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Author Topic: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)  (Read 34427 times)

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #50 on: November 29, 2017, 05:39:42 PM »
Quote
Losing all ice from GIS in 500 years is not something I have seen
Right, sidd. No such claim has ever been made in a peer-reviewed article.

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

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

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

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

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

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

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

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

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

Edit: In Reply #40, I discuss how high values of radiative forcing (Watts/sq meter) could be reached when following RCP 8.5 until 2050.
« Last Edit: November 29, 2017, 05:57:42 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #51 on: November 29, 2017, 05:43:00 PM »
" I note that some researchers indicate that based on these new findings that the GIS could lose all of its ice mass in as little as 500 years "

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

sidd

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

Furthermore, my point in raising the issue of ice mass loss from the GIS is that even after mankind stops making large GHG emissions, the bipolar seesaw could stay very active in a run away greenhouse situation.
« Last Edit: November 29, 2017, 05:51:51 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #52 on: November 29, 2017, 06:33:16 PM »
While it is not necessary to follow a RCP 8.5/SSP5 pathway until 2050 for the peak ice mass discharge of a WAIS collapse to occur this century; nevertheless, the following is a short list of conceptual Catch 22's associated with climate change that may keep society on such a pathway until a socioeconomic collapse by 2050 stops significant further anthropogenic GHG emissions:

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

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

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

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

https://climateandsecurity.org/epicenters/

Extract: "… security experts identify 12 key climatic risks to international security that may shape the geostrategic landscape of the 21st century. In the wake of extraordinary upheaval in the international effort to address climate change, the report presents a compelling case for why tackling these climate and security “epicenters” – major categories of climate-driven risks to international security – should be a top priority for governments and institutions around the world. The report also outlines the key tools for managing systemic risks that should be included in every climate security practitioner’s and policy-maker’s toolbox."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #53 on: November 29, 2017, 06:46:45 PM »
I have repeatedly noted that Hansen's ice-climate feedback mechanism results in a warming of the tropical oceans which results in an expansion of the Hadley cells (see the attached image); and the linked reference indicates that the ITCZ moves poleward with the Hadley cell expansion, and that it narrows as it migrates.  This will cause a lot of changes to effected local climates, and could lead to an equable climate in the NH if the WAIS collapses this century due to anthropogenic radiative forcing:

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

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

Abstract: "The Intertropical Convergence Zone (ITCZ) narrows in response to global warming in both observations and climate models. However, a physical understanding of this narrowing is lacking. Here we show that the narrowing of the ITCZ in simulations of future climate is related to changes in the moist static energy (MSE) budget. MSE advection by the mean circulation and MSE divergence by transient eddies tend to narrow the ITCZ, while changes in net energy input to the atmosphere and the gross moist stability tend to widen the ITCZ. The narrowing tendency arises because the meridional MSE gradient strengthens with warming, whereas the largest widening tendency is due to increasing shortwave heating of the atmosphere. The magnitude of the ITCZ narrowing depends strongly on the gross moist stability and clouds, emphasizing the need to better understand these fundamental processes in the tropical atmosphere."
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A-Team

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #54 on: November 29, 2017, 08:18:28 PM »
Quote
reference that with a GMSTA of 9C indicates a 7m
Cheap shot there. Sure, with a preposterous enough temperature rise scenario, anything is possible in models. Greenland could melt tomorrow if enough neutron bombs were detonated over it.

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

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

« Last Edit: November 29, 2017, 08:38:33 PM by A-Team »

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #55 on: November 29, 2017, 09:34:49 PM »
That Applegate paper does not use global T increase, but rather greenland T increase. So 12 K over greenland would be more like 6K global, as in fig 4 of the paper. I attach. This is for RCP 8.5 showing 12 K is reached over greenland around 2200.

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

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

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

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #56 on: November 29, 2017, 10:37:41 PM »
That Applegate paper does not use global T increase, but rather greenland T increase. So 12 K over greenland would be more like 6K global, as in fig 4 of the paper. I attach. This is for RCP 8.5 showing 12 K is reached over greenland around 2200.

sidd,

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

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

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

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

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

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

Best regards,
ASLR
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #57 on: November 29, 2017, 10:50:24 PM »
So, 2012 in Greenland was predicted decades in advance? I must have missed it. Then the cold year 2017 thickening of Greenland played out just like they said it would? I must have missed that too, amidst all the doom and gloom coming off 2012.

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

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

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

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

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

I see very few working scientists venturing testable predictions say for Arctic sea ice. No one has any real idea when or what comes next for mid-latitude. That doesn't exactly inspire confidence in model ruminations for 2025 or beyond. There's plenty of vapor steaming out of the cubicles though.
 
Consider a range of scenarios? Sure why not. Andorra unleashing a barrage of missiles against Liechtenstein? It could happen, fat tail risk. So the Pentagon long ago wrote up a scenario for that. It's sitting on the shelf: there are far more pressing risks by orders of magnitude than further documentation of impacts to Monaco.
« Last Edit: November 29, 2017, 10:58:43 PM by A-Team »

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #58 on: November 29, 2017, 11:08:50 PM »
"As the elevation of the ice surface drops ..."

The ice elevation SMB feedback is already in SICOPOLIS.

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #59 on: November 29, 2017, 11:43:55 PM »
As I am promoting that ESM modelers adopt a more dynamical interpretation (considering possible chain reactions of smaller trigger mechanisms) of their results, I will also try to make future posts that describe a probable chain of events that could trigger the WAIS to make a peak contribution to SLR by/before 2100, and in this regards, I begin with Jakobshavn Glacier.

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

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

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

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

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

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

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

I also note that monitoring snowfall and surface mass balance is a secondary issue to ice cliffs and hydrofracturing, as in the WAIS at least more snowfall until 2040 will increase the gravitational driving force on Thwaites after 2040.
« Last Edit: November 29, 2017, 11:52:24 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #60 on: November 29, 2017, 11:54:28 PM »
"As the elevation of the ice surface drops ..."

The ice elevation SMB feedback is already in SICOPOLIS.

sidd

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

Edit: I repost the attached image to indicate that CO2 emissions are tracking SSP5/RCP 8.5 thru 2017.
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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #61 on: November 30, 2017, 12:22:28 AM »
I have made my prediction for Jacobshawn grounding line in the Jacobshawn thread.

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #62 on: November 30, 2017, 12:46:59 AM »
I have made my prediction for Jacobshawn grounding line in the Jacobshawn thread.

sidd

sidd,

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

Best,
ASLR

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

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

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

Abstract. The impact of melt water injection into ice streams over the Greenland Ice Sheet is not well understood. Water-filled crevasses along the shear margins of Jakobshavn Isbræ are known to fill and drain, resulting in weakening of the shear margins due to reduced basal friction. Seasonal variability in the hydrologic dynamics of these features has not been quantified. In this work, we characterize the spatial and temporal variability in the hydrological state (filled or drained) of these water-filled crevasse systems. A fusion of multi-sensor optical satellite imagery was used to examine hydrologic states from 2000 to 2015. The monthly distribution of crevasse systems observed as water filled is unimodal with peak number of filled days during the month of July at 329 days, while May has the least at 15. Over the study period the occurrence of drainage within a given season increases. Inter-seasonal drain frequencies over these systems ranged from 0 to 5. The frequency of multi-drainage events are correlated with warmer seasons and large strain rates. Over the study period, summer temperatures averaged from −1 and 2 °C and tensile strain rates have increased to as high as ~ 1.2 s. Intermittent melt water input during hydrofracture drainage responsible for transporting surface water to the bed is largely facilitated by high local tensile stresses. Drainage due to fracture propagation may be increasingly modulated by ocean-induced calving dynamics for the lower elevation ponds. Water-filled crevasses could expand in extent and volume as temperatures increase resulting in regional amplification of ice mass flux into the ice stream system.
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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #63 on: November 30, 2017, 05:09:10 AM »
No. I mean that the grounding line will be close to A45. But lets take this to the Jacobshawn thread.

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #64 on: November 30, 2017, 05:52:39 AM »
In a larger sense, and more to the topic of this thread (threat?), the great glaciers will not, i think, be the dominant factor in greenland ice mass waste. As Enderlin saw and the models in Applegate indicate, dynamic ice loss in greenland becomes less and less important wth larger forcing.

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

 ΔTgrl is the temperature anomaly imposed over greenland.

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

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

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

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

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

sidd
« Last Edit: November 30, 2017, 06:19:41 AM by sidd »

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #65 on: November 30, 2017, 06:12:26 PM »
Just for the record, I generally concur with sidd's analysis (in Reply #64) of the stability of the GIS, including his opinion that the groundling line for Jakobshavn will have retreated to location A45 by 2028 (which Rignot et al 2017 indicates represents at least a 50% increase in annual ice mass loss from Jakobshavn).  However, my point is that consensus climate scientists do not adequately the dynamical/periodic climate attractor associated with the on-going synergy between such Earth Systems as: the bipolar seesaw, ice-climate feedback, ENSO trends/cycles, cloud feedback, polar amplification Hadley cell expansion and precipitation patterns.  For example, an acceleration of ice mass loss from Jakobshavn thru 2028 would contribute to the North Atlantic cold spot (regardless of possible increased net snowfall on Greenland in this timeframe); which will serve to somewhat slow the MOC, which in turn will increase the absorption of heat by the tropical oceans, and thus will contribute somewhat to increased extreme ENSO events.

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

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

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

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

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

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

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

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

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

That means seeing an extreme El Niño on average every 10 years, rather every 20 years."
« Last Edit: November 30, 2017, 06:40:59 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #66 on: November 30, 2017, 06:46:58 PM »
I provide the first linked paleo research as evidence that ice mass loss from the GIS can contribute to MIS 11 type value for ECS, and the second linked paleo research that shows that the MIS 11 ECS was higher than current ESM models can simulate.  This is indirect evidence supporting my assumption that ECS is now about 4.5C (which supports my projection of significant cliff failures for Thwaites circa 2040, when GMSTA may approach 2.7C).

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

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

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

&

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

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

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

Extract: "The timing of significant warming in the circum-Arctic can be linked to major deglaciation events in Antarctica, demonstrating possible interhemispheric linkages between the Arctic and Antarctic climate on glacial–interglacial timescales, which have yet to be explained."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #67 on: November 30, 2017, 07:17:03 PM »
To continue with my list of near-term predictions, I predict that satellite observations will continue to observe that "… high clouds are likely to get higher, cloudy and clear bands may shift from lower latitudes towards the poles, and clouds may become less icy and more watery…"; which will contribute to positive cloud feedback, and an ECS near 4.5C this century, partially due to the tropical atmospheric convective mixing shown in the first image from Sherwood et al. 2014, and the second image that shows how this deep convection help expands the Hadley cell.

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

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

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

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

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

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

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

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

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

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

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

Caption for the third image: "Figure 5 Upper three panels are from Hartmann et al (1992) who estimate the contribution to the cloud radiative effects (CRE) of five classes of clouds as defined according to the ISCCP radiance classification (upper left). The bottom panels are the equivalent analysis but with classification determined by the radar-lidar data of CloudSat and CALIPSO where true cloud heights establish the types and cloud thickness (x axis) are from water and ice path information which is proportional to cloud optical depth. The differences in CRE between this latter analysis and that of Hartmann et al underscores the effects of misclassification of clouds on the interpretation of their radiative effects. Ci=cirrus, D.C.=Deep Convection, M.L.=multi-layer, AS=Altostratus, AC-Alto-cumulus, NS=Nimbostratus, St=stratus, SC=stratocumulus and Cu=cumulus."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #68 on: November 30, 2017, 09:36:54 PM »
With regards to a more specific near-term cryosphere prediction, I predict that in less than 2.5-years, the PIIS and the SW Tributary Ice Shelf will experience a concurrent major calving event (along the intersecting cracks shown in the attached Sentinel-1 image from Nov 28 2017) that will temporarily cause the ice velocities in the SW Tributary Glacier to accelerate.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #69 on: November 30, 2017, 10:48:36 PM »
Based on my interpretation of the two linked references, I predict that local ice cliff failures near the base of the Thwaites Ice Tongue (see the four images) will begin sometime 2025 and 2033, and will be initiated due to influences from Super El Nino events in that timeframe:

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

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

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

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

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

&

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

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

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

Abstract: "Using empirical orthogonal function (EOF) analysis and atmospheric reanalyses, we examine the principal patterns of seasonal West Antarctic surface air temperature (SAT) and their connection to sea ice and the Amundsen Sea Low (ASL). During austral summer, the leading EOF (EOF1) explains 35% of West Antarctic SAT variability and consists of a widespread SAT anomaly over the continent linked to persistent sea ice concentration anomalies over the Ross and Amundsen Seas from the previous spring. Outside of summer, EOF1 (explaining ~40-50% of the variability) consists of an east-west dipole over the continent with SAT anomalies over the Antarctic Peninsula opposite those over western West Antarctica. The dipole is tied to variability in the Southern Annular Mode (SAM) and in-phase El Niño-Southern Oscillation (ENSO) / SAM combinations that influence the depth of the ASL over the central Amundsen Sea (near 105°W). The second EOF (EOF2) during autumn, winter, and spring (explaining ~15-20% of the variability) consists of a dipole shifted approximately 30 degrees west of EOF1 with a widespread SAT anomaly over the continent. During winter and spring, EOF2 is closely tied to variability in ENSO and a tropically-forced wavetrain that influences the ASL in the western Amundsen / eastern Ross Seas (near 135°W) with an opposite sign circulation anomaly over the Weddell Sea; the ENSO-related circulation brings anomalous thermal advection deep onto the continent. We conclude the ENSO-only circulation pattern is associated with SAT variability across interior West Antarctica, especially during winter and spring, while the SAM circulation pattern is associated with an SAT dipole over the continent."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #70 on: November 30, 2017, 11:27:52 PM »
While Transient Climate Response, TCR, only addresses fast feedback mechanisms (and not the slow feedback confirmed by PH17), I note that the linked reference indicates that a "... stronger constraint on forcing will bring a significant reduction in the uncertainty of observation-based estimates of the transient climate response, with a 50% reduction in its uncertainty range expected by 2030.  This will help to verify my assumption that ECS is currently around 4.5C:

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

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

Abstract: "Carbon dioxide has exerted the largest portion of radiative forcing and surface temperature change over the industrial era, but other anthropogenic influences have also contributed. However, large uncertainties in total forcing make it difficult to derive climate sensitivity from historical observations. Anthropogenic forcing has increased between the Fourth and Fifth Assessment Reports of the Intergovernmental Panel of Climate Change (IPCC) although its relative uncertainty has decreased. Here we show, based on data from the two reports, that this evolution towards lower uncertainty can be expected to continue into the future. Because it is easier to reduce air pollution than carbon dioxide emissions and because of the long lifetime of carbon dioxide, the less uncertain carbon dioxide forcing is expected to become increasingly dominant. Using a statistical model, we estimate that the relative uncertainty in anthropogenic forcing of more than 40% quoted in the latest IPCC report for 2011 will be almost halved by 2030, even without better scientific understanding. Absolute forcing uncertainty will also decline for the first time, provided projected decreases in aerosols occur. Other factors being equal, this stronger constraint on forcing will bring a significant reduction in the uncertainty of observation-based estimates of the transient climate response, with a 50% reduction in its uncertainty range expected by 2030."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #71 on: December 01, 2017, 05:37:43 PM »
As it is relevant to my prior posts in this thread, I provide the linked article and subsequent associated linked references, address efforts to improve/advance climate forecasting.  While the article addresses a range of efforts from correcting model bias to predicting snow (& associated albedo effects) distribution, in this post I only extract sections related to efforts to better understand the telecommunication of tropical heat energy to the Arctic (see the attached image & caption, which does not show telecommunications of tropical heat energy to Antarctica, which also occurs).  While climate modelers are working hard to improve their projections, I noted that none of the efforts discussed consider the impacts of freshwater hosing events (such as the possible collapse of the WAIS this century).  A major freshwater hosing event (or events) and its associated telecommunications and a snow albedo flip, would have major consequences on future climate that are not adequately addressed in current publically available forecasts.

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

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

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

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

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

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

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

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

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

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

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

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

Abstract: "Skilful climate predictions of the winter North Atlantic Oscillation and Arctic Oscillation out to a few months ahead have recently been demonstrated, but the source of this predictability remains largely unknown. Here we investigate the role of the Tropics in this predictability. We show high levels of skill in tropical rainfall predictions, particularly over the Pacific but also the Indian and Atlantic Ocean basins. Rainfall fluctuations in these regions are associated with clear signatures in tropical and extratropical atmospheric circulation that are approximately symmetric about the Equator in boreal winter. We show how these patterns can be explained as steady poleward propagating linear Rossby waves emanating from just a few key source regions. These wave source ‘hotspots’ become more or less active as tropical rainfall varies from winter to winter but they do not change position. Finally, we show that predicted tropical rainfall explains a highly significant fraction of the predicted year-to-year variation of the winter North Atlantic Oscillation."
&

Tompkins, A. M., et al. (2017), The Climate-system Historical Forecast Project: Providing open access to seasonal forecast ensembles from centers around the globe, Bull. Am. Meteorol. Soc., https://doi.org/10.1175/BAMS-D-16-0209.1.

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

&

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

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #72 on: December 01, 2017, 07:02:20 PM »
I point-out that I have already made a lot of other predictions (related to an Ice Apocalypse) in a variety of other threads, e.g. I provided the attached image in Reply #21 of the "Potential Collapse Scenario for the WAIS" on February 24, 2013; which is still relevant to all I have stated in this thread so long as one understands that the green areas (that I drew on Vaughan et al. 2011's plan of the WAIS) represent grounding line retreats, to 2040, with cliff faces only near the base of the Thwaites Ice Tongue, and with grounding line retreats beneath ice shelves everywhere else.  Therefore, I will stop summarizing past predictions here, unless someone asks some specific questions about my assumed scenario (which I acknowledge has evolved somewhat since 2013, and which requires BAU forcing at least until about 2040) for a WAIS collapse this century.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #73 on: December 04, 2017, 08:59:51 PM »
The linked Climate Feedback article gives Holthaus' "Ice Apocalypse" a 'high' credibility rating by a panel of experts, including Richard Alley who highlights the fact that DeConto & Pollard (2016) ice mass loss projections for the WAIS in the coming 500-years may be very conservative due to the deep uncertainty associated with this issue.  While the following linked reference by Scambos et al (2017) indicates that this matter is sufficiently important to warrant a major research effort.

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

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

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

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

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

See also:

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

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

Abstract: "Constraining how much and how fast the West Antarctic Ice Sheet (WAIS) will change in the coming decades has recently been identified as the highest priority in Antarctic research (National Academies, 2015). Here we review recent research on WAIS and outline further scientific objectives for the area now identified as the most likely to undergo near-term significant change: Thwaites Glacier and the adjacent Amundsen Sea. Multiple lines of evidence point to an ongoing rapid loss of ice in this region in response to changing atmospheric and oceanic conditions. Models of the ice sheet's dynamic behavior indicate a potential for greatly accelerated ice loss as ocean-driven melting at the Thwaites Glacier grounding zone and nearby areas leads to thinning, faster flow, and retreat. A complete retreat of the Thwaites Glacier basin would raise global sea level by more than three meters by entraining ice from adjacent catchments. This scenario could occur over the next few centuries, and faster ice loss could occur through processes omitted from most ice flow models such as hydrofracture and ice cliff failure, which have been observed in recent rapid ice retreats elsewhere. Increased basal melt at the grounding zone and increased potential for hydrofracture due to enhanced surface melt could initiate a more rapid collapse of Thwaites Glacier within the next few decades."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #74 on: December 04, 2017, 11:45:22 PM »
The paleo findings of the following linked reference indicate to me that we are playing Russian roulette w.r.t. the possible collapse of the WAIS this century.  The extreme storm activity and high sea levels in the Bahamas cited in Hearty & Tormey (2017) and in Rovere et al. (2017) indicate to me that the ice-climate feedback was very strong during the late MIS 5e highstand (circa 119.5 kya).  Furthermore, when one looks at the sea level error bars in the attached image [from O'Leary et al. (2013)] around 119.5 kya it is clear that there is a reasonable probability that the WAIS could substantially collapse in less than a century.  People who demand absolute proof of such a possible event, are likely to be able to directly observe it from 2040 to 2100.

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

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

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

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

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

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

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

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

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

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

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

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #75 on: December 11, 2017, 06:41:39 PM »
Personally, I think that the first linked article and the associated second linked reference increases the probability that the WAIS will enter a main phase collapse period by 2040.  The article indicates that ice mass loss from Greenland has been contributing to feedback mechanisms that has caused the Beaufort Gyre to progressively stockpile more freshwater than all of the great lakes combined (see the first image).  While some consensus scientists will undoubtable emphasize that an eventual release of this freshwater in coming years will result in a temporary cooling of the North Atlantic and Europe, which may decrease GMSTA; I note that

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


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

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

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

http://onlinelibrary.wiley.com/doi/10.1002/jqs.1423/full
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #76 on: December 12, 2017, 06:20:51 PM »
The linked August 2016 Special Edition of Past Global Changes (PAGES) Magazine examines paleo evidence for multiple different mechanisms for tipping points including the synergistic interactions between various mechanism resulting in a chain reaction leading to abrupt climate change.  While the entire issue is valuable, I extract from two article in the Special Edition by Fogwill et al (2016), and Praetorius & Mix (2016); which highlight the importance of ice (or freshwater hosing)-climate interaction.  The first image, from Fogwill et al (2016), shows that for Pliocene conditions (which we might reach without adequate mitigation), it is impossible to reproduce the paleo reported ice mass loss from Antarctica (both West and East) without invoking both cliff failures and hydrofracturing.  The second image, from Praetorius & Mix (2016), highlight paleo evidence that oceanic feedback mechanisms can synchronize warming of both the North Atlantic and the North Pacific in order contribute to relatively high Arctic Amplification:

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

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

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

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

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

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

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

Outlook
New high-resolution paleoceanographic records from the subpolar North Pacific document rapid changes during the last deglacial transition similar in timing to those observed in the Greenland ice cores. Rather than deglacial changes in the North Pacific merely reflecting a downstream response to changes in the North Atlantic region, interactions between basins may be a key element in the emergence of abrupt climate transitions in the Northern Hemisphere."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #77 on: December 12, 2017, 08:36:25 PM »
The linked reference indicates that an abrupt cooling of the subpolar gyre, SPG, (say due to an abrupt release of freshwater from the Beaufort Gyre), could abruptly slow the AMOC. This reference indicates that the CMIP5 ensemble underestimates the risk of future abrupt cooling of the subpolar North Atlantic, SPG.  This increases the probability of the reality of Hansen's ice-climate feedback mechanism.

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

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

Abstract: "Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models’ varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #78 on: December 12, 2017, 09:14:15 PM »
Thanks for this, ASLR, and of course for all of your excellent posts.

So what do you or others think is the likely consequence of this for European and North American weather patterns?
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #79 on: December 12, 2017, 10:56:20 PM »
So what do you or others think is the likely consequence of this for European and North American weather patterns?

wili,

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

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

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

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

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

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

Best regards,
ASLR
« Last Edit: December 12, 2017, 11:23:37 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #80 on: December 12, 2017, 11:59:25 PM »
The linked reference shows that ice mass loss from the WAIS is a nonlinear function of ocean forcing period.  While many consensus scientists consider ocean forcing a slow response mechanism, reasons to suspect that such nonlinear behavior could be trigger in the next few decades include:

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

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

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

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

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

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

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

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wili

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #81 on: December 13, 2017, 12:10:08 AM »
Thanks again, ASLR. So it's more about the storms than some new 'Little Ice Age'?
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #82 on: December 13, 2017, 12:27:06 AM »
Thanks again, ASLR. So it's more about the storms than some new 'Little Ice Age'?

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

Furthermore, Hansen et al (2016) assume that ECS is 3C, so if ECS is 4.5C you can expect Arctic Amplification to continue increasing; and also Hansen acknowledges that his model projections are conservative for his assumed inputs.
« Last Edit: December 13, 2017, 12:32:14 AM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #83 on: December 13, 2017, 12:53:44 AM »
Ah. Thanks again.
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #84 on: December 13, 2017, 02:48:04 AM »
Ah. Thanks again.

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

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

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

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

Edit: Just to clarify this point about different values for climate sensitivity, the first attached image from Hansen et al 2011 shows three possible representative climate response functions for use in climate models, and notes that models typically use the curve labeled 'slow' response (comparable to ECS =3C).  The curve labeled 'intermediate' response can be compared to ECS equal to 4 to 4.5C, while the curve labeled 'fast' response assumes that several ESS (Earth System Sensitivity) feedback mechanisms kick-in this century and temporarily raise the effective ECS above 4.5C as indicated by the temporary bump up to 7C in second attached image from Hansen & Sato 2012.  The third attached image is from Hansen et al. (2016) and confirms that for that analysis Hansen et al (2016) assumed a slow climate response function.
« Last Edit: December 13, 2017, 04:25:23 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #85 on: December 13, 2017, 05:33:18 PM »
While Hansen et al. (2016) used an intermediate ESM with a slow response function (ECS~3C) for their projections, I provide the following references about results using more advance versions of Community Earth Systems Model, CESM; which is the foundation of ACME (for which no results have been published), to indicate that the effective climate sensitivity this century could be well above 4.5C, to which one would need to add the impacts of freshwater hosing not included in the CESM (nor the CMIP5) projections:

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

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

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

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

&

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

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

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

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

&

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

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

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

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

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

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

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


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

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

http://www.earthsystemgrid.org/

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #86 on: December 14, 2017, 03:48:56 PM »
The linked open access reference estimates sea level rise values by 2100 that are about twice those projected by AR5.  However, due to conservative assumptions made by the study w.r.t. timing of contributions from both the GIS and the AIS, these projected SLR values by 2100 could be increased again in several years time:

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

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

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

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

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

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


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

http://mashable.com/2017/12/13/sea-level-rise-could-be-double-previous-estimates-climate-change-study/#ZTMaw6OSwSq8
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #87 on: December 21, 2017, 04:57:12 PM »
This selected abstract comes from the IGSOC 2017 conference, and concludes that a possible positive feedback between ice mass loss in the WAIS and decompression-melt-induced subglacial volcanism would result in an acceleration of the collapse of the WAIS:

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

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


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


Extract: "Geophysical evidence of Ice-Magma interactions beneath the West Antarctic Ice Sheet in the West Antarctic Rift System
John C. Behrendt
INSTAAR University of Colorado, Boulder
And USGS, Denver
Radar Ice Sounding and Aeromagnetic Surveys reported over the West Antarctic Ice Sheet WAIS have been interpreted as evidence of subglacial eruptions. Several active volcanoes have shown evidence of eruption through the WAIS and several other active volcanoes are present beneath the WAIS (e.g. Corr et al., 2009; Blankenship et al., 1993) reported from radar ice sounding and aeromagnetic data (Behrendt et al., 1995; 2004). Aeromagnetic profiles (>10,000 km) acquired in the early 1960s over the West Antarctic Ice Sheet (WAIS) combined with coincident aeromagnetic and radar ice sounding in 1978-79 indicated numerous high-amplitude, shallow-source, magnetic anomalies over a very extensive area of the volcanically active West Antarctic rift system interpreted as caused by subglacial volcanic rocks. These early aerogeophysical surveys defined this area as >500,000 km2. Five-kilometer spaced coincident aeromagnetic and radar ice sounding surveys since 1990 provide three dimensional characterization of the magnetic field and bed topography beneath the ice sheet. These 5-50-km width, semicircular magnetic anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick ice have been interpreted as evidence of subglacial eruptions. Behrendt et al, (2005, 2008) interpreted these anomalies as indicating >1000 "volcanic centers." requiring high remanent normal (and at least 10% reversed) magnetizations in the present field direction. These data have shown that >80% of the anomaly sources at the bed of the WAIS, have been modified by the moving ice into which they were injected, requiring a younger age than the WAIS (about 25 Ma). Although exposed volcanoes surrounding the WAIS extend in age to ~34 m.y., Mt Erebus, (<1 Ma) Mt. Melbourne, (<0.26 Ma), and Mt. Takahae (<0.1 Ma) are examples of exposed active volcanoes in the WAIS area. However, the great volume of volcanic centers is buried beneath the WAIS. If only a very small percentage of these >1000 volcanic, magnetic-anomaly sources are active today, or in the recent past, in the drainage area of the WAIS, subglacial volcanism may still have a significant effect on the dynamics of the WAIS. Interpreted active subglacial volcanism is revealed by aerogeophysical data reported by Blankenship et al., (1993, Mt. Casertz), and Corr and Vaughan, (2008, near Hudson Mts.), who raised the question of possible volcanic effects on the regime of the WAIS. Wingham et al. (2009) reported an average rate of volume loss from 2.6 to 10.1 km3 /yr from 1995 to 2006 for the Pine Island Glacier in the vicinity of the active subglacial volcano near the Hudson Mts. Probably wet-based areas of the WAIS would be the most likely to be impacted. Here I discuss these geophysical data over the WAIS, and conclude that even if there is a very low probability, future effects on the stability of the WAIS and associated sea-level rise should not be ignored, as changes observed in the past 20 years resulting from global warming, could be accelerated by subglacial volcanism."
« Last Edit: December 23, 2017, 05:40:02 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #88 on: December 22, 2017, 12:36:08 AM »
The linked reference finds that algae driven darkening of bare ice in Greenland reduced albedo more than nonalgal impurities.  Furthermore, they find that a global warming continues the impact of the algae on albedo will also increase:

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

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

Abstract: "Surface ablation of the Greenland ice sheet is amplified by surface darkening caused by light-absorbing impurities such as mineral dust, black carbon, and pigmented microbial cells. We present the first quantitative assessment of the microbial contribution to the ice sheet surface darkening, based on field measurements of surface reflectance and concentrations of light-absorbing impurities, including pigmented algae, during the 2014 melt season in the southwestern part of the ice sheet. The impact of algae on bare ice darkening in the study area was greater than that of nonalgal impurities and yielded a net albedo reduction of 0.038 ± 0.0035 for each algal population doubling. We argue that algal growth is a crucial control of bare ice darkening, and incorporating the algal darkening effect will improve mass balance and sea level projections of the Greenland ice sheet and ice masses elsewhere."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #89 on: December 23, 2017, 06:25:53 PM »
The first attached image from the conservative DeConto & Pollard (2016) analysis, that in panel "c" the "T" stands for Totten Glacier and the "TG" stands for Thwaites Glacier contribution to SLR, with RCP 8.5 radiative forcing.  If it is not clear, let me note that it is note reasonable that Totten's SLR contribution would peak amore 75 years earlier than that from Thwaites; while in reality this order is a manifestation of DeConto & Pollard (2016)'s arbitrary assumption that cliff failures in Antarctica will occur in the future at a rate of ½ of the current calving rate of Jakobshavn.  Due to the 3D nature of possible future cliff failures for Thwaites it will more reasonably calve at a rate several times higher than that of the current rate of calving for Jakobshavn

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

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

Edit: For clarity, I provide the third image which is a blow-up of panel 'c' from the first image.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #90 on: December 23, 2017, 06:46:00 PM »
The first image shows zones of relatively cool to relatively warm ocean heat content around Antarctica, near the depth necessary to melt either grounding line ice of marine glaciers and/or basal ice for ice shelves.  Note that both the Filchner-Ronne Ice Shelf and the Ross Ice Shelf have cool sea water under them.

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

The third image shows how climate change-induced changes in local wind effects on the ocean near the Weddell Sea can direct warm water through the Filchner Trough in order to warm the water beneath the Filchner-Ronne Ice Shelf, FRIS.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #91 on: December 31, 2017, 02:26:18 AM »
This is just a quick post to remind people that the CMIP5 projections do not consider freshwater hosing events; however, Antarctic ice shelves have lost so much ice mass in recent decades that Hansen's ice-climate positive feedback mechanism is already being activated even without a large SLR contribution from Antarctica.

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

The attached image illustrates the extent of recent (1994-2012) ice mass loss from Antarctic ice shelves.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #92 on: December 31, 2017, 03:28:57 AM »
"freshwater hosing events"

Sorry, could you briefly explain what that is, or provide a link that does. Thanks.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #93 on: December 31, 2017, 07:00:05 AM »
I searched for "freshwater hosing" and found the following:
Quote
Numerous modelling experiments have now been carried out in which freshwater is introduced into the ocean ('freshwater hosing').

This is the Google search result (screen print):
Arctic ice is healthy for children and other living things.

oren

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #94 on: December 31, 2017, 08:43:37 AM »
"freshwater hosing events"

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

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

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #95 on: December 31, 2017, 12:34:22 PM »
Thanks, oren and TB.

That concept was familiar to me, but I hadn't heard the phrase 'freshwater hosing' applied to it. Makes sense, though.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #96 on: December 31, 2017, 05:53:15 PM »
Thanks, oren and TB.

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

wili,

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

Best,
ASLR
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #97 on: January 25, 2018, 04:36:51 PM »
I provide links to the following 2015 article (& associated 2016 reference) to remind us all that while most consensus discussion of climate sensitivity focuses on feedbacks due to increases in global temperatures, that feedbacks based on increases in polar precipitation can create a positive feedback comparable to a doubling of global carbon dioxide:

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

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

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

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

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

Abstract: "Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. However, the quantitative link between precipitation and sea ice extent is poorly constrained. Here we present observational evidence for the response of precipitation to sea ice reduction and assess the sensitivity of the response. Changes in the proportion of moisture sourced from the Arctic with sea ice change in the Canadian Arctic and Greenland Sea regions over the past two decades are inferred from annually averaged deuterium excess (d-excess) measurements from six sites. Other influences on the Arctic hydrologic cycle, such as the strength of meridional transport, are assessed using the North Atlantic Oscillation index. We find that the independent, direct effect of sea ice on the increase of the percentage of Arctic sourced moisture (or Arctic moisture proportion, AMP) is 18.2 ± 4.6% and 10.8 ± 3.6%/100,000 km2 sea ice lost for each region, respectively, corresponding to increases of 10.9 ± 2.8% and 2.7 ± 1.1%/1 °C of warming in the vapor source regions. The moisture source changes likely result in increases of precipitation and changes in energy balance, creating significant uncertainty for climate predictions."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #98 on: January 25, 2018, 04:38:48 PM »
The linked reference confirms that most climate simulations do not capture the greater polar amplification during the equable climate of the Eocene.  As CO2e approaches 560ppm this type of information could become highly relevant to modern times:

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

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

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

Abstract: "Past greenhouse periods with elevated atmospheric CO2 were characterized by globally warmer sea-surface temperatures (SST). However, the extent to which the high latitudes warmed to a greater degree than the tropics (polar amplification) remains poorly constrained, in particular because there are only a few temperature reconstructions from the tropics. Consequently, the relationship between increased CO2, the degree of tropical warming, and the resulting latitudinal SST gradient is not well known. Here, we present coupled clumped isotope (Δ47)-Mg/Ca measurements of foraminifera from a set of globally distributed sites in the tropics and midlatitudes. Δ47 is insensitive to seawater chemistry and therefore provides a robust constraint on tropical SST. Crucially, coupling these data with Mg/Ca measurements allows the precise reconstruction of Mg/Casw throughout the Eocene, enabling the reinterpretation of all planktonic foraminifera Mg/Ca data. The combined dataset constrains the range in Eocene tropical SST to 30–36 °C (from sites in all basins). We compare these accurate tropical SST to deep-ocean temperatures, serving as a minimum constraint on high-latitude SST. This results in a robust conservative reconstruction of the early Eocene latitudinal gradient, which was reduced by at least 32 ± 10% compared with present day, demonstrating greater polar amplification than captured by most climate models."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #99 on: February 08, 2018, 05:12:58 PM »
As sidd has questions about why abrupt sea level rise from ice mass loss might increase the risks of flipping the Earth's magnetic poles, I am reposting the following from the 'Adapting to the Anthropocene' thread:

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

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

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

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

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

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

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

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

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

Again, while it is not a certainty that the switch will happen soon, this activity at the Earth's core suggests that it is possible in the near future.""
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson