/6/eaao7212

Abstract: "Ice shelves control sea-level rise through frictional resistance, which slows the seaward flow of grounded glacial ice. Evidence from around Antarctica indicates that ice shelves are thinning and weakening, primarily driven by warm ocean water entering into the shelf cavities. We have identified a mechanism for ice shelf destabilization where basal channels underneath the shelves cause ice thinning that drives fracture perpendicular to flow. These channels also result in ice surface deformation, which diverts supraglacial rivers into the transverse fractures. We report direct evidence that a major 2016 calving event at Nansen Ice Shelf in the Ross Sea was the result of fracture driven by such channelized thinning and demonstrate that similar basal channel–driven transverse fractures occur elsewhere in Greenland and Antarctica. In the event of increased basal and surface melt resulting from rising ocean and air temperatures, ice shelves will become increasingly vulnerable to these tandem effects of basal channel destabilization."

Caption for the attached image: " (A) Schematic of an ice shelf basal channel and a coincident ice surface depression that funnels meltwater, resulting in river formation and incision. The ice shelf is shown in gray. (B to D) Surface (red) and basal (blue) ice cross-sectional profiles from radar along the flight lines in Fig. 2A for (B) October 2011 and (C and D) December 2014. The green arrows indicate the location of the parallel surface rivers identified from Landsat imagery. The black arrows indicate the extent of the basal channel. The data gap in (D) is due to the ice shelf rift. m asl, meters above sea level."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 06, 2018, 06:00:16 PM
...

ITCZ shifts north in response to antarctic ice melt seems to be a robust response. I have seen this now in a buncha papers. ...


For those who do not know (aside from the unsettled question of associated cloud feedbacks) when the ITCZ (see the first image showing the location of the ITCZs) shifts poleward (and the oceanic overturning circulation slows) more radiative solar energy is absorbed by the equatorial ocean water; which increases the moist static energy (MSE) resulting from increased evaporation from that warmer equatorial ocean water.  This energy is telecommunicated through the atmosphere to the appropriate pole by Rossby Waves (see the second image showing a typical atmospheric bridge from the Equatorial Pacific to the Arctic); which contributes to accelerated polar amplification.  This is true whether the shift in the ITCZ is due to increases in GHGs or due to increased ice-climate feedback mechanisms.

Furthermore, I note that most consensus climate scenarios aimed at keeping GMSTA below 2C involve the use of geoengineering (see the linked article below); typically to allow GMSTA to temporarily peak near 2C and then to drop-off due to the application of geoengineering.  However, it is important to note that the application of such geoengineering scenarios are at best ineffective at (and at worse contribute to) stopping abrupt climate change driven by ice-climate feedback mechanisms that once initiated (say by temporarily allowing GMSTA to approach 2C) are driven by gravity induced ice mass loss from key marine (& marine-terminating) glaciers.

Russotto, R. D. and Ackerman, T. P.: Energy transport, polar amplification, and ITCZ shifts in the GeoMIP G1 ensemble, Atmos. Chem. Phys., 18, 2287-2305, https://doi.org/10.5194/acp-18-2287-2018, 2018.

https://www.atmos-chem-phys.net/18/2287/2018/

Abstract. The polar amplification of warming and the ability of the Intertropical Convergence Zone (ITCZ) to shift to the north or south are two very important problems in climate science. Examining these behaviors in global climate models (GCMs) running solar geoengineering experiments is helpful not only for predicting the effects of solar geoengineering but also for understanding how these processes work under increased carbon dioxide (CO2). Both polar amplification and ITCZ shifts are closely related to the meridional transport of moist static energy (MSE) by the atmosphere. This study examines changes in MSE transport in 10 fully coupled GCMs in experiment G1 of the Geoengineering Model Intercomparison Project (GeoMIP), in which the solar constant is reduced to compensate for the radiative forcing from abruptly quadrupled CO2 concentrations. In G1, poleward MSE transport decreases relative to preindustrial conditions in all models, in contrast to the Coupled Model Intercomparison Project phase 5 (CMIP5) abrupt4xCO2 experiment, in which poleward MSE transport increases. We show that since poleward energy transport decreases rather than increases, and local feedbacks cannot change the sign of an initial temperature change, the residual polar amplification in the G1 experiment must be due to the net positive forcing in the polar regions and net negative forcing in the tropics, which arise from the different spatial patterns of the simultaneously imposed solar and CO2 forcings. However, the reduction in poleward energy transport likely plays a role in limiting the polar warming in G1. An attribution study with a moist energy balance model shows that cloud feedbacks are the largest source of uncertainty regarding changes in poleward energy transport in midlatitudes in G1, as well as for changes in cross-equatorial energy transport, which are anticorrelated with ITCZ shifts.

Edit: see also the third image to help understand how ECS increases as the Hadley Cell expands.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 06, 2018, 08:37:27 PM
...
Furthermore, I note that most consensus climate scenarios aimed at keeping GMSTA below 2C involve the use of geoengineering ...

Even if green geoengineering pathways such as those discussed in the linked article (& associated image) were to be fully implemented (which is doubtful), they may well not be sufficient to stop an abrupt collapse of the WAIS beginning circa 2040.

Title: "Explainer: Why some US Democrats want a 'Green New Deal' to tackle climate change"

https://www.carbonbrief.org/explainer-why-some-us-democrats-want-a-green-new-deal-to-tackle-climate-change

Extract: "A growing number of Democrats in the US Congress are hoping to create a new set of policies which would trigger a rapid decarbonisation of the US economy. They have labelled the plan as the “green new deal”."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 06, 2018, 10:05:47 PM
This linked review indicates that CMIP6 will include some feedback mechanism associate with ice mass loss from simulated interactive ice sheets; however, none of these simulations will include ice-cliff or hydrofracturing mechanisms:

Heinze, C., Eyring, V., Friedlingstein, P., Jones, C., Balkanski, Y., Collins, W., Fichefet, T., Gao, S., Hall, A., Ivanova, D., Knorr, W., Knutti, R., Löw, A., Ponater, M., Schultz, M. G., Schulz, M., Siebesma, P., Teixeira, J., Tselioudis, G., and Vancoppenolle, M.: Climate feedbacks in the Earth system and prospects for their evaluation, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-84, in review, 2018.

https://www.earth-syst-dynam-discuss.net/esd-2018-84/

Abstract. Earth system models (ESMs) are key tools for providing climate projections under different scenarios of human-induced forcing. ESMs include a large number of additional processes and feedbacks such as biogeochemical cycles that traditional physical climate models do not consider. Yet, some processes such as cloud dynamics and ecosystem functional response still have fairly high uncertainties. In this article, we present an overview of climate feedbacks for Earth system components currently included in state-of-the-art ESMs and discuss the challenges to evaluate and quantify them. Uncertainties in feedback quantification arise from the interdependencies of biogeochemical matter fluxes and physical properties, the spatial and temporal heterogeneity of processes, and the lack of long-term continuous observational data to constrain them. We present an outlook for promising approaches that can help quantifying and constraining the large number of feedbacks in ESMs in the future. The target group for this article includes generalists with a background in natural sciences and an interest in climate change as well as experts working in interdisciplinary climate research (researchers, lecturers, and students). This study updates and significantly expands upon the last comprehensive overview of climate feedbacks in ESMs, which was produced 15 years ago (NRC, 2003).

Extract: "ESMs are being continuously expanded to include additional processes. For example, the ESMs which form part of the Coupled Model Intercomparison Project Phase 6 (CMIP6, Eyring et al. (2016a)) will for the first time include interactive ice sheets (Nowicki et al., 2016) and several models will have interactive chemistry and aerosols (Collins et al., 2017)."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 06, 2018, 10:59:47 PM
In the linked article the Bulletin of the Atomic Scientists supports the position that consensus climate science is under representing the risk of abrupt climate change (and even it does not clearly identify the ice-climate feedback risks):

Title: "Climate report understates threat"

https://thebulletin.org/2018/10/climate-report-understates-threat/

Extract: "The UN’s Intergovernmental Panel on Climate Change’s Special Report on Global Warming of 1.5 degrees Celsius, released on Monday, is a major advance over previous efforts to alert world leaders and citizens to the growing climate risk. But the report, dire as it is, misses a key point: Self-reinforcing feedbacks and tipping points—the wildcards of the climate system—could cause the climate to destabilize even further. The report also fails to discuss the five percent risk that even existing levels of climate pollution, if continued unchecked, could lead to runaway warming—the so-called “fat tail” risk. These omissions may mislead world leaders into thinking they have more time to address the climate crisis, when in fact immediate actions are needed. To put it bluntly, there is a significant risk of self-reinforcing climate feedback loops pushing the planet into chaos beyond human control."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 01:10:23 AM
While the linked article has no new information about how unstable Thwaites is, it does indicate just how concerned the global community is about this glacier, & the associated research may provide some more information in a year or two:

Title: "Just how unstable is the massive Thwaites glacier? Scientists are about to find out."

https://www.pri.org/stories/2018-05-01/just-how-unstable-massive-thwaites-glacier-scientists-are-about-find-out

Extract: "US and British scientific agencies announced their biggest joint Antarctic research effort in more than a generation on Monday.

The focus is Thwaites Glacier, which is roughly the size of Florida and sits on the western edge of Antarctica.

"Thwaites is the 800-pound gorilla, just because of how big and wide and deep into West Antarctica this particular outlet glacier goes,” says Chris Shuman, a University of Maryland Baltimore County professor working at the NASA's Goddard Space Flight Center and who is unaffiliated with the project. “So understanding it will greatly improve our ability to understand the response of the entire West Antarctic Ice Sheet.""
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 01:32:48 AM
The linked article provides a brief summary about the stability of Antarctic ice shelves, but you have to read between the lines to gain an understanding of the stability of the Thwaites Ice Shelf:

Title: "SOTC: Ice Shelves"

https://nsidc.org/cryosphere/sotc/iceshelves.html

Extract: "The Thwaites and Pine Island Glaciers flow into Pine Island Bay, and drain the West Antarctic Ice Sheet. These glaciers would only need to retreat a short distance before leading to accelerated retreat. Such a process may have happened before (Wise et al. 2017)."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 02:10:19 AM
The linked reference provides more insights about the instability of Thwaites; however, I note that projections from models of marine glaciers typically still err on the side of least drama:

Yu, H., Rignot, E., Seroussi, H., and Morlighem, M.: Retreat of Thwaites Glacier, West Antarctica, over the next 100 years using various ice flow models, ice shelf melt scenarios and basal friction laws, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-104, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2018-104/

Abstract. Thwaites Glacier (TG), West Antarctica, experiences rapid, potentially irreversible grounding line retreat and mass loss in response to enhanced ice shelf melting. Several numerical models of TG have been developed recently, showing a large spread in the evolution of the glacier in the coming decades to a century. It is, however, not clear how different parameterizations of basal friction and ice shelf melt or different approximations in ice stress balance affect projections.Here, we simulate the evolution of TG using different ice shelf melt, basal friction laws and ice sheet models of varying levels of complexity to quantify the effect of these model configurations on the results. We find that the grounding line retreat and its sensitivity to ocean forcing is enhanced when a full-Stokes model is used, ice shelf melt is applied on partially floating elements, and a Budd friction is used. Initial conditions also impact the model results. Yet, all simulations suggest a rapid, sustained retreat along the same preferred pathway. The highest retreat rate occurs on the eastern side of the glacier and the lowest rate on a subglacial ridge on the western side. All the simulations indicate that TG will undergo an accelerated retreat once it retreats past the western ridge. Combining the results, we find the uncertainty is small in the first 30 years, with a cumulative contribution to sea level rise of 5mm, similar to the current rate. After 30 years, the mass loss depends on the model configurations, with a 300% difference over the next 100 years, ranging from 14 to 42mm.

Edit: Also, I note that none of the models used in this study included either ice-cliff, or hydrofracturing, failure mechanisms.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 03:35:29 AM
As background information (for those who do not already know) the linked 2015 reference and associated image indicates that ice volume loss from Antarctic ice shelves has accelerated since 2003, and makes a contribution to the freshening of the surface waters of the Southern Ocean (and thus contributing to the ice-climate feedback mechanism), without making big change in sea level:

Fernando S. Paolo et al. (17 Apr 2015), "Volume loss from Antarctic ice shelves is accelerating", Science, Vol. 348, Issue 6232, pp. 327-331, DOI: 10.1126/science.aaa0940

http://science.sciencemag.org/content/348/6232/327

Abstract: "The floating ice shelves surrounding the Antarctic Ice Sheet restrain the grounded ice-sheet flow. Thinning of an ice shelf reduces this effect, leading to an increase in ice discharge to the ocean. Using 18 years of continuous satellite radar altimeter observations, we have computed decadal-scale changes in ice-shelf thickness around the Antarctic continent. Overall, average ice-shelf volume change accelerated from negligible loss at 25 ± 64 cubic kilometers per year for 1994–2003 to rapid loss of 310 ± 74 cubic kilometers per year for 2003–2012. West Antarctic losses increased by ~70% in the past decade, and earlier volume gain by East Antarctic ice shelves ceased. In the Amundsen and Bellingshausen regions, some ice shelves have lost up to 18% of their thickness in less than two decades."

See also:
Title: "Antarctic ice shelves rapidly thinning"

https://phys.org/news/2015-03-antarctic-ice-shelves-rapidly-thinning.html

Caption: "Eighteen years of change in thickness and volume of Antarctic ice shelves. Rates of thickness change (m/decade) are color-coded from -25 (thinning) to +10 (thickening). Circles represent percentage of thickness lost (red) or gained (blue) in 18 years. The central circle demarcates the area not surveyed by the satellites (south of 81.5ºS). Original data were interpolated for mapping purposes. Background is the Landsat Image Mosaic of Antarctica (LIMA). Credit: Scripps Institution of Oceanography, UC San Diego"


Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 03:52:56 AM
The linked reference indicates that the projected increase (with continued global warming) of more frequent strong El Nino events combined with the projected increase in positive SAM, will significantly increase ice mass loss from the ASE, which will increase the risk of a collapse of the WAIS:

Deb, P., A. Orr, D. H. Bromwich, J. P. Nicolas, J. Turner, and J. S. Hosking, 2018: Summer drivers of atmospheric variability affecting ice shelf thinning in the Amundsen Sea Embayment, West Antarctica. Geophy. Res. Lett., 45. doi: 10.1029/2018GL077092.

http://polarmet.osu.edu/PMG_publications/deb_bromwich_grl_2018.pdf

Abstract:  "Satellite data and a 35-year hindcast of the Amundsen Sea Embayment summer climate using the Weather Research and Forecasting model are used to understand how regional and large-scale atmospheric variability affects thinning of ice shelves in this sector of West Antarctica by melting from above and below (linked to intrusions of warm water caused by anomalous westerlies over the continental shelf edge). El Niño episodes are associated with an increase in surface melt but do not have a statistically significant impact on westerly winds over the continental shelf edge. The location of the Amundsen Sea Low and the polarity of the Southern Annular Mode (SAM) have negligible impact on surface melting, although a positive SAM and eastward shift of the Amundsen Sea Low cause anomalous westerlies over the continental shelf edge. The projected future increase in El Niño episodes and positive SAM could therefore increase the risk of disintegration of West Antarctic ice shelves."

Extract: "Our study suggests that ASE ice shelves could experience an intensification of melt in the future from both above and below as a result of both regional and large-scale atmospheric changes, potentially increasing the risk of their disintegration, which in turn could potentially trigger a collapse of the West Antarctic ice sheet (DeConto & Pollard, 2016). To better understand this threat will require further detailed investigation of the impacts of ENSO, the polarity of the SAM, and the depth/location of the ASL on ASE ice shelves. Also necessary is improving the reliability of future projections, such as ENSO and its teleconnections, as well as the response of the SAM to recovery of the Antarctic ozone hole and increased greenhouse gas emissions (Polvani, Waugh, et al., 2011)."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 04:42:03 PM
One key problem associated with reducing the 'Deep Uncertainty' associate with ice-climate feedback mechanisms is the problems of correct attribution, especially when consensus climate change studies such as the first linked report (for decision makers) essentially ignore this consideration, even though Hansen's book "Storms of my Grandchildren" clearly warns about the consequence of this important feedback:

Title: "Fingerprints Everywhere 2018"

http://www.climatesignals.org/fingerprints-everywhere-2018
http://www.climatesignals.org/sites/default/files/Fingerprints-Everywhere.pdf

Indeed, the second linked reference highlights the difficulties of climate change attribution; which makes it even harder for ice-climate feedback mechanisms to gain traction in the attribution game:

Judith L. Lean (22 February 2018), "Observation‐based detection and attribution of 21st century climate change", WIREs Climate Change, https://doi.org/10.1002/wcc.511

https://onlinelibrary.wiley.com/doi/abs/10.1002/wcc.511

Abstract: "Climate change detection and attribution have proven unexpectedly challenging during the 21st century. Earth’s global surface temperature increased less rapidly from 2000 to 2015 than during the last half of the 20th century, even though greenhouse gas concentrations continued to increase. A probable explanation is the mitigation of anthropogenic warming by La Niña cooling and declining solar irradiance. Physical climate models overestimated recent global warming because they did not generate the observed phase of La Niña cooling and may also have underestimated cooling by declining solar irradiance. Ongoing scientific investigations continue to seek alternative explanations to account for the divergence of simulated and observed climate change in the early 21st century, which IPCC termed a “global warming hiatus.” Amplified by media commentary, the suggestions by these studies that “missing” mechanisms may be influencing climate exacerbates confusion among policy makers, the public and other stakeholders about the causes and reality of modern climate change.

Understanding and communicating the causes of climate change in the next 20 years may be equally challenging. Predictions of the modulation of projected anthropogenic warming by natural processes have limited skill. The rapid warming at the end of 2015, for example, is not a resumption of anthropogenic warming but rather an amplification of ongoing warming by El Niño. Furthermore, emerging feedbacks and tipping points precipitated by, for example, melting summer Arctic sea ice may alter Earth’s global temperature in ways that even the most sophisticated physical climate models do not yet replicate."

For example, when non-experts think of the impacts of ice loss on the climate they typically think of the ice-albedo feedback and the potential rapid loss of Arctic Sea Ice; however, the third linked reference indicates the attribution problems associated with this feedback due to the influences of both natural GHG emissions and of anthropogenic aerosol forcing (which have been suppressing Arctic Sea Ice losses for decades until the recent reduction in anthropogenic aerosol emissions).  Furthermore, ice-albedo feedback can be one of the many different mechanisms contributing to ice-climate feedback, which further complicates attribution.

B. L. Mueller et al (2018), "Attribution of Arctic Sea Ice Decline from 1953 to 2012 to Influences from Natural, Greenhouse Gas, and Anthropogenic Aerosol Forcing", Journal of Climate,
https://doi.org/10.1175/JCLI-D-17-0552.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0552.1

Abstract: "The paper presents results from a climate change detection and attribution study on the decline of Arctic sea ice extent in September for the 1953–2012 period. For this period three independently derived observational datasets and simulations from multiple climate models are available to attribute observed changes in the sea ice extent to known climate forcings. Here we direct our attention to the combined cooling effect from other anthropogenic forcing agents (mainly aerosols), which has potentially masked a fraction of greenhouse gas–induced Arctic sea ice decline. The presented detection and attribution framework consists of a regression model, namely, regularized optimal fingerprinting, where observations are regressed onto model-simulated climate response patterns (i.e., fingerprints). We show that fingerprints from greenhouse gas, natural, and other anthropogenic forcings are detected in the three observed records of Arctic sea ice extent. Beyond that, our findings indicate that for the 1953–2012 period roughly 23% of the greenhouse gas–induced negative sea ice trend has been offset by a weak positive sea ice trend attributable to other anthropogenic forcing. We show that our detection and attribution results remain robust in the presence of emerging nonstationary internal climate variability acting upon sea ice using a perfect model experiment and data from two large ensembles of climate simulations."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Gray-Wolf on December 07, 2018, 04:57:48 PM


https://onlinelibrary.wiley.com/doi/abs/10.1002/wcc.511

Abstract: "Climate change detection and attribution have proven unexpectedly challenging during the 21st century. Earth’s global surface temperature increased less rapidly from 2000 to 2015 than during the last half of the 20th century, even though greenhouse gas concentrations continued to increase. A probable explanation is the mitigation of anthropogenic warming by La Niña cooling and declining solar irradiance.

I think it could be argued that the period highlighted was blighted by the flip side of the global warming coin, that of global dimming? The fact the the Pacific was ground zero for the incredible increase in Chinese 'dimming' lead to imbalance between the tropical Pacific/tropical Atlantic.
In its turn this lead to the increase in upper level winds over the Caribbean as the basins struggled to find parity and this began to lower Atlantic hurricane numbers via the aggressive shear environment any forming storms encountered.
It also lead to the uptick in the trades over the ENSO regions leading to the huge warm pool at the western extremes of that area.

A combination of China's scrabble to clean up its urban pollution and so save the population ( nobody wants to only be able to see the sun via TV screens in the city centres!) and the flipping of the Pacific 'Naturals' in 2014 helped us suddenly balance out the Basins and so allow warming to return to above the rates of warming measured over the last spurt of warming post our 'dimmed period ( 1980's/90's ).

I know it is early doors yet but I think we will find the years up to 2025 warming at rates well above those of the late 20th century both via the clearing of the airs over the Pacific but also the impacts of open water Arctic ( and recently Antarctic?) able to capture energy that used to be bounced harmlessly back into space and introduce it into the climate system?

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 06:26:45 PM
To provide additional background information on why consensus climate science and decision makers have not yet been adequately portraying the true risks associated with ice-climate feedback mechanism, I provide the first image from Roe and Armour 2011, showing how a positive feedback mechanism pdf results in a skewed pdf for the contribution of that feedback mechanism to GMSTA.  Reticent climate scientists and policy makers tend to ignore the long-tail of the skewed GMSTA pdf (which is a measure of climate sensitivity) by limiting the confidence range under consideration.

Next, the second image, from Roe and Baker 2007, shows the relationship of fat-tailed climate sensitivity (a measure of GMSTA) pdf to a combination of positive feedback mechanisms (such as is the case for the ice-climate feedback) and different feedback parameters; which determine the fatness of the climate sensitivity tail that is being ignored by consensus climate scientists and policy makers.

Next, the third image shows the influence of different time durations on the pdf for climate sensitivity due to an assumed instantaneous doubling of atmospheric CO2, from Roe and Bauman 2011.  Policy makers assume that they are entitled to use the short-term climate sensitivity pdf for calculating the remaining carbon budget, but then the decline to correct their calculations for this duration effect when they delay their climate action by decades.

Lastly, for this post, the fourth image show that the BAU forcing pathway that we are currently following, resulting in a rate of forcing that is approximately 100 times faster than during the PETM.  Unfortunately, ECS will increase from our present value with such a high rate of forcing, but policy makers choice to ignore this consideration.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 07:22:26 PM
While I have cited Pattyn et al. (2018)'s finding previously, I put it again as an illustration of how climate scientists (including Rob DeConto) tend to bury this risk of abrupt ice-climate global response by watering that projected response down by various means including:
1. Mixing consideration of responses from ice-sheet models with and without ice-cliff failures and hydrofracting and with and without interaction with global circulation models and by not even mentioning responses such as those reported by Hansen et al. (2016) that consider ice-climate feedback for assumed ice mass loss scenarios.
2. Using IPCC values for climate sensitivity, which blend together many different means of estimating climate sensitivity, which tends to undervalue the relatively high values of ECS estimated by the best climate models.
3. Focusing of low emission forcing scenarios that tend to indicate that the response of ice sheets that have moved past their tipping points will take at least a millennia to develop; thus de-emphasizing the risk risks of our current BAU pathway which could result in ice sheet responses that develop within a century once they have passed their tipping points.
4. De-emphasizing the self-reinforcing and cascading risks of the hundreds of positive feedback mechanisms (including ice-climate mechanisms) with continued warming.

Pattyn, et al. (2018), "The Greenland and Antarctic ice sheets under 1.5 °C global warming", Nature Climate Change, DOI: 10.1038/s41558-018-0305-8 , https://www.nature.com/articles/s41558-018-0305-8

https://www.nature.com/articles/s41558-018-0305-8

Abstract: "Even if anthropogenic warming were constrained to less than 2 °C above pre-industrial, the Greenland and Antarctic ice sheets will continue to lose mass this century, with rates similar to those observed over the past decade. However, nonlinear responses cannot be excluded, which may lead to larger rates of mass loss. Furthermore, large uncertainties in future projections still remain, pertaining to knowledge gaps in atmospheric (Greenland) and oceanic (Antarctica) forcing. On millennial timescales, both ice sheets have tipping points at or slightly above the 1.5–2.0 °C threshold; for Greenland, this may lead to irreversible mass loss due to the surface mass balance–elevation feedback, whereas for Antarctica, this could result in a collapse of major drainage basins due to ice-shelf weakening."

Extract: "Evidence from the observed Larsen B collapse, and rapid front retreat of Jakobshavn Isbrae in Greenland, suggests that hydrofracturing could lead to the rapid collapse of ice shelves and potentially produce high ice cliffs with vertical exposure above 90 m rendering the cliffs mechanically unsustainable, possibly resulting in what has been termed marine ice cliff instability"

See also:

Title: "Modest warming risks 'irreversible' ice sheet loss, study warns"

https://phys.org/news/2018-11-modest-irreversible-ice-sheet-loss.html
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 07:33:20 PM
...
I think it could be argued that the period highlighted was blighted by the flip side of the global warming coin, that of global dimming?
...

Gray-Wolf,

Thanks for your comments.  Certainly the variable and chaotic nature of both natural and anthropogenic forcing adds to the 'Deep Uncertainty' that tends to obscure the very real risks of abrupt ice-climate feedback this century.  The truth is that mankind is headed into uncharted waters within the next couple of decades, and we are not appropriately facing the warning provided by researchers such as James Hansen, & others, all of whom have to partially mute their warning in order to even be published [witness the difficulties that were encountered getting Hansen et al (2016) published and how infrequently it has been cited by consensus climate science].

I strongly suspect that mankind will not be willing to accept the risks of abrupt ice-climate feedback until it is both manifest and unstoppable (at least for the next few centuries).

Best,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 07, 2018, 07:52:23 PM
I have previously posted (e.g.: see various posts from 163 thru 178) about the risks that potentially abrupt ice mass loss from Antarctica (in the next century) could have on the Earth's geomagnetic field; and the linked article emphasizes that the biggest risks to modern society is posed by the possibility that the field strength could degrade to zero within the next century, even if it takes a millennia to flip:

Title: "Earth's magnetic poles could start to flip. What happens then?"

https://phys.org/news/2018-12-earth-magnetic-poles-flip.html

Extract: " As Earth's magnetic shield fails, so do its satellites. First, our communications satellites in the highest orbits go down. Next, astronauts in low-Earth orbit can no longer phone home. And finally, cosmic rays start to bombard every human on Earth.

This is a possibility that we may start to face not in the next million years, not in the next thousand, but in the next hundred. If Earth's magnetic field were to decay significantly, it could collapse altogether and flip polarity – changing magnetic north to south and vice versa. The consequences of this process could be dire for our planet.

Most worryingly, we may be headed right for this scenario.

'The geomagnetic field has been decaying for the last 3,000 years,' said Dr. Nicolas Thouveny from the European Centre for Research and Teaching of Environmental Geosciences (CEREGE) in Aix-en-Provence, France. 'If it continues to fall down at this rate, in less than one millennium we will be in a critical (period).'

In the Atlantic Ocean between South America and Africa, there is a vast region of Earth's magnetic field that is about three times weaker than the field strength at the poles.

This is called the South Atlantic Anomaly (SAA), and it's the focus of the CoreSat project being led by Professor Chris Finlay from the Technical University of Denmark (DTU) near Copenhagen. Using data from multiple satellites, including the European Space Agency's (ESA) three Swarm satellites launched in 2013, this project is trying to figure out what is causing the SAA.
'This is a region where we see that satellites consistently (experience) electronic failures,' said Prof. Finlay. 'And we don't understand where this weak field region is coming from, what's producing it, and how it might change in the future.'

'The decrease in geomagnetic field is much more important and dramatic than the reversal,' said Dr. Thouveny. 'It is very important to understand if the present field will decay to zero in the next century, because we will have to prepare.' "
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on December 09, 2018, 01:45:45 AM
Re: ITCZ, question for abruptSLR

in the ACME modelling efforts, have they fixed the double ITCZ problem that most GCMs have ?

sidd


Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 09, 2018, 02:40:18 AM
Re: ITCZ, question for abruptSLR

in the ACME modelling efforts, have they fixed the double ITCZ problem that most GCMs have ?

sidd

That last time I looked it was still there, but who knows what changes that they are continually making as they transform ACME into E3SM.

Edit: You can monitor the progress being made on the E3SM model at:

https://esgf-node.llnl.gov/projects/e3sm/
&
https://e3sm.org/about/events/all-hands-presentations/
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 09, 2018, 02:41:35 AM
There is a reasonable likelihood that the projected acceleration in Greenland ice mass loss in the circa 2040 (see the first linked reference and associate first image) could trigger an acceleration of ice mass loss from key marine glaciers in the AIS (particularly in the WAIS):

Calov, R., Beyer, S., Greve, R., Beckmann, J., Willeit, M., Kleiner, T., Rückamp, M., Humbert, A., and Ganopolski, A.: Simulation of the future sea level contribution of Greenland with a new glacial system model, The Cryosphere, 12, 3097-3121, https://doi.org/10.5194/tc-12-3097-2018, 2018.

https://www.the-cryosphere.net/12/3097/2018/tc-12-3097-2018.pdf

Abstract
We introduce the coupled model of the Greenland glacial system IGLOO 1.0, including the polythermal ice sheet model SICOPOLIS (version 3.3) with hybrid dynamics, the model of basal hydrology HYDRO and a parameterization of submarine melt for marine-terminated outlet glaciers. The aim of this glacial system model is to gain a better understanding of the processes important for the future contribution of the Greenland ice sheet to sea level rise under future climate change scenarios. The ice sheet is initialized via a relaxation towards observed surface elevation, imposing the palaeo-surface temperature over the last glacial cycle. As a present-day reference, we use the 1961–1990 standard climatology derived from simulations of the regional atmosphere model MAR with ERA reanalysis boundary conditions. For the palaeo-part of the spin-up, we add the temperature anomaly derived from the GRIP ice core to the years 1961–1990 average surface temperature field. For our projections, we apply surface temperature and surface mass balance anomalies derived from RCP 4.5 and RCP 8.5 scenarios created by MAR with boundary conditions from simulations with three CMIP5 models. The hybrid ice sheet model is fully coupled with the model of basal hydrology. With this model and the MAR scenarios, we perform simulations to estimate the contribution of the Greenland ice sheet to future sea level rise until the end of the 21st and 23rd centuries. Further on, the impact of elevation–surface mass balance feedback, introduced via the MAR data, on future sea level rise is inspected. In our projections, we found the Greenland ice sheet to contribute between 1.9 and 13.0 cm to global sea level rise until the year 2100 and between 3.5 and 76.4 cm until the year 2300, including our simulated additional sea level rise due to elevation–surface mass balance feedback. Translated into additional sea level rise, the strength of this feedback in the year 2100 varies from 0.4 to 1.7 cm, and in the year 2300 it ranges from 1.7 to 21.8 cm. Additionally, taking the Helheim and Store glaciers as examples, we investigate the role of ocean warming and surface runoff change for the melting of outlet glaciers. It shows that ocean temperature and subglacial discharge are about equally important for the melting of the examined outlet glaciers.

Caption for the first image: "Figure 10. Contribution of the Greenland ice sheet to future sea level rise under MAR forcing for different scenarios. Sea level rise is referenced to the year 2000. Beyond 2100, the forcings of the projections are from prolongations of the original MAR data (see main text for details). This is indicated by the vertical grey line at the year 2100 in panels (b) and (d). RCP 4.5 projections: (a) years 2000–2100 and (b) years 2000–2300. RCP 8.5 projections: (c) years 2000–2100 and (d) years 2000–2300. The different CMIP5 general circulation models utilized by MAR are indicated by colours. Different line characteristics specify optimal simulations with (solid) and without (long dashed) elevation correction for the SMB. The grey curves in panels (a) to (d) indicate a control simulation with solely the implied SMB (iSMB) as forcing. All simulations are with hybrid ice dynamics and HYDRO basal hydrology.
&

Furthermore, meltwater in the Greenland Ice Sheet deep percolation zone could have a significant impact on mass loss from Greenland by 2040.  The second linked reference discusses a new field method for better monitoring the accumulation of meltwater in this zone.  Obviously, ice mass loss from Greenland impacts ice mass loss from Antarctica via the bipolar seesaw mechanism:

Heilig, A., Eisen, O., MacFerrin, M., Tedesco, M., and Fettweis, X.: Seasonal monitoring of melt and accumulation within the deep percolation zone of the Greenland Ice Sheet and comparison with simulations of regional climate modeling, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-277, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2017-277/

Abstract. Increasing melt over the Greenland ice sheet (GrIS) recorded over the past years has resulted in significant changes of the percolation regime of the ice sheet. It remains unclear whether Greenland's percolation zone will act as meltwater buffer in the near future through gradually filling all pore space or if near-surface refreezing causes the formation of impermeable layers, which provoke lateral runoff. Homogeneous ice layers within perennial firn, as well as near-surface ice layers of several meter thickness are observable in firn cores. Because firn coring is a destructive method, deriving stratigraphic changes in firn and allocation of summer melt events is challenging. To overcome this deficit and provide continuous data for model evaluations on snow and firn density, temporal changes in liquid water content and depths of water infiltration, we installed an upward-looking radar system (upGPR) 3.4 m below the snow surface in May 2016 close to Camp Raven (66.4779° N/46.2856° W) at 2120 m a.s.l. The radar is capable to monitor quasi-continuously changes in snow and firn stratigraphy, which occur above the antennas. For summer 2016, we observed four major melt events, which routed liquid water into various depths beneath the surface. The last event in mid-August resulted in the deepest percolation down to about 2.3 m beneath the surface. Comparisons with simulations from the regional climate model MAR are in very good agreement in terms of seasonal changes in accumulation and timing of onset of melt. However, neither bulk density of near-surface layers nor the amounts of liquid water and percolation depths predicted by MAR correspond with upGPR data. Radar data and records of a nearby thermistor string, in contrast, matched very well, for both, timing and depth of temperature changes and observed water percolations. All four melt events transferred a cumulative mass of 56 kg/m2 into firn beneath the summer surface of 2015. We find that continuous observations of liquid water content, percolation depths and rates for the seasonal mass fluxes are sufficiently accurate to provide valuable information for validation of model approaches and help to develop a better understanding of liquid water retention and percolation in perennial firn.
&

It is imaginable that an acceleration of ice mass loss from the GIS circa 2040 might possibly trigger an eruption of Mt Takahe in the Byrd Subglacial Basin, BSB (see the second attached image), which could accelerate ice mass loss in Antarctica just as happen about 17.7 kya as the linked article entitled: "Massive Antarctic volcanic eruptions linked to abrupt Southern hemisphere climate changes", cites that abrupt climate change was associated with a series of halogen rich eruptions from Mt Takahe in the BSB.  Who knows what lies in mankind's future should a collapse of the WAIS this century should trigger similar volcanic eruptions in West Antarctica:

https://phys.org/news/2017-09-massive-antarctic-volcanic-eruptions-linked.html

Extract: ""Detailed chemical measurements in Antarctic ice cores show that massive, halogen-rich eruptions from the West Antarctic Mt. Takahe volcano coincided exactly with the onset of the most rapid, widespread climate change in the Southern Hemisphere during the end of the last ice age and the start of increasing global greenhouse gas concentrations," according to McConnell, who leads DRI's ultra-trace chemical ice core analytical laboratory.

Climate changes that began ~17,700 years ago included a sudden poleward shift in westerly winds encircling Antarctica with corresponding changes in sea ice extent, ocean circulation, and ventilation of the deep ocean. Evidence of these changes is found in many parts of the Southern Hemisphere and in different paleoclimate archives, but what prompted these changes has remained largely unexplained.

"We know that rapid climate change at this time was primed by changes in solar insolation and the Northern Hemisphere ice sheets," explained McConnell. "Glacial and interglacial cycles are driven by the sun and Earth orbital parameters that impact solar insolation (intensity of the sun's rays) as well as by changes in the continental ice sheets and greenhouse gas concentrations."
"We postulate that these halogen-rich eruptions created a stratospheric ozone hole over Antarctica that, analogous to the modern ozone hole, led to large-scale changes in atmospheric circulation and hydroclimate throughout the Southern Hemisphere," he added. "Although the climate system already was primed for the switch, we argue that these changes initiated the shift from a largely glacial to a largely interglacial climate state. The probability that this was just a coincidence is negligible."

See also the subject reference:

Joseph R. McConnell el al., "Synchronous volcanic eruptions and abrupt climate change ∼17.7 ka plausibly linked by stratospheric ozone depletion," PNAS (2017). https://doi.org/10.1073/pnas.1705595114 

www.pnas.org/cgi/doi/10.1073/pnas.1705595114

Extract: "Glacial-state greenhouse gas concentrations and Southern Hemisphere climate conditions persisted until ∼17.7 ka, when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the Southern Hemisphere, with many changes ascribed to a sudden poleward shift in the Southern Hemisphere westerlies and subsequent climate impacts. We used high-resolution chemical measurements in the West Antarctic Ice Sheet Divide, Byrd, and other ice cores to document a unique, ∼192-y series of halogen-rich volcanic eruptions exactly at the start of accelerated deglaciation, with tephra identifying the nearby Mount Takahe volcano as the source. Extensive fallout from these massive eruptions has been found >2,800 km from Mount Takahe. Sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface UV radiation indicate that the eruptions led to stratospheric ozone depletion. Rather than a highly improbable coincidence, circulation and climate changes extending from the Antarctic Peninsula to the subtropics—similar to those associated with modern stratospheric ozone depletion over Antarctica—plausibly link the Mount Takahe eruptions to the onset of accelerated Southern Hemisphere deglaciation ∼17.7 ka."

Extract: "Previous studies (e.g., ref. 42) suggested that rising insolation initiated melting of Northern Hemisphere (NH) ice sheets at 19 ka, which triggered a reduction in the strength of the Atlantic overturning circulation, and, through the bipolar seesaw, resulted in SH warming and CO2 release from the Southern Ocean, although the exact mechanisms driving the CO2 release are still debated. We postulate that the ∼192-y series of halogen-rich eruptions of Mount Takahe and the subsequent ozone hole (26) initiated a series of events analogous to the modern ozone hole that acted to accelerate deglaciation at 17.7 ka. First, stratospheric ozone depletion changed SH atmospheric circulation, resulting in a rapid increase and poleward shift in the westerlies (35) (SI Appendix, Fig. S7). Second, consequent widespread perturbations in SH hydrometeorology, including increased austral summer subtropical precipitation between ∼15°S and ∼35°S (Figs. 1F and 5), led to enhanced CH4 wetland emissions (43)."

Caption for the second image: "Spatial extent of the glaciochemical anomaly. Evidence of the ∼192-y anomaly has been found >2,800 km from Mount Takahe in ice core (circles) chemical records (SI Appendix, Fig. S3) as well as radar surveys from much of West Antarctica. Also shown are area volcanoes (triangles). September/October horizontal wind vectors at 600 hPa based on 1981–2010 National Centers for Environmental Prediction reanalysis fields show transport patterns consistent with observations."
&

Furthermore, via the bipolar seesaw mechanism and a rapid freshening of the Southern Ocean (due to the initial collapse of the WAIS after 2040) could be rapidly telecommunicated back to the North Hemisphere [see Turney et al (2017)] where it might trigger rapid ice mass loss from the Northeast Greenland Ice Stream (NEGIS) as occurred from 7.8 to 1.2 kya [see Larsen et al (2018) and the third attached image]:

Turney, et al. (2017), "Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial", Nature Communications 8, Article No. 520, https://doi.org/10.1038/s41467-017-00577-6

https://www.nature.com/articles/s41467-017-00577-6

Extract: "An ensemble of transient meltwater simulations show that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train."
&

Nicolaj K. Larsen et al. (14 May 2018), "Instability of the Northeast Greenland Ice Stream over the last 45,000 years", Nature Communications, Volume 9, Article number: 1872, doi:10.1038/s41467-018-04312-7

http://www.nature.com/articles/s41467-018-04312-7

Abstract: "The sensitivity of the Northeast Greenland Ice Stream (NEGIS) to prolonged warm periods is largely unknown and geological records documenting such long-term changes are needed to place current observations in perspective. Here we use cosmogenic surface exposure and radiocarbon ages to determine the magnitude of NEGIS margin fluctuations over the last 45 kyr (thousand years). We find that the NEGIS experienced slow early Holocene ice-margin retreat of 30–40 m a−1, likely as a result of the buttressing effect of sea-ice or shelf-ice. The NEGIS was ~20–70 km behind its present ice-extent ~41–26 ka and ~7.8–1.2 ka; both periods of high orbital precession index and/or summer temperatures within the projected warming for the end of this century. We show that the NEGIS was smaller than present for approximately half of the last ~45 kyr and is susceptible to subtle changes in climate, which has implications for future stability of this ice stream."


See also: "Antarctica: What Would Happen if All the Volcanoes Buried Beneath the Ice Erupted?"

http://www.newsweek.com/antarctica-subglacial-volcanoes-eruption-risk-sea-ice-659537

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 09, 2018, 03:08:36 AM
Re: ITCZ, question for abruptSLR

in the ACME modelling efforts, have they fixed the double ITCZ problem that most GCMs have ?

sidd

That last time I looked it was still there, but who knows what changes that they are continually making as they transform ACME into E3SM.

Edit: You can monitor the progress being made on the E3SM model at:

https://esgf-node.llnl.gov/projects/e3sm/
&
https://e3sm.org/about/events/all-hands-presentations/

I note that the CMIP6 model output is starting to come out and can be accessed at the following links:

https://esgf-node.llnl.gov/projects/cmip6/
&
https://esgf-node.llnl.gov/search/cmip6/

If David Pollard has the time and money available, maybe he should take the output (maybe from the E3SM output) from one of these models with interactive ice sheets (and which thus theoretically should include the influence of associated freshwater hosing) circa 2040 and use it as input to their AIS model with ice-cliff failure mechanisms and hydrofracturing and see what happens by 2100.  Such runs may inspire CMIP7 models to also incorporate ice-cliff failure mechanisms and hydrofracturing.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 09, 2018, 03:44:02 AM
With West Antarctic ice shelves progressively becoming more fragile with continuing warming; and with storm activity trending higher (see the attached image); who knows what future damage both storm surge and long period gravity waves will do to these ice shelves (see the following two references):

ZHAO CHEN et al. (2018), "Ocean-excited plate waves in the Ross and Pine Island Glacier ice shelves", Journal of Glaciology, Volume 64, Issue 247, pp. 730-744 https://doi.org/10.1017/jog.2018.66

https://www.cambridge.org/core/journals/journal-of-glaciology/article/oceanexcited-plate-waves-in-the-ross-and-pine-island-glacier-ice-shelves/B7339CE9FD25772A9157259076623C5E

Abstract: "Ice shelves play an important role in buttressing land ice from reaching the sea, thus restraining the rate of grounded ice loss. Long-period gravity-wave impacts excite vibrations in ice shelves that can expand pre-existing fractures and trigger iceberg calving. To investigate the spatial amplitude variability and propagation characteristics of these vibrations, a 34-station broadband seismic array was deployed on the Ross Ice Shelf (RIS) from November 2014 to November 2016. Two types of ice-shelf plate waves were identified with beamforming: flexural-gravity waves and extensional Lamb waves. Below 20 mHz, flexural-gravity waves dominate coherent signals across the array and propagate landward from the ice front at close to shallow-water gravity-wave speeds (~70 m s−1). In the 20–100 mHz band, extensional Lamb waves dominate and propagate at phase speeds ~3 km s−1. Flexural-gravity and extensional Lamb waves were also observed by a 5-station broadband seismic array deployed on the Pine Island Glacier (PIG) ice shelf from January 2012 to December 2013, with flexural wave energy, also detected at the PIG in the 20–100 mHz band. Considering the ubiquitous presence of storm activity in the Southern Ocean and the similar observations at both the RIS and the PIG ice shelves, it is likely that most, if not all, West Antarctic ice shelves are subjected to similar gravity-wave excitation."

See also:

P. D. Bromirski et al. (16 June 2017), "Tsunami and infragravity waves impacting Antarctic ice shelves", JGR Oceans, https://doi.org/10.1002/2017JC012913

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JC012913

Abstract
The responses of the Ross Ice Shelf (RIS) to the 16 September 2015 8.3 (Mw) Chilean earthquake tsunami (>75 s period) and to oceanic infragravity (IG) waves (50–300 s period) were recorded by a broadband seismic array deployed on the RIS from November 2014 to November 2016. Here we show that tsunami and IG‐generated signals within the RIS propagate at gravity wave speeds (∼70 m/s) as water‐ice coupled flexural‐gravity waves. IG band signals show measureable attenuation away from the shelf front. The response of the RIS to Chilean tsunami arrivals is compared with modeled tsunami forcing to assess ice shelf flexural‐gravity wave excitation by very long period (VLP; >300 s) gravity waves. Displacements across the RIS are affected by gravity wave incident direction, bathymetry under and north of the shelf, and water layer and ice shelf thicknesses. Horizontal displacements are typically about 10 times larger than vertical displacements, producing dynamical extensional motions that may facilitate expansion of existing fractures. VLP excitation is continuously observed throughout the year, with horizontal displacements highest during the austral winter with amplitudes exceeding 20 cm. Because VLP flexural‐gravity waves exhibit no discernable attenuation, this energy must propagate to the grounding zone. Both IG and VLP band flexural‐gravity waves excite mechanical perturbations of the RIS that likely promote tabular iceberg calving, consequently affecting ice shelf evolution. Understanding these ocean‐excited mechanical interactions is important to determine their effect on ice shelf stability to reduce uncertainty in the magnitude and rate of global sea level rise.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 09, 2018, 04:10:53 AM
With sufficient global warming who knows what extinctions are in the Earth's future (in the next few centuries):

J.L. Penn el al. (2018), "Temperature-dependent hypoxia explains biogeography and severity of end-Permian marine mass extinction", Science, Vol. 362, Issue 6419, eaat1327, DOI: 10.1126/science.aat1327

http://science.sciencemag.org/content/362/6419/eaat1327

Abstract: "Rapid climate change at the end of the Permian Period (~252 million years ago) is the hypothesized trigger for the largest mass extinction in Earth’s history. We present model simulations of the Permian/Triassic climate transition that reproduce the ocean warming and oxygen (O2) loss indicated by the geologic record. The effect of these changes on animal survival is evaluated using the Metabolic Index (Φ), a measure of scope for aerobic activity governed by organismal traits sampled in diverse modern species. Modeled loss of aerobic habitat predicts lower extinction intensity in the tropics, a pattern confirmed with a spatially explicit analysis of the marine fossil record. The combined physiological stresses of ocean warming and O2 loss can account for more than half the magnitude of the “Great Dying.”"
See also:

Title: "Biggest mass extinction caused by global warming leaving ocean animals gasping for breath"

https://phys.org/news/2018-12-biggest-mass-extinction-global-ocean.html

Extract: ""Under a business-as-usual emissions scenarios, by 2100 warming in the upper ocean will have approached 20 percent of warming in the late Permian, and by the year 2300 it will reach between 35 and 50 percent," Penn said. "This study highlights the potential for a mass extinction arising from a similar mechanism under anthropogenic climate change." "
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on December 09, 2018, 05:27:54 AM
Re: ITCZ

thanks for recalling the pointer to ACME/ESM.

Re: GIS

I think is is becoming clear that melt will overwhelm firn retention and will run to the ocean. Watching melt lakes climb as ELA climbs is disquieting. I see that meltlakes are close to the top of 67N saddle now. What is worse is the huge latent heat the water sheds to ice upon any refreeze. That raises ice temperature and Glen's law exponent kills you with warmer ice speeding out the big tidewater outlets. 79N is still remarkably quiescent in spite of substantial melt lakes over NEGIS.

But perhaps this discussion should move to one of the Greenland threads.

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 09, 2018, 04:16:40 PM
...
 79N is still remarkably quiescent in spite of substantial melt lakes over NEGIS.

But perhaps this discussion should move to one of the Greenland threads.

sidd

In my opinion a possible Ice Apocalypse (named by prokaryotes) includes all aspects of the multiple ice-climate feedback mechanisms, including those dealing with Greenland including: its bipolar interaction with Antarctica, its slowing of the oceans overturning current and its feedback with Arctic Amplification (etc.)
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 09, 2018, 04:42:26 PM
Future freshwater exports from the Arctic into the North Atlantic can come several sources including: a) the Beaufort Gyre, b) melting Arctic Sea Ice and c) ice mass loss from the Greenland Ice Sheet.  Furthermore, this Arctic freshwater can follow different pathways, and the cited reference indicates that these different pathways would have different (but significant) impacts on both the North Atlantic Convection and on the AMOC.  This research provide insights into Hansen's ice-climate feedback mechanism:

Wang, He, Sonya Legg, and Robert Hallberg, July 2018: The Effect of Arctic Freshwater Pathways on North Atlantic Convection and the Atlantic Meridional Overturning Circulation. Journal of Climate, 31(13), DOI:10.1175/JCLI-D-17-0629.1 .

https://journals.ametsoc.org/doi/10.1175/JCLI-D-17-0629.1
&
https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-17-0629.1

Abstract: "This study examines the relative roles of the Arctic freshwater exported via different pathways on deep convection in the North Atlantic and the Atlantic meridional overturning circulation (AMOC). Deep water feeding the lower branch of the AMOC is formed in several North Atlantic marginal seas, including the Labrador Sea, Irminger Sea, and the Nordic seas, where deep convection can potentially be inhibited by surface freshwater exported from the Arctic. The sensitivity of the AMOC and North Atlantic to two major freshwater pathways on either side of Greenland is studied using numerical experiments. Freshwater export is rerouted in global coupled climate models by blocking and expanding the channels along the two routes. The sensitivity experiments are performed in two sets of models (CM2G and CM2M) with different control simulation climatology for comparison. Freshwater via the route east of Greenland is found to have a larger direct impact on Labrador Sea convection. In response to the changes of freshwater route, North Atlantic convection outside of the Labrador Sea changes in the opposite sense to the Labrador Sea. The response of the AMOC is found to be sensitive to both the model formulation and mean-state climate."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 09, 2018, 06:50:45 PM
In Replies #219 & #220 I noted that Bronselaer et al (2018); Hansen (2018); and Pollard, DeConto & Alley (2018) could be taken together to support the idea that the WAIS could start to exhibit rapid ice mass loss beginning about 2040.  However, in this post I note that these three references all deal with trends rather than with the possible impacts of episodic events and chaotic variability; which could trigger a rapid ice mass loss from the WAIS earlier than 2040.

For example, currently extreme El Nino events occur about every 20-years, with the last such occurrence being the 2015-16 event; which on average would put such another extreme event around 2035-36.  However, the linked article (and associated research) indicates that such extreme events will occur about every 10-years when GMSTA reaches about 1.5C, while Gavin Schmidt projects that GMSTA will be about 1.23C in 2019; which raises the probability that we will experience another extreme El Nino event sometime between 2030 and 2035.  Furthermore, the 2015-16 event resulted in significant amounts of surface ice melting on many West Antarctic ice shelves.  Thus, it is possible that hydrofracturing could lead to a collapse of the Thwaites Glacier residual Ice Tongue and Eastern Ice Shelf between 2031 and 2036.

Title: "‘Extreme’ El Niños to double in frequency under 1.5C of warming, study says"

https://www.carbonbrief.org/extreme-el-ninos-double-frequency-under-one-point-five-celsius-warming-study

Extract: "If global warming reaches 1.5C above pre-industrial levels – the aspirational limit of the Paris Agreement – extreme El Niño events could happen twice as often, the researchers find.

That means seeing an extreme El Niño on average every 10 years, rather every 20 years."

Also, in Replies #242 and #243, I discuss a subglacial lake drainage event beneath the Thwaites Glacier that occurred from June 2013 to January 2014; which may have been triggered by a September 2012 event [see Kim et al (2018)] that resulted in the formation of an abrupt drop in the local surface elevation in the trough shown in the first image by Tinto & Bell and the second and third images by Kim et al. (2018).  The September 2012 event also triggered a surge in the ice flow of the Thwaites Ice Tongue.

Seung Hee Kim, Duk-jin Kim and Hyun-Cheol Kim (2018), "Progressive Degradation of an Ice Rumple in the Thwaites Ice Shelf, Antarctica, as Observed from High-Resolution Digital Elevation Models", Remote Sens, 9, 1236; doi:10.3390/rs1008123

Abstract: "Ice rumples are locally-grounded features of flowing ice shelves, elevated tens of meters above the surrounding surface. These features may significantly impact the dynamics of ice-shelf grounding lines, which are strongly related to shelf stability. In this study, we used TanDEM-X data to construct high-resolution DEMs of the Thwaites ice shelf in West Antarctica from 2011 to 2013. We also generated surface deformation maps which allowed us to detect and monitor the elevation changes of an ice rumple that appeared sometime between the observations of a grounding line of the Thwaites glacier using Double-Differential Interferometric SAR (DDInSAR) in 1996 and 2011. The observed degradation of the ice rumple during 2011–2013 may be related to a loss of contact with the underlying bathymetry caused by the thinning of the ice shelf. We subsequently used a viscoelastic deformation model with a finite spherical pressure source to reproduce the surface expression of the ice rumple. Global optimization allowed us to fit the model to the observed deformation map, producing reasonable estimates of the ice thickness at the center of the pressure source. Our conclusion is that combining the use of multiple high-resolution DEMs and the simple viscoelastic deformation model is feasible for observing and understanding the transient nature of small ice rumples, with implications for monitoring ice shelf stability."

Extract: "…  we monitored the surface features of the ice rumple using Landsat 7 ETM+ images from 2003–2014 (Figure 7). The images in this time series showed a gradual dissipation of the ice rumple, strongly indicating continuous thinning of the Thwaites ice shelf. Furthermore, the disappearance of surface features (e.g., crevasses and surface gradient) from 2013 onwards suggests that the ice shelf has been ungrounded, removing the pressure point that had been maintaining the ice rumple. Nonetheless, the ice shelf might have been in contact with the pinning point even after the disappearance of surface features, as intermittent ice contact to the pinning point could be possible due to ice shelf thickness fluctuations [29].

According to the optimization result, the ice thickness was 711.64 ± 14.25 m and 683.76 ± 12.48 m in 2011 and 2012, respectively. This is quite different from the known ice thickness of the Thwaites ice shelf near the grounding line (~1 km), despite the low vertical resolution of the radar sounder used for such measurements [7]. This indicates a thickness decrease of 36.17 ± 17.27 m during that one-year period. However, as the center of the pressure source in 2012 was located 341.96 m upstream and 210.10 m to the west from that in 2011, it is difficult to substantiate the thickness and thickness change with the obtained datasets. Our results for the surface depression and thinning of the ice rumple in the Thwaites ice shelf were much higher than that previously reported. It is rather surprising to observe such high (>10 m) surface depressions in an ice shelf in such a short time; Rignot et al. [30] and Paolo et al. [14] reported that the thinning rate of the Thwaites ice shelf was 6.13 and 2.80 m/year, respectively. …
From 2011–2013, our deformation maps showed the recent fading of a small ice rumple in the surface of the Thwaites ice shelf, West Antarctica. The pinning point was located nearly 5 km offshore from the previously estimated grounding line in 2011, and appeared sometime between 1996 and 2011 when the grounding line of Thwaites Glacier retreated. The deformation pattern we found, along with a time series of Landsat 7 ETM+ imagery, showed that the ice was still in contact with the basal topography as late as 2013 but is likely to have since been unpinned. We then used the deformation maps with the simple viscoelastic deformation model (widely used in volcanic studies) to interpret the surface changes in terms of pressure changes at the bottom of the ice shelf by applying an idealized spherical pressure source. The estimated numbers were reasonable and the ice shelf thickness at the center of the spherical pressure source was also estimated using the depth and radius. The surface depression and thinning of this ice rumple were found to be much higher than those of previously reported levels for the broader region, …"

Caption for second image: "Figure 1. Grounding lines of Thwaites Glacier in 1996 (green) and 2011 (red) estimated using the DDInSAR method with European remote sensing (ERS) satellites [13,15]. The orange dotted rectangle in the eastern shelf indicates a larger ice rumple previously discussed by Tinto and Bell [7]. A newly generated digital elevation model derived from TanDEM-X data on 10 June 2011 is shown within the yellow rectangle. The small red feature inside the yellow dotted square indicates the smaller ice rumple considered in this study. The background image is the MODIS Mosaic of Antarctica (MOA) image map [16]. The overlaid ice velocity map was extracted from Rignot et al. [17].

Caption for the third image: "Figure 7. Landsat 7 ETM+ images from 2003–2014 showing the gradual disappearance of the studied ice rumple in the Thwaites ice shelf. Crevasses and surface gradients are generally created atop an ice rumple due to surface extension and elevation increase. Such features were visible as late as 2011 but disappeared by 2013, indicating gradual ice thinning. Larger images are magnifications of selected areas indicated by red boxes. The yellow dotted line was extracted from the grounding line of the MEaSUREs dataset [13,15]."

Regarding the possible implications of both event driven events cited previously in this post, if the Thwaites Glacier Ice Tongue and Ice Shelf collapse due to hydrofracturing circa 2031 to 2036 followed by the loss of an ice rumple in the trough identified by Tinto & Bell together with a subglacial lake draining event that drains through the very same trough, this might flush-out any floating icebergs within the trough; which might well move the location of the local grounding line towards the upstream in of the trough where ice cliff failure mechanisms might possibly occur before 2040.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 09, 2018, 11:28:24 PM
My last post focused on potential impacts of events not accounted for by Pollard, DeConto & Alley (2018) ice mass loss projections for Antarctica subjected to Pliocene conditions (which I had previously might occur as early as 2040), on potentially initiating rapid ice mass loss from the WAIS before 2040.  In this post, I briefly cite some initial conditions not assumed by Pollard, DeConto & Alley (2018), that might similarly advance the date for initiating rapid ice mass loss from the WAIS if they were considered in appropriate ice sheet model projections.

The first example is that the AIS may be currently losing more ice mass then is currently being measured even by data such as that reported by Slater & Shepherd (2018) (see the first image); because such ice mass loss data has primarily been gathered by the GRACE satellite; and this data is corrected to account for an assumed amount of glacial isostatic rebound; which may very well result in ice mass lose estimates that err on the side of least drama.  This is relevant because if ice mass is being lost from the AIS faster than expected, then Bronselaer et al (2018)'s projections of ice-climate feedback by 2040 may also err on the side of least drama, and the ocean temperatures at the grounding lines of key Antarctic marine glaciers may well reach Pliocene-levels prior to 2040.

Slater & Shepherd (2018), "Antarctic ice losses tracking high", Nature Climate Change. doi:10.1038/s41558-018-0284-9, https://doi.org/10.1038/s41558-018-0284-9


Extract: "To the Editor — Satellite observations show that ice losses from Antarctica have accelerated over the past 25 years. Since 1992, the continent has contributed 7.6 mm to global sea levels, with 40% of this occurring in the past 5 years. Glaciers draining West Antarctica have retreated, thinned and accelerated due to ocean-driven melting at their termini, and the collapse of ice shelves at the Antarctic Peninsula has led to reduced buttressing and increased ice discharge. Of the 3.2 mm yr−1 sea-level rise (SLR) measured during the satellite era, Antarctica has contributed 0.27 mm yr−1. The magnitude of SLR from Antarctica is the largest source of uncertainty in global sea-level projections, which are key to appropriate climate change policy."

Caption: "Fig. 1 | Observed and predicted SLR due to Antarctica. The global sea-level contribution from Antarctica according to the IMBIE satellite record (shaded envelope indicates 1σ) and IPCC AR5 upper, mid, and lower projections is shown from 1992–2040 (left) and 2040–2100 (right; values on the right-hand side indicate the average sea-level contribution predicted at 2100). Darker coloured lines represent pathways from the five scenarios used in AR5 in order of increasing emissions: RCP2.6, RCP4.5, RCP6.0, SRES A1B and RCP8.5. The circle plot (inset) shows the rate of SLR (in mm yr−1) during the overlap period 2007–2017 (vertical dashed lines). All AR5 projections have been offset by 0.66 ±  0.21 mm (range is 1σ) on average, to make them equal to the observational record at their start date (2007)."

Second, Pollard, DeConto and Alley (2018) assume that for ice-cliff failures to initiate, the cliff-face needs to extend from 90m to 110m above sea level; however, if the ice upstream of the ice face has more crevasses than assumed by Pollard, DeConto and Alley (2018), then ice-cliff failures could occur with lower heights of ice faces.  In this regard the second attached image shows that upstream of the current grounding line of the ice in the Thwaites Glacier threshold, the ice has an unusually large extent of crevassing, due to the bed topology.  Thus locally, ice-cliff failure mechanisms may develop sooner than Pollard, DeConto and Alley (2018) indicate.

Third, the Thwaites Glacier Ice Tongue and Eastern Ice Shelf may be more degraded than assumed in Pollard, DeConto and Alley (2018)'s model.  In this regards, the third image shows a Sentinel 1a image of the Thwaites Glacier Ice Tongue and Eastern Ice Shelf on Dec 8 2018; and while it is subjective, in my opinion it is highly likely that both the Thwaites Ice Tongue and Ice Shelf and the Pine Island Ice Shelf are currently both in more degraded conditions than assumed by Pollard, DeConto and Alley (2018); which indicates that by might break-up sooner than assumed by Pollard, DeConto and Alley (2018).

Finally, I have previously noted that the Beaufort Sea Gyre may well release a major discharge of relatively freshwater into the North Atlantic before 2040 and if so, the Ocean Overturning Current may soon be moving slower than assumed by Pollard, DeConto and Alley (2018), and if so they may well be erring on the side of least drama with regard to the impact of the ocean on grounding line retreat around the AIS.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 10, 2018, 12:24:43 AM
While my last two posts addressed various issues related to the potential initiation of rapid ice mass loss from the AIS; so in this post I briefly touch upon the other primary issue about ice mass loss from the AIS; which is once initiated 'How fast will it proceed".  As Lennart van der Linde states in Reply # 278:

"Thanks for the Rob DeConto presentation of March 30th 2018, ASLR.

From 56m-66m I find particularly interesting, where he talks about (quite arbitrary) speed limits for cliff failure in his model, and stretching these limits in newer versions, as yet unpublished, if I understand correctly. Also atmospheric modelling would seem to slow melt in the first decades (compared to an earlier version), but cliff failure could speed it up more later, it seems from what he says here."


First, regarding Lennart's observation that the Pollard/DeConto AIS model now uses less atmospherically induced surface temperature increases than their earlier work; I believe, that the true value of ECS is actually higher than any of their models have assumed and that masking factors (like anthropogenic aerosols, etc.) have biased their (and most CMIP5 models) projections to err on the side of least drama.  Thus if these various masking factors are reduced (or eliminated) faster than expected by 2040; then the ice mass loss from Antarctica will proceed faster after 2040 than projected by Pollard, DeConto and Alley (2018).

Second, regarding Lennart's observation that ice-cliff failures may occur faster than project by the Pollard/DeConto AIS model indicates, I note that Pollard/DeConto/Alley limited the rate of ice-cliff retreat to the maximum observed for the Jakobshavn Glacier of about 13 km/a (see the first attached image); however:

a. Jakobshavn ice flow is restrained on both sides by the wall of the fjord; while the Thwaites Glacier does not have comparable side restaints.
b. Jakobshavn is currently retreating up a positively sloped ice bed; while the Thwaites Glacier may very soon be retreating down a negatively sloped ice bed.
c. The current height of the Jakobshavn ice face is in the 100 to 120m range, while after a few tens of kilometers of retreat, the ice face for the Thwaites Glacier could be several hundred meters high and with a relative water depth w = D/H (water dept/ice face height) of 0.6 to 0.8; and the second attached image from Schlemm & Levermann (2018) indicates that the actual retreat rate could be well over 60 km/a.

Tanja Schlemm and Anders Levermann (2018), "A simple stress-based cliff-calving law", The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-205

https://www.the-cryosphere-discuss.net/tc-2018-205/tc-2018-205.pdf

Abstract. Over large coastal regions in Greenland and Antarctica the ice sheet calves directly into the ocean. In contrast to ice-shelf calving, an increase in cliff calving directly contributes to sea-level rise and a monotonously increasing calving rate with ice thickness can constitute a self-amplifying ice loss mechanism that may significantly alter sea-level projections both of Greenland and Antarctica. Here we seek to derive a minimalistic stress-based parameterization for cliff calving. To this end we compute the stress field for a glacier with a simplified two-dimensional geometry from the two-dimensional Stokes equation. First we assume a constant yield stress to derive the failure region at the glacier front from the stress field within the ice sheet. Secondly, we assume a constant response time of ice failure due to exceedance of the yield stress. With this strongly constraining but very simple set of assumption we propose a cliff-calving law where the calving rate follows a power-law dependence on the freeboard of the ice with exponents between 2 and 3 depending on the relative water depth at the calving front. The critical freeboard below which the ice front is stable decreases with increasing relative water depth of the calving front. For a dry water front it is, for example, 75m. The purpose of this study is not to provide a comprehensive calving law, but to derive a particularly simple equation with a transparent and minimalistic set of assumptions.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: sidd on December 10, 2018, 05:21:47 AM
Re: "Jakobshavn is currently retreating up a positively sloped ice bed"

Wait, what ? There's a big hole behind the current grounding line ...

sidd
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: SteveMDFP on December 10, 2018, 03:33:56 PM
I thought this was a rather good popular press article about Thwaites, who studies it and how, and potential risks for civilization:

THE RACE TO UNDERSTAND ANTARCTICA’S MOST TERRIFYING GLACIER
https://www.wired.com/story/antarctica-thwaites-glacier-breaking-point/ (https://www.wired.com/story/antarctica-thwaites-glacier-breaking-point/)

It actually explains matters such as the implications of a retrograde glacier bed geometry, ice-cliff failure, and the proposal to construct an artificial sill, among other concepts that have been raised here.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 10, 2018, 04:36:02 PM
Re: "Jakobshavn is currently retreating up a positively sloped ice bed"

Wait, what ? There's a big hole behind the current grounding line ...

sidd

As you point out yourself the grounding line has not yet reached the retrograde slope, thus the measured rate of retreat of the Jakobshavn grounding line of 13 km/yr (per averaged calving event) only includes its retreat up the positive slope of the ice bed.

Edit: I further note that as the Jakobshavn calving face can advance by about 12 km/yr, the actual net retreat of the Jakobshavn grounding line is only about 1 km/yr.

Edit2: The attached image makes it clearer that the Jakobshavn calving face (issued 2017) is still climbing a positive bed slope.  But perhaps sidd's point is that after this calving face retreats down the retrograde (negative) bed slope, then Pollard, DeConto and Alley can take new measurements of the average rate of calving face retreat per year and then update their model projections with rates above their current maximum assumed rate of retreat of 13 km/yr.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 10, 2018, 05:24:30 PM
If the rate of potential collapse of the WAIS is relatively fast (once initiated) then within a few decades (say starting 2060) potential new seaways through the WAIS may become increasingly important (see the linked reference and attached image):

David G. Vaughan et al. (07 October 2011), "Potential seaways across West Antarctica", Geochemistry, Geophysics, Geosystems, https://doi.org/10.1029/2011GC003688

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2011GC003688

Abstract
The West Antarctic ice sheet (WAIS) has long been considered vulnerable to rapid retreat and today parts are rapidly losing ice. Projection of future change in WAIS is, however, hampered by our poor understanding of past changes, especially during interglacial periods that could be analogs for the future, but which undoubtedly provide an opportunity for testing predictive models. We consider how ice‐loss would open seaways across WAIS; these would likely alter Southern Ocean circulation and climate, and would broadly define the de‐glacial state, but they may also have left evidence of their existence in the coastal seas they once connected. We show the most likely routes for such seaways, and that a direct seaway between Weddell and Ross seas, which did not pass through the Amundsen Sea sector, is unlikely. Continued ice‐loss at present rates would open seaways between Amundsen and Weddell seas (A‐W), and Amundsen and Bellingshausen seas (A‐B), in around one thousand years. This timescale indicates potential future vulnerability, but also suggests seaways may have opened in recent interglacial periods. We attempt to test this hypothesis using contemporary bryozoan species assemblages around Antarctica, concluding that anomalously high similarity in assemblages in the Weddell and Amundsen seas supports recent migration through A‐W. Other authors have suggested opening of seaways last occurred during Marine Isotope Stage 7a (209 ka BP), but we conclude that opening could have occurred in MIS 5e (100 ka BP) when Antarctica was warmer than present and likely contributed to global sea levels higher than today.

Caption: "Figure 1. Map of Antarctica (with inset of West Antarctica) showing the thickness of ice that would need to be removed before flotation would occur, calculated assuming an ice‐density of 910 kg m−3,seawater‐density of 1030 kg m−3, a satellite‐ derived ice‐surface elevation model [Bamber et al., 2009a] and sub‐glacial bed elevation [Le Brocq et al., 2010] supplemented with unpublished data collected inland of Eltanin Bay in 2009/10. Elevationsreferenced to the EIGEN‐GL04c geoid and current sea level. The labeled sections, defining our hypothesized seaways,were chosen as the routes requiring least ice loss. The location of Up‐ B is shown according to the position given by Whillans et al. [1987]."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 10, 2018, 05:46:55 PM
For those who want to know more about the International Thwaites Glacier Collaboration's field investigation program, I provide the following linked website and the associated attached image:

Title: "The International Thwaites Glacier Collaboration"

https://thwaitesglacier.org/projects

Extract: "Disintegration of Marine Ice-sheets Using Novel Optimised Simulations
Acronym/nickname
DOMINOS

 Projected rates of sea level rise from the West Antarctic Ice Sheet (and Thwaites Glacier in particular) have large uncertainties due to difficulties in understanding and projecting the calving and dynamic processes that control the ice sheet stability. This uncertainty is magnified by the poorly understood connection between calving processes, ice sheet stability and climate. To address these uncertainties, our proposal seeks to explicitly resolve the processes that could cause retreat and collapse of Thwaites Glacier using a novel ice-dynamics model suite. This model suite includes a discrete element model capable of simulating coupled fracture and ice-flow processes, a 3D full Stokes continuum model, and the continental scale ice-dynamics model BISICLES. Ice dynamics models will be coupled to an ocean forcing model suite including simple plume models, intermediate complexity 2-layer ocean models and fully 3D regional ocean models. This hierarchical approach will use high-fidelity process models to inform and constrain the sequence of lower-order models needed to extrapolate improved understanding to larger scales and has the potential to radically reduce uncertainty of rates of marine ice sheet collapse and associated sea level rise. The large-scale modeling approach will be tested and implemented within the open source BISICLES ice dynamics model and made publicly available to other researchers via a “calving package.”
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 10, 2018, 06:55:25 PM
If the WAIS were to collapse abruptly it would produce an armada of icebergs from the WAIS in the Southern Ocean that would last for decades.  I note that debris fields in Drake Passage have shown that during Meltwater Pulse 1A (with different conditions than today) such iceberg armadas did exist and circled around the Southern Ocean.  The attached image shows how the iceberg rafted debris mechanism works:

Weber, M. E., Clark, P. U., Kuhn, G., Timmermann, A., Sprenk, D., Gladstone, R., … Ohlwein, C. (2014). Millennial-scale variability in Antarctic ice-sheet discharge during the last deglaciation. Nature, 510(7503), 134–138. doi:10.1038/nature13397

http://www.nature.com/nature/journal/v510/n7503/abs/nature13397.html

Abstract: "Our understanding of the deglacial evolution of the Antarctic Ice Sheet(AIS) following the Last Glacial Maximum (26,000–19,000years ago) is based largely on a few well-dated but temporally and geographically restricted terrestrial and shallow-marine sequences. This sparseness limits our understanding of the dominant feedbacks between the AIS, Southern Hemisphere climate and global sea level. Marine records of iceberg-rafted debris (IBRD) provide an early continuous signal of ice-sheet dynamics and variability. IBRD records from the North Atlantic Ocean have been widely used to reconstruct variability in Northern Hemisphere ice sheets, but comparable records from the Southern Ocean of the AIS are lacking because of the low resolution and large dating uncertainties in existing sediment cores. Here we present two well-dated, high-resolution IBRD records that capture a spatially integrated signal of AIS variability during the last deglaciation. We document eight events of increased iceberg flux from various parts of the AIS between 20,000 and 9,000 years ago, in marked contrast to previous scenarios which identified the main AIS retreat as occurring after meltwater pulse 1A and continuing into the late Holocene epoch. The highest IBRD flux occurred 14,600 years ago, providing the first direct evidence for an Antarctic contribution to meltwater pulse 1A. Climate model simulations with AIS freshwater forcing identify a positive feedback between poleward transport of Circumpolar Deep Water, subsurface warming and AIS melt, suggesting that small perturbations to the ice sheet can be substantially enhanced, providing a possible mechanism for rapid sea-level rise."

See also the research published in Nature Communications showing that current Southern Ocean waters are becoming more layered with cold water on top and warm water below; which promotes ice melting near the grounding lines of Antarctic marine glaciers, as occurred 14,000 years ago during the Meltwater Pulse 1A.  This clearly indicates an increasing risk of multiple meters of SLR this century:

http://www.sciencecodex.com/changing_antarctic_waters_could_trigger_steep_rise_in_sea_levels-142713

Extract: "The research published in Nature Communications found that in the past, when ocean temperatures around Antarctica became more layered - with a warm layer of water below a cold surface layer - ice sheets and glaciers melted much faster than when the cool and warm layers mixed more easily.

This defined layering of temperatures is exactly what is happening now around the Antarctic.
"The reason for the layering is that global warming in parts of Antarctica is causing land-based ice to melt, adding massive amounts of freshwater to the ocean surface," said ARC Centre of Excellence for Climate System Science researcher Prof Matthew England an author of the paper.
"At the same time as the surface is cooling, the deeper ocean is warming, which has already accelerated the decline of glaciers on Pine Island and Totten. It appears global warming is replicating conditions that, in the past, triggered significant shifts in the stability of the Antarctic ice sheet.""
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: gerontocrat on December 10, 2018, 07:38:55 PM

This defined layering of temperatures is exactly what is happening now around the Antarctic.
"The reason for the layering is that global warming in parts of Antarctica is causing land-based ice to melt, adding massive amounts of freshwater to the ocean surface," said ARC Centre of Excellence for Climate System Science researcher Prof Matthew England an author of the paper.
"At the same time as the surface is cooling, the deeper ocean is warming, which has already accelerated the decline of glaciers on Pine Island and Totten. It appears global warming is replicating conditions that, in the past, triggered significant shifts in the stability of the Antarctic ice sheet.""

There is a consistent narrative -

AGW is causing land-based ice to melt faster, adding massive additional amounts of freshwater to the ocean surface.

You would think that cold surface water (also low salinity with a higher freezing temperature) would encourage sea ice freeze as winter approaches and discourage sea ice melt as summer commences. Since 1979 up to recently, there has been a slow but measurable increase in Antarctic sea ice extent (maximum extent in 2014). Hypothesis confirmed.

BUT since then the opposite. Antarctic sea ice extent is in decline, not just at max and min but during the melt season. Temporary aberration? Or is something  extra going on?
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 10, 2018, 07:49:45 PM
The linked reference provides paleo data (from the past 360,000 years) that the ENSO assumes a La Nina like pattern during glacial periods and assumes an El Nino like pattern during rapidly changing portions of interglacial periods.  As we are in the most rapidly changing interglacial period on record, this is not good news (as El Nino like Earth System patterns can result in effective ECS values in the range of 5C):

Zhang, S., Li, T., Chang, F. et al. Chin. J. (2017), "Correspondence between the ENSO-like state and glacial-interglacial condition during the past 360 kyr", Ocean. Limnol., 35: 1018. https://doi.org/10.1007/s00343-017-6082-9

https://link.springer.com/article/10.1007/s00343-017-6082-9#citeas

Abstract: "In the warming world, tropical Pacific sea surface temperature (SST) variation has received considerable attention because of its enormous influence on global climate change, particularly the El Niño-Southern Oscillation process. Here, we provide new high-resolution proxy records of the magnesium/calcium ratio and the oxygen isotope in foraminifera from a core on the Ontong-Java Plateau to reconstruct the SST and hydrological variation in the center of the Western Pacific Warm Pool (WPWP) over the last 360 000 years. In comparison with other Mg/Ca-derived SST and δ18O records, the results suggested that in a relatively stable condition, e.g., the last glacial maximum (LGM) and other glacial periods, the tropical Pacific would adopt a La Niña-like state, and the Walker and Hadley cycles would be synchronously enhanced. Conversely, El Niño-like conditions could have occurred in the tropical Pacific during fast changing periods, e.g., the termination and rapidly cooling stages of interglacial periods. In the light of the sensitivity of the Eastern Pacific Cold Tongue (EPCT) and the inertia of the WPWP, we hypothesize an inter-restricted relationship between the WPWP and EPCT, which could control the zonal gradient variation of SST and affect climate change."

Extract: "Previous research has discussed super-ENSO events in interglacial periods (Beaufort et al., 2001; Rincón-Martínez et al., 2010; Zhang et al., 2015). Nevertheless, interglacial periods defined by marine isotopes are not consistent with SST variations in the tropical Pacific (Fig.4), i.e., tropical SSTs during such periods are not as stable as in glacial periods. The real warm time in an interglacial period generally persists for 10–30 kyr, and it is always combined with a subsequent cooling process that involves a sequence of global fluctuations. Accordingly, an interglacial period should not be regarded as a single entity, as discussed in previous studies."

Edit: I think that this paper is important and verifies the ice-climate feedback mechanism associated with the ENSO cycles, and may explain how the Eemain got a double bump in sea level rise.  The attached image is Figure 4 from Zhang et al. (2017).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 10, 2018, 08:43:42 PM
The linked reference provides a mathematical framework for modeling cascading tipping mechanisms resulting in abrupt climate change; and as an illustration of this methodology it provides a conceptual model for coupling the North Atlantic Ocean Overturning Current and the ENSO system in the Pacific.  Consensus climate science should use such a methodology to better evaluate the risks associated with Hansen's ice-climate feedback mechanism:

Dekker, M. M., von der Heydt, A. S., and Dijkstra, H. A.: Cascading transitions in the climate system, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-26, 2018.

https://www.earth-syst-dynam-discuss.net/esd-2018-26/
https://www.earth-syst-dynam.net/9/1243/2018/esd-9-1243-2018.pdf

Abstract. We provide a theory of cascading tipping, i.e., a sequence of abrupt transitions occurring because a transition in one subsystem changes the background conditions for another subsystem. A mathematical framework of elementary deterministic cascading tipping points in autonomous dynamical systems is presented containing the double-fold, fold-Hopf, Hopf-fold and double-Hopf as most generic cases. Statistical indicators which can be used as early warning indicators of cascading tipping events in stochastic, non-stationary systems are suggested. The concept of cascading tipping is illustrated through a conceptual model of the coupled North Atlantic Ocean – El-Niño Southern Oscillation (ENSO) system, demonstrating the possibility of such cascading events in the climate system.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 10, 2018, 10:11:20 PM
...
You would think that cold surface water (also low salinity with a higher freezing temperature) would encourage sea ice freeze as winter approaches and discourage sea ice melt as summer commences. Since 1979 up to recently, there has been a slow but measurable increase in Antarctic sea ice extent (maximum extent in 2014). Hypothesis confirmed.

BUT since then the opposite. Antarctic sea ice extent is in decline, not just at max and min but during the melt season. Temporary aberration? Or is something  extra going on?
The ice-climate feedback mechanism is not dependent on the presences of Antarctic sea ice, as the linked reference and associated image show that this feedback mechanism works with low salinity surface water (and/or sea ice) along the Antarctic coastline:

Bronselaer, B. et al. (2018) Change in future climate due to Antarctic meltwater, Nature, doi:s41586-018-0712-z

https://www.nature.com/articles/s41586-018-0712-z

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wdmn on December 11, 2018, 02:11:35 AM
I just posted this in the "modelling the Anthropocene thread," but seems to fit here also (and I'm curious to hear your response ASLR).

New study published today: Pliocene and Eocene provide best analogs for near-future climatesmates https://www.pnas.org/content/early/2018/12/05/1809600115 (https://www.pnas.org/content/early/2018/12/05/1809600115).

Quote
Abstract
Past Earth system states offer possible model systems for the warming world of the coming decades. These include the climate states of the Early Eocene (ca. 50 Ma), the Mid-Pliocene (3.3–3.0 Ma), the Last Interglacial (129–116 ka), the Mid-Holocene (6 ka), preindustrial (ca. 1850 CE), and the 20th century. Here, we quantitatively assess the similarity of future projected climate states to these six geohistorical benchmarks using simulations from the Hadley Centre Coupled Model Version 3 (HadCM3), the Goddard Institute for Space Studies Model E2-R (GISS), and the Community Climate System Model, Versions 3 and 4 (CCSM) Earth system models. Under the Representative Concentration Pathway 8.5 (RCP8.5) emission scenario, by 2030 CE, future climates most closely resemble Mid-Pliocene climates, and by 2150 CE, they most closely resemble Eocene climates. Under RCP4.5, climate stabilizes at Pliocene-like conditions by 2040 CE. Pliocene-like and Eocene-like climates emerge first in continental interiors and then expand outward. Geologically novel climates are uncommon in RCP4.5 (<1%) but reach 8.7% of the globe under RCP8.5, characterized by high temperatures and precipitation. Hence, RCP4.5 is roughly equivalent to stabilizing at Pliocene-like climates, while unmitigated emission trajectories, such as RCP8.5, are similar to reversing millions of years of long-term cooling on the scale of a few human generations. Both the emergence of geologically novel climates and the rapid reversion to Eocene-like climates may be outside the range of evolutionary adaptive capacity.

graph source: Bob Kopp @bobkopp
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wdmn on December 11, 2018, 02:21:09 AM
More Glaciers in East Antarctica Are Waking Up https://www.nasa.gov/feature/goddard/2018/more-glaciers-in-antarctica-are-waking-up (https://www.nasa.gov/feature/goddard/2018/more-glaciers-in-antarctica-are-waking-up)

Quote
East Antarctica has the potential to reshape coastlines around the world through sea level rise, but scientists have long considered it more stable than its neighbor, West Antarctica. Now, new detailed NASA maps of ice velocity and elevation show that a group of glaciers spanning one-eighth of East Antarctica’s coast have begun to lose ice over the past decade, hinting at widespread changes in the ocean.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 11, 2018, 07:35:49 PM
I just posted this in the "modelling the Anthropocene thread," but seems to fit here also (and I'm curious to hear your response ASLR).

New study published today: Pliocene and Eocene provide best analogs for near-future climatesmates https://www.pnas.org/content/early/2018/12/05/1809600115 (https://www.pnas.org/content/early/2018/12/05/1809600115).

wdmn,

Thanks for you post about Burke et al (2018), which indicate that the Pliocene and Eocene provide the best analogs for near-future climates (see the first attached image of Figure 4 from that reference).

K. D. Burke, J. W. Williams, M. A. Chandler, A. M. Haywood, D. J. Lunt, and B. L. Otto-Bliesner (December 10, 2018), "Pliocene and Eocene provide best analogs for near-future climates", PNAS, https://doi.org/10.1073/pnas.1809600115

See also the supplemental material at:
https://www.pnas.org/content/suppl/2018/12/06/1809600115.DCSupplemental

Regarding my thoughts, I have both positive and negative opinions including the following:

Regarding positive thoughts:
a) It is valuable to nudge both the public and decision makers to better appreciate the seriousness of our situation and this paper provides such a valuable nudge.
b) I think that the statement that we will likely reach Mid-Pliocene surface conditions (beginning in the middle of continents) by 2030 is the most accurate and valuable, and it supports the position in many of my posts in this thread that it is appropriate to take the Pollard, DeConto and Alley (2018) for instant Mid-Pliocene conditions in Antarctica as beginning by (or before) 2040.

Regarding my negative thoughts:
a) I do not believe that any of the models cited use freshwater hosing appropriate to simulate ice-climate feedback mechanisms (as least that is the case when they were run for CMIP5), and the second image from Brown & Caldeira (2017) shows that the CMIP5 model projections likely underestimate ECS (with the higher ECS now being unmasked due to reduced SO2 emissions). However, this is more of a short-coming for projections after 2040.
b) The risks thru at least 2070 that Burke et al (2018) are ignoring by not accounting for ice-climate feedbacks can be approximated by the gold/orange curve in the third attached image from Hansen et al (2016).  Unfortunately, Hansen used a model of intermediate complexity with an ECS of about 3C and thus returned to this level of climate sensitivity after about 2080 (when the perturbation from the abrupt ice mass ends).
c) However, the fourth image from Zhang et al (2017), makes it clear that for the Early Eemian (or LIG) circa 129kya, the perturbation of abrupt ice mass loss prior to that time (i.e. before 129kya) cause a period of at least 20,000 years (see Reply #332) with frequent El Nino activity which is indicative of higher values of ECS (say at least 4.5C).
d) Paleo-radiative forcings all occurred many times slower than during modern times so it is likely that all comparisons of the near-term future to paleo cases all err on the side of least drama.

Best,
ASLR

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 11, 2018, 07:59:18 PM
As a follow-on to my last post (#337), as to why Hansen et al (2016) intermediate ESM projections of ice-climate interaction dampen-out rapidly after circa 2080 (for the orange curves) I briefly note that:

a. The first image shows that currently Arctic Amplification is increasing much faster than Antarctic Amplification, and I suspect that Hansen et al (2016)'s model simulates this response into the near-term future.

b. However, most of the suppression of the rate of increase of Antarctic Amplification is due to the relatively high surface elevations of both the WAIS and the EAIS, while after a WAIS collapse (with the associated slow-down of the Overturning Current) both the surface elevation of most of the WAIS would be near sea level and the strong El Nino activity from the slow-down of the Overturning Current would continue to telecommunicate heat from the Tropical Pacific directly to West Antarctica  (the second image shows how a collapse of only the ASE marine glaciers would suppress Antarctic Bottom Water, AABW (which helps drive the Overturning Circulation current), formation for hundreds of years.

c. Also, the third image (from the following linked website) shows the location of AABW formation around Antarctica, which indicates that a collapse of the WAIS would suppress AABW formation both in the Ross and the Weddell Seas.  Furthermore, the fourth image (also from the following linked website) shows the areas of high Antarctic Sea Ice formation, & which indicates that both the Ross and the Weddell Sea regions currently produce relatively large amounts of Antarctic Sea Ice, which would be suppressed after the collapse of the WAIS [which might contribute to a slow transition to a La Nina dominated period by the Mid-Eemian (Mid-LIG)].

In my opinion these considerations help to illustrate how the nominally 20,000 year period of high frequency El Nino events occurred in the early Eemian (early LIG); while this is not indicated by Hansen et al (2016)'s model projections.

Website title: "Polar Oceanography"

http://wwwoa.ees.hokudai.ac.jp/research/polar_e.html

Caption for the third image: "The amount of Antarctic bottom water generated governs the relative strength of global deep ocean circulation. The Weddell and Ross Seas are well known regions of Antarctic bottom water formation, but in recent years it has emerged that the waters off Adelie Land in the vicinity of East 140 degrees Longitude is also an important region for bottom water generation"

Caption for the fourth image: "Mapping of annual quantity survey of sea ice production levels in Antarctic Sea (converted in thickness). & Extract of associated text: The below figure illustrates the first spatial distribution (mapping) of annual sea ice production levels in the Antarctic by combining satellite data and site survey and meteorological data. The body of water with the highest sea ice production is the Ross Sea, which corresponds well with this area being the production area of the Antarctic bottom water with the highest salinity. It is also understood that second to the Ross Sea, the region of highest sea ice production is approximately 1200 km East of Japan's Showa South Pole Base. It has been suggested that this may be an undiscovered Antarctic bottom water generation region, so intensive observation began in 2008 to confirm this possibility."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 11, 2018, 08:30:49 PM
As a follow-on to my last post, as to why Hansen et al (2016)'s model projections many not fully simulate the longer term impacts of a potential abrupt collapse of the WAIS beginning circa 2040, I also note that:

a. The first image shows projections from an ESM indicating that with continued BAU radiative forcing (here labeled A2), that a warm pulse of North Atlantic water would enter the Arctic Ocean Basin and rapidly reduce Arctic Sea Ice Extents, ASIE, and I note that models including freshwater hosing from an abrupt collapse of the WAIS indicate that this rapid loss of ASIE could happen in as little as 5-years after the collapse of the ASE marine glaciers.

b. The second image shows that the synergist telecommunication of warm evaporation from the Tropical Atlantic to the Tropical Pacific is strongest during periods of rising CO2 emissions, and I highly doubt that Hansen et al (2016)'s model simulated this positive forcing bipolar seesaw mechanism.

c. The third image shows how large radiative forcing from accelerated CH4 emissions (direct, indirect and from associated O3, Strat. H2O and CO2) for the indicated cases, and I note that methane emissions from the Arctic permafrost regions could accelerate rapidly with a collapse of the WAIS due to such sources as Thermokarst Lakes and increase rainfall in the Arctic.

d. The fourth image shows paleo data that ESS (Earth System Sensitivity) increased up to 7C during the Pliocene (presumably over several thousand years); and with our current radiative forcing occurring at a rate of about 100 times fast than that during the PETM, who knows how fast we might ratchet up (due to a cascade of positive feedback tipping points) from ECS to ESS conditions.

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 11, 2018, 10:26:53 PM
More Glaciers in East Antarctica Are Waking Up https://www.nasa.gov/feature/goddard/2018/more-glaciers-in-antarctica-are-waking-up (https://www.nasa.gov/feature/goddard/2018/more-glaciers-in-antarctica-are-waking-up)
...

wdmn,

I concur that ice mass loss from the EAIS is of concern, and is included in Pollard, DeConto and Alley (2018)'s projections for Pliocene conditions (which we are likely to reach by 2040).  However, the old questions of 'how soon?' and 'how fast?' always get asked by decision makers.  In this regards:

A. The first image from Sweet et al (2017) show that after several millennia of Pliocene conditions mean global sea level might rise by as much as 30m (most of which would come from the GIS, the WAIS and the EAIS); and the second image from the same source shows a US government recommended upper bound of 2.5 m of global mean sea level rise by 2100 (including from all sources including the EAIS).

Sweet, W.V., R. Horton, R.E. Kopp, A.N. LeGrande, and A. Romanou, 2017: Sea level rise. In: Climate Science Special Report: Fourth National Climate Assessment, Volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 333-363, doi: 10.7930/J0VM49F2.

https://science2017.globalchange.gov/downloads/CSSR_Ch12_Sea_Level_Rise.pdf

Caption for the first image: "Figure 12.2: (a) The relationship between peak global mean temperature, atmospheric CO2, maximum global mean sea level (GMSL), and source(s) of meltwater for two periods in the past with global mean temperature comparable to or warmer than present. Light blue shading indicates uncertainty of GMSL maximum. Red pie charts over Greenland and Antarctica denote fraction, not location, of ice retreat. Atmospheric CO2 levels in 2100 are shown under RCP8.5. (b) GMSL rise from −500 to 1900 CE, from Kopp et al.’s geological and tide gauge-based reconstruction (blue), from 1900 to 2010 from Hay et al.’s tide gauge-based reconstruction (black), and from 1992 to 2015 from the satellite-based reconstruction updated from Nerem et al. (magenta). (Figure source: (a) adapted from Dutton et al. 2015 and (b) Sweet et al. 2017).

Caption for the second image: "Figure 12.4: (a) Global mean sea level (GMSL) rise from 1800 to 2100, based on Figure 12.2b from 1800 to 2015, the six Interagency GMSL scenarios (navy blue, royal blue, cyan, green, orange, and red curves), the very likely ranges in 2100 for different RCPs (colored boxes), and lines augmenting the very likely ranges by the difference between the median Antarctic contribution of Kopp et al. and the various median Antarctic projections of DeConto and Pollard. (b) Relative sea level (RSL) rise (feet) in 2100 projected for the Interagency Intermediate Scenario (1-meter [3.3 feet] GMSL rise by 2100) (Figure source: Sweet et al. 2017)."

See also:
Sweet, W.V., R.E. Kopp, C.P. Weaver, J. Obeysekera, R.M. Horton, E.R. Thieler, and C. Zervas, 2017: Global and Regional Sea Level Rise Scenarios for the United States. National Oceanic and Atmospheric Administration, National Ocean Service, Silver Spring, MD. 75 pp. https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf

B. The third image, from Wilson et al (2018) shows the extent of ice loss from the Wilkes Basin after several millennia of Pleistocene conditions for different assumptions

Wilson, D. J., Bertram, R. A., Needham, E. F., van de Flierdt, T., Welsh, K. J., McKay, R. M., … Escutia, C. (2018). Ice loss from the East Antarctic Ice Sheet during late Pleistocene interglacials. Nature. doi:10.1038/s41586-018-0501-8

https://www.nature.com/articles/s41586-018-0501-8

Abstract: "Understanding ice sheet behaviour in the geological past is essential for evaluating the role of the cryosphere in the climate system and for projecting rates and magnitudes of sea level rise in future warming scenarios. Although both geological data and ice sheet models indicate that marine-based sectors of the East Antarctic Ice Sheet were unstable during Pliocene warm intervals, the ice sheet dynamics during late Pleistocene interglacial intervals are highly uncertain. Here we provide evidence from marine sedimentological and geochemical records for ice margin retreat or thinning in the vicinity of the Wilkes Subglacial Basin of East Antarctica during warm late Pleistocene interglacial intervals. The most extreme changes in sediment provenance, recording changes in the locus of glacial erosion, occurred during marine isotope stages, when Antarctic air temperatures were at least two degrees Celsius warmer than pre-industrial temperatures for 2,500 years or more. Hence, our study indicates a close link between extended Antarctic warmth and ice loss from the Wilkes Subglacial Basin, providing ice-proximal data to support a contribution to sea level from a reduced East Antarctic Ice Sheet during warm interglacial intervals. While the behaviour of other regions of the East Antarctic Ice Sheet remains to be assessed, it appears that modest future warming may be sufficient to cause ice loss from the Wilkes Subglacial Basin."

Extract: "The key finding from our new data set is that the Wilkes Subglacial Basin has been susceptible to ice loss not only during warm Pliocene intervals [Ref. 5] with CO2 levels of approximately 400 p.p.m., but also during the late Pleistocene despite CO2 levels [Ref. 25] remaining below 300 p.p.m. Hence, we provide data-based evidence in support of recent ice sheet models that simulate margin retreat and ice loss during late Pleistocene interglacials [Refs. 2,3,9] (Fig. 1b)"

"Based on the ice sheet response during past interglacial periods, we estimate that substantial ice loss within the Wilkes Subglacial Basin would be likely to occur with approximately 2 °C warming (above pre-industrial) if sustained for a few millennia."

Caption for the third image: "Fig. 1 | Setting of IODP Site U1361 offshore of the Wilkes Subglacial Basin. a, Map of Antarctica showing subglacial bedrock elevation above sea level12,31 and the U1361A coring location. b, Detailed map of the Wilkes Subglacial Basin, with lines illustrating positions of the ice sheet margin in different ice sheet models and scenarios: red dashed line, fully retreated state of Mengel and Levermann under 1.8 °C ocean warming; black dashed line, maximum simulated MIS 5e retreat of DeConto and Pollard, equivalent to approximately 2 °C ocean and atmospheric warming; and modelled retreat of Golledge et al. for both 2 °C ocean and atmospheric warming (ochre dotted line) and 4 °C ocean and atmospheric warming (white dotted line). C, N, and M indicate positions of Cook, Ninnis, and Mertz ice shelves, respectively."

C. The fourth image from: A dynamic early East Antarctic Ice Sheet suggested by ice-covered fjord landscapes by Young et al, 2011, doi:10.1038/nature10114; show where the Aurora Subglacial Basin (ASB) is located and how its bottom topology feed basal meltwater down towards the Totten Glacier (whose catchment basin forms a major part of the ASB), which could serve to accelerate the ice mass loss from this area.  Furthermore, the Young et al 2011 paper notes that the Aurora Basin contains several paleo-fjords; which, indicate that in the past the EAIS had on at least two occasions retreated into this subglacial basin.  This clearly raises concerns about the potential SLR contributions from this area (including the Totten and Moscow University Ice Shelf areas) during this century.

Best,
ASLR
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 11, 2018, 10:39:32 PM
As a follow-on to my last post, I provide the four attached images that show:

1. The location and 2008-2009 ice velocities of key marine glaciers around Antarctica.

2. The location of the Totten Basin.

3. The ocean upwelling of CDW that is currently impacting ice mass loss from the Totten Glacier.

4. The 'ice plug' (or the ice that must be lost before either MISI or MICI occurs) for the Wilkes Basin; and which is similar to most other key Antarctic marine glaciers.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 11, 2018, 11:48:36 PM
As a follow-on to my last two posts, I note that:

1. The first image [from Wilson et al (2018)], highlights that the sea level rise during MIS 11 (the Holsteinian) was higher (6 to 13m) than for MIS5 (the Eemian, 6 to 9m), even though its radiative forcing and Antarctic temperature increase were both less than for MIS 5.  As no current ESM projection can match the sensitivity of MIS 11, this is an indication that all reported projections err on the side of least drama.

Wilson, D. J., Bertram, R. A., Needham, E. F., van de Flierdt, T., Welsh, K. J., McKay, R. M., … Escutia, C. (2018). Ice loss from the East Antarctic Ice Sheet during late Pleistocene interglacials. Nature. doi:10.1038/s41586-018-0501-8

https://www.nature.com/articles/s41586-018-0501-8

Caption for the first attached image: "Fig. 3 | Comparison of U1361A records to regional palaeoclimate and global sea level records. a, Antarctic ice core temperature difference (ΔT, difference from mean values of the last millennium) derived from deuterium isotopes at EPICA Dome C (EDC)11 plotted on EDC3 age scale. bp, before present. b, Southern Ocean bottom water temperature (BWT) from Mg/Ca at Ocean Drilling Program (ODP) Site 1123 (ref. 18).  c, Southern Ocean sea surface temperature (SST) from alkenones at ODP Site 1090 (ref. 19). d, Ba/Al ratios (XRF-scanner counts; three-point smoothed) in U1361A. e, Bulk detrital sediment Nd isotopes in U1361A (error bars are 2 s.d. external reproducibility). f, Sea level proxy from benthic oxygen isotopes28, labelled with MIS numbers and sea level estimates17 from MIS 5e and MIS 11. Shading in a–c, f represents intervals with values above modern (or late Holocene core top); red dashed line in e indicates the core top εNd value of U1361A. For chronostratigraphic constraints on U1361A, see Supplementary Table 8 and Methods."

2. The second image [from Weber et al (2014)] shows that an iceberg armada from the ASE (Amundsen Sea Embayment, say from 2040 to 2060) would be initially carried eastward by the Antarctic Coastal Current where it would provide meltwater that would disrupt AABW formation in East Antarctica until it was kicked northward in 'Iceberg Alley' in the Weddell Sea, into the ACC stream.  This parallels the scenario modeled by Fogwill et al with a figure showing impact on AABW formation in my Reply #338.

3. The third image shows the findings of a field survey of the Recovery Ice Stream, indicating the presences of subglacial lakes that could well accelerate ice mass loss from this EAIS glacier beyond that indicated by Pollard, DeConto and Alley (2018) for Pliocene conditions. The linked article talks about the IceBridge mission to investigate the Recovery Glacier area from which the third image was taken:

http://blogs.ei.columbia.edu/2012/10/29/a-recovery-mission/

Also, I note that almost all other key Antarctic marine glacier have extensive systems of subglacial lakes and streams that could accelerate ice flow in the near-term future with continued global warming.

4.  The fourth image shows the location of key gyres around Antarctica including the 'Unnamed Gyre' that is probably driving upwelling of warm CDW towards the grounding line of Totten Glacier (and thus likely which is accelerating ice mass loss from this key EAIS marine glacier beyond that accounted for in any model that I know of).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wdmn on December 12, 2018, 08:19:48 AM
Many thanks ASLR. I have to read your posts very slowly and several times to begin to understand. The amount of work you put into them is greatly appreciated.

It's hard to reconcile mid-Pliocene conditions beginning around 2030 with the IPCC report.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2018, 07:30:20 PM
...

It's hard to reconcile mid-Pliocene conditions beginning around 2030 with the IPCC report.

Not to repeat myself, but per the linked Gavin Schmidt tweeter thread, for a 20yr loess trend line Gavin is predicting that the GMSTA in 2019 will be 1.2+/-0.15C (see the first attached image) or 1.23C for a 15yr loess trend line (see the extract below).  I note that this prediction is in line with Hansen's prediction that I cited in Reply #220 and as is indicated by the second attached image.  So if one takes Gavin's estimate of +1.23C by the end of 2019 together with Hansen's value of 0.38C/decade one gets GMSTAs of +1.61C by 2030 and +1.99C by 2040 (note in most of my posts I take 2040 as the date when conditions for key West Antarctic marine glaciers reaching Mid-Pliocene oceanic and atmospheric conditions).

https://twitter.com/ClimateOfGavin/status/1068336654887337984

Extract: "ENSO forecast for DJF here: https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/ … (I used 1±0.6 (95% CI)). Note there is also some dependence on the smoothing; predictions for 2019 would be 1.23 or 1.17 using a 15yr or 30yr loess smooth....1.2±0.15 ºC above the late 19th C. A warmer yr than 2018 (which will #4), almost certain >1ºC yr, and 1 in 3 chance of a new record."

Next, it is somewhat unclear what Mid-Pliocene conditions, in West Antarctica, actually means.  Per the third image, from Sweet et al. 2017) GMSTA (from pre-industrial) during the Pliocene ranges from +1.8C to +3.6C; while the fourth image from Hansen & Sato shows Pliocene GMSTA relative to the Holocene Optimum.

Thus to begin to reconcile Mid-Pliocene conditions circa 2040 with AR5, one needs to believe (at least) that IPCC underestimates:

a) ECS and negative forcing from anthropogenic aerosols,
b) the role of ENSO (& IPO) in determining GMSTA in the coming decades,
c) the role of ice-climate feedback mechanisms that have already been triggered.

Edit, there currently are 2,387 posts in the "Conservative Scientists & its Consequences" thread related to why the IPCC is likely erring of the side of least drama in its climate change projections:
 
https://forum.arctic-sea-ice.net/index.php/topic,1053.0.html

Edit2, with regard to the 2030 date, I suspect that Burke et al (2018) are likely referring to the CO2 concentration by 2030 (see the CO2 concentrations given in the third image).
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: RoxTheGeologist on December 12, 2018, 07:32:33 PM

Excellent graphs, thanks ASLR.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2018, 07:55:53 PM
As a follow-on to my last post, the first two images from the first linked website entitled "Figures from the Global Carbon Budget 2018", show (respectively) that we are currently following the SSP5 baseline scenario, and that we are above the SSP scenarios required to state below the 1.5C goal.

http://folk.uio.no/roberan/GCB2018.shtml

Also, by the end of 2018 the world population will be about 7.7 million people, which, per the third & fourth images, slightly exceeds that assumed by SSP5.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2018, 08:31:43 PM
We should also keep in mind the ice-climate feedback risks associated with both nonlinear surface melting of the GIS (see the first linked reference and image); and of increasing rainfall around the Artic (see the second linked reference) and in Greenland (see the third linked reference w.r.t. atmospheric rivers):

Trusel, L. D., Das, S. B., Osman, M. B., Evans, M. J., Smith, B. E., Fettweis, X., … van den Broeke, M. R. (2018). Nonlinear rise in Greenland runoff in response to post-industrial Arctic warming. Nature, 564(7734), 104–108. doi:10.1038/s41586-018-0752-4, https://doi.org/10.1038/s41586-018-0752-4

https://www.nature.com/articles/s41586-018-0752-4

Abstract: "The Greenland ice sheet (GrIS) is a growing contributor to global sea-level rise, with recent ice mass loss dominated by surface meltwater runoff. Satellite observations reveal positive trends in GrIS surface melt extent, but melt variability, intensity and runoff remain uncertain before the satellite era. Here we present the first continuous, multi-century and observationally constrained record of GrIS surface melt intensity and runoff, revealing that the magnitude of recent GrIS melting is exceptional over at least the last 350 years. We develop this record through stratigraphic analysis of central west Greenland ice cores, and demonstrate that measurements of refrozen melt layers in percolation zone ice cores can be used to quantifiably, and reproducibly, reconstruct past melt rates. We show significant (P < 0.01) and spatially extensive correlations between these ice-core-derived melt records and modelled melt rates and satellite-derived melt duration across Greenland more broadly, enabling the reconstruction of past ice-sheet-scale surface melt intensity and runoff. We find that the initiation of increases in GrIS melting closely follow the onset of industrial-era Arctic warming in the mid-1800s, but that the magnitude of GrIS melting has only recently emerged beyond the range of natural variability. Owing to a nonlinear response of surface melting to increasing summer air temperatures, continued atmospheric warming will lead to rapid increases in GrIS runoff and sea-level contributions."

Caption for the image: "Fig. 4 | Exceptional rise in Greenland ice-sheet runoff and climate warming context. a, GrIS-integrated meltwater runoff, as simulated by regional climate models (coloured lines; 5-year smoothed) and reconstructed using the NU and CWG ice-core-derived melt records (black line; 95% confidence interval shaded; see Methods). b, Median onset of significant trends (vertical black dotted lines) and climate emergence above pre-industrial (vertical red dotted lines) for mean  Arctic temperatures (top), our ice-core-derived runoff reconstruction (middle) and two summer Arctic sea-ice extent datasets (bottom;  Methods). Median absolute deviations of trend onsets and climate  emergence shown as shaded boxes. Thin and bold black lines denote  15-year and 50-year Gaussian smoothed series. c, Recent modelled evolution of mean summer (JJA) near-surface air temperature and surface
melt (in millimetres of water equivalent per year) across CWG. Ice core sites are shown as coloured points, and a Jakobshavn basin (basin 7.1; Fig. 1) elevational transect as grey points from RACMO2.3p2 (circles) and MARv3.7 (squares). Means over the past 20 years of the ice-core records (1994–2013) at core sites are denoted by points with single black border, and peak melting in 2012 by double black borders. The evolution of CWG ice-sheet melt in response to a warming climate is well represented by an exponential function (black curve). Recent melt rates at our percolation zone core sites approach conditions where the models have recently begun to simulate meltwater runoff (blue dashed line indicates mean runoff-linked melt rate and the shaded region corresponds to ±1 s.d.; see Methods for details)."

Richard Bintanja and Olivier Andry (2017), “Towards a rain-dominated Arctic”, Geophysical Research Abstracts Vol. 19, EGU2017-4402

http://meetingorganizer.copernicus.org/EGU2017/EGU2017-4402.pdf

Abstract: “Current climate models project a strong increase in Arctic precipitation over the coming century, which has been attributed primarily to enhanced surface evaporation associated with sea-ice retreat. Since the Arctic is still quite cold, especially in winter, it is often (implicitly) assumed that the additional precipitation will fall mostly as snow. However, very little is known about future changes in rain/snow distribution in the Arctic, notwithstanding the importance for hydrology and biology. Here we use 37 state-of-the-art climate models in standardised twenty-first century (2006–2100) simulations to show that 70◦ – 90◦N average annual Arctic snowfall will actually decrease, despite the strong increase in precipitation, and that most of the additional precipitation in the future (2091– 2100) will fall as rain. In fact, rain is even projected to become the dominant form of precipitation in the Arctic region. This is because Arctic atmospheric warming causes a greater fraction of snowfall to melt before it reaches the surface, in particular over the North Atlantic and the Barents Sea. The reduction in Arctic snowfall is most pronounced during summer and autumn when temperatures are close to the melting point, but also winter rainfall is found to intensify considerably. Projected (seasonal) trends in rain/snowfall will heavily impact Arctic hydrology (e.g. river discharge, permafrost melt), climatology (e.g. snow, sea ice albedo and melt) and ecology (e.g. water and food availability).”

Also as a repost of Reply #195: continued global warming should increase the frequency with which atmospheric rivers reach Greenland, we may be in for some rude surprises in the coming decades (w.r.t. increasing rates of ice mass loss from the Greenland Ice Sheet):

William Neff (2018), "Atmospheric rivers melt Greenland", Nature Climate Change 8, 857-858, DOI: https://doi.org/10.1038/s41558-018-0297-4

http://www.nature.com/articles/s41558-018-0297-4

Abstract: "Recent years have seen increased melting of the Greenland Ice Sheet, contributing to accelerated rates of sea-level rise.  New research suggests that this melting due to an increased frequency of atmospheric rivers, narrow filaments of moist air moving polewards."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2018, 09:00:57 PM
For what it is worth, SSP5 will be used in the upcoming AR6, and per the linked reference & associated image), following the SSP5-Baseline scenario through at least 2035 (due to the lag in time between the forcing and the change in surface temperature), GMSTA (above pre-industrial) would be about +1.6C in 2030 and +2C in 2040, which agrees with my estimates in Reply #344:

Kriegler et al. (2017), "Fossil-fueled development (SSP5): An energy and resource intensive scenario for the 21st century", Global Environmental Change, Volume 42, January 2017, Pages 297-315, https://doi.org/10.1016/j.gloenvcha.2016.05.015

http://www.sciencedirect.com/science/article/pii/S0959378016300711?via%3Dihub

Abstract: "This paper presents a set of energy and resource intensive scenarios based on the concept of Shared Socio-Economic Pathways (SSPs). The scenario family is characterized by rapid and fossil-fueled development with high socio-economic challenges to mitigation and low socio-economic challenges to adaptation (SSP5). A special focus is placed on the SSP5 marker scenario developed by the REMIND-MAgPIE integrated assessment modeling framework. The SSP5 baseline scenarios exhibit very high levels of fossil fuel use, up to a doubling of global food demand, and up to a tripling of energy demand and greenhouse gas emissions over the course of the century, marking the upper end of the scenario literature in several dimensions. These scenarios are currently the only SSP scenarios that result in a radiative forcing pathway as high as the highest Representative Concentration Pathway (RCP8.5). This paper further investigates the direct impact of mitigation policies on the SSP5 energy, land and emissions dynamics confirming high socio-economic challenges to mitigation in SSP5. Nonetheless, mitigation policies reaching climate forcing levels as low as in the lowest Representative Concentration Pathway (RCP2.6) are accessible in SSP5. The SSP5 scenarios presented in this paper aim to provide useful reference points for future climate change, climate impact, adaption and mitigation analysis, and broader questions of sustainable development."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2018, 09:24:27 PM
The linked refence works to try to explain why the surface temperatures for the Early Pliocene was so much warmer than for the Mid-Pliocene, and points to this nonlinear saddlenode bifurcation being associated with primarily Arctic Amplification but also probably due to both increased El Nino frequency and an expanded Hadley Cell (see the first image).  As I have previously noted that ice-climate feedback from a collapse of the WAIS would contribute to all three (Arctic Amplification, more frequent El Nino events and an expanded Hadley Cell); it is possible/probable that as early as 2060 Earth could be in conditions comparable to the Early Pliocene (with GMSTA up to +3.6C) even if we stop following SSP5-Baseline after 2035.  To emphasize this point I repost the second image of how such a bifurcation can lead to an abrupt change in climate state (due to a tipping perturbation such as abrupt ice mass loss from the WAIS).  Also as precaution, I note that Energy Balance Models are associated with inferred climate sensitivity which is lower than true climate sensitivity as shown in the third image.

Brady Dortmans et al. (2018), "An Energy Balance Model for Paleoclimate Transitions', Clim. Past Discuss., https://doi.org/10.5194/cp-2018-56

https://www.clim-past-discuss.net/cp-2018-56/cp-2018-56.pdf

Abstract. A new energy balance model (EBM) is presented and is used to study Paleoclimate transitions. While most previous EBMs dealt only with the globally averaged climate, this new EBM has three variants: Arctic, Antarctic and Tropical climates. This EBM incorporates the greenhouse warming effects of both carbon dioxide and water vapour, and also includes ice-albedo feedback. The main conclusion to be drawn from the EBM is that the climate system possesses multiple equilibrium states, both warm and frozen, which coexist mathematically. 5 While the actual climate can exist in only one of these states at any given time, the climate can undergo transitions between the states, via mathematical saddlenode bifurcations. This paper proposes that such bifurcations have actually occurred in Paleoclimate transitions. The EBM is applied to the study of the Pliocene Paradox, the Glaciation of Antarctica and the so-called warm, equable climate problem of both the mid-Cretaceous Period and the Eocene Epoch. In all cases, the EBM is in qualitative agreement with the geological record.

Extract: "During the early Pliocene Epoch, 3–5 Ma, the climate of the Arctic region of Earth changed abruptly from ice-free to ice-capped. The climate forcing factors then (solar constant, orbital parameters, CO2 concentration and locations of the continents) were all very similar to today. Therefore, it is difficult to explain why the early Pliocene climate was so different from that of today. That problem is known as the Pliocene Paradox, (Cronin (2010); Fedorov et al. (2006, 2010)). This paper presents a plausible explanation of the Pliocene paradox.

As stated above, a key feature of this family of mathematical models is that they incorporate physical principles that are nonlinear. As is well known, nonlinear equations can have multiple solutions, unlike linear equations which can have only one unique solution (if well-posed). In our mathematical models, the same set of equations can have two or more co-existing solutions, for example an ice-capped solution (like today’s climate) and an ice-free solution (like the Cretaceous climate), even with the same values of the forcing parameters. The determination of which solution is actually realized by the planet at a given time is dependent on past history. Changes in forcing parameters may drive the system abruptly from one stable state to another, at so-called “tipping points”. In this paper, these tipping points are investigated mathematically, and are shown to be bifurcation points, which can be investigated using mathematical bifurcation theory. Bifurcation theory tells us that the existence of bifurcation points is preserved (but the numerical values may change) under small deformations of the model equations. Thus, even though this conceptual model may not give us precise quantitative information about climate changes, qualitatively there is good reason to believe that the existence of the bifurcation points in the model will be preserved in similar more refined models and in the real world.

The change from ice-free to ice-covered in the Arctic occurred abruptly, during the Pliocene Epoch, 5.3 to 2.6 Ma. It has been a longstanding challenge for paleoclimatologists to explain this dramatic change in the climate.

During the Pliocene Epoch, all of the important forcing factors that determine climate were very similar to those of today. The Earth orbital parameters, the CO2 concentration, solar radiation intensity, position of the continents, ocean currents and atmospheric circulation all had values close to the values they have today. Yet, in the early Pliocene, 4–5 million years ago, the Arctic climate was much milder than that of today. Arctic surface temperatures were 8−19_C warmer than today and global sea levels were 15−20 m higher than today, and yet CO2 levels are estimated to have been 340−400 ppm, about the same as 20th Century values; see Ballantyne et al. (2010); Csank et al. (2011); Tedford and Harington (2003). As mentioned in the Introduction, the problem of explaining how such different climates could exist with such similar forcing parameter values has been called the Pliocene Paradox (Cronin (2010); Fedorov et al. (2006, 2010)).

Another interesting paradox concerning Polar glaciation is the fact that, although both poles have transitioned abruptly from ice-free to ice-covered, they did so at very different geological times. The climate forcing conditions of Earth are highly symmetric between the two hemispheres and for most of the history of Earth the climates of the two poles have been very similar. However, there was an anomalous period of about 30 million years, from the Eocene-Oligocene boundary (34 Ma) to the early Pliocene (4 Ma), when the Antarctic was largely ice-covered but the Arctic was ice-free.

Thus, the EBM presented here, as illustrated in Figure 7, provides a plausible explanation for the Pliocene paradox. The slowly-acting physical forcings of decreasing CO2 concentration and decreasing ocean heat transport FO were amplified by the mechanisms of ice-albedo feedback and water vapour feedback, both of which act very strongly when the temperature crosses the freezing point of water. For millions of years before the Pliocene, while the Arctic temperature remained well above freezing, the climate changed very little. However, once the freezing temperature was reached, the Arctic climate changed abruptly via a saddlenode bifurcation as in Figure 7 b), to a new frozen state. This simple mechanism suffices to explain the Pliocene paradox. No more complicated explanations are necessary.

Several other explanations have been proposed for the Pliocene paradox. There is convincing evidence that, at the beginning of the Pliocene, there was a permanent El Niño condition in the tropical Pacific ocean, see Cronin (2010); Fedorov et al. (2006, 2010). (However, some have disputed this finding, see Watanabe et al. (2011).) It has been suggested that a permanent El Niño condition could explain the warm early Pliocene, and that the onset of the El Niño – La Niña Southern Oscillation (ENSO) was the cause of sudden cooling of the Arctic during the Pliocene. Today, it is known that ENSO can influence weather patterns as far away as the Arctic.

Another suggestion is that Hadley cell feedback contributed to the abrupt cooling of the Arctic during the Pliocene. Recent work shows that an increase in pole-to-equator temperature gradient causes the Hadley cells to contract towards the equator, while increasing in circulation velocity, see Lewis and Langford (2008); Langford and Lewis (2009). This would cause a decrease in equator to pole atmospheric heat transport, which would in turn accelerate Arctic cooling; this is called Hadley cell feedback.  Further work on modelling this mechanism is in progress. It is conjectured here that Hadley cell feedback may in fact have caused the end of a permanent El Niño condition in the Pliocene, as follows. It is known that the La Niña phase of ENSO is forced in part by the Trade Winds blowing East to West across the tropical Pacific Ocean. The Trade Winds are the surface component of the Hadley circulation. Therefore, acceleration of the Hadley circulation would strengthen the Trade Winds, enhancing the conditions for La Niña and ending the permanent El Niño. Further work on this conjecture also is in progress.

In the Tropics, many of the values of the forcing parameters are different from their values in the Arctic and Antarctic, see Table 2. The geological record shows little change in the tropical climate over the past 100 million years, other than a little cooling. Even when Arctic climate changed dramatically in the Pliocene, the Tropical climate changed very little.

The new entry in this Table, one that did not appear in the polar models, is FC, which represents transport of heat away from the surface to the atmosphere, by conduction / convection / change of state of water. The most important of these is the upward transport of latent heat. Surface water evaporates, taking heat from the surface. As warm moist air rises and cools, the water vapour condenses, releasing its latent heat into the surrounding atmosphere."


Caption for the first attached image: "Figure 7. Pliocene Arctic EBM (36)(37). Parameter values δ = 0.67, FA = 115; other parameters as in Table 1. Subfigure a): CO2 takes valuesµ = 1200, 1000, 800, 600, 400, 200ppm,from top to bottom on the blue curves, with fixed FO = 50 Wm−2. The warm equilibrium state disappears as µ decreases. Subfigure b): Bifurcation Diagram for the Pliocene Paradox. Here, CO2 concentration µ and ocean heat transport FO decrease simultaneously, with increasing ν, (0≤ν ≤1), as given by equations (42). As ν increases, the warm equilibrium solution (τS > 1) disappears in a saddlenode bifurcation, at approximately ν = 0.9, corresponding to forcing parameter µ = 343 ppm and FO = 51 Wm2. To the right of this point, only the frozen equilibrium state exists. To the left of this point, the frozen and warm equilibrium states coexist, separated by the unstable intermediate state."

Edit, W.r.t. coming Arctic Amplification, see the following linked article:

Title: "New and emerging threats continue to appear in Arctic as region warms, 2018 Arctic Report Card says"

https://www.accuweather.com/en/weather-news/warming-and-melting-arctic-has-global-impacts-2018-arctic-report-card-says/70006872

Extract: "The Arctic Ocean has lost 95 percent of its oldest, thickest ice. In 2018, Arctic sea ice remained younger and thinner and covered less area than in the past. The 12 lowest extents in the satellite record have occurred in the last 12 years, according to the report."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 12, 2018, 11:54:13 PM
First, I note that a jökulhlaup is a glacial outburst of meltwater, and the first linked article demonstrates that with Antarctic subglacial lakes and drainage systems such event can be regulated by the nature of pressure waves passing through the system over multiple years; and that the pressures associated with such waves can regulate the glacial ice flow velocities.

C. F. Dow et al. (22 March 2018), "Dynamics of Active Subglacial Lakes in Recovery Ice Stream", JGR Earth Surface, https://doi.org/10.1002/2017JF004409

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017JF004409

Abstract
Recovery Ice Stream has a substantial number of active subglacial lakes that are observed, with satellite altimetry, to grow and drain over multiple years. These lakes store and release water that could be important for controlling the velocity of the ice stream. We apply a subglacial hydrology model to analyze lake growth and drainage characteristics together with the simultaneous development of the ice stream hydrological network. Our outputs produce a good match between modeled lake location and those identified using satellite altimetry for many of the lakes. The modeled subglacial system demonstrates development of pressure waves that initiate at the ice stream neck and transit to within 100 km of the terminus. These waves alter the hydraulic potential of the ice stream and encourage growth and drainage of the subglacial lakes. Lake drainage can cause large R‐channels to develop between basal overdeepenings that persist for multiple years. The pressure waves, along with lake growth and drainage rates, do not identically repeat over multiple years due to basal network development. This suggests that the subglacial hydrology of Recovery Ice Stream is influenced by regional drainage development on the scale of hundreds of kilometers rather than local conditions over tens of kilometers.

Plain Language Summary
Ice streams are fast‐flowing areas of the Antarctic ice sheet that drain large quantities of ice into the ocean, contributing to sea level rise. We have run a model of water flow underneath Recovery Ice Stream to examine lakes that build up and drain underneath kilometers of ice to find out whether they have an impact on the speed of the overlying ice. We find that the timing of the lake growth and drainage is determined by the hydrological conditions underneath the entirety of the ice stream, stretching over hundreds of kilometers. As the lakes drain, they melt channels that connect as sub‐ice rivers between the drainage basins. We also find that the regions of highest water pressure, and therefore the fastest‐moving overlying ice, are concentrated in the deepest parts of the trough that the ice stream flows through. This is an important finding for determining the controls on fast ice stream flow speed and therefore the stability of the Antarctic ice sheet.

Extract: "Antarctic subglacial lakes have been modeled within synthetic ice dynamics models (Pattyn, 2008; Sergienko et al., 2007) and as basins that are filled and drained by tuning with satellite altimetry data (Carter & Fricker, 2012; Carter et al., 2009, 2011). Recent work by Carter et al. (2017) suggests that Antarctic lake dynamics cannot be influenced by the formation of Röthlisberger (R-) channels that melt upward into the ice, instead arguing that sediment canals are necessary to allow lake drainage. These treatments of Antarctic subglacial lakes are different from those models that examine ice marginal lake outburst floods or subglacial jökulhlaups, where rapid (on the scale of days to weeks) drainage occurs. Models examining the latter focus on the water pressure allowing ice uplift and downstream lake drainage (e.g., Ng & Liu, 2009; Nye, 1976) or negative pressure gradients that prevent outflow of the lakes until they are reversed by hydrological development (e.g., Evatt et al., 2006; Fowler, 1999; Kingslake, 2015). In contrast, the active Antarctic subglacial lakes differ because they drain over a timescale of years and can become much larger (>10km2), although often shallower (e.g., <10m deep) than ice marginal or jökulhlaup lakes. The work of Dow et al. (2016) found that at no time were hydraulic pressure gradients reversed when applying a synthetic hydrology model to Antarctic lakes. Instead, lake dynamics were driven by spatially and temporally varying conductivity of the basal drainage system including the growth of R-channels that drained the lake. The Dow et al. (2016) study applied a synthetic, planar topography with one overdeepening, designed to emulate Recovery Ice Stream. However, until now, a 2-D approach to catchment-scale hydrology modeling with Antarctic topography including multiple lake basins has not been attempted.

This suggests that the water pressure plays a more important role in the ice stream velocity than the water thickness, which as we demonstrate with our model outputs is not always coincident with water pressure, either spatially or temporally."
&

Next, I note that the first two attached images are from the second linked reference, and they show the extensive subglacial lake and meltwater drainage systems in Antarctica (with increasing warming these systems should become more extensive and important in the future):

S. J. Livingstone, C. D. Clark, and J. Woodward (2013), "Predicting subglacial lakes and meltwater drainage pathways beneath the Antarctic and Greenland ice sheets", The Cryosphere Discuss., 7, 1177–1213, www.the-cryosphere-discuss.net/7/1177/2013/, doi:10.5194/tcd-7-1177-2013

The caption for the first image is: "In (B), the blue colour illustrates regions below the pressure melting point. This is used as a simple mask to remove all subglacial lakes that fall within the cold-bedded zones. Note, the subglacial drainage network is still treated as though the bed was wholly warm based."

The caption for the second image is:  "(B) the fraction of the grounded ice-sheet bed occupied by subglacial lakes vs ice-sheet area, with both the Antarctic and Greenland subglacial lake data plotted."
&

Next, the following link leads to findings presented at the AGU 2013 conference about new evidence characterizing the nature of the subglacial hydrological system in Antarctica:

http://www.livescience.com/41994-antarctica-new-lakes-streams.html

In the third attached image, the red dots mark surface changes that scientists think are caused by water moving beneath Antarctica's ice. The blue and magenta colors indicate ice velocity, with the magenta showing the fastest-moving ice.
&

Finally, the following linked reference by Bell discusses the importance of correctly modeling the influence of subglacial hydrology on ice mass loss from AIS:

Robin E. Bell (2008), "The role of subglacial water in ice-sheet mass balance", Nature Geoscience, doi:10.1038/ngeo186

http://www.nature.com/ngeo/journal/v1/n5/abs/ngeo186.html

Abstract: "In the coming decades, significant changes in the polar regions will increase the contribution of ice sheets to global sea-level rise. Under the ice streams and outlet glaciers that deliver ice to the oceans, water and deformable wet sediments lubricate the base, facilitating fast ice flow. The influence of subglacial water on fast ice flow depends on the geometry and capacity of the subglacial hydrologic system: water moving rapidly through a well-connected system of conduits or channels will have little impact on ice-sheet velocities, but water injected into a spatially dispersed subglacial system may reduce the effective pressure at the base of the ice sheet, and thereby trigger increased ice-sheet velocities. In Greenland, the form of the subglacial hydrologic system encountered by increasing surface melt water will determine the influence of changing atmospheric conditions on ice-sheet mass balance. In Antarctica, subglacial lakes have the capacity to both modulate velocities in ice streams and outlet glaciers and provide nucleation points for new fast ice-flow tributaries. Climate models of ice-sheet responses to global change remain incomplete without a parameterization of subglacial hydrodynamics and ice dynamics."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 12:08:04 AM
As anthropogenic forcing is the largest source of climate change, one of the 'Deepest Uncertainties' is whether decision makers will accept that the probability of near-term abrupt climate change is serious enough to do something effective about it.  In this regard, I provide the attached image from the linked article that indicates that scientific education about climate change is insufficient to prevent tribalism among conservatives, but rather it takes 'science curiosity' to be open-minded enough to accept this risk.  It is not clear to me that decision makers exhibit sufficient 'science curiosity' to avoid ice-climate induced abrupt climate change in the coming decades:

Title: "Why Smart People Are Vulnerable to Putting Tribe Before Truth" by Dan Kahan, SciAm 2018.

https://blogs.scientificamerican.com/observations/why-smart-people-are-vulnerable-to-putting-tribe-before-truth/

Extract: "Science literacy is important, but without the parallel trait of 'science curiosity," it can lead us astray."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 05:03:52 PM
I note that I remember four different definitions of pre-industrial in AR5, while the summary declines to specify which definition policy makers should follow.  Furthermore, the linked reference indicates that the proper definition of the pre-industrial baseline could add up to +0.2C to IPCC projections of GMSTA; while the Paris Accord has declined to adopt Schurer et al. (2017)'s proposed definition.

Schurer et al (2017), "Importance of the pre-industrial baseline for likelihood of exceeding Paris goals", Nature Climate Change 7, 563-567, doi:10.1038/nclimate3345

http://www.nature.com/nclimate/journal/v7/n8/full/nclimate3345.html?foxtrotcallback=true

Abstract: "During the Paris conference in 2015, nations of the world strengthened the United Nations Framework Convention on Climate Change by agreeing to holding ‘the increase in the global average temperature to well below 2◦C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5◦C’ (ref. 1). However, ‘pre-industrial’ was not defined. Here we investigate the implications of different choices of the pre-industrial baseline on the likelihood of exceeding these two temperature thresholds. We find that for the strongest mitigation scenario RCP2.6 and a medium scenario RCP4.5, the probability of exceeding the thresholds and timing of exceedance is highly dependent on the pre-industrial baseline; for example, the probability of crossing 1.5◦C by the end of the century under RCP2.6 varies from 61% to88% depending on how the baseline is defined. In contrast, in the scenario with no mitigation, RCP8.5, both thresholds will almost certainly be exceeded by the middle of the century with the definition of the pre-industrial baseline of less importance. Allowable carbon emissions for threshold stabilization are similarly highly dependent on the pre-industrial baseline. For stabilization at 2◦C, allowable emissions decrease by as much as 40% when earlier than nineteenth-century climates are considered as a baseline."
Extract: "In total, spatially complete blended global temperatures from 23 simulations, from 7 different models, were analysed with the means of each model for the period 1401–1800 found to be cooler than the late-nineteenth-century baseline (1850–1900) by 0.03◦C to 0.19◦C (multi-model mean of 0.09◦C, Fig.2b). In these simulations, and in temperature reconstructions of the past millennium, there is considerable centennial variability. Some periods, such as the sixteenth century, are of comparable warmth to the late nineteenth century, while other periods have a multi-model mean nearly 0.2◦C cooler."

Caption of attached image: "Figure2 | Model-simulated difference in global mean temperature between different pre-industrial periods and 1850–1900. a, Range of ensemble means for different models, and for different forcing combinations. Model distribution fitted with a kernel density estimate (violin plot)—red, all forcings combined; green, greenhouse gas forcing alone; blue, volcanic forcing alone; yellow, solar forcing alone. Model mean: circle; 10–90% model range: bar. Differences refer to the mean of the period enclosed by the dashed lines; except on the far right, where they are means for the full period 1401–1800 (relative to 1850–1900). b–e, Model means for different forcing combinations—colours, ensemble means for individual models; black line, mean over all models."

Obviously, such definitions matter when we are trying to decide by which decade we have approached Mid-Pliocene conditions, and can also impact estimates of ECS.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 06:06:04 PM
I have read that AR6 will provide more guidance to policy makers on the nature and possible consequences of 'Deep Uncertainty', for example the linked reference & associated first image [which show that long-tailed ECS values represent the highest risk (probability times consequences) to society], provides one simple example of how the possible consequences of long-tailed risk (per AR5) could be conveyed better.

Rowan T. Sutton (2018), "ESD Ideas: a simple proposal to improve the contribution of IPCC WGI to the assessment and communication of climate change risks", Earth Syst. Dynam., 9, 1155–1158, https://doi.org/10.5194/esd-9-1155-2018

https://www.earth-syst-dynam.net/9/1155/2018/esd-9-1155-2018.pdf

Abstract: "The purpose of the Intergovernmental Panel on Climate Change (IPCC) is to provide policy-relevant assessments of the scientific evidence about climate change. Policymaking necessarily involves risk assessments, so it is important that IPCC reports are designed accordingly. This paper proposes a specific idea, illustrated with examples, to improve the contribution of IPCC Working Group I to informing climate risk assessments."

Extract: "Some will argue that the WGII report is needed to provide information on impacts. For detailed information this is certainly the case, but the general shape of the damage function for a large basket of impacts (Fig. 1) is insensitive to such details and is all that is needed to justify WGI providing a much more thorough assessment of relevant scenarios. Other critics will suggest that for WGI to explicitly identify high-impact scenarios would constitute scaremongering; this concern is no doubt one reason why previous WGI reports have focused so much on the likely range. But it is misguided (see also Emanuel, 2014). Policymakers need to know about high-impact scenarios and WGI has a responsibility to contribute its considerable expertise to making the appropriate assessments."

Caption for the attached image: "Figure 1. A schematic representation of how climate change risk depends on equilibrium climate sensitivity (ECS). (a) A possible likelihood distribution consistent with the IPCC AR5 assessment that “Equilibrium climate sensitivity is likely in the range 1.5 to 4.5 _C (high confidence), extremely unlikely less than 1C (high confidence) and very unlikely greater than 6C (medium confidence)”. (b) A schematic illustration of the fact that, for a given emissions scenario, the cost of impacts and adaptation rises very rapidly (shown here as an exponential damage function) with ECS. (c) In this example, the resultant risk (quantified here as likelihood x impact) is highest for high ECS values. The precise shape of the risk curve is dependent on assumptions about the shape of the likelihood and damage functions at high sensitivity (Weitzman, 2011) (figure by Ed Hawkins)."

Furthermore, I believe that plots such as the second image could better convey the need to design civil features (say flood protection) to meet much higher capacity levels than the mean demand levels typically discussed in the media.

Lastly, I hope that AR6 provides much better guidance than AR5 did, with regard to such matters as the risks and consequences associated with:

1. Various ice-climate feedback mechanisms associated with rapid ice mass loss from ice sheets.

2. Risks off abrupt changes in climate state (say from Mid-Pliocene conditions to Early-Pliocene conditions) due to potential cascading of tipping points for different feedback mechanisms.

3. The potential impacts of the current very high rates of radiative forcing as compared to all paleo cases evaluated.

4. The fact that PDFs (probability density functions) shift with continued warming, so there are consequences with delaying effective climate action [see the third image from Steffen et al (2018)].
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 07:01:50 PM
With regards to my last post, some readers may wonder what Steffen et al (2018) mean by 'Hothouse' conditions (as opposed to Pliocene or Miocene conditions).  Generally, 'Hothouse' conditions can be taken as Early Eocene Climatic Optimum (EECO; ∼52–50 Ma) conditions as discussed in the linked reference Evans et al. (2018) and the associated attached images.  Note that as the reference demonstrates that no current ESM (including FAMOUS which has been tailored for the EECO) can accurately project the full extent of Polar Amplification during the EECO; this means that if we keep following SSP5-Baseline long enough to reach atmospheric CO₂ concentrations around 560 ppm, then depending on the history of our climate change momentum, the Earth's climate could flip into an equable conditions (characterized by warm poles):

David Evans, Navjit Sagoo, Willem Renema, Laura J. Cotton, Wolfgang Müller, Jonathan A. Todd, Pratul Kumar Saraswati, Peter Stassen, Martin Ziegler, Paul N. Pearson, Paul J. Valdes, and Hagit P. Affek (January 22, 2018), "Eocene greenhouse climate revealed by coupled clumped isotope-Mg/Ca thermometry", PNAS February 6, 2018 115 (6) 1174-1179; https://doi.org/10.1073/pnas.1714744115

https://www.pnas.org/content/115/6/1174
https://www.pnas.org/content/pnas/115/6/1174.full.pdf

Significance
Reconstructing the degree of warming during geological periods of elevated CO2 provides a way of testing our understanding of the Earth system and the accuracy of climate models. We present accurate estimates of tropical sea-surface temperatures (SST) and seawater chemistry during the Eocene (56–34 Ma before present, CO2 >560 ppm). This latter dataset enables us to reinterpret a large amount of existing proxy data. We find that tropical SST are characterized by a modest warming in response to CO2. Coupling these data to a conservative estimate of high-latitude warming demonstrates that most climate simulations do not capture the degree of Eocene polar amplification.

Abstract

Past greenhouse periods with elevated atmospheric CO2 were characterized by globally warmer sea-surface temperatures (SST). However, the extent to which the high latitudes warmed to a greater degree than the tropics (polar amplification) remains poorly constrained, in particular because there are only a few temperature reconstructions from the tropics. Consequently, the relationship between increased CO2, the degree of tropical warming, and the resulting latitudinal SST gradient is not well known. Here, we present coupled clumped isotope (Δ47)-Mg/Ca measurements of foraminifera from a set of globally distributed sites in the tropics and midlatitudes. Δ47 is insensitive to seawater chemistry and therefore provides a robust constraint on tropical SST. Crucially, coupling these data with Mg/Ca measurements allows the precise reconstruction of Mg/Casw throughout the Eocene, enabling the reinterpretation of all planktonic foraminifera Mg/Ca data. The combined dataset constrains the range in Eocene tropical SST to 30–36 °C (from sites in all basins). We compare these accurate tropical SST to deep-ocean temperatures, serving as a minimum constraint on high-latitude SST. This results in a robust conservative reconstruction of the early Eocene latitudinal gradient, which was reduced by at least 32 ± 10% compared with present day, demonstrating greater polar amplification than captured by most climate models.

Caption for second image: "Fig. 2 Seawater Mg/Ca reconstruction for the Eocene and early Oligocene based on coupled Δ47-Mg/Ca LBF and ridge-flank CaCO3 vein (CCV) data, shown in the context of previous Cenozoic reconstructions (33, 34, 56, 57) and box models (refs. 35, 36, and 58; WA89, SH98, and HS15, respectively), that are commonly used for calculating planktonic and deep-benthic foraminifera Mg/Ca data. Coral-derived data younger than 20 Ma are omitted. The 95% confidence intervals on our Eocene Mg/Casw curve are derived from bootstrapping 1,000 locally weighted scatterplot smoothing (LOWESS) fits, including both geochemical and dating uncertainties."

Caption for third image: "Fig. 5. Early Eocene (48–56 Ma) model-data comparison. (A) Zonally averaged latitudinal gradients based on proxy CO2 and SST data (gray box) and climate models over a range of CO2 (circles) (12, 46–48, 60). Proxy CO2 range is from ref. 1; the gradient uncertainty is the combined 2 SE of the tropical and high-latitude proxy data (see text). Proxy-derived gradient is shown relative to present day; Eocene climate model simulations are shown relative to their preindustrial counterpart. Most model simulations do not capture the reduced latitudinal gradient within the range of proxy CO2 (<2,250 ppm). (B) Site-specific model-data comparison for both the tropics and high latitudes. Model SST competency assessed by comparing the mean difference between the model and proxy data for low and high latitudes. Quadrants reflect different overall patterns of model-data offset. Hypothetical simulations falling on the 1:1 line would reconstruct the same latitudinal gradient as the data but not the same absolute SST, except at the origin. All models fall below this line, indicating that Eocene polar amplification is underestimated."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wdmn on December 13, 2018, 07:30:45 PM
ASLR,

Considering that you frequently talk about the importance of ENSO events to the pace of Antarctic melt, I thought I should post this new paper (out yesterday) here:

Increased variability of eastern Pacific El Niño under greenhouse warming Wenju Cai, Guojian Wang, Boris Dewitte, Lixin Wu, Agus Santoso, Ken Takahashi, Yun Yang, Aude Carréric & Michael J. McPhaden https://www.nature.com/articles/s41586-018-0776-9 (https://www.nature.com/articles/s41586-018-0776-9)

Quote
Abstract: The El Niño–Southern Oscillation (ENSO) is the dominant and most consequential climate variation on Earth, and is characterized by warming of equatorial Pacific sea surface temperatures (SSTs) during the El Niño phase and cooling during the La Niña phase. ENSO events tend to have a centre—corresponding to the location of the maximum SST anomaly—in either the central equatorial Pacific (5° S–5° N, 160° E–150° W) or the eastern equatorial Pacific (5° S–5° N, 150°–90° W); these two distinct types of ENSO event are referred to as the CP-ENSO and EP-ENSO regimes, respectively. How the ENSO may change under future greenhouse warming is unknown, owing to a lack of inter-model agreement over the response of SSTs in the eastern equatorial Pacific to such warming. Here we find a robust increase in future EP-ENSO SST variability among CMIP5 climate models that simulate the two distinct ENSO regimes. We show that the EP-ENSO SST anomaly pattern and its centre differ greatly from one model to another, and therefore cannot be well represented by a single SST ‘index’ at the observed centre. However, although the locations of the anomaly centres differ in each model, we find a robust increase in SST variability at each anomaly centre across the majority of models considered. This increase in variability is largely due to greenhouse-warming-induced intensification of upper-ocean stratification in the equatorial Pacific, which enhances ocean–atmosphere coupling. An increase in SST variance implies an increase in the number of ‘strong’ EP-El Niño events (corresponding to large SST anomalies) and associated extreme weather events.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 08:30:57 PM
ASLR,

Considering that you frequently talk about the importance of ENSO events to the pace of Antarctic melt, I thought I should post this new paper (out yesterday) here:

Increased variability of eastern Pacific El Niño under greenhouse warming Wenju Cai, Guojian Wang, Boris Dewitte, Lixin Wu, Agus Santoso, Ken Takahashi, Yun Yang, Aude Carréric & Michael J. McPhaden https://www.nature.com/articles/s41586-018-0776-9 (https://www.nature.com/articles/s41586-018-0776-9)
...

This is an indication of both increasingly high values of ECS and of increasingly high levels of telecommunication of energy from the Tropical Pacific directly to West Antarctica.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 09:13:04 PM
As the poles continue to warm, we should not forget that blooms of microbes on the ice surface can decrease albedo and increase the rate of ice mass loss both in Greenland and Antarctica:

Title: "Guest post: Is ‘glacier carbon’ good or bad for the climate?"

https://www.carbonbrief.org/guest-post-is-glacier-carbon-good-or-bad-for-the-climate

Extract: "When microbes draw down CO2, they grow and divide, leading to increased biomass on the ice surface.
This accumulation of organic matter on the ice surface is very dark in colour and, therefore, quickly absorbs sunlight, transferring the excess energy into the ice as heat."
&

Title: "Mysterious Microbes Turning Polar Ice Pink, Speeding Up Melt"

https://www.nationalgeographic.com/environment/2018/09/news-greenland-ice-sheet-melting-arctic-algae/

Extract: "Thriving communities of red algae are doing something nefarious to the world's ice sheets: melting them more quickly."

See also:
https://www.nature.com/articles/s41467-018-03353-2

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 10:08:53 PM
The attached image is from the linked open access reference & provides background information relevant to different possible definitions for the Anthropocene.  This image implies that without anthropogenic radiative forcing Earth would now be headed for another glacial period; and I wonder whether this temperature trend may also act as yet another factor masking a relatively high value of ECS; also I wonder whether the upward tend of atmospheric methane concentration since 5,000 years ago, makes the Anthropocene's radiative forcing signature much different than past interglacial periods such as that for the Mid-Pliocene.

Lewis, S. L.; Maslin, M. A. (12 March 2015). "Defining the Anthropocene". Nature 519: 171–180. doi:10.1038/nature14258

http://www.nature.com/nature/journal/v519/n7542/full/nature14258.html
https://eorder.sheridan.com/3_0/app/orders/4609/article.php#171

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 10:18:51 PM
The first image shows the Antarctic Bedmap with the ice instantly removed, while the second image shows the Antarctic Bedmap with the ice removed and all associated isostatic rebound recovered.  Also, the dotted lines on the five cross-sections thru the WAIS on the third image shows the hundreds of meters of rebound that would be recovered if the WAIS were to abruptly collapse.  This much rebound would certainly contribute to an increase in local seismic and volcanic activity.

Edit: For a plan view of the candidate seaways proposed by Vaughan in the third image, see Reply #328
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 10:45:39 PM
The linked reference provides novel evidence from coral samples recovered from a few sites on Antarctica's continental shelf and slope, that indicate an intrusion of warm CDW occurred in these locations (see the attached image) around 1830 AD, which was likely associated with both a reduction of the Overturning Current and an increases in the circumpolar westerly wind.  This paleo evidence provides support for two ice-climate feedback mechanisms.

Theresa M. King et al. (24 October 2018), "Large‐Scale Intrusion of Circumpolar Deep Water on Antarctic Margin Recorded by Stylasterid Corals", Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2018PA003439

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018PA003439

Abstract: "We present centennial-scale radiocarbon (14C) records archived by deep sea stylasterid corals from the outer shelf and upper slope of the Antarctic margin.  These novel stylasterids (Errina spp.) were collected from the western Ross Sea shelf (500 m) and slope (1700 m), as well as the eastern Wilkes Land shelf (670 m).  We provide two corals from each region and document an abrupt reversal of 14C ages in the upper (younger) part of each coral.  We test the statistical robustness of each record and demonstrate the significance of the age reversals, as well as the ability of these corals to record environmental change.   We discuss a variety of possible drivers for this 14C reversal, and conclude that it is most likely an encroachment of 14C-depeleted Circumpolar Deep Water (CDW).  This water mass has regionally intruded onto the Antarctic margin in recent decades, facilitating loss of grounded Antarctic ice; this has implications for global sea level, deep water formation, and carbon sequestration in the Southern Ocean.  Thus, understanding past variability of CDW on the margin is vital to better constrain climate change trajectories in the near future.   We estimate large-scale encroachment of CDW onto the shelf likely commencing after 1830 CE (±120 yr).  We present possible drivers for the intrusion, but highlight the need for additional chronologic constraint.  This study not only demonstrates the utility of a novel coral taxon, but also presents the paleoceanographic community with testable hypothesis concerning recent, widespread CDW intrusion."

Extract: "Based on estimated calibrated calendar ages, our records suggest that the onset of the intrusion could have aligned with the termination of the Little Ice Age event.  This time period is accompanied by both reduction of deep water formation and strengthening of the westerly winds, two mechanisms that could be responsible for the shoaling of CDW onto the shelf."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 13, 2018, 11:03:40 PM
For those who are interested, I provide the attached schedule for the IPCC AR6 WG1 authors from the linked website.  Maybe there will be leaks of the first draft after April 2019 and the final version should be made public in 2021:

https://wg1.ipcc.ch/AR6/AR6.html

Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 14, 2018, 03:54:33 AM
I have not had time to review the linked reference, so I am just posting here without comment:

Qin Wen and Jie Yao (2018), "Decoding Hosing and Heating Effects on Global Temperature and Meridional Circulations in a Warming Climate", Journal of Climate, https://doi.org/10.1175/JCLI-D-18-0297.1

https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-18-0297.1

Abstract: "The global temperature changes under global warming result from two effects: one is the pure radiative heating effect caused by a change in greenhouse gases, and the other is the freshwater effect related to changes in precipitation, evaporation, and sea ice. The two effects are separated in a coupled climate model through sensitivity experiments in this study. It is indicated that freshwater change has a significant cooling effect that can mitigate the global surface warming by as much as ~30%. Two significant regional cooling centers occur: one in the subpolar Atlantic and one in the Southern Ocean. The subpolar Atlantic cooling, also known as the “warming hole,” is triggered by sea ice melting and the southward cold-water advection from the Arctic Ocean, and is sustained by the weakened Atlantic meridional overturning circulation. The Southern Ocean surface cooling is triggered by sea ice melting along the Antarctic and is maintained by the enhanced northward Ekman flow. In these two regions, the effect of freshwater flux change dominates over that of radiation flux change, controlling the sea surface temperature change in the warming climate. The freshwater flux change also results in the Bjerknes compensation, with the atmosphere heat transport change compensating the ocean heat transport change by about 80% during the transient stage of global warming. In terms of global temperature and Earth’s energy balance, the freshwater change plays a stabilizing role in a warming climate."
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: wdmn on December 14, 2018, 08:08:43 AM
For those who are interested, I provide the attached schedule for the IPCC AR6 WG1 authors from the linked website.  Maybe there will be leaks of the first draft after April 2019 and the final version should be made public in 2021:

https://wg1.ipcc.ch/AR6/AR6.html

Maybe ASIF contributors should write them a well sourced letter encouraging them to take into account some of what they have been leaving out from previous reports.
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: Sleepy on December 14, 2018, 10:30:22 AM
As I noted in the Paris thread, Glen Peters is a lead author for AR6-WG3 (chapter three). But the scientific base has never been the real problem, apart from beeing late to the party, it's what's been softened towards policy makers out of those old findings. SR15 was much better, but still this happened:
Quote
The Swedish Society for Nature Conservation's member journal headline was hilarious:
clear-message-from-IPCC-15-degree target-still-attainable
 ::)
They were probably not among those ~450 viewers that watched the press conference live.

Personally, I would vote for banning all new ff-construction right now. But that. or rather those parts, was left to policy makers... So in essence, nothing new happened tonight.
I watched it live, the contrast when reading the headlines later was stunning. Policy makers, and even worse, organizations that should understand the message, clearly did not.
If the world continues like today, I don't think it matters what IPCC writes in 2021.  :(
Title: Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
Post by: AbruptSLR on December 14, 2018, 05:51:52 PM
I have not had time to review the linked reference, so I am just posting here without comment:

Qin Wen and Jie Yao (2018), "Decoding Hosing and Heating Effects on Global Temperature and Meridional Circulations in a Warming Climate", Journal of Climate, https://doi.org/10.1175/JCLI-D-18-0297.1

https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-18-0297.1

...

I have now reviewed Wen et al (2018), and perhaps I am over reacting to the fact that several media reports that I saw headlined the finding that: '… freshwater change has a significant cooling effect that can mitigate the global surface warming by as much as ~30%. … In terms of global temperature and Earth’s energy balance, the freshwater change plays a stabilizing role in a warming climate.'.  Nevertheless, I first note that 'All models are wrong, but some models are useful', and I offer the following comments about the following extracts and first two images from Wen et al (2018), as related to the following three linked references:

1. The extract and the second linked reference shows that the authors used an older version of CESM that has been superseded since June 2018 by a version with many improvements/corrections including improved subroutines for ice sheet behavior and for cloud feedback, which are both important when talking about 'Decoding Hosing and Heating Effects on Global Temperature and Meridional Circulations in a Warming Climate'.

2. The first two images make it clear that the authors' model considers a relatively slow rate of ice mass loss from the GIS and the AIS over many hundreds of years, and thus clearly does not consider abrupt ice mass loss such as that induced by ice-cliff failures and/or hydrofracturing.  Thus, the estimated 30% reduction in global warming occurs over a 2,000 year period, while Hansen et al (2016)'s larger reduction in global warming occurs over several decades and then this cooling dissipates in subsequent decades.  Furthermore, Wen et al (2018)'s findings that freshwater hosing stabilizes the Earth's energy balances is likely similarly related to the hosing scenario that they assume [which is radically less dynamic than that of Hansen et al (2016)].

3. Wen et al. (2018) acknowledge that they only consider two feedback mechanisms (i.e. the long wave and short wave radiation due to surface temperature and the impacts on the MOC) of the may involved in the net ice-climate feedback mechanism. and they ignore other such hosing feedback mechanisms as the influence of: '… the wind-driven circulations and subduction in the midlatitudes, the intermediate water formation in the subpolar Antarctic, and the atmospheric monsoon system? How are climate variabilities, such as El Niño–Southern Oscillation, the Pacific decadal oscillation, and the Atlantic multidecadal oscillation, modulated by freshwater change and radiation forcing?'. In this regards the authors' findings would have more meaning if they had bothered to calibrate their models response to match paleo data [see the third linked reference, Maier et al (2018)], as E3SM has done and I note that CESM 2.0 (which superseded the version used by the authors) adopted many of the calibrations identified by E3SM.

4. The authors define numerous terms that are consistent within the reference (and thus acceptable in peer review), but that differ from common usage, e.g.: their definition of 'sea ice' includes marine glacial ice.

5. I could go on with my critiques but leave it to say that within the author's limited set of assumptions their work appears to be consistent with other CMIP5 era of projections, but in my option they fall behind the CMIP6 level of sophistication, so I look forward to seeing the CMIP6 (and AR6) findings for freshwater hosing impact (while noting that none of them are currently considering ice-cliff failures nor hydrofracting of ice sheets).

Extract: "The hosing effect, in this work, refers to ocean freshwater flux change, which can directly change ocean salinity (Durack and Wijffels 2010) and thus upper-ocean buoyancy, affecting mainly the thermohaline circulation and thus the oceanic heat transport (OHT) (Swingedouw et al. 2007, 2009; Yang et al. 2013, 2017).

In this study, the heating and hosing effects are separated in a coupled climate model through two groups of global warming experiments. It is shown that the freshwater change has a significant cooling effect that can mitigate the global surface warming by as much as ~30%. Two significant regional cooling centers appear: one in the subpolar Atlantic and one in the Southern Ocean; both are triggered by sea ice melting but are sustained by different mechanisms. The subpolar Atlantic cooling is maintained by the weakened AMOC in the NH, while the Southern Ocean surface cooling is maintained by the enhanced northward Ekman flow related to strengthened westerly wind (Ferreira et al. 2015; Kostov et al. 2017). In these two regions, the effect of freshwater flux change dominates over that of radiation flux change, controlling the SST change in the warming climate.

The model used in this study is the Community Earth System Model (CESM) of the National Center for Atmospheric Research (NCAR), which was used in our previous studies (e.g., Dai et al. 2017). CESM is a fully coupled global climate model that provides state-of-the-art simulations of Earth’s past, present, and future climate states (http://www.cesm.ucar.edu/). CESM (version 1.0) consists of five components and one coupler: The Community Atmosphere Model, version 5 (CAM5; Park et al. 2014); the Community Land Model, version 4 (CLM4; Lawrence et al. 2012); the Community Ice Code, version 4 (CICE4; Hunke and Lipscomb 2008); the Parallel Ocean Program, version 2 (POP2; Smith et al. 2010); the Community Ice Sheet Model (Glimmer-CISM); and the CESM coupler, version 7 (CPL7). CESM1.0 is widely used and validated by researchers in the community.

This work is the first step toward quantifying the individual contributions of the heating and hosing effects to an evolving climate. Only the surface temperature and large-scale circulations are examined in this paper. Many other aspects have not been considered in the present study. For example, how do the hosing effect and the heating effect influence the wind-driven circulations and subduction in the midlatitudes, the intermediate water formation in the subpolar Antarctic, and the atmospheric monsoon system? How are climate variabilities, such as El Niño–Southern Oscillation, the Pacific decadal oscillation, and the Atlantic multidecadal oscillation, modulated by freshwater change and radiation forcing? It should be recognized that climate models have many limitations and that a climate shift in the model experiments may also exist. Many questions remain about the roles of the hydrological cycle in global change."

Caption for the first image: "FIG. 1. (a) Temporal evolutions of globally integrated net radiative flux (black), net downward SW (blue), and outgoing LW (red) at TOA (PW; positive for downward anomaly) under 2CO2 forcing. The red line at the top denotes the CO2 forcing. (b),(c) As in (a), but showing the hosing effect and heating effect, respectively. Each curve is smoothed with a 20-yr running mean. (d) Radiative flux change at the TOA in stage I of global warming, with net radiative flux (black), SW (blue), and LW (red). Stage I spans the years 200–500. (e),(f) As in (d), but showing the hosing effect and heating effect, respectively."

Caption for the second image: "FIG. 2. Temporal evolutions of (a)–(c) SST (thick solid curves) and SAT (thin dashed curves) averaged over the globe (black), NH (red), and SH (blue) (°C); (d)–(f) percentage changes of the AMOC (black), the Indo-Pacific STC (blue), and HC (red; %); and (g)–(i) AHT (red), global OHT (blue), Atlantic OHT (green), and Indo-Pacific OHT (light blue) averaged over 30°–70°N (PW). The AMOC index is defined as the maximum of the streamfunction in the range of 0°–10°C isotherms over 20°–70°N in the Atlantic. The Indo-Pacific STC is similarly defined, but in the range of 20°–30°C isotherms over 0°–30°N. The HC index is defined as the maximum streamfunction between 200 and 1000 hPa over 0°–30°N. All indexes are normalized by their time-mean values in CTRL, which are 18, 36, and 92 Sv, respectively (1 Sv = 106 m3 s−1 for the ocean; 1 Sv = 109 kg s−1 for the atmosphere). Each curve is smoothed with a 20-yr running mean. Stage I spans the years 200–500 and represents an earlier quasi-equilibrium stage of global warming, based on the AMOC evolution. Stage II spans the years 800–1100 and represents the recovery stage of the AMOC. Stage III spans the years 1700–2000 and represents the equilibrium stage of global warming for (a),(d),(g) 2CO2 forcing; (b),(e),(h) hosing effect; and (c),(f),(i) heating effect."

See also:

Qian