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Author Topic: Discussion of WAIS Collapse Main Period from 2060 to 2100  (Read 28309 times)

AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #50 on: August 28, 2013, 01:45:57 AM »
The recent findings presented in the following two links imply that later this century there is a good probability that Antarctic amplification will be higher than most current GCM project because the cloud cover over the Southern Ocean will move southward and will be less reflective:

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1981.html

http://www.huffingtonpost.com/2013/08/09/antarctic-ozone-hole_n_3731877.html

Edited addition:  See also the following link to related discussion in the "Science" folder:

http://forum.arctic-sea-ice.net/index.php/topic,545.0.html


Such increased Antarctic amplification would increase the probability of the WAIS collapse presented in this thread.
« Last Edit: August 28, 2013, 02:13:59 AM by AbruptSLR »
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AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #51 on: September 01, 2013, 05:33:12 PM »

The following linked reference highlights the need to better understand the interactions between: basal conditions, grounding-zone processes, and ocean-ice interactions, for Antarctica:

http://onlinelibrary.wiley.com/doi/10.1002/jgrf.20081/abstract

Nowicki, S., et al. (2013), Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project I: Antarctica, J. Geophys. Res. Earth Surf., 118, 1002–1024, doi:10.1002/jgrf.20081.


Abstract:
"Atmospheric, oceanic, and subglacial forcing scenarios from the Sea-level Response to Ice Sheet Evolution (SeaRISE) project are applied to six three-dimensional thermomechanical ice-sheet models to assess Antarctic ice sheet sensitivity over a 500 year timescale and to inform future modeling and field studies. Results indicate (i) growth with warming, except within low-latitude basins (where inland thickening is outpaced by marginal thinning); (ii) mass loss with enhanced sliding (with basins dominated by high driving stresses affected more than basins with low-surface-slope streaming ice); and (iii) mass loss with enhanced ice shelf melting (with changes in West Antarctica dominating the signal due to its marine setting and extensive ice shelves; cf. minimal impact in the Terre Adelie, George V, Oates, and Victoria Land region of East Antarctica). Ice loss due to dynamic changes associated with enhanced sliding and/or sub-shelf melting exceeds the gain due to increased precipitation. Furthermore, differences in results between and within basins as well as the controlling impact of sub-shelf melting on ice dynamics highlight the need for improved understanding of basal conditions, grounding-zone processes, ocean-ice interactions, and the numerical representation of all three."
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AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #52 on: September 01, 2013, 05:42:51 PM »
The following linked reference indicates that while the paleorecord indicates that meltwater out-flow typically build-up sediment wedges that can serve to stabilize ice stream; no such sediment wedge formation is currently observed for the Whillans ice stream, or for nearby grounding line locations, thus indicating that the current dynamic ice mass loss conditions may be less stable than those indicated in the paleorecord.


http://onlinelibrary.wiley.com/doi/10.1002/grl.50712/abstract


Horgan, H. J., K. Christianson, R. W. Jacobel, S. Anandakrishnan, and R. B. Alley (2013), Sediment deposition at the modern grounding zone of Whillans Ice Stream, West Antarctica, Geophys. Res. Lett., 40, 3934–3939, doi:10.1002/grl.50712.


Abstract:

"Much of the threshold behavior of marine ice sheets is thought to result from processes occurring at the grounding zone, where the ice sheet transitions into the ice shelf. At short timescales (decades to centuries), grounding zone behavior is likely to be influenced by ongoing sediment deposition, which can stabilize the grounding zone position. We present a ground-based geophysical study across the modern grounding zone of Whillans Ice Stream. Within an embayment setting, where subglacial meltwater drains, we image sedimentary deposits; however, we do not observe the classic asymmetric grounding zone wedge deposits, which are found in the paleorecord and are thought to stabilize the grounding zone position. At an adjacent peninsula, we image the grounding zone and an ice-shelf pinning point and again observe no wedge deposits."
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AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #53 on: December 14, 2013, 05:29:23 PM »
For some reason, I never posted the accompanying images of my assumed grounding line retreat plan (and profile) area map(s) associated with my 95% CL RCP 8.5 (with some enhanced methane emissions) scenario.  This image indicates the potential for significant ice mass loss from Recovery Glacier (under this extreme scenario) by 2100 as discussed in posts #43 to #48 in the EAIS thread (see link below):

http://forum.arctic-sea-ice.net/index.php/topic,263.0.html#lastPost
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icebgone

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #54 on: December 14, 2013, 08:51:32 PM »
ASLR, Do any of the long-term climate models include changes in glacier behavior from deflation due to bottom melting?  I am thinking of Jakobshaven and it's increase in forward speed as the grounding line moves up glacier.  Is it possible that an equilibrium point for a particular glacier, (PIG for instance) could be reached and a sudden change in behavior similar to Jakobshaven be observed?  I seem to remember that the glaciers that fed Larsen B speeded up once the ice shelf disintegrated.  With continued warming the loss of snow insulation could expose ice to atmospheric as well as oceanic influences.  I have to wonder if we are being too conservative.

AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #55 on: December 14, 2013, 09:13:42 PM »
icebgone,

First, I would like to say that I think that a complete collapse of the WAIS (and triggering of adjoining EAIS glaciers) this century is still a low probability event, but that the longer we stay on our current BAU path the greater that probability becomes.

Next to respond to your questions, about various ice mass loss mechanisms that are currently not fully represented by our local circulation models for marine terminating glacier and marine ice sheets:
(a) I am not aware of any marine terminating glacier models that fully about for all considerations of basal ice melting (including feedback mechanism); which in my opinion is a major short-coming for models of the various WAIS drainage basins where is it likely that isostatic rebound from modern ice mass loss is actively increasing local geothermal basal heating (due to local upwelling of mantle magma) which is acting as a positive feedback mechanism for ice mass loss both due to draining of the subglacial hydrological systems and due to lubrication of the basal friction.
(b) The periodic acceleration of calving (and associated grounding line retreat) of Jakoshavn is related to the loss of local force equilbrium stability of the calving face due to such factors as: ice face geometry, reduction of basal friction, reduction of buttressing, and reduction of ice viscosity.  So yes PIG, Thwaites and Recovery Glaciers could all start acting like Jackoshavn (or worse) in the future.

I need to go so I will comment more later.
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AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #56 on: December 15, 2013, 12:02:03 AM »
continuation of my prior post to icebgone:

(c) Certainly there is more evidence that various ice shelves in Antarctica could collapse prematurely than just the Larsen B ice shelf.  For example: (i) the lateral ice boundaries near the calving face of the Pine Island Ice Shelf (PIIS) show extensive shear cracking, which threaten to accelerate calving on this ice shelf and other ice shelves are likely to show similar behavior as they both thin and as their flow velocities increase; (ii) Sub-ice shelve basal ice melt water (due to the circulation of warm Circumpolar Deep Water (CDW), warmer than normal Antarctic Bottom Water (AABW), tidal water, or high salinity shelf water (HSSW), has been found to induce ruts/grooves in the bottom of the ice shelves that cause stress concentrations that induce crevasses and premature calving; and (iii) warm austral summers normally follow multi-year cycles and as we have not had a warm austral summer since 2006 we are soon likely to experience such warm austral summers that will likely cause surface melting of ice shelves which could contribute to the "melt pond" mechanism that caused the Larsen B shelf to collapse.  Clearly the loss of buttressing action of ice shelves will cause the adjoining glacier ice flow to accelerate.

(d)  Certainly with continued global warming the Antarctic Sea Ice extent will eventually decrease (projected by 2070) which at least for the Filchner Ronne Ice Shelf, FRIS, should induce warm ocean currents beneath the FRIS.

Clearly, current models cannot yet fully model such effects, so yes I think that most current estimates of SLR contribution from Antarctica are too low.

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

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #57 on: December 16, 2013, 02:20:37 AM »
AbruptSLR, Thank you for your explanation.  The current IPCC report is definitely in need of better glacier behavior information.  The impact on SLR, storm surge strengthening, tidal erosion, salt water intrusion and biodiversity loss all hinge on change in glacier behavior.  What percent of sea terminating glaciers have a detailed history and/or photographic data that extends back at least 10 years? 

AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #58 on: December 16, 2013, 04:02:27 AM »
icebgone,

You make an excellent point that most of what we know about maine terminating glaciers as come during the satellite era; and that is very limited indeed.  AR5 cited SLR projections that were about 50% greater than those from AR4; and I would not be surprised if the AR6 SLR projections are 50% greater than those from AR5, and the same for AR7.  I realize that modelers are doing the best that they can with the money and tools that they have; nevertheless, I recently posted in the Paleo folder links to an article that presents analysis of paleo-evidence that gives a 1.8m 95% SLR value by 2100 which is higher than the corresponding AR5 value which is supposedly using radiative forcing scenarios that are over ten times higher than any observed in the paleo-record.  It is difficult for me to accept IPCC processes that produce lower SLR projections than conservative (stationary) projections of the historical record, into a very much non-stationary future.
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AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #59 on: January 31, 2014, 11:16:16 PM »
Due to the long term importance of this topic, I thought that I would repost this information here:

The referenced paper (with a link to a free access pdf), adds concerns of firn air depletion to the list of factors to consider with regard to the potential collapse of Antarctic ice shelves:

"Firn air depletion as a precursor of Antarctic ice-shelf Collapse" Peter Kuipers Munneke1, Stefan R.M. Ligtenberg1, Michiel van den Broeke1, David G. Vaughan2, Journal of Glaciology, 60 (220), (2014). DOI: 10.3189/2014JoG13J183.

http://www.igsoc.org/journal/60/220/t13J183.pdf
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sidd

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #60 on: February 01, 2014, 06:20:21 AM »
The Kuipers paper is good, now couple with Banwell(2013)

doi:10.1002/2013GL057694

i note that MacAyeal (author of one of the shallow ice approximations) and rising star Sergienko are on the author list.

I quote:

"We show that the spacing of these fractures caused a large proportion of the LBIS fragments
to have aspect ratios that were unstable to capsize. We also show that the filling or drainage of a single starter lake can produce multiple fractures that are able to drain hundreds of surrounding lakes through a chain reaction process. Thus, we argue that this chain reaction contributed to the abruptness of the explosive disintegration of the LBIS."

LBIS is larsen B

i find it neat that they found a length scale (the spacing referred to)  for the collapse. there is another paper on ice collapse that suggests the appearance of a natural length scale, but i cannot immediately recall.

sidd
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sidd

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #61 on: February 01, 2014, 07:10:36 AM »
I found the paper i was thinking about, it has already been mentioned on one of the Antarctica threads

Bassis(2013)

DOI: 10.1038/NGEO1887

specifically fig 1b)

which shows a natural length scale also

 http://membrane.com/sidd/bassis-1b.png

sidd

AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #62 on: February 01, 2014, 01:10:52 PM »
sidd,

Thanks for connecting the dots on these interrelated papers.  However, watching the continuing calving in the new notch in the PIIS and the network crevasse cracking at the base of the Thwaites Ice Tongue, I think of how complex the different types of cracking/calving processes are, and how challenging it is to try to connect the dots on all of these different phenomena that could result in abrupt ice mass loss. 


For those who would like a more complete reference on the Banwell et al paper, I provide the following:

Alison F. Banwell, Douglas R. MacAyeal, Olga V. Sergienko, (2013), "Breakup of the Larsen B Ice Shelf triggered by chain reaction drainage of supraglacial lakes" Geophysical Research Letters, Volume 40, Issue 22, pages 5872–5876, 28 November 2013, doi:10.1002/2013GL057694

Abstract: "The explosive disintegration of the Larsen B Ice Shelf poses two unresolved questions: What process (1) set a horizontal fracture spacing sufficiently small to predispose the subsequent ice shelf fragments to capsize and (2) synchronized the widespread drainage of >2750 supraglacial meltwater lakes observed in the days prior to break up? We answer both questions through analysis of the ice shelf's elastic flexure response to the supraglacial lakes on the ice shelf prior to break up. By expanding the previously articulated role of lakes beyond mere water reservoirs supporting hydrofracture, we show that lake-induced flexural stresses produce a fracture network with appropriate horizontal spacing to induce capsize-driven breakup. The analysis of flexural stresses suggests that drainage of a single lake can cause neighboring lakes to drain, which, in turn, causes farther removed lakes to drain. Such self-stimulating behavior can account for the sudden, widespread appearance of a fracture system capable of driving explosive break up."
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AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #63 on: October 17, 2015, 07:41:51 PM »
The linked reference supports my WAIS main phase collapse scenario under the assumption that BAU anthropogenic forcing continues to about 2020 to 2025, and then sufficient natural positive feedbacks are activated to continue following RCP 8.5 through at least 2070 to 2090 (thus contributing to hydrofracturing):

Luke D. Trusel, Karen E. Frey, Sarah B. Das, Kristopher B. Karnauskas, Peter Kuipers Munneke, Erik van Meijgaard & Michiel R. van den Broeke (2015), "Divergent trajectories of Antarctic surface melt under two twenty-first-century climate scenarios", Nature Geoscience, doi:10.1038/ngeo2563


http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2563.html

Abstract: "Ice shelves modulate Antarctic contributions to sea-level rise1 and thereby represent a critical, climate-sensitive interface between the Antarctic ice sheet and the global ocean. Following rapid atmospheric warming over the past decades, Antarctic Peninsula ice shelves have progressively retreated, at times catastrophically. This decay supports hypotheses of thermal limits of viability for ice shelves via surface melt forcing. Here we use a polar-adapted regional climate model and satellite observations to quantify the nonlinear relationship between surface melting and summer air temperature. Combining observations and multimodel simulations, we examine melt evolution and intensification before observed ice shelf collapse on the Antarctic Peninsula. We then assess the twenty-first-century evolution of surface melt across Antarctica under intermediate and high emissions climate scenarios. Our projections reveal a scenario-independent doubling of Antarctic-wide melt by 2050. Between 2050 and 2100, however, significant divergence in melt occurs between the two climate scenarios. Under the high emissions pathway by 2100, melt on several ice shelves approaches or surpasses intensities that have historically been associated with ice shelf collapse, at least on the northeast Antarctic Peninsula."
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AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #64 on: August 14, 2016, 07:13:02 PM »
While I have previously posted about the following reference in both the "Hansen et al paper: 3+ meters SLR by 2100" thread and the "Risks and Challenges for Regional Circulation Models of the Southern Ocean", thread; here I focus on the threats of the identified "domino effect" on the stability of both large sections of the WAIS and of the marine portions of the AIS by 2100.  This research explicitly cites that meltwater from the Wilkes Basin (see the attached image) can help destabilize the Weddell Sea Sector of the WAIS; which to me indicates that a partial collapse of the BSB will help to destabilize the Amery Ice Shelf sector.  Neither of these probable occurrences this century are considered by AR5:

Steven J. Phipps, Christopher J. Fogwill, and Christian S. M. Turney (2016), "Impacts of marine instability across the East Antarctic Ice Sheet on Southern Ocean dynamics", The Cryosphere Discuss., doi:10.5194/tc-2016-111


http://www.the-cryosphere-discuss.net/tc-2016-111/tc-2016-111.pdf

Abstract: "Recent observations and modelling studies have demonstrated the potential for rapid and substantial retreat of large sectors of the East Antarctic Ice Sheet (EAIS). This has major implications for ocean circulation and global sea level. Here we examine the effects of increasing meltwater from the Wilkes Basin, one of the major marine-based sectors of the EAIS, on Southern Ocean dynamics. Climate model simulations reveal that the meltwater flux rapidly stratifies surface waters, leading to a dramatic decrease in the rate of Antarctic Bottom Water formation. The surface ocean cools but, critically, the Southern Ocean warms by more than 1oC at depth. This warming is accompanied by a Southern Ocean-wide ‘domino effect’, whereby the warming signal propagates westward with depth. Our results suggest that melting of one sector of the EAIS could result in accelerated warming across other sectors, including the Weddell Sea sector of the West Antarctic Ice Sheet. Thus localized melting of the EAIS could potentially destabilise the wider Antarctic Ice Sheet."

Extract: "Remarkably, we therefore find that the largest changes in convective depth occur on the opposite side of the continent from the region of freshwater input. Furthermore, this outcome occurs despite the fact that the salinity signal in the Weddell Sea is weak; the average decrease in SSS over the eastern half of the sea, where the greatest reduction in convective depth occurs, is only 0.13psu. This demonstrates that the Weddell Sea is extremely sensitive to freshwater input within the model and can be significantly impacted by melting on the other side of the continent, as a result of the surface freshening being carried westwards by the coastal counter-currents.



Furthermore, recent work has highlighted the sensitivity of the Weddell Sea sector of the WAIS to changes in local ocean circulation (Hellmer et al., 2012). This is exacerbated by the presence of steep reverse slope beds in regional ice streams (Ross et al., 2012), making this sector particularly vulnerable to warming (Humbert, 2012; Fogwill et al., 2014a).We have established in this study that melting of the EAIS can lead to reduced convection and warming at depth in the Weddell Sea, suggesting that localised melting of one sector of the EAIS might be sufficient to destabilise at least one key sector of the WAIS as well."

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AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #65 on: July 18, 2017, 05:38:17 PM »
The linked reference indicates that the Ross Ice Shelf, RIS, is currently being stabilized by 'nails' from adjoining EAIS outlet glaciers (like Byrd Glacier) that are pinning the ice shelf to the Transantarctic Mountains.  In the "Hazard Analysis for the FRIS/RIS in the 2012 to 20160 Timeframe" thread  (see Replies #3, 4, 7 & 18 in that thread) I make the case that global warming related changes in the Ross Gyre (and the associate collapse of the Getz Ice Shelf) will unpin the RIS by extracting the 'nail' from the Byrd Glacier by 2050.  In this scenario the RIS would substantially collapse circa 2060 (largely due to hydrofracturing); which would allow the collapse of the marine portions of the WAIS to proceed to completion circa 2100:

Terence Hughes, Zihong Zhao, Raymond Hintz & James Fastook (27 May 2017), "Instability of the Antarctic Ross Sea Embayment as climate warms", Reviews of Geophysics, DOI: 10.1002/2016RG000545

http://onlinelibrary.wiley.com/doi/10.1002/2016RG000545/abstract

Abstract: "Collapse of the Antarctic Ice Sheet since the Last Glacial Maximum 18,000 years ago is most pronounced in the Ross Sea Embayment, which is partly ice-free during Antarctic summers, thereby breaching the O-ring of ice shelves and sea ice surrounding Antarctica that stabilizes the ice sheet. The O-ring may have vanished during Early Holocene (5000 to 3000 B.C.), Roman (1 to 400 A.D.), and Medieval (900 to 1300 A.D.) warm periods and reappeared during the Little Ice Age (1300 to 1900 A.D.). We postulate further collapse in the embayment during the post-1900 warming may be forestalled because East Antarctic outlet glaciers “nail” the Ross Ice Shelf to the Transantarctic Mountains so it can resist the push from West Antarctic ice streams. Our hypothesis is examined for Byrd Glacier and a static ice shelf using three modeling experiments having plastic, viscous, and viscoplastic solutions as more data and improved modeling became available. Observed crevasse patterns were not reproduced. A new research study is needed to model a dynamic Ross Ice Shelf with all its feeder ice streams, outlet glaciers, and ice calving dynamics in three dimensions over time to fully test our hypothesis. The required model must allow accelerated calving if further warming melts sea ice and discerps the ice shelf. Calving must then successively pull the outlet glacier “nails” so collapse of the marine West Antarctic Ice Sheet proceeds to completion."

See also:

Title: "The Uncertain Future of the West Antarctic Ice Sheet"

https://eos.org/editors-vox/the-uncertain-future-of-the-west-antarctic-ice-sheet
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AbruptSLR

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Re: Discussion of WAIS Collapse Main Period from 2060 to 2100
« Reply #66 on: July 18, 2017, 07:48:33 PM »
The linked reference finds that: "The increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major melt events.":

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

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

Abstract: "Over the past two decades the primary driver of mass loss from the West Antarctic Ice Sheet (WAIS) has been warm ocean water underneath coastal ice shelves, not a warmer atmosphere. Yet, surface melt occurs sporadically over low-lying areas of the WAIS and is not fully understood. Here we report on an episode of extensive and prolonged surface melting observed in the Ross Sea sector of the WAIS in January 2016. A comprehensive cloud and radiation experiment at the WAIS ice divide, downwind of the melt region, provided detailed insight into the physical processes at play during the event. The unusual extent and duration of the melting are linked to strong and sustained advection of warm marine air toward the area, likely favoured by the concurrent strong El Niño event. The increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major melt events."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson