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FishOutofWater

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3500 on: July 14, 2020, 03:25:34 PM »
It's shocking that 2020 could be the warmest year on record while the cold tongue is strong in the eastern equatorial Pacific. This may not be a La Niña year but it certainly is not an El Niño when we normally see the highest global temperatures.

There's some hard to explain things happening with the intense end stratospheric warmings in the northern hemisphere the past 2 years.  The physics is beyond me but what's happening is consistent with research papers that report an increase in the up - down circulation from the troposphere to the stratosphere and back. Whatever, these strong end warmings apparently have transferred momentum from the winter polar vortex downwards to the polar jet stream in the troposphere in May of both years and pushed the jet stream south. That has led to more heat transfer by Rossby waves to the polar region.

I await the publication of research papers by atmospheric physicists to get the story right. I'm just giving you my best take that something is amiss.

kassy

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3501 on: July 14, 2020, 04:16:49 PM »
Could that work like:

Warmer atmosphere with more water in the atmosphere.
And due to the extra polar warming we have something like a bigger gradient or the cold pole protection system broke down (or both) so more is going north.

The cold poles would be at different places and now they look settled in Greenland and Canada which opens the Siberian side. Not that i know that much about that i just read wayne´s blog about that. No direct links since it has been ages but searching that site for ´cold pole´ should yield some results.

http://eh2r.blogspot.com/

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3502 on: July 14, 2020, 06:59:11 PM »
The linked reference indicates that the observed slowing of the AMOC has contributed to cooling in both the North Atlantic and the in the Southern Ocean that so far has outweighed the associated warming of the tropical ocean SST, indicating for some years to come:

"… the slowing of the overturning will likely continue to slightly reduce the effect of the general warming due to increasing greenhouse gas concentrations."

To me this slight reduction in GMSTA is a red herring that diverts from much more significant issues such as the fact that the slowdown of the flow (Sv) of the AMOC results in an increase in the rate of ocean heat uptake (see the attached image) as the associated increase in ocean heat content in both the Southern Ocean and in the waters around Greenland results in increase subsea melting of ice near the grounding lines of key marine glaciers (marine terminating glaciers) in both the AIS and the GIS, respectively:

L Caesar, S Rahmstorf and G Feulner (20 January 2020), "On the relationship between Atlantic meridional overturning circulation slowdown and global surface warming", Environmental Research Letters, Volume 15, Number 2, https://doi.org/10.1088/1748-9326/ab63e3

https://iopscience.iop.org/article/10.1088/1748-9326/ab63e3

Abstract
According to established understanding, deep-water formation in the North Atlantic and Southern Ocean keeps the deep ocean cold, counter-acting the downward mixing of heat from the warmer surface waters in the bulk of the world ocean. Therefore, periods of strong Atlantic meridional overturning circulation (AMOC) are expected to coincide with cooling of the deep ocean and warming of the surface waters. It has recently been proposed that this relation may have reversed due to global warming, and that during the past decades a strong AMOC coincides with warming of the deep ocean and relative cooling of the surface, by transporting increasingly warmer waters downward. Here we present multiple lines of evidence, including a statistical evaluation of the observed global mean temperature, ocean heat content, and different AMOC proxies, that lead to the opposite conclusion: even during the current ongoing global temperature rise a strong AMOC warms the surface. The observed weakening of the AMOC has therefore delayed global surface warming rather than enhancing it.

Social Media Abstract: The overturning circulation in the Atlantic Ocean has weakened in response to global warming, as predicted by climate models. Since it plays an important role in transporting heat, nutrients and carbon, a slowdown will affect global climate processes and the global mean temperature. Scientists have questioned whether this slowdown has worked to cool or warm global surface temperatures. This study analyses the overturning strength and global mean temperature evolution of the past decades and shows that a slowdown acts to reduce the global mean temperature. This is because a slower overturning means less water sinks into the deep ocean in the subpolar North Atlantic. As the surface waters are cold there, the sinking normally cools the deep ocean and thereby indirectly warms the surface, thus less sinking implies less surface warming and has a cooling effect. For the foreseeable future, this means that the slowing of the overturning will likely continue to slightly reduce the effect of the general warming due to increasing greenhouse gas concentrations.

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3503 on: July 14, 2020, 07:02:48 PM »
Could that work like:

Warmer atmosphere with more water in the atmosphere.
And due to the extra polar warming we have something like a bigger gradient or the cold pole protection system broke down (or both) so more is going north.

The cold poles would be at different places and now they look settled in Greenland and Canada which opens the Siberian side. Not that i know that much about that i just read wayne´s blog about that. No direct links since it has been ages but searching that site for ´cold pole´ should yield some results.

http://eh2r.blogspot.com/

Don't forget that due to both the reduction of sulfur in ship bunker fuel and the reduction in aerosol emissions due to COVID-19, the negative feedback from anthropogenic aerosols has been markedly reduced so far in 2020; which should result in rapid increases in GMSTA.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3504 on: July 14, 2020, 07:32:23 PM »
Without much comment (as I am busy), the linked session from the Ocean Sciences Meeting, February 16-21, 2020, focuses on many different issues associated with the AMOC and among this many issues some of the linked research indicates that: a) data uncertainty accounts for some of the observed fluctuations and b) some of the observed fluctuations of the AMOC can be associated with changes in large eddies and gyres in the North Atlantic:

Title: "PC24A - Atlantic Meridional Overturning Circulation: An Ongoing Challenge III Posters"

https://agu.confex.com/agu/osm20/meetingapp.cgi/Session/84627

&

Title: "PC24A-1744 - A joint Analysis of the Atlantic Meridional Overturning Circulation at 26.5oN using two Observations-based Time Series"

https://agu.confex.com/agu/osm20/meetingapp.cgi/Paper/651773

Abstract: "Observations from satellite altimetry, Argo floats and wind stress fields are used to construct three dimensional, monthly absolute geostrophic velocity fields (hereinafter, Argo & altimetry) in the North Atlantic during 1993 to 2018. This velocity product together with volume transport estimates of Florida Current from a submarine cable between Florida and Bahamas near 26.5oN and the monthly climatology from the World Ocean Atlas are used to derive time series of volume and heat transports associated with the Atlantic Meridional Overturning Circulation (AMOC). It is found that the mean and standard deviation of the meridional volume and heat transports from Argo & altimetry agree quite well with those from MOCHA/RAPID. However, there are some significant differences in their interannual variability. The main time period with a large difference is 5/2004 to 4/2009 during which MOCHA/RAPID reveals a negative trend of -4.3 Sv/decade while the Argo & altimetry time series has no significant trend. Another period with significant differences is 1/2013 to 12/2016. The main goal of this work is to analyze the differences between the two time series by using multiple combinations of the two primary date sets and methodologies as well as data withholding experiments. The differences during this time will be analyzed to investigate the potential causes for them. The strategy is to apply the MOCHA/RAPID technique to the data from Argo & altimetry and vice versa. In addition to that, transports are estimated with the MOCHA/RAPID technique after withholding data at selected longitudes as well as after swapping out data in selected depth ranges. These results will elucidate the role of the observational strategies and the associated computational methodologies have on the derived transport."

&
https://agu.confex.com/agu/osm20/meetingapp.cgi/Paper/653927
&
https://agu.confex.com/agu/osm20/meetingapp.cgi/Paper/642031

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3505 on: July 14, 2020, 10:08:32 PM »
The linked article on the consequences of Arctic amplification in Siberia has too many consequences to summarize here, so I just highlight the impacts (& positive feedbacks) associated with peat fires in the Siberian tundra:

Title: "Record heat wave in Siberia has far-flung consequences"

https://www.dw.com/en/siberia-fires-permafrost/a-54120019

Extract: "Oil spills, intense heat waves, smoldering wildfires and thawing permafrost: Siberia is experiencing the destructive effects of climate change. And scientists say if action isn't taken soon, it's only going to get worse.

"Every single time peat burns, it is a net carbon contribution to climate change. And you cannot undo it," he said. Plus, peatland blazes are extremely difficult to extinguish. 
"I've been at a peat fire and it's rained for an hour very heavily, and it's still burning at the end," said Smith. "They will just smolder away. And some peat fires are known to last for months." They have even been known to survive underground through the winter months as "zombie fires," flaring up again on the surface in the spring.

Rein called it a "positive feedback loop" with a negative impact: The more peat and trees that burn, the greater the greenhouse gases that are released into the atmosphere. That leads in turn to hotter temperatures and drier, less resilient forests and peatlands — and more wildfires.

Much of the burning peat in Siberia sits on permafrost, only adding to scientists' concerns. Climate change, helped along by increased wildfire activity, is melting this frozen ground and creating a host of new problems."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3506 on: July 14, 2020, 10:29:23 PM »
It's shocking that 2020 could be the warmest year on record while the cold tongue is strong in the eastern equatorial Pacific. This may not be a La Niña year but it certainly is not an El Niño when we normally see the highest global temperatures.

...

Per the attached image from the BoM, both the ENSO and the IOD are forecast to remain neutral for the rest of 2020.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3507 on: July 15, 2020, 01:11:28 AM »
The linked references, and associated article, discuss the sources of the current record anthropogenic methane emissions:

“Increasing anthropogenic methane emissions arise equally from agricultural and fossil fuel sources” by R B Jackson, M Saunois, P Bousquet, J G Canadell, B Poulter, A R Stavert, P Bergamaschi, Y Niwa, A Segers and A Tsuruta, 15 July 2020, Environmental Research Letters.
DOI: 10.1088/1748-9326/ab9ed2

https://iopscience.iop.org/article/10.1088/1748-9326/ab9ed2

Extract: "Climate stabilization remains elusive, with increased greenhouse gas concentrations already increasing global average surface temperatures 1.1 °C above pre-industrial levels (World Meteorological Organization 2019). Carbon dioxide (CO2) emissions from fossil fuel use, deforestation, and other anthropogenic sources reached ~ 43 billion metric tonnes in 2019 (Friedlingstein et al 2019, Jackson et al 2019). Storms, floods, and other extreme weather events displaced a record 7 million people in the first half of 2019 (IDMC 2019). When global mean surface temperature four million years ago was 2 °C–3 °C warmer than today (a likely temperature increase before the end of the century), ice sheets in Greenland and West Antarctica melted and parts of East Antarctica's ice retreated, causing sea levels to rise 10–20 m (World Meteorological Organization 2019).

Methane (CH4) emissions have contributed almost one quarter of the cumulative radiative forcings for CO2, CH4, and N2O (nitrous oxide) combined since 1750 (Etminan et al 2016). Although methane is far less abundant in the atmosphere than CO2, it absorbs thermal infrared radiation much more efficiently and, in consequence, has a global warming potential (GWP) ~86 times stronger per unit mass than CO2 on a 20-year timescale and 28-times more powerful on a 100-year time scale (IPCC 2014).

Global average methane concentrations in the atmosphere reached ~1875 parts per billion (ppb) at the end of 2019, more than two-and-a-half times preindustrial levels (Dlugokencky 2020). The largest methane sources include anthropogenic emissions from agriculture, waste, and the extraction and use of fossil fuels as well as natural emissions from wetlands, freshwater systems, and geological sources (Kirschke et al 2013, Saunois et al 2016a, Ganesan et al 2019). Here, we summarize new estimates of the global methane budget based on the analysis of Saunois et al (2020) for the year 2017, the last year of the new Global Methane Budget and the most recent year data are fully available. We compare these estimates to mean values for the reference 'stabilization' period of 2000–2006 when atmospheric CH4 concentrations were relatively stable. We present data for sources and sinks and provide insights for the geographical regions and economic sectors where emissions have changed the most over recent decades."

&

Earth System Science Data, doi: 10.5194/essd-12-1561-2020

https://essd.copernicus.org/articles/12/1561/2020/

See also:

Title: "Global Methane Emissions Soar to Record High, Even As Pandemic Has Reduced Carbon Emissions"

https://scitechdaily.com/global-methane-emissions-soar-to-record-high-even-as-pandemic-has-reduced-carbon-emissions/

Extract: "Global emissions of methane have reached the highest levels on record. Increases are being driven primarily by growth of emissions from coal mining, oil and natural gas production, cattle and sheep ranching, and landfills.

Between 2000 and 2017, levels of the potent greenhouse gas barreled up toward pathways that climate models suggest will lead to 3-4 degrees Celsius of warming before the end of this century. This is a dangerous temperature threshold at which scientists warn that natural disasters, including wildfires, droughts and floods, and social disruptions such as famines and mass migrations become almost commonplace. The findings are outlined in two papers published today (July 14, 2020) in Earth System Science Data and Environmental Research Letters by researchers with the Global Carbon Project, an initiative led by Stanford University scientist Rob Jackson."
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Hefaistos

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3508 on: July 15, 2020, 10:08:43 AM »
It's shocking that 2020 could be the warmest year on record while the cold tongue is strong in the eastern equatorial Pacific. This may not be a La Niña year but it certainly is not an El Niño when we normally see the highest global temperatures.

There's some hard to explain things happening with the intense end stratospheric warmings in the northern hemisphere the past 2 years.  The physics is beyond me but what's happening is consistent with research papers that report an increase in the up - down circulation from the troposphere to the stratosphere and back. Whatever, these strong end warmings apparently have transferred momentum from the winter polar vortex downwards to the polar jet stream in the troposphere in May of both years and pushed the jet stream south. That has led to more heat transfer by Rossby waves to the polar region.

I await the publication of research papers by atmospheric physicists to get the story right. I'm just giving you my best take that something is amiss.

Which part of the stratosphere (altitude) would that be?
The lower stratosphere has declining anomalies for 30 years or so. See attached chart.
Some disturbances in the beginning of 2020, but they are in SH.

The second chart shows the Northern Polar region. Also here we have pronounced negative trend.
Lot's of volatility, but the beginning of 2020 actually shows big drops.
This is satellite data from UAH6.
« Last Edit: July 15, 2020, 01:11:11 PM by Hefaistos »

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3509 on: July 15, 2020, 05:44:34 PM »
The linked references, and associated article, discuss the sources of the current record anthropogenic methane emissions:

“Increasing anthropogenic methane emissions arise equally from agricultural and fossil fuel sources” by R B Jackson, M Saunois, P Bousquet, J G Canadell, B Poulter, A R Stavert, P Bergamaschi, Y Niwa, A Segers and A Tsuruta, 15 July 2020, Environmental Research Letters.
DOI: 10.1088/1748-9326/ab9ed2

https://iopscience.iop.org/article/10.1088/1748-9326/ab9ed2

...

Here is a follow-on article about this topic, which indicates that once triggered permafrost degradation could reduce the carbon budget by about 5-years in coming decades:

Title: "Scientists concerned by ‘record high’ global methane emissions"

https://www.carbonbrief.org/scientists-concerned-by-record-high-global-methane-emissions

Extract: "Permafrost – perennially frozen rock and soils – is found across vast swaths of the northern hemisphere’s high latitudes. This ground holds billions of tonnes of carbon, which could be released – as CO2 and/or methane – as the region warms and the soil thaws. This is an example of a “positive feedback” where more greenhouse gases are released as global temperatures rise, thus reinforcing the warming.

Research by Jones and colleagues has suggested that greater emissions of CO2 and methane from wetlands and thawing permafrost as the climate warms could cut the carbon budget for the Paris Agreement temperature limits by around five years."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3510 on: July 15, 2020, 06:02:42 PM »
The linked video provides a consensus science explainer of why/how the Thwaites Glacier is currently falling apart (including the recently identified subglacial cavities); however, it omits consideration of MICI-types of potential collapse:

Title: " Why scientists are so worried about this glacier"

https://www.youtube.com/watch?v=XRUxTFWWWdY&feature=youtu.be

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3511 on: July 15, 2020, 06:17:22 PM »
The linked open access reference indicates that 16 CMIP6 model projections indicate that the projected increase in El Nino-like warming pattern this century will contribute to an abrupt 77% decrease of the upper-level tropical easterly jet over the tropical eastern Pacific.  I note that if the MOC slows abruptly due to one, or more, significant freshwater hosing events in coming decades that this timeline could be appreciably accelerated:

Sihua Huang, Bin Wang and Zhiping Wen (2020)," Dramatic Weakening of the Tropical Easterly Jet Projected by CMIP6 Models", J. Climate, https://doi.org/10.1175/JCLI-D-19-1002.1

https://journals.ametsoc.org/jcli/article/doi/10.1175/JCLI-D-19-1002.1/353358/Dramatic-Weakening-of-the-Tropical-Easterly-Jet?searchresult=1

Abstract
The upper-level tropical easterly jet (TEJ) is a crucial component of the summer monsoon system and tropical general circulation. The simulation and projection of the TEJ, however, have not been assessed. Here we evaluate models’ fidelity and assess the future change of the TEJ by utilizing 16 models that participated in phase six of the Coupled Model Intercomparison Project (CMIP6). Most of the models can reproduce the TEJ reasonably well in terms of climatology, seasonal evolution and interannual variability. Nevertheless, underestimation of the TEJ’s intensity and extent is identified, with the maximum bias occurring in the jet centers over the tropical Indian Ocean (IO) and the tropical eastern Pacific (EP). Under the Shared Socioeconomic Pathway 5-8.5, the multimodel ensemble projects a remarkable reduction in the central TEJ intensity by about 18% over the IO and 77% over the EP toward the end of the 21st century. The mean intensity of TEJ will weaken by about 11%, and the extent will reduce by 6%, suggesting a significantly weakened upper-level monsoon circulation in the future climate. The projected El Niño-like warming pattern over the tropical Pacific may play a critical role in the future weakening of the TEJ via inducing suppressed rainfall over the tropical eastern IO and Central America. The model uncertainties in the projected TEJ changes may arise from the uncertainties in models’ projected tropical EP warming. The sensitivity of future projections to model selection is also examined. Results show that the selection of models based on different physical considerations does not yield a significantly different projection.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3512 on: July 15, 2020, 07:20:36 PM »
While the linked consensus climate science article provides useful information on how climate change might be impacting wildfires around the world; it does not discuss the probably positive feedback between wildfires and climate change:

Title: "Explainer: How climate change is affecting wildfires around the world"

https://www.carbonbrief.org/explainer-how-climate-change-is-affecting-wildfires-around-the-world

Extract: "This year has seen unprecedented wildfires cause havoc across the world. Australia recently battled its largest bushfire on record, while parts of the Arctic, the Amazon and central Asia have also experienced unusually severe blazes.

It follows on from “the year rainforests burned” in 2019."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3513 on: July 16, 2020, 08:57:15 AM »
It is regrettable that the economist Martin Weitzman died last year as without his 'fat-tail' climate change economic analysis it is not likely that the 2015 Paris Agreement would have adopted its formal goal of staying well below 2oC GMSTA and preferably to stay below 1.5oC GMSTA.  While it is good that his work did result in the formal adoption these goals for limiting climate change; since the time that he published his works on this topic the 'fat-tail' has become fatter but decision makers still belittle these increasingly likely right-tail catastrophes by pretending that tipping points are not real and that mankind can always reverse future climate impacts by eventually limiting anthropogenic GHG emissions at some point in the future.  Unfortunately, such pretenses are not real, and considering the higher ECS values projected by CMIP6 and the positive ice-climate feedback mechanisms not fully evaluated by CMIP6, it is my opinion that we should stay well below 1.5oC GMSTA, and a man like Martin Weitzman may have been capable of conveying that matter to current decision makers as his earlier works were able to impact the 2015 Paris Agreement.

Title: "The Man Who Got Economists to Take Climate Nightmares Seriously"

https://www.bloomberg.com/news/articles/2019-08-29/the-man-who-got-economists-to-take-climate-nightmares-seriously

Extract: "This is the hallmark of traditional cost-benefit analysis: Figure out the benefits of keeping the climate stable, compare that to the costs of preventing change, and then determine which policies make the most sense.

Weitzman used technical math to make the case that climate change is different because what’s most likely to happen doesn’t matter as much when there’s a possibility of total catastrophe. “Even when you have a low probability of a highly consequential event, those consequences—when they’re of a significant enough magnitude—can really overwhelm your thinking,” said Richard Newell, chief executive of the research nonprofit Resources for the Future and a former Weitzman teaching assistant.
...
Weitzman’s analysis was influential in helping convince global diplomats to adopt a goal for limits on warming—1.5 and 2 degree Celsius—in the 2015 Paris Agreement. Robert Stavins, director of the Harvard Environmental Economics Program, said the Paris targets may not have passed “an economic analysis, unless you take account of Weitzman’s fat tails.”
...
“His fat-tail story in many ways was the story,” Wagner said, “of how those uncertainties could potentially drive everything. He called it the Dismal Theorem. The burden of proof is on those who think that those risks don’t matter. It’s not the other way around.”
...
Newell said one of Weitzman’s biggest accomplishments was “challenging historical orthodoxy concerning long-term discounting, and doing so in a way that has had direct influence on government policy.” President Barack Obama’s team cited Weitzman’s work in technical material supporting its cost estimates for each metric ton of emitted C02."

I point out that Weitzman's work on fat-tailed risk is even more compelling when one considered a possible cascade of tipping points (driven largely from freshwater hosing events) possibly leading to a post-PETM situation such as that evaluated by Romps (2020) where ECS might approach 15C as shown in the first image.  The second image (see caption) shows a risk analysis using likelihood and damage functions (by Weitzman) at ECS up to about 8C.  If decision makers understood this long-tailed risk appropriately they would take immediate action to make sure that it never occurs as an ECS of 15C would likely be an extinction level event for mankind.

Caption for the second 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)."

Edit: I note that a nuclear winter would short-circuit such a freshwater driven cascade of tipping points, but that a major conventional war would increase the probability of such a scenario.
« Last Edit: July 16, 2020, 03:59:11 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3514 on: July 16, 2020, 11:03:37 PM »
The linked reference indicates that anthropogenic aerosols increase the life of clouds; which it assumes will result in more negative cloud feedback.  However, high altitude clouds produce positive climate change feedback, so if future global warming creates more high altitude clouds (as projected by many CMIP6 models), then in the future longer-lived clouds may produce more positive feedback than previously assumed:

Matthew W. Christensen et al. (July 13, 2020); "Aerosols enhance cloud lifetime and brightness along the stratus-to-cumulus transition", PNAS, https://doi.org/10.1073/pnas.1921231117

https://www.pnas.org/content/early/2020/07/09/1921231117.short?rss=1

Significance
All cloud droplets on Earth form from tiny airborne particles known as aerosols. Additional aerosols from anthropogenic activity have produced more cloud droplets but at smaller sizes. The smaller, more numerous droplets in clouds do not collide as effectively, therefore resulting in less precipitation. Using a combination of time-lapse satellite imagery and air mass trajectory modeling, we show that aerosols can enhance cloud fraction and extend the lifetime of overcast cloud fields primarily under stable atmospheric conditions as typically found off the west coasts of subtropical stratocumulus-dominated regions. Longer-lived clouds have a stronger cooling influence on climate and therefore, need to be correctly parameterized in atmospheric models so that accurate projections of climate change can be achieved.

Abstract
Anthropogenic aerosols are hypothesized to enhance planetary albedo and offset some of the warming due to the buildup of greenhouse gases in Earth’s atmosphere. Aerosols can enhance the coverage, reflectance, and lifetime of warm low-level clouds. However, the relationship between cloud lifetime and aerosol concentration has been challenging to measure from polar orbiting satellites. We estimate two timescales relating to the formation and persistence of low-level clouds over 1○×1○1○×1○ spatial domains using multiple years of geostationary satellite observations provided by the Clouds and Earth’s Radiant Energy System (CERES) Synoptic (SYN) product. Lagrangian trajectories spanning several days along the classic stratus-to-cumulus transition zone are stratified by aerosol optical depth and meteorology. Clouds forming in relatively polluted trajectories tend to have lighter precipitation rates, longer average lifetime, and higher cloud albedo and cloud fraction compared with unpolluted trajectories. While liquid water path differences are found to be negligible, we find direct evidence of increased planetary albedo primarily through increased drop concentration (NdNd) and cloud fraction, with the caveat that the aerosol influence on cloud fraction is positive only for stable atmospheric conditions. While the increase in cloud fraction can be large typically in the beginning of trajectories, the Twomey effect accounts for the bulk (roughly 3/4) of the total aerosol indirect radiative forcing estimate.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3515 on: July 16, 2020, 11:14:45 PM »
The linked reference reminds us that an increase in strong summer atmosphere river events in Greenland with continued global warming would lead to accelerated ice melt into the North Atlantic where it would contribute to a slowing of the AMOC:

Kyle S. Mattingly et al. (2020), "Strong Summer Atmospheric Rivers Trigger Greenland Ice Sheet Melt through Spatially Varying Surface Energy Balance and Cloud Regimes, J. Climate, 33, (16), 6809–6832.
https://doi.org/10.1175/JCLI-D-19-0835.1

https://journals.ametsoc.org/jcli/article/33/16/6809/348249/Strong-Summer-Atmospheric-Rivers-Trigger-Greenland

ABSTRACT
Mass loss from the Greenland Ice Sheet (GrIS) has accelerated over the past two decades, coincident with rapid Arctic warming and increasing moisture transport over Greenland by atmospheric rivers (ARs). Summer ARs affecting western Greenland trigger GrIS melt events, but the physical mechanisms through which ARs induce melt are not well understood. This study elucidates the coupled surface–atmosphere processes by which ARs force GrIS melt through analysis of the surface energy balance (SEB), cloud properties, and local- to synoptic-scale atmospheric conditions during strong summer AR events affecting western Greenland. ARs are identified in MERRA-2 reanalysis (1980–2017) and classified by integrated water vapor transport (IVT) intensity. SEB, cloud, and atmospheric data from regional climate model, observational, reanalysis, and satellite-based datasets are used to analyze melt-inducing physical processes during strong, >90th percentile “AR90+” events. Near AR “landfall,” AR90+ days feature increased cloud cover that reduces net shortwave radiation and increases net longwave radiation. As these oppositely signed radiative anomalies partly cancel during AR90+ events, increased melt energy in the ablation zone is primarily provided by turbulent heat fluxes, particularly sensible heat flux. These turbulent heat fluxes are driven by enhanced barrier winds generated by a stronger synoptic pressure gradient combined with an enhanced local temperature contrast between cool over-ice air and the anomalously warm surrounding atmosphere. During AR90+ events in northwest Greenland, anomalous melt is forced remotely through a clear-sky foehn regime produced by downslope flow in eastern Greenland.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3516 on: July 16, 2020, 11:59:54 PM »
The title of the linked article says it all:

Title: "Siberia’s 2020 heatwave made ‘600 times more likely’ by climate change"

https://www.carbonbrief.org/siberia-s-2020-heatwave-made-600-times-more-likely-by-climate-change

Extract: "Siberia’s prolonged heat from January to June this year – which broke temperature records and drove polluting megafires – would have been “almost impossible” without human-caused climate change, according to new analysis."
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FishOutofWater

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3517 on: July 17, 2020, 02:16:55 AM »
End warmings are the events that end the cold winter polar vortex in the polar region of the stratosphere. the end warming event happens every year from the top to the bottom of the stratosphere. They have taken place suddenly and had anomalously high heating the past 2 years.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3518 on: July 17, 2020, 03:50:31 AM »
The linked video provides a consensus science explainer of why/how the Thwaites Glacier is currently falling apart (including the recently identified subglacial cavities); however, it omits consideration of MICI-types of potential collapse:

Title: " Why scientists are so worried about this glacier"

https://www.youtube.com/watch?v=XRUxTFWWWdY&feature=youtu.be

In the interview the demise of Thwaites Glacier and the WAIS is referred to in time-frames of 'hundreds' and 'thousands' of years.

Not only does the interview omit reference to MICI-types of potential collapse, it omits reference to many relevant factors. The Greenland Ice Sheet will substantially melt out within a hundred years and no scientific study that I have seen about the Thwaites Glacier takes into account a rising sea level rise of up to  of up to 7 M.

IMO the current research will read as no more than interesting historic anecdotes after the event. Too late will be the cry!

 
Remember...it's all about the Jet Stream you dummy...just a personal reminder!

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3519 on: July 17, 2020, 02:49:09 PM »
...

Edit: I note that a nuclear winter would short-circuit such a freshwater driven cascade of tipping points, but that a major conventional war would increase the probability of such a scenario.

FYI

Robock, A. and Zambri, B. (2018) Did smoke from city fires in World War II cause global cooling? Journal of Geophysical Research: Atmospheres, doi:10.1029/2018JD028922

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JD028922

Abstract
Between 3 February and 9 August 1945, an area of 461 km2 in 69 Japanese cities, including Hiroshima and Nagasaki, was burned during the U.S. B‐29 Superfortress air raids. In the previous 5 years, 205 km2 in German cities were destroyed, so the smoke that was generated was spread out over a much longer period of time than that from Japan in 1945. Observations of solar irradiance show reductions consistent with the hypothesis that smoke was injected into the stratosphere by the city fires. Historical simulations from the Coupled Model Intercomparison Project 5, with no smoke in their forcing, showed no postwar cooling. Global average surface air temperature observations during and following World War II are problematic, because of issues with measuring sea surface temperatures, but there were no large volcanic eruptions, El Niño, or La Niña during this period to confuse the record. Nevertheless, 1945 and 1946 global average land surface air temperatures were not significantly lower than the average for 1940–1944. Estimates of the amount of smoke generated by the fires are somewhat uncertain. Although the climate record is consistent with an expected 0.1–0.2 K cooling, because of multiple uncertainties in smoke injected to the stratosphere, solar radiation observations, and surface temperature observations, it is not possible to formally detect a cooling signal from World War II smoke.

Plain Language Summary
Nuclear winter theory says that smoke from burning cities targeted with nuclear weapons would rise into the upper atmosphere and spread around the world, absorbing sunlight and cooling the surface. Unfortunately, we have two real‐world examples of this, Hiroshima and Nagasaki, which were burned by U.S. atomic bombs on 6 and 9 August 1945. We discovered that this was actually the culmination of a genocidal U.S. bombing campaign. Between 3 February and 9 August 1945, an area of 461 square kilometers in 69 Japanese cities, including Hiroshima and Nagasaki, was burned during the U.S. B‐29 Superfortress air raids, and the Hiroshima and Nagasaki smoke was less than 5% of the total. We calculated how much smoke was emitted and how much climate change would have been expected. Although there was a small cooling, because of multiple uncertainties in smoke injected to the stratosphere, sunlight observations, and surface temperature observations, we found that it is not possible to say for sure that this was a cooling signal from World War II smoke. However, these results do not invalidate nuclear winter theory that much more massive smoke emissions from nuclear war would cause large climate change and impacts on agriculture.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3520 on: July 17, 2020, 02:52:03 PM »
The linked video provides a consensus science explainer of why/how the Thwaites Glacier is currently falling apart (including the recently identified subglacial cavities); however, it omits consideration of MICI-types of potential collapse:

Title: " Why scientists are so worried about this glacier"

https://www.youtube.com/watch?v=XRUxTFWWWdY&feature=youtu.be

In the interview the demise of Thwaites Glacier and the WAIS is referred to in time-frames of 'hundreds' and 'thousands' of years.

Not only does the interview omit reference to MICI-types of potential collapse, it omits reference to many relevant factors. The Greenland Ice Sheet will substantially melt out within a hundred years and no scientific study that I have seen about the Thwaites Glacier takes into account a rising sea level rise of up to  of up to 7 M.

IMO the current research will read as no more than interesting historic anecdotes after the event. Too late will be the cry!

I believe that a cascade of freshwater hosing events working together with the bipolar seesaw mechanism and ice-climate feedbacks will result in at least 3m of mean SLR by 2090.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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D-Penguin

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3521 on: July 17, 2020, 11:34:24 PM »
The linked video provides a consensus science explainer of why/how the Thwaites Glacier is currently falling apart (including the recently identified subglacial cavities); however, it omits consideration of MICI-types of potential collapse:

Title: " Why scientists are so worried about this glacier"

https://www.youtube.com/watch?v=XRUxTFWWWdY&feature=youtu.be



In the interview the demise of Thwaites Glacier and the WAIS is referred to in time-frames of 'hundreds' and 'thousands' of years.

Not only does the interview omit reference to MICI-types of potential collapse, it omits reference to many relevant factors. The Greenland Ice Sheet will substantially melt out within a hundred years and no scientific study that I have seen about the Thwaites Glacier takes into account a rising sea level rise of up to  of up to 7 M.

IMO the current research will read as no more than interesting historic anecdotes after the event. Too late will be the cry!

I believe that a cascade of freshwater hosing events working together with the bipolar seesaw mechanism and ice-climate feedbacks will result in at least 3m of mean SLR by 2090.

Fascinating and way outside current projections based on 'the science'. I would not disagree with one jot of your belief and reasoning related to SLR.

Unfortunately the science is creating 'Fake News' because the scientists are not connecting the 'dots' and the decision makers do not posses the highest level of intellect necessary for creative thought to make the 'intuitive leap' required to create a truthful picture upon which policy and action must be based to avoid the Ice Apocalypse.
Remember...it's all about the Jet Stream you dummy...just a personal reminder!

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3522 on: July 18, 2020, 04:35:29 AM »
..

Fascinating and way outside current projections based on 'the science'. I would not disagree with one jot of your belief and reasoning related to SLR.

...

Here, I imagine that 'the science' can be translated as 'consensus science' like NOAA (2017). ;)
« Last Edit: July 18, 2020, 11:11:34 AM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3523 on: July 18, 2020, 11:15:15 AM »
The attached image is from the linked NOAA reference, which indicates a global mean sea level rise of 2.5m for the central 90% probability range augmented by MICI-type of Antarctic SLR contribution for RCP 8.5 to 2100.

Title: "Global and Regional Sea Level Rise Scenarios for the United States", January 2017.

https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf

While this does not constitute proof of abrupt sea level rise; it does constitute an official warning from NOAA of this possibility.

For those who want a link to NOAA's 2017 report see the link in the quote above and the attached image.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3524 on: July 18, 2020, 07:52:16 PM »
...
Title: "Global and Regional Sea Level Rise Scenarios for the United States", January 2017.

https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf

...

As ShortBrutishNasty is interested in how SLR could impact Miami, I attach an image extracted from NOAA (2017) Technical Paper 083 together with the following text extract as to how to apply NOAA's guidance.  I note (as a Civil Engineer) that selection of which of the the NOAA (2017) SLR curves to apply depends on the impacts on key infrastructure and that the Miami area has nuclear power plants (like the St. Lucie nuclear power plant) that merit consideration of NOAA's extreme (upper) SLR curve.  Furthermore, that such key infrastructure is typically designed to a 1% probability of exceedance; which indicates that in the attached image the upper dashed curve should be used for evaluation purposes (together with local relative sea level rise considerations:

Extract: "Key to the decision process is determining the extent to which a given amount of RSL rise may cause impacts to either newly built or existing infrastructure.

For many decisions, it is essential to assess worst-case scenarios, not only those assessed as the scientifically ‘likely’ to happen. For example, drawing on the references cited above, the following is suggested as a potential initial scenario selection strategy for decisions and planning processes for which long-term risk management is paramount:

● Define a scientifically plausible upper-bound (which might be thought of as a worst-case or extreme scenario) as the amount of sea level rise that, while low probability, cannot be ruled out over the time horizon being considered. Use this upper-bound scenario as a guide for overall system risk and long-term adaptation strategies.

● Define a central estimate or mid-range scenario (given assumptions about greenhouse gas emissions and other major drivers). Use this scenario as baseline for shorter-term planning, such as setting initial adaptation plans for the next two decades. This scenario and the upperbound scenario can together be thought of as providing a general planning envelope."
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D-Penguin

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3525 on: July 19, 2020, 12:51:29 AM »
..

Fascinating and way outside current projections based on 'the science'. I would not disagree with one jot of your belief and reasoning related to SLR.

...

Here, I imagine that 'the science' can be translated as 'consensus science' like NOAA (2017). ;)

A very fair point and good example of where the science has joined some of the 'dots' for the purpose of informing the decision makers.

However, I still feel uncomfortable about the way in which the 'science' is being conducted despite the example of 'consensual science' viz. "Global and Regional Sea Level Rise Scenarios for the United States", January 2017 as referenced in your follow-up posting.

I find it very difficult to conceptualize my concerns; I think this is because of the way in which the science is presented and the methodology. The scientist has an idea or a question that requires an answer (understanding) and so seeks verifiable data to 'prove' or dis-prove'. Over time a 'consensus' emerges. So, the 'consensus' is founded on results of individual studies.

IMO the individual studies are interesting and sometimes brilliant but of very limited value because they lack the component that provides the 'intuitive leap' that gives 'usefulness' to the study. In the case of an 'Ice Apocalypse', a more rationalized and realistic time-frame.

An example of my concern for a more 'applied science' approach would be:-
- The ice shelves that protect the glaciers are cantilever structures
- Ice is structurally weak in tensile strength
- A 1 M SLR will increase the hydro-static pressure on the underside of the ice sheet
What would be the fracture point leading to the complete demise of the ice shelf that would allow the previously retained glacier to flow directly into the open sea?

It just seems to me that this type of 'applied science' would be more relevant.

THEN the known science could be applied to the future of the land bound ice sheets of Greenland and Antarctica AND greater insight to the time frame and sequence of an Ice Apocalypse event.

..

Fascinating and way outside current projections based on 'the science'. I would not disagree with one jot of your belief and reasoning related to SLR.

...

Here, I imagine that 'the science' can be translated as 'consensus science' like NOAA (2017). ;)
Remember...it's all about the Jet Stream you dummy...just a personal reminder!

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3526 on: July 19, 2020, 04:46:00 PM »
...
A very fair point and good example of where the science has joined some of the 'dots' for the purpose of informing the decision makers.
...

D-Penguin,

I have made more posts critiquing consensus climate science projections than anyone else on this forum so I certainly share many of your reservations about 'the science' and/or 'consensus science'.  The fact of the matter is that the world is a much more complicated place than any Earth System Model, ESM, can replicate; therefore, projections from 'the science' can only represent a part of reality, and the parts left unmodeled represent uncertainty (or deep uncertainty); which decision makers can either use to try to ignore consensus science projections (such as the Trump Administration) or they can shoulder responsibility for the uncertainties and evaluate risks (probability times impact) associated with a range of possible scenarios (using the Precautionary Principle) ranging from mild to extreme.

As consensus climate science has a proven bias to err on the side of least drama; I try to use published (peer reviewed) scientific reports (consensus or otherwise) as a starting point and then I try to discuss many of the considerations that they have omitted from their models due to uncertainty/ignorance and/or lack of computational power (note that E3SMv4 will use exascale computers to partially address this short-coming).  For example, in an earlier post that you commented on, I cited the risk of cascading freshwater-hosing-related tipping points accelerated by the bipolar seesaw mechanism, so here I elaborate a little bit on what such an extreme scenario could build on the projections of E3SMv1 presented in CMIP6:

1. E3SMv1 projections indicate that glacial (including ice shelf) ice melting from both the GIS and the AIS is currently contributing to a slow-down of the MOC and that MISI-types of calving will accelerate this slow-down in coming decade, resulting in a relatively high value for TCR of about 2.93C for the rest of this century.  However, this projection ignores both MICI-types of mechanisms and a cascade of freshwater hosing events modulated by the bipolar seesaw mechanism via both atmospheric and oceanic telecommunication mechanism.

2. In my opinion there is a reasonable chance that the current slow-down of the AMOC (which is increasing the ocean heat content particularly in both the Southern Ocean and the North Atlantic Ocean, see the first attached image) will serve to increase the frequency and magnitude of periodic warm ocean water fluxes into the fjords of key marine terminating glaciers in Greenland (and also in Antarctica) so (in my opinion) that in the 2025 to 2030 timeframe that there will be a 5-year long surge of (ice cliff related) accelerated calving events from such key marine terminating glaciers as: Jakobshavn, Petermann, Zachariae, etc. that would both accelerate the slow-down of the MOC (thus warming the SST in the Tropical Pacific which would then atmospherically telecommunicate additional heat to the WAIS) and would contribute to a small increase in sea level in coastal West Antarctica.

3.  The result of the freshwater hosing event cited in item 2 would serve to help destabilize the marine glaciers in the Amundsen Sea Embayment, ASE; which together with a likely Super El Nino event and a likely subglacial lake drainage event beneath Thwaites, in the 2030-2035 timeframe; might likely both cause the PIIS to collapse and cause the Thwaites Glacier to undergo an MICI-type of collapse of the entire Byrd Subglacial Basin (BSB) by 2035.  Such a freshwater hosing event would not only further slow the MOC [by slowing AABW formation, around Antarctica, see Nakayama et al (2020)]; but would also slight rise sea level around Greenland and would push relatively warm Pacific water through the Bering Strait into the Beaufort Sea (see the second attached image from NOAA 2017).

3. The warm Pacific water intruding into the Beaufort Sea by 2035 cited in item 3 would likely trigger an abrupt release of freshwater from the Beaufort Gyre into first the Arctic Ocean (where it would destabilize the halocline resulting in abrupt melting of the Arctic Sea Ice) and then into the North Atlantic, where it would likely contribute to an abrupt slow-down of the AMOC, possibly in the 2035 to 2040 timeframe; which by the bipolar seesaw mechanism could trigger the abrupt collapse of both the FRIS and the RIS in the 2040 to 2045 timeframe that could contribute to the collapse of the vast majority of the remaining WAIS within the 2045 to 2090 time frame.


Nakayama, Y., Timmermann, R., and H. Hellmer, H.: Impact of West Antarctic ice shelf melting on Southern Ocean hydrography, The Cryosphere, 14, 2205–2216, https://doi.org/10.5194/tc-14-2205-2020, 2020.

https://tc.copernicus.org/articles/14/2205/2020/

Abstract
Previous studies show accelerations of West Antarctic glaciers, implying that basal melt rates of these glaciers were previously small and increased in the middle of the 20th century. This enhanced melting is a likely source of the observed Ross Sea (RS) freshening, but its long-term impact on the Southern Ocean hydrography has not been well investigated. Here, we conduct coupled sea ice–ice shelf–ocean simulations with different levels of ice shelf melting from West Antarctic glaciers. Freshening of RS shelf and bottom water is simulated with enhanced West Antarctic ice shelf melting, while no significant changes in shelf water properties are simulated when West Antarctic ice shelf melting is small. We further show that the freshening caused by glacial meltwater from ice shelves in the Amundsen and Bellingshausen seas can propagate further downstream along the East Antarctic coast into the Weddell Sea. The freshening signal propagates onto the RS continental shelf within a year of model simulation, while it takes roughly 5–10 and 10–15 years to propagate into the region off Cape Darnley and into the Weddell Sea, respectively. This advection of freshening modulates the shelf water properties and possibly impacts the production of Antarctic Bottom Water if the enhanced melting of West Antarctic ice shelves continues for a longer period.

Edit: Obviously, this cascade of freshwater-hosing-event-related tipping points modulated by bipolar seesaw mechanisms would likely continue beyond 2090 (and would likely trigger other positive feedback mechanisms prior to 2090); such as:

a) an increase in the frequency and intensity of both El Nino events (promoting more surface melting events in West Antarctica) and of Atmospheric River events impacting Greenland (promoting more surface melting events) both of which should increase hydrofracking of ice cliffs and of ice shelves.

b) Activation of MICI-type of behavior in key EAIS marine glaciers like Totten, and Byrd, possibly as early as 2060 to 2070.

« Last Edit: July 19, 2020, 06:15:45 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3527 on: July 19, 2020, 05:02:46 PM »
ShortBrutishNasty was thoughtful enough to send a link to me about James Hansen's latest article about paleo, and model, evidence about slowing of the MOC during periods of high GMSTA, see below:

Title: "Every Rock Has a Story & The Rock Whisperer" by James Hansen July 17, 2020

http://www.columbia.edu/~jeh1/mailings/2020/20200717_RockStories.pdf

Extract: "Curiously, at almost exactly the same moment that I received an e-mail from Ethan Baxter, I received one from the Rock Whisperer, my friend Paul Hearty, with a copy of his current paper on rocks in South Africa. He and co-authors show that in the Mid-Pliocene (about 3 million years ago), when atmospheric CO2 was about the same as today, it was a few degrees warmer and sea level was 15-30 meters higher (50-100 feet). One of Paul’s co-authors is Maureen Raymo, the new Director of Columbia’s Lamont-Doherty Earth Observatory, who dubbed Paul the Rock Whisperer for his remarkable ability to read the story in the rocks.

In 2006, when I was concerned that the IPCC projections of sea level rise were unrealistically conservative, I suspected that something was wrong with the ocean models that IPCC relied on. For one thing, the models did not properly include the cooling effect of ice melt on the North Atlantic and Southern Oceans. So, we ran climate simulations with our coarse-resolution global model, and were startled by the result: we found that the world was on the verge of shutting down both the Southern Ocean and North Atlantic overturning circulations, with enormous potential consequences for future sea level, because of amplifying feedbacks for Antarctic ice.

This would be a hard story to sell, given the coarse resolution of our model, and the fact that our result seemed to differ from all the other models. And why did Earth’s history not reveal such rapid feedback-driven change in the past? That’s when I discovered the papers of Paul Hearty for the last interglacial period, the Eemian, about 120,000 years ago, when global temperature reached levels perhaps as much as 1-2°C warmer than the preindustrial (1880-1920) level.

Hearty’s reading of the rocks painted a picture of the Eemian that was consistent with what we were finding in our climate modeling. We needed to develop that story, so we started to work with Paul Hearty, but first we needed an explanation for what was wrong with the ocean models.

The most crucial information about the ocean models was provided by observations of heat uptake by the oceans. Here the expert, the ocean heat whisperer if there is such a thing, was a young post-doc, Karina von Schuckmann, with whom we began to collaborate in about 2010."

Hearty, P. J., Rovere, A., Sandstrom, M. R., O'Leary, M. J., Roberts, D., & Raymo, M. E. (2020). Pliocene‐Pleistocene stratigraphy and sea‐level estimates, Republic of South Africa with implications for a 400 ppmv CO2 world. Paleoceanography and Paleoclimatology, 35, e2019PA003835. https://doi.org/10.1029/2019PA003835

https://www.essoar.org/doi/10.1002/essoar.10503699.1

Abstract: "The Mid-Pliocene Warm Period (MPWP, 2.9 to 3.3 Ma), along with older Pliocene (3.2 to 5.3 Ma) records, offers potential past analogues for our 400-ppmv world. The coastal geology of western and southern coasts of the Republic of South Africa expose an abundance of marine deposits of Pliocene and Pleistocene age. In this study, we report differential GPS elevations, detailed stratigraphic descriptions, standardized interpretations, and dating of relative sea-level indicators measured across ~700 km from the western and southern coasts of the Cape Provinces. Wave abrasion surfaces on bedrock, intertidal sedimentary structures, and in situ marine invertebrates including oysters and barnacles provide precise indicators of past sea levels. Multiple sea-level highstands imprinted at different elevations along South African coastlines were identified. Zone I sites average +32 ± 5 m (6 sites). A lower topographic Zone II of sea stands were measured at several sites around +17 ± 5 m. Middle and late Pleistocene sites are included in Zone III. Shoreline chronologies using 87Sr/86Sr ages on shells from these zones yield ages from Zone I at 4.6 and 3.0 Ma, and Zone II at 1.04 Ma. Our results show that polar ice sheets during the Plio-Pleistocene were dynamic and subject to significant melting under modestly warmer global temperatures. These processes occurred during a period when CO2 concentrations were comparable to our current and rapidly rising values above 400 ppmv."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3528 on: July 19, 2020, 06:42:30 PM »
...
IMO the individual studies are interesting and sometimes brilliant but of very limited value because they lack the component that provides the 'intuitive leap' that gives 'usefulness' to the study. In the case of an 'Ice Apocalypse', a more rationalized and realistic time-frame.

...

Regarding consensus climate science repeated reference to ice sheets losing ice over periods of centuries or millennia, I note that what most people think of as 'the science' is limited to Frequentist (as opposed to Bayesian) interpretation of the scientific method.  A Frequentist interpretation requires the establishment of experiments that simulate all key considerations, run a sufficient number of times to generate statistics that the Frequentists use as probabilities for possible future events.  To generate climate change statistics Frequentists primarily look at: a) the paleoclimate-record; b) the observed climate record and c) climate model projections.  Unfortunately, our current Anthropocene Period has no direct parallel in the paleoclimate record; and the observed record is too short to say much about long-tail climate risks and current climate models (including CMIP6 models) are not yet sufficiently sophisticated to simulate nonlinear extreme/abrupt climate behavior.

Therefore, when Frequentist/consensus climate scientists look at the paleoclimate record they average-out possible MICI-types of event citing poor resolution of the paleo-record and then focus on the slower trends of ice sheet ice mass loss; and when they look at the observed record they only see limited ice cliff failures for individual glaciers (like Jakobshavn) but no MICI-type events and when they look at model results like those of DeConto & Pollard (2016) or James Hansen et al (2016) they discount these preliminary findings as these models depend on some human judgement (which is commonly used in Bayesian methodologies).  Thus if abrupt freshwater hosing events do occur in the coming decades they will likely catch the Frequentist/consensus climate scientists by surprise and they will say that such abrupt behavior reflect 'Black Swan' events that could not be projected, even thou numerous warnings have been made public by the likes of James Hansen, DeConto and Pollard.  At the end of the day, many decision makers like to shirk responsibility for using human judgement and until they start choosing to shoulder responsibility the consensus climate scientists who report to these decision makers will continue to discount long-tail risks and will caveat their incomplete Frequentist statistics (that they present as true probabilities) with small print footnotes that ease their collective guilty consciousness over not presenting the actual risks associated with 'Ice Apocalypse' scenarios.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3529 on: July 20, 2020, 04:20:00 PM »
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."

While I have previously cited the quoted research, here I would like to emphasize the cited finding that such recent (in the past 15,000 years, see the attached image showing Meltwater Pulse 1A thru 1C) abrupt sea level rise events actually occurred in a rapid series of decadal sea level rise bursts as pointed-out by the following extract.  This finding supports my assertion that a cascading freshwater-hosing-related tipping points related to the bipolar seesaw mechanisms may well contribute to an 'Ice Apocalypse" in the coming decades:

Title: "Oceans Can Rise in Sudden Bursts"

https://www.scientificamerican.com/article/oceans-can-rise-in-sudden-bursts/

Extract: “We've known for quite some time that there was at least one very rapid pulse of sea-level rise during the deglaciation between the last ice age and the present — we've known for a very long time that sea level can rise with a sudden jump related to the dynamics of the ice sheet,” she said. “What's new here is you can have a bunch of kind of smaller pulses that are spaced really closely together, and that's kind of the new idea that they're putting forward.”
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3530 on: July 20, 2020, 04:51:57 PM »
Andrew Dessler understands that it is not alarmist to be alarmed about something that is alarming (like the potential for an 'Ice Apocalypse' this century):
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3531 on: July 20, 2020, 05:19:56 PM »
The linked video provides a consensus science explainer of why/how the Thwaites Glacier is currently falling apart (including the recently identified subglacial cavities); however, it omits consideration of MICI-types of potential collapse:

Title: " Why scientists are so worried about this glacier"

https://www.youtube.com/watch?v=XRUxTFWWWdY&feature=youtu.be

I think that the first attached image from the linked video illustrating the existing subglacial cavity at the base of the Thwaites Ice Tongue is key to appreciating just how close the grounding line of the Thwaites Glacier is to abruptly retreating (see the second attached image) along an existing seafloor trench to the lip of the Byrd Subglacial Basin where the glacial would likely be subject to an MICI-type of collapse in the coming decades.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3532 on: July 20, 2020, 09:36:47 PM »
As many people have challenged how well DeConto (& Pollard) has calibrated his (their) ice sheet models (for both the GIS and AIS); the linked article indicates that Penn State will soon start gathering bedrock cores from Greenland in order to better understand how quickly and frequently the GIS has changed its volume/extent:

Title: "Greenland bedrock drilling project to understand past, future ice sheet melting"

https://eurekalert.org/pub_releases/2020-07/ps-gbd071720.php

Extract: "Scientists from Penn State, Columbia University, the University at Buffalo and the University of Massachusetts at Amherst recently received a $3 million research grant and $4 million in field operations support from the National Science Foundation for the project, called GreenDrill. This ambitious five-year endeavor aims to uncover the exact extent, timing and frequency of periods when the Greenland Ice Sheet was much smaller or completely gone.

Rob DeConto, a climate scientist at the University of Massachusetts at Amherst, will integrate the findings into models that simulate the ice sheets' physical processes and future behavior.

"It's absolutely critical that we know how much ice Greenland lost in the past -- and this is still very uncertain," said DeConto. "GreenDrill will help reduce this uncertainty. This knowledge of the past informs us about the ice sheet's overall sensitivity to a warming climate and, hopefully, even how fast the ice sheet might melt in the future.""
« Last Edit: July 20, 2020, 11:09:29 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3533 on: July 20, 2020, 11:25:57 PM »
In general terms, current ice sheet models (both consensus models & other models) need a lot of work before they provide reasonably accurate projections of future ice mass loss.  Thus the linked article discusses a new effort to improve models of both glaciers and ice sheets:

Title: "Modeling: A Powerful and Versatile Tool in Glaciology"

https://eos.org/editors-vox/modeling-a-powerful-and-versatile-tool-in-glaciology

Extract: "Glaciology is an observation-driven field. Its major discoveries such as the existence of ice streams in Antarctica (e.g. Rose, 1979), wide-spread water-filled aquifers in Greenland (e.g. Brangers et al., 2020), accelerating ice loss from ice sheets and glaciers (e.g. Shepherd et al., 2019) and Antarctica’s floating ice shelves (e.g. Paolo et al., 2015), and many others have been made by observations, either in the field, from aircraft, or from satellites. However, to understand the glaciological processes that manifest themselves in such observations, unravel their interactions, and predict their evolution, a different research tool is needed: modeling.

Models are indispensable for understanding how glaciers and ice sheets might behave under climatic conditions substantially different from the present ones. The general characteristics of paleo ice sheets can be inferred from geological evidence, but understanding the processes driving the evolution of ice sheets requires physically realistic models. Ice-sheet models (e.g. Peltier and Marshall, 1995) provide an idea about how they might have behaved, including how they form and disappear. Understanding how glaciers and ice sheets will respond under future climate conditions is an urgent issue, and modeling is a key to making progress in it."

See also:
https://agupubs.onlinelibrary.wiley.com/hub/jgr/journal/21699011/features/call-for-papers


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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3534 on: July 21, 2020, 12:05:45 AM »
The attached tweet/image indicates that 2020 has experienced the earliest opening of the Arctic's Northeast Passage than any year on record.  This is likely an indicator of high Arctic Amplification:
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3535 on: July 21, 2020, 03:39:30 PM »
The linked reference notes that rhizosphere priming effect is currently not included in any climate model projects but that this effect '… amplifies overall soil respiration in permafrost-affected ecosystems by ~12%, which translates to a priming-induced absolute loss of ~40 Pg soil carbon from the northern permafrost area by 2100.'

Keuper, F., Wild, B., Kummu, M. et al. Carbon loss from northern circumpolar permafrost soils amplified by rhizosphere priming. Nat. Geosci. (2020). https://doi.org/10.1038/s41561-020-0607-0

https://www.nature.com/articles/s41561-020-0607-0

Abstract
As global temperatures continue to rise, a key uncertainty of climate projections is the microbial decomposition of vast organic carbon stocks in thawing permafrost soils. Decomposition rates can accelerate up to fourfold in the presence of plant roots, and this mechanism—termed the rhizosphere priming effect—may be especially relevant to thawing permafrost soils as rising temperatures also stimulate plant productivity in the Arctic. However, priming is currently not explicitly included in any model projections of future carbon losses from the permafrost area. Here, we combine high-resolution spatial and depth-resolved datasets of key plant and permafrost properties with empirical relationships of priming effects from living plants on microbial respiration. We show that rhizosphere priming amplifies overall soil respiration in permafrost-affected ecosystems by ~12%, which translates to a priming-induced absolute loss of ~40 Pg soil carbon from the northern permafrost area by 2100. Our findings highlight the need to include fine-scale ecological interactions in order to accurately predict large-scale greenhouse gas emissions, and suggest even tighter restrictions on the estimated 200 Pg anthropogenic carbon emission budget to keep global warming below 1.5 °C.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3536 on: July 21, 2020, 04:12:55 PM »
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."

While I have previously cited the quoted research, here I would like to emphasize the cited finding that such recent (in the past 15,000 years, see the attached image showing Meltwater Pulse 1A thru 1C) abrupt sea level rise events actually occurred in a rapid series of decadal sea level rise bursts as pointed-out by the following extract.  This finding supports my assertion that a cascading freshwater-hosing-related tipping points related to the bipolar seesaw mechanisms may well contribute to an 'Ice Apocalypse" in the coming decades:

Title: "Oceans Can Rise in Sudden Bursts"

https://www.scientificamerican.com/article/oceans-can-rise-in-sudden-bursts/

Extract: “We've known for quite some time that there was at least one very rapid pulse of sea-level rise during the deglaciation between the last ice age and the present — we've known for a very long time that sea level can rise with a sudden jump related to the dynamics of the ice sheet,” she said. “What's new here is you can have a bunch of kind of smaller pulses that are spaced really closely together, and that's kind of the new idea that they're putting forward.”
This reminds me of yet another implication, which I first spotted in this 2007 article


Quote
Each time the ice retreated, sea levels shot up again, sometimes at rates as high as several metres a century. In the mid 1990s, as part of a study funded by the European Union, we discovered that in the Mediterranean region there was a close correlation between how quickly sea levels went up and down during the last ice age and the level of explosive activity at volcanoes in Italy and Greece.

The link was most obvious following the retreat of the glaciers around 18,000 years ago, after which sea levels jumped back up to where they are today, triggering a 300% increase in explosive volcanic activity in the Mediterranean in doing so. Further evidence for a flurry of volcanic action at this time comes from cores extracted from deep within the Greenland ice sheet, which yield increased numbers of volcanic dust and sulphate layers from eruptions across the northern hemisphere, if not the entire planet.

But how can rising sea levels cause volcanoes to erupt? The answer lies in the enormous mass of the water pouring into the ocean basins from the retreating ice sheets. The addition of over a hundred metres depth of water to the continental margins and marine island chains, where over 60% of the world's active volcanoes reside, seems to be sufficient to load and bend the underlying crust.
https://www.theguardian.com/science/2007/aug/07/disasters
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3537 on: July 21, 2020, 05:16:35 PM »
The linked reference/presentation indicates that while earlier models struggled to simulate equable climates, CESM1 has managed to reasonable simulate mean/equilibrium values for such conditions (see the first image); however, it notes that when the authors used CESM1 to project future conditions under RCP 8.5 forcing they found that their model was far from equilibrium by 2100.  Furthermore, I note that:

•   The second and third images show that one of the key physics that they modeled was that under equable conditions as the temperature gradient from the tropics to the poles decreased the moisture gradient from the tropics to the poles increased.
•   By slowing the MOC freshwater hosing events (or a cascade of bipolar seesaw related hosing events) directly increases the moisture gradient from the tropics to the poles and thus serve to drive current conditions towards equable climate conditions even in the absence of RCP 8.5 GHG forcing after say 2025.

Baatsen, M., von der Heydt, A., Kliphuis, M., van Westen, R., Oldeman, A., van Delden, A., and Dijkstra, H.: Equable climates: a meridional flux paradox?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1739, https://doi.org/10.5194/egusphere-egu2020-1739, 2019

https://meetingorganizer.copernicus.org/EGU2020/EGU2020-1739.html

Abstract: "A commonly found property of warmer climates on Earth is the tendency, principally through polar amplification, towards more equable conditions with reduced meridional temperature contrasts. Numerical climate models historically have had quite some difficulty in reproducing meridional temperature gradients as low as those suggested by various proxies.
It seems self-evident that an equable climate is governed by enhanced meridional fluxes of heat, to sustain mild high latitude temperatures while keeping low latitudes from becoming exceedingly warm. However, a common hypothesis, borrowed from turbulence theory, is that the meridional heat flux is proportional to the meridional temperature gradient. A more equable climate should, therefore, exhibit reduced rather than enhanced meridional heat fluxes, posing a physical paradox.

Here, we use a unique set of long and well equilibrated (~25.000 years combined) climate simulations for various past periods using the CESM1. In terms of complexity and resolution, this climate model is comparable to the CMIP5 suite. Comparing the modelled climates of the Eocene (~40Ma), Oligocene (~30Ma), Pliocene (3Ma), pre-industrial era and present-day equilibrium climate confirms the hypothesis that warmer and more equable states overall feature weaker meridional heat fluxes (Figure1).

This effectively shows that meridional heat fluxes on a global scale are a result of, rather than the driver of the climate state. It is, therefore, the regional radiative balance that determines the temperature distribution and by extension the meridional heat flux. Still, the different components of that flux (atmospheric vs oceanic; sensible vs latent) are crucial in shaping the climate and these are strongly dependent on the background state. Meanwhile, a strongly divergent behaviour is seen in response to an imposed RCP8.5 future scenario which drives the model far from equilibrium. In this presentation, we will address why all of the cases follow a similar slope (with a different reference) in the considered para-meter space, the roles of related heat flux components, and the processes responsible.

Using appropriate boundary conditions, sufficient resolution and an adequate level of equilibration, the model is able to reproduce the warmer and more equable climates of the past. This gives confidence that the physics determining the modelled climate states under a widely varying external forcing are sound and should help us understand meridional temperature gradients in a future warmer climate."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3538 on: July 21, 2020, 05:36:42 PM »
...

But how can rising sea levels cause volcanoes to erupt? The answer lies in the enormous mass of the water pouring into the ocean basins from the retreating ice sheets. The addition of over a hundred metres depth of water to the continental margins and marine island chains, where over 60% of the world's active volcanoes reside, seems to be sufficient to load and bend the underlying crust.

I note that while the eustatic SLR this century may be limited to the 3 to 4m range; nevertheless, the change in the weight of grounded ice bearing on the bed of the WAIS could well be equal to many hundreds of meter of equivalent water height.  Thus, volcanic and seismic activity could become very active in the WAIS region after about 2045 (assuming an MICI-type of collapse of the ice in the Byrd Subglacial Basin, BSB); which would likely accelerate ice mass loss from the Bellingshausen, Weddell, and Ross Sea sectors after this time.  Furthermore, I note that McConnell et al. (2017) provides evidence that about 17.7 ka Mt Takahe (on the edge of the BSB, see the attached image) erupted and sent halogen-rich emissions high into the atmosphere that caused ozone depletion of the stratosphere over Antarctica, and I note that such an ozone depletion could well keep the westerly winds over the Southern Ocean in a range that promotes upwelling of warm CDW that would promote grounding line retreat for key Antarctic marine glaciers (including Totten and Byrd Glaciers in the EAIS).

Joseph R. McConnell el al., "Synchronous volcanic eruptions and abrupt climate change ∼17.7 ka plausibly linked by stratospheric ozone depletion," PNAS (2017). www.pnas.org/cgi/doi/10.1073/pnas.1705595114

https://www.pnas.org/content/114/38/10035

Significance
Cold and dry glacial-state climate conditions persisted in the Southern Hemisphere until approximately 17.7 ka, when paleoclimate records show a largely unexplained sharp, nearly synchronous acceleration in deglaciation. Detailed measurements in Antarctic ice cores document exactly at that time a unique, ∼192-y series of massive halogen-rich volcanic eruptions geochemically attributed to Mount Takahe in West Antarctica. Rather than a coincidence, we postulate that halogen-catalyzed stratospheric ozone depletion over Antarctica triggered large-scale atmospheric circulation and hydroclimate changes similar to the modern Antarctic ozone hole, explaining the synchronicity and abruptness of accelerated Southern Hemisphere deglaciation.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3539 on: July 21, 2020, 06:25:09 PM »
One problem with playing brinksmanship with the 1.5C aspirational goal is the possible triggering of tipping point for the Thwaites Glacier due to perturbations [such as a Super El Nino and/or a freshwater hosing event] into a MICI-type of collapse in the coming decades [note that the attached image from the IPCC SROCC (2019) shows that a MICI type of mechanism could occur with a relatively flat bed slope say in the seabed trench at the base of the Thwaites Ice Tongue that leads directly to the Byrd Subglacial Basin, BSB].

Frank Pattyn and Mathieu Morlighem (20 Mar 2020), "The uncertain future of the Antarctic Ice Sheet", Science, Vol. 367, Issue 6484, pp. 1331-1335, DOI: 10.1126/science.aaz5487

https://science.sciencemag.org/content/367/6484/1331?rss%253D1=

Abstract: "The Antarctic Ice Sheet is losing mass at an accelerating pace, and ice loss will likely continue over the coming decades and centuries. Some regions of the ice sheet may reach a tipping point, potentially leading to rates of sea level rise at least an order of magnitude larger than those observed now, owing to strong positive feedbacks in the ice-climate system. How fast and how much Antarctica will contribute to sea level remains uncertain, but multimeter sea level rise is likely for a mean global temperature increase of around 2°C above preindustrial levels on multicentennial time scales, or sooner for unmitigated scenarios."

See also:

Title: "How close is the West Antarctic ice sheet to a ‘tipping point’?"

https://www.weforum.org/agenda/2020/02/west-antarctic-ice-sheet-tipping-point/

Extract: "The IPCC’s SROCC says that “Thwaites Glacier is particularly important because it extends into the interior of the WAIS, where the bed is >2000m below sea level in places”. (Although, the SROCC also notes that while MISI requires a retrograde bed slope to occur, MICI could even happen on a flat or seaward-inclined bed.)

This recently identified process is not as well studied as MISI, but this is sure to change in the years ahead, as scientists continue to observe fast-changing systems such as the Thwaites Glacier.

Late last year, a large team of modellers assessed different studies of ice sheet response to the Paris climate target to keep global average warming “well below” 2C.

The models all point in the same direction. Namely, that the threshold for irreversible ice loss in both the Greenland ice sheet and the WAIS is somewhere between 1.5C and 2C global average warming. And we are already at a bit more than 1C warming right now."

Edit: I note that hydro-fracturing can drive calving in a MICI mechanism with ice cliff faces much lower than 100m above sea level (see the image), and that surface ice melting at the base of the Thwaites Ice Tongue already periodically occurs in January months and that a possible future Super El Nino event (say in the 2030 to 2035 timeframe) could provide sufficient surface ice melting at the base of the Thwaites Ice Tongue to drive hydro-fracture-driving calving if the melange permits such calving in that timeframe.
« Last Edit: July 21, 2020, 06:47:16 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3540 on: July 21, 2020, 06:37:51 PM »
Furthermore, I note that McConnell et al. (2017) provides evidence that about 17.7 ka Mt Takahe (on the edge of the BSB, see the attached image) erupted and sent halogen-rich emissions high into the atmosphere that caused ozone depletion of the stratosphere over Antarctica, and I note that such an ozone depletion could well keep the westerly winds over the Southern Ocean in a range that promotes upwelling of warm CDW that would promote grounding line retreat for key Antarctic marine glaciers (including Totten and Byrd Glaciers in the EAIS).

Joseph R. McConnell el al., "Synchronous volcanic eruptions and abrupt climate change ∼17.7 ka plausibly linked by stratospheric ozone depletion," PNAS (2017). www.pnas.org/cgi/doi/10.1073/pnas.1705595114

https://www.pnas.org/content/114/38/10035
Okay this is new for me, see my recent post on this phenomena taken place in Alaska

Quote
An enhanced volcanic activity has been observed due to deglaciation in Arctic has led to a hypothesis that the unloading of the glaciated ice in a volcanic terrains can increase volcanism through decompression melting in the shallow mantle or storage time reduction in crustal magma. Recently, the enhanced deglacial volcanic activity in Southeast Alaska sourced from Mount Edgecumbe Volcanic field has been correlated with the rapid isostatic adjustment, occurred following a retreat of regional glaciers.

We constrain the timing of this regional eruptive sequence to 14.6–13.1 ka. The sudden increase in volcanic activity from the MEVF coincides with the onset of Bølling–Allerød interstadial warmth https://www.sciencedirect.com/science/article/abs/pii/S0012821X16303892?via%3Dihub

Related Reading The Bølling-Allerød warming https://forum.arctic-sea-ice.net/index.php/topic,1952.msg109582.html?PHPSESSID=fe48180180aa28525c89eeb65d6c2577#msg109582

The finding is consistent with the hypothesis that isostatic rebound is associated with ice-unloading which increases the volcanism, that can possibly influence the frequency of the earthquakes as well. A certain earthquake is related to climate change? Surely not, but the earthquake activity can be linked to climate change, at least in a mountainous region where glaciers form and later they melt.
http://climatestate.com/2019/06/06/enhanced-seismic-activity-observed-due-to-climate-change/
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3541 on: July 21, 2020, 06:53:42 PM »
To continue my series of posts listing various ice-climate feedback mechanisms:

13. The first image (and first linked article) discuss the Moho discontinuity near a subduction zone such as is the case for the West Antarctic Rift System (see the second image [which also shows active volcanoes near both PIG and Thwaites] and the second linked article).  The third image makes it clear that the depth to the Moho discontinuity in West Antarctica is notable shallow; thus if the Thwaites Glacier were to collapse abruptly due to an ice cliff mechanism; the associated uplift of the local lithosphere would increase both the geothermal heat flux in the BSB but also would increase volcanic activity potentially in the Hudson and/or Takahe volcanoes; which would likely trigger an abrupt increase in ice mass loss from the WAIS:

Title: "Mohorovičić discontinuity"

https://en.wikipedia.org/wiki/Mohorovi%C4%8Di%C4%87_discontinuity

Extract: " The Moho lies almost entirely within the lithosphere; only beneath mid-ocean ridges does it define the lithosphere–asthenosphere boundary. The Mohorovičić discontinuity is 5 to 10 kilometres (3–6 mi) below the ocean floor, and 20 to 90 kilometres (10–60 mi) beneath typical continental crusts, with an average of 35 kilometres (22 mi)."

&

Title: "West Antarctic Rift"

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

Extract: "The West Antarctic Rift is the source of all the recently active volcanoes within Antarctica and all the recently active volcanoes on the continent. It is responsible for most of the major mountain systems outside the Antarctic Peninsula. Volcanism has been attributed to the rifting and also a mantle hotspot.

Glaciology

The WARS is also believed to have a major influence on ice flows in West Antarctica. In western Marie Byrd Land active glaciers flow through fault-bounded valleys (grabens) of the WARS. Sub-ice volcanism has been detected and proposed to influence ice flow. Fast-moving ice streams in the Siple Coast adjacent to the east edge of the Ross Ice Shelf are influenced by the lubrication provided by water-saturated till within fault-bounded grabens within the rift, which could cause rapid breakup of the ice sheet if global warming accelerates."

Bump
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3542 on: July 21, 2020, 07:43:58 PM »
The linked reference (& associated article) reminds us that with continued global warming, Super El Nino events will become more frequent; which will more frequently telecommunicate large amounts of atmospheric heat energy from particularly the Central Tropical Pacific to the West Antarctica coastal regions, where it may likely accelerate the risk of hydro-fracturing inducing calving events, say for Thwaites:

Bin Wang, Xiao Luo, Young-Min Yang, Weiyi Sun, Mark A. Cane, Wenju Cai, Sang-Wook Yeh, and  Jian Liu (November 5, 2019), "Historical change of El Niño properties sheds light on future changes of extreme El Niño", PNAS, 116 ,(45), 22512-22517; https://doi.org/10.1073/pnas.1911130116

https://www.pnas.org/content/116/45/22512

Significance
How the magnitude of El Niño will change is of great societal concern, yet it remains largely unknown. Here we show analysis of how changing El Niño properties, due to 20th century climate change, can shed light on changes to the intensity of El Niño in the future. Since the 1970s, El Niño has changed its origination from the eastern Pacific to the western Pacific, along with increased strong El Niño events due to a background warming in the western Pacific warm pool. This suggests the controlling factors that may lead to increased extreme El Niño events in the future. If the observed background changes continue under future anthropogenic forcing, more frequent extreme El Niño events will induce profound socioeconomic consequences.

Abstract
El Niño’s intensity change under anthropogenic warming is of great importance to society, yet current climate models’ projections remain largely uncertain. The current classification of El Niño does not distinguish the strong from the moderate El Niño events, making it difficult to project future change of El Niño’s intensity. Here we classify 33 El Niño events from 1901 to 2017 by cluster analysis of the onset and amplification processes, and the resultant 4 types of El Niño distinguish the strong from the moderate events and the onset from successive events. The 3 categories of El Niño onset exhibit distinct development mechanisms. We find El Niño onset regime has changed from eastern Pacific origin to western Pacific origin with more frequent occurrence of extreme events since the 1970s. This regime change is hypothesized to arise from a background warming in the western Pacific and the associated increased zonal and vertical sea-surface temperature (SST) gradients in the equatorial central Pacific, which reveals a controlling factor that could lead to increased extreme El Niño events in the future. The Coupled Model Intercomparison Project phase 5 (CMIP5) models’ projections demonstrate that both the frequency and intensity of the strong El Niño events will increase significantly if the projected central Pacific zonal SST gradients become enhanced. If the currently observed background changes continue under future anthropogenic forcing, more frequent strong El Niño events are anticipated. The models’ uncertainty in the projected equatorial zonal SST gradients, however, remains a major roadblock for faithful prediction of El Niño’s future changes.

See also:

Title: "Super El Niño events may become more frequent as the climate warms"

https://www.washingtonpost.com/weather/2019/10/22/super-el-nio-events-may-become-more-frequent-climate-warms/

Extract: "Study co-author Mark Cane of Columbia University, who is a pioneer in El Niño forecasting, says computer models have failed to accurately simulate changes in the tropical Pacific Ocean during the past few decades.

He says if the West Pacific heats up faster than the East Pacific, it’ll cause more El Niño events to be centered toward the international date line, rather than farther east."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3543 on: July 21, 2020, 08:01:58 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."

For those who do not know, the magma beneath the WAIS has a particularly low viscosity; which implies that the WAIS would contribute to more future SLR than previously assumed by consensus climate science.

Edit, for details of how low the magma viscosity is beneath the WAIS (however, I note that the reference's statement that a low magma viscosity increases the stability of the WAIS is predicated on the assumption of MISI-type of behavior instead of MICI-type of behavior), see:

Barletta et 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.
« Last Edit: July 21, 2020, 08:10:51 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3544 on: July 21, 2020, 08:39:25 PM »
For those who are interested, I provide the following open access linked reference (& associated article) about the thermal and compositional structure of the Antarctic lithosphere (which is thin beneath the WAIS):

F. Pappa, J. Ebbing, F. Ferraccioli and W. van der Wal (25 October 2019), "Modeling Satellite Gravity Gradient Data to Derive Density, Temperature, and Viscosity Structure of the Antarctic Lithosphere", Journal of Geophysical Research: Solid Earth, Volume 124, Issue 11, https://doi.org/10.1029/2019JB017997

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JB017997

Abstract
In this study we combine seismological and petrological models with satellite gravity gradient data to obtain the thermal and compositional structure of the Antarctic lithosphere. Our results indicate that Antarctica is largely in isostatic equilibrium, although notable anomalies exist. A new Antarctic Moho depth map is derived that fits the satellite gravity gradient anomaly field and is in good agreement with independent seismic estimates. It exhibits detailed crustal thickness variations also in areas of East Antarctica that are poorly explored due to sparse seismic station coverage. The thickness of the lithosphere in our model is in general agreement with seismological estimates, confirming the marked contrast between West Antarctica (<100 km) and East Antarctica (up to 260 km). Finally, we assess the implications of the temperature distribution in our model for mantle viscosities and glacial isostatic adjustment. The upper mantle temperatures we model are lower than obtained from previous seismic velocity studies. This results in higher estimated viscosities underneath West Antarctica. When combined with present‐day uplift rates from GPS, a bulk dry upper mantle rheology appears permissible.

Plain Language Summary
The solid Earth structure of the Antarctic continent is still poorly explored due to the coverage of up to 4‐km‐thick ice sheets and its remote location. Robust knowledge of its characteristics is, however, essential to understand the Earth's response to ice mass changes (glacial isostatic adjustment). Of particular interest are the depth and geometry of the main subsurface boundaries, which are the interface between crustal and mantle rocks (Moho discontinuity) and the base of the rigid tectonic plate (lithosphere). Since both of them are accompanied by changes in rock density, we used gravimetric data from the Gravity Field and Steady‐State Ocean Circulation Explorer satellite to build a 3‐D model of Antarctica's deep structure. Rock composition according to temperature and pressure is taken into account. Rock composition according to temperature and pressure is taken into account and the model as a whole is internally consistent. As a result, we present a continental‐scale Moho depth map that shows novel details. From the temperature distribution in our model, we derive present‐day uplift rates of the solid Earth's surface, which are a key parameter in estimating the future ice sheet evolution.

&

Title: "GOCE reveals what’s going on deep below Antarctica"

https://yubanet.com/scitech/goce-reveals-whats-going-on-deep-below-antarctica/

Extract: "“Under West Antarctica, Earth’s crust is comparatively thin at about 25 kilometres, and the mantle is viscous at less than 100 kilometres. East Antarctica, on the other hand, is an old cratonic shield. Here, the mantle rock still has solid properties at a depth of more than 200 kilometres.”"
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3545 on: July 21, 2020, 11:46:30 PM »
With a hat-tip to BornFromTheVoid, the attached images shows a Landsat 8 RGB composite of Petermann Glacier, from July 17th (click to see a larger image).

https://twitter.com/Icy_Samuel/status/1285656073517531138

I wonder how the implied up-coming major calving event will impact the 'Cold Blob' when the resulting icebergs finally float down into the North Atlantic.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3546 on: July 22, 2020, 12:19:02 AM »
The first reference indicates that in West Antarctica subglacial lake formation/filling is related to ice velocities.  The second reference and associated image show the catchment area and ice velocities for the PIG and Thwaite Glacier.  Furthermore, I highlight the following passage from the second reference (as the active subglacial lakes, in a cascade system-type, beneath the trunk of Thwaites Glacier, are currently refilling and could readily cause a surge in ice flow at the base of the Thwaites Ice Tongue circa 2030 to 2035):

"… the subglacial water drainage area of TG is bigger than previously thought and recent investigations (e.g., Smith et al., 2017) have demonstrated the presence of active subglacial lakes, in a cascade system-type, beneath the trunk of TG. Any water accumulation/drainage (e.g., chain of active subglacial lakes) in this area may affect the basal friction of the ice and therefore the ice flow velocity."

E. J. MacKie, D. M. Schroeder, J. Caers, M. R. Siegfried and C. Scheidt (08 March 2020), "Antarctic Topographic Realizations and Geostatistical Modeling Used to Map Subglacial Lakes", JGR Earth Surface, https://doi.org/10.1029/2019JF005420

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JF005420

Abstract
Antarctic subglacial lakes can play an important role in ice sheet dynamics, biology, geology, and oceanography, but it is difficult to definitively constrain their character and locations. Subglacial lake locations are related to factors including heat flux, ice surface slope, ice thickness, and bed topography, though these relationships are not fully quantified. Bed topography is particularly important for determining where water flows and accumulates, but digital elevation models of the ice sheet bed rely on interpolation and are unrealistically smooth, biasing estimates of subglacial lake location and surface area. To address this issue, we use geostatistical methods to simulate realistically rough bed topography. We use our simulated topography to predict subglacial lake distribution across the continent using a binomial logistic regression, which uses physical parameters and known lake locations to calculate the probabilities of lake occurrences. Our results suggest that topography models interpolated without appropriate geostatistics overestimate subglacial lake surface area and that total lake surface area is lower than previously predicted. We find that radar‐detected lakes are more likely to occur in the interior of East Antarctica, while altimetry‐detected (active) lakes are expected to be found in West Antarctica and near the grounding line. We observe that radar‐detected lakes have a high correlation with heat flux and ice thickness, while active lakes are associated with higher ice velocity.

&

Felipe Napoleoni et al. (20 March 2020), "Subglacial lakes and hydrology across the Ellsworth Subglacial Highlands, West Antarctica", The Cryosphere Discussions, http://doi.org/10.5194/tc-2020-68

https://tc.copernicus.org/preprints/tc-2020-68/tc-2020-68.pdf

Extract: "The subglacial hydrological catchments of Pine Island and Thwaites Glaciers We observe that most of the subglacial water draining towards ASE is routed through the Bentley Subglacial Trench in the upper part of the hydrological catchment and driven through the Byrd Subglacial Basin towards the trunk of Thwaites Glacier. The high topography in the mid PIG catchment (Vaughan et al., 2006) means that the hydrological drainage system does not link to the faster flowing trunk of PIG. Instead, the basal hydrological system is captured by Thwaites. This drainage pattern has two main implications. Firstly, the subglacial hydrological catchments of PIG and Thwaites do not correspond to the ice catchments; they do not coincide either in position or size. Secondly, the hydrological system of TG trunk (Schroeder et al., 2013) may be fed by water sourced in the upper glaciological catchment of PIG, within the ESH.

Any change in the water catchment of the TG, at the head of PIG, could therefore have important glaciological consequences for the ice dynamics of Thwaites Glacier and the wider ASE. This is particularly critical since the subglacial water drainage area of TG is bigger than previously thought and recent investigations (e.g., Smith et al., 2017) have demonstrated the presence of active subglacial lakes, in a cascade system-type, beneath the trunk of TG. Any water accumulation/drainage (e.g., chain of active subglacial lakes) in this area may affect the basal friction of the ice and therefore the ice flow velocity. Conversely, this pattern may have a reduced importance for PIG in terms of magnitude or timing due to the topographic barrier disconnecting the drainage upstream with the lower/marginal section of PIG. If we are to clearly understand the potential role of subglacial water on the ice dynamics of the PIG and Thwaites systems, then more investigations of the detailed subglacial and hydrological conditions are required."

Caption: "Figure 9. Mean annual ice surface velocity (Mouginot et al., 2019) of Pine Island Glacier, Rutford Ice Stream, Institute Ice Stream, Bindschedler Ice Stream and Thwaites Glacier. Black line shows ice surface velocities higher than 250 myr−1 . The red line indicates the boundary of the water catchment. The blue lines show the subglacial water drainage and the arrows indicates the general flow direction. The Cryosat-2 Elevation model (1 km), virtual hillshade (Helm et al., 2014) is showed in the background. ASE: Amundsen Sea Embayment; BSB: Byrd Subglacial Basin; BST: Bentley Subglacial Trench. Projection: Antarctic Polar Stereographic (EPSG 3031). B) shows the histogram of surface ice velocity over the central part of each subglacial lakes."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3547 on: July 22, 2020, 02:27:40 AM »
The linked article indicates that NSF has now approved $3 million for ice coring on the WAIS/EAIS divide to help determine whether the WAIS collapsed during the Eemian as some climate scientists believe:

Title: "NSF campaign will drill for ice capturing West Antarctica’s last collapse", Jul. 10, 2020

https://www.sciencemag.org/news/2020/07/nsf-campaign-will-drill-ice-capturing-west-antarctica-s-last-collapse

Extract: "Next week, the National Science Foundation will fund a 5-year project, costing more than $3 million, that will seek evidence of this collapse from gases trapped in tiny bubbles encased in a 2.5 kilometer-long tube of ice. The core drilling, likely to start in 2023, will target Hercules Dome, an expanse of ice 400 kilometers from the South Pole. Hercules sits at the saddle between the continent’s western and eastern ice sheets; if the western one collapsed, “Hercules Dome would be sitting on the waterfront, so to speak,” says Eric Steig, the project’s principal investigator and a glaciologist at the University of Washington, Seattle.

The Eemian, the last warm period between the ice ages, lasting from 129,000 to 116,00 years ago, is one of the best analogs for modern Earth. Temperatures were about 1° warmer than now, yet sea levels were 6 meters to 9 meters higher. And recent work, some still unpublished, has suggested much of this melt must have come from Antarctica."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3548 on: July 22, 2020, 04:27:56 PM »
...

As it only takes one sufficiently intensive surface ice melt event to hydrofracture an ice shelf, looking at averages (even for just the ASE) is not good science, as intense surface ice melt events happen more frequently during intense El Nino events as occurred in January 2016.  In this regard, the first 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."

Furthermore, I repost the second attached image to remind readers that the recent past observed rate of warming of the Southern Ocean is not relevant to a possible MICI-type of event in the WAIS in coming decades, because what matters is the increase in temperature of the warm CDW that is advected over the various continental shelves to the grounding lines of the key West Antarctic marine glaciers (which the second image show will increase by about 1.5C by 2050 as compared to 1960).

I reiterate that surface melt from the next Super El Nino might be sufficient to cause a hydro-fracturing triggered MICI-type of failure beginning at the base of the Thwaites Ice Tongue say around 2030-2035.  Furthermore, I note that since the AIS formed about 30 million years ago, there has likely been a lot of MICI-types of failures initiating in this same area; which has likely pre-conditioned the glacial/sea bed to facilitate such failures.  This implies that it is now more likely that a MICI-type of failure of the BSB is more probable than during say the Eemian.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3549 on: July 22, 2020, 06:05:28 PM »
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."

This is a reminder to readers that if the BSB were to experience an MICI-type of collapse beginning possibly as early as 2030 due to hydrofacturing of the calving front of the Thwaites Ice Tongue due to a Super El Nino event, then it is possible that significant amounts of methane could be emitted into the atmosphere from the associated rapid degradation of seabed methane hydrates in the BSB bed.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson