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Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE

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AbruptSLR:
The linked reference indicates that from 1994 to 2018, Antarctic ice shelves have lost enough ice mass to fill the Grand Canyon.

Adusumilli, S., Fricker, H.A., Medley, B. et al. Interannual variations in meltwater input to the Southern Ocean from Antarctic ice shelves. Nat. Geosci. (2020). https://doi.org/10.1038/s41561-020-0616-z

https://www.nature.com/articles/s41561-020-0616-z

Abstract: "Ocean-driven basal melting of Antarctica’s floating ice shelves accounts for about half of their mass loss in steady state, where gains in ice-shelf mass are balanced by losses. Ice-shelf thickness changes driven by varying basal melt rates modulate mass loss from the grounded ice sheet and its contribution to sea level, and the changing meltwater fluxes influence climate processes in the Southern Ocean. Existing continent-wide melt-rate datasets have no temporal variability, introducing uncertainties in sea level and climate projections. Here, we combine surface height data from satellite radar altimeters with satellite-derived ice velocities and a new model of firn-layer evolution to generate a high-resolution map of time-averaged (2010–2018) basal melt rates and time series (1994–2018) of meltwater fluxes for most ice shelves. Total basal meltwater flux in 1994 (1,090 ± 150 Gt yr–1) was similar to the steady-state value (1,100 ± 60 Gt yr–1), but increased to 1,570 ± 140 Gt yr–1 in 2009, followed by a decline to 1,160 ± 150 Gt yr–1 in 2018. For the four largest ‘cold-water’ ice shelves, we partition meltwater fluxes into deep and shallow sources to reveal distinct signatures of temporal variability, providing insights into climate forcing of basal melting and the impact of this melting on the Southern Ocean."

AbruptSLR:
The linked article indicates that a CMIP6 version of HadGEM3 (the UK's most advanced model) indicates that the Arctic may become seasonally sea ice free by 2035 (see also the associated attached image w.r.t. ECS).  If so, this would greatly increase the probability of a freshwater hosing event from the Beaufort Gyre, which, could likely trigger a bipolar seesaw cascade of subsequent freshwater hosing event such as: hosing from key ASE marine glaciers triggering hosing from key GIS marine terminating glaciers, triggering key AIS marine glaciers etc.  If so this might lead to 4 to 5m of SLR circa 2100.

Title: "Past evidence supports complete loss of Arctic sea ice by 2035"

https://phys.org/news/2020-08-evidence-loss-arctic-sea-ice.html

Extract: "During spring and early summer, shallow pools of water form on the surface of Arctic sea-ice. These 'melt ponds' are important for how much sunlight is absorbed by the ice and how much is reflected back into space. The new Hadley Centre model is the UK's most advanced physical representation of the Earth's climate and a critical tool for climate research and incorporates sea-ice and melt ponds.

Using the model to look at Arctic sea ice during the last interglacial, the team concludes that the impact of intense springtime sunshine created many melt ponds, which played a crucial role in sea-ice melt. A simulation of the future using the same model indicates that the Arctic may become sea ice-free by 2035."

&

Guarino, M., Sime, L.C., Schröeder, D. et al. Sea-ice-free Arctic during the Last Interglacial supports fast future loss. Nat. Clim. Chang. (2020). doi.org/10.1038/s41558-020-0865-2

https://www.nature.com/articles/s41558-020-0865-2

Abstract: "The Last Interglacial (LIG), a warmer period 130,000–116,000 years before present, is a potential analogue for future climate change. Stronger LIG summertime insolation at high northern latitudes drove Arctic land summer temperatures 4–5 °C higher than in the pre-industrial era. Climate model simulations have previously failed to capture these elevated temperatures, possibly because they were unable to correctly capture LIG sea-ice changes. Here, we show that the latest version of the fully coupled UK Hadley Center climate model (HadGEM3) simulates a more accurate Arctic LIG climate, including elevated temperatures. Improved model physics, including a sophisticated sea-ice melt-pond scheme, result in a complete simulated loss of Arctic sea ice in summer during the LIG, which has yet to be simulated in past generations of models. This ice-free Arctic yields a compelling solution to the long-standing puzzle of what drove LIG Arctic warmth and supports a fast retreat of future Arctic summer sea ice."

AbruptSLR:
The linked reference (& associated article) indicates that the Arctic is both warming faster and losing sea ice faster than projected by consensus climate models, and that Arctic Amplification is indeed currently proceeding at a rate indicating a present era of abrupt Arctic climate change.

Eystein Jansen et al. Past perspectives on the present era of abrupt Arctic climate change, Nature Climate Change (2020). DOI: 10.1038/s41558-020-0860-7

https://www.nature.com/articles/s41558-020-0860-7

Abstract: "Abrupt climate change is a striking feature of many climate records, particularly the warming events in Greenland ice cores. These abrupt and high-amplitude events were tightly coupled to rapid sea-ice retreat in the North Atlantic and Nordic Seas, and observational evidence shows they had global repercussions. In the present-day Arctic, sea-ice loss is also key to ongoing warming. This Perspective uses observations and climate models to place contemporary Arctic change into the context of past abrupt Greenland warmings. We find that warming rates similar to or higher than modern trends have only occurred during past abrupt glacial episodes. We argue that the Arctic is currently experiencing an abrupt climate change event, and that climate models underestimate this ongoing warming."

See also:

Title: "New study warns: We have underestimated the pace at which the Arctic is melting"

https://phys.org/news/2020-08-underestimated-pace-arctic.html

Extract: "Arctic sea ice is melting more quickly than once assumed. Today's climate models have yet to incorporate the steep rise in temperatures that have occurred over the past 40 years. This, according to a new study by researchers at the University of Copenhagen and other institutions.

Temperatures in the Arctic Ocean between Canada, Russia and Europe are warming faster than researchers' climate models have been able to predict.

Over the past 40 years, temperatures have risen by one degree every decade, and even more so over the Barents Sea and around Norway's Svalbard archipelago, where they have increased by 1.5 degrees per decade throughout the period."

AbruptSLR:
The linked video discusses how E3SM uses MPAS-Analysis and discusses how this helps to analysis the pattern effect of both SSTA, and sea ice, patterns.  For those only interested in findings you can skip ahead to minutes 9:25 to 14:50.

Title: "An Introduction to MPAS-Analysis"

https://www.youtube.com/watch?v=TCEzv7Vr3vc&feature=youtu.be

See also the pdf at:

https://e3sm.org/wp-content/uploads/2020/08/200806_Z_Davis_opt.pdf

Tom_Mazanec:

--- Quote --- A simulation of the future using the same model indicates that the Arctic may become sea ice-free by 2035."

--- End quote ---
Does this mean for a few days in September, or all year around? I would guess the former, but would not be surprised by the later.

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