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kassy

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Re: What's new in Antarctica ?
« Reply #600 on: July 08, 2020, 10:11:14 AM »
Esa and Nasa line up satellites to measure Antarctic sea-ice

US and European scientists are about to get a unique view of polar ice as their respective space agencies line up two satellites in the sky.

Authorisation was given on Tuesday for Europe's Cryosat-2 spacecraft to raise its orbit by just under one kilometre.

This will hugely increase the number of coincident observations it can make with the Americans' Icesat-2 mission.

One outcome from this new strategy will be the first ever reliable maps of Antarctic sea-ice thickness.

Currently, the floes in the far south befuddle efforts to measure their vertical dimension.

Heavy snow can pile on top of the floating ice, hiding its true thickness. Indeed, significant loading can even push Antarctic sea-ice under the water.

But researchers believe the different instruments on the two satellites working in tandem can help them tease apart this complexity.

Nasa's Icesat-2, which orbits the globe at about 500km in altitude, uses a laser to measure the distance to the Earth's surface - and hence the height of objects. This light beam reflects directly off the top of the snow.

Esa's Cryosat-2, on the other hand, at around 720km in altitude, uses radar as its height tool, and this penetrates much more deeply into the snow cover before bouncing back.

and more on:
https://www.bbc.com/news/science-environment-53326490
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vox_mundi

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Re: What's new in Antarctica ?
« Reply #601 on: August 24, 2020, 03:35:54 PM »
Japanese Expedition Identifies East Antarctic Melting Hotspot
https://phys.org/news/2020-08-japanese-east-antarctic-hotspot.html

Ice is melting at a surprisingly fast rate underneath Shirase Glacier Tongue in East Antarctica due to the continuing influx of warm seawater into the Lützow-Holm Bay.



... "Our data suggests that the ice directly beneath the Shirase Glacier Tongue is melting at a rate of seven to 16 meters per year," says Assistant Professor Daisuke Hirano of Hokkaido University's Institute of Low Temperature Science. "This is equal to or perhaps even surpasses the melting rate underneath the Totten Ice Shelf, which was thought to be experiencing the highest melting rate in East Antarctica, at a rate of 10 to 11 meters per year."

... The data suggests the melting is occurring as a result of deep, warm water flowing inward, toward the base of the Shirase Glacier Tongue. The warm water moves along a deep underwater ocean trough and then flows upward along the tongue's base, warming and melting the ice. The warm waters carrying the melted ice then flow outwards, mixing with the glacial meltwater.

The team found this melting occurs year-round, but is affected by easterly, winds alongshore that vary seasonally. When the winds diminish in the summer, the influx of the deep warm water increases, speeding up the melting rate.



Daisuke Hirano et al., Strong ice-ocean interaction beneath Shirase Glacier Tongue in East Antarctica. Nature Communications (2020)
https://www.nature.com/articles/s41467-020-17527-4
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baking

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Re: What's new in Antarctica ?
« Reply #602 on: September 11, 2020, 01:39:24 PM »
Discovery of new colonies by Sentinel2 reveals good and bad news for emperor penguins
https://zslpublications.onlinelibrary.wiley.com/doi/full/10.1002/rse2.176

Lots of information on how to find Emperor Penguin colonies using Sentinel 2 imaging with a complete list of known and recently discovered colonies.  I stumbled across this while searching for info on when we can expect to find new Sentinel 2 images for this upcoming season.

Juan C. García

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Re: What's new in Antarctica ?
« Reply #603 on: September 25, 2020, 10:17:42 PM »
Just to have it on this thread:  ;)

So if we manage to get CO2e past 750 ppm Antarctica melts to the bedrock and the seas rise 70 meters or more?
     70 meters will take a long while, but if 3.3 meters floats your boat that can happen at just  650ppm held steady long enough according to a study published yesterday.
 
      Study out yesterday found that eventually West Antarctic Ice Sheet is drinkable at 2.36C above preindustrial.  IPPC 2014 CO2 and Temp tables for RCP8.5 (closest analog to path we are currently on) put 2.36C at about 650 ppm CO2.  Quick skim of article did not find any timeline should that occur, and they take pain to say their report is NOT a projection or forecast.  Based on Deconto and Pollard 2016 simulation, my guess is that to reach that new equilibrium would take 100 years or more.  Then again, who's to say we would stop at 650ppm CO2 (even less likely for 650 ppm CO2e)?
   
     (Speaking of Dec and Poll 2016, the new paper does NOT account for their proposed ice cliff instability, which apparently is still being debated for validity.  If it does apply, then it seems the new study's melt rates would be underestimates by leaving it out.  On the other hand, the new paper mentions both negative and postive feedbacks that could affect this new disaster scenario.) 

     See animated simulation posted yesterday by Potsdam Institute: 
The Hysteresis of the Antarctic Ice Sheet
Sep 23, 2020


Journal article - The hysteresis of the Antarctic Ice Sheet
Julius Garbe, Torsten Albrecht, Anders Levermann, Jonathan F. Donges & Ricarda Winkelmann
Nature volume 585, pages538–544(2020)
https://www.nature.com/articles/s41586-020-2727-5
    New (to me) term - "Creep instability"   Good fit for the times.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

wili

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Re: What's new in Antarctica ?
« Reply #604 on: October 12, 2020, 01:58:08 PM »
Not sure if this is the right thread, but here is a new piece out from Skeptical Science:

https://www.skepticalscience.com/bleak-views-melting-antarctic.html

   
Bleak views of melting Antarctic ice, from above and below


Quote
Images from satellites high above the Earth have helped a research team put together a stark visual chronicle of decades of glacier disintegration in Antarctica. Meanwhile, a separate international research team has taken the opposite perspective – studying the ice from its underbelly. Both teams are documenting the stress on two glaciers in West Antarctica that so far have helped check a massive stream of melting ice responsible for about 5 percent of Earth’s rising sea levels.

Climate researchers have long monitored ice sheet dynamics in the Amundsen Sea, focusing specifically on the Thwaites and Pine Island glaciers. The two sit side by side on Antarctica’s western peninsula covering an area roughly the size of nine U.S. coastal states stretching from Maine to Maryland.

The two glaciers alone store ice that could account for about 4 feet (1.2 meters) of global sea level rise. Their “seaboard” location may help bring increased public attention and interest to the West Antarctic Ice Sheet, which if it melted could raise seas by a catastrophic 11 feet (3.4 meters).

An international effort led by the British Antarctic Survey recently published two papers (Hogan et al. and Jordan et al.) showing the first detailed maps of the seafloor at the edge of the Thwaites Glacier. The team mapped deep submarine channels that have been funneling warm water to this vulnerable location. High-resolution imagery pinpoints the pathways that allow warm water to undermine the ice shelf. Lead author Kelly Hogan of the British Antarctic Survey says the findings will improve estimates of sea-level rise from Thwaites Glacier. “We can go ahead and make those calculations about how much warm water can get under the ice and melt it,” Hogan said.

The other researchers, led by Stef Lhermitte, found stark visual confirmation of glacier disintegration using decades of time-lapse satellite imagery. Their work sheds light on the accelerating feedback process, wherein the rapid loss of ice is opening the door to ever-increasing melting...
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Tor Bejnar

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Re: What's new in Antarctica ?
« Reply #605 on: October 12, 2020, 05:24:02 PM »
I have some problem with the highlighted paragraph:
Quote
The two glaciers alone store ice that could account for about 4 feet (1.2 meters) of global sea level rise. Their “seaboard” location may help bring increased public attention and interest to the West Antarctic Ice Sheet, which if it melted could raise seas by a catastrophic 11 feet (3.4 meters).
I wish the green-glow phrase had been written
When it melts (which it will do under current atmospheric greenhouse gas levels) it will ...
[I believe this recently published paper supports this modified conclusion.]

Arctic ice is healthy for children and other living things.

Tom_Mazanec

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Re: What's new in Antarctica ?
« Reply #606 on: October 12, 2020, 06:21:14 PM »
What would be the timescale for that 11 feet? If it is a millennium it is a problem. If it is a century it is a cataclysm.
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Tor Bejnar

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Re: What's new in Antarctica ?
« Reply #607 on: October 12, 2020, 07:10:52 PM »
That's a function of future greenhouse gas emissions.  The article was specifically talking about 2 major glaciers.  With 'all' inputs (especially the expansion of warming sea water) there are projections that vary quite a bit.  (See ASLR postings for all the scientifically documented reasons he believes the following 'published' estimates are on the low side.)

For 300 million people, sea level 'problems' will occur during my children's life time.  11' (3.3 meters) sea level rise (over the year 2000 sea level) will be attained in 1-400 years, as best I can tell.  11 meters (36') will be attained in 400-1000 years, as best I can tell.

So there is definitely a cataclysmic problem for many, which might turn into a cataclysmic problem for the rest of us.  (For example, where will that 'first' 300 million go?)

Some quotes:
Forbes:
Quote
By 2050, sea-level rise will push average annual coastal floods higher than land now home to 300 million people, according to a study published in Nature Communications.
Skeptical Science:
Quote
the most likely sea level rise by 2100 is betweem 80cm and 1 metre.  Longer term, sea levels will continue to rise even after emissions have been reduced or eliminated.
Forbes:
Quote
The IPCC’s range for “multi-millennial” [400 years] commitment is 3 to 13 meters (10 to 36 feet) for warming of 2 degrees C.
Express:
Quote
“Our research reveals that ice melt in the last interglacial period caused global seas to rise about 10 metres above the present level. The ice melted first in Antarctica, then a few thousand years later in Greenland.

“Sea levels rose at up to 3 metres per century, far exceeding the roughly 0.3-metre rise observed over the past 150 years.
ASLR's latest post:
Quote
coming climate changes:
"… will continue throughout the decades and the millennia – some occurring abruptly and (others) being irreversible."
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Tom_Mazanec

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Re: What's new in Antarctica ?
« Reply #608 on: October 12, 2020, 07:20:35 PM »
Quote
11' (3.3 meters) sea level rise (over the year 2000 sea level) will be attained in 1-400 years,
You mean 100-400 years, right?
Not a single year!
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Tor Bejnar

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Re: What's new in Antarctica ?
« Reply #609 on: October 12, 2020, 08:32:36 PM »
yes
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AbruptSLR

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Re: What's new in Antarctica ?
« Reply #610 on: October 13, 2020, 03:05:24 AM »
I have some problem with the highlighted paragraph:
Quote
The two glaciers alone store ice that could account for about 4 feet (1.2 meters) of global sea level rise. Their “seaboard” location may help bring increased public attention and interest to the West Antarctic Ice Sheet, which if it melted could raise seas by a catastrophic 11 feet (3.4 meters).
I wish the green-glow phrase had been written
When it melts (which it will do under current atmospheric greenhouse gas levels) it will ...
[I believe this recently published paper supports this modified conclusion.]

It goes without saying that the cited research does not consider MICI types of failures which could cause an armada of icebergs (as noted by James Hansen) from the WAIS; which would raise sea level as soon as the associate calving events (without melting).
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nukefix

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Re: What's new in Antarctica ?
« Reply #611 on: October 13, 2020, 02:44:37 PM »
It goes without saying that the cited research does not consider MICI types of failures which could cause an armada of icebergs (as noted by James Hansen) from the WAIS; which would raise sea level as soon as the associate calving events (without melting).
Let's see if we can observe some failures of that type in the nearish future, or whether something stops those from taking place. Fingers crossed...

AbruptSLR

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Re: What's new in Antarctica ?
« Reply #612 on: October 13, 2020, 06:40:27 PM »
It goes without saying that the cited research does not consider MICI types of failures which could cause an armada of icebergs (as noted by James Hansen) from the WAIS; which would raise sea level as soon as the associate calving events (without melting).
Let's see if we can observe some failures of that type in the nearish future, or whether something stops those from taking place. Fingers crossed...

In my opinion, the first place that we are likely to MICI types of ice cliff failures in the WAIS will be near the base of the Thwaites Ice Tongue, and if so such ice cliff failure are likely to rapidly propagate upstream into the BSB within years of the initial ice cliff events in this area.
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Paddy

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Re: What's new in Antarctica ?
« Reply #613 on: October 21, 2020, 08:19:47 AM »
So why are Antarctic sea ice losses running so slow this year?

Gerntocratis#1

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Re: What's new in Antarctica ?
« Reply #614 on: October 21, 2020, 08:30:49 AM »
So why are Antarctic sea ice losses running so slow this year?

Well the temperature anomalies for Antarctica have been 1.5 to 3 Celsius colder than average for months now. That could be one reason. Maybe the La Nina has some effect as well?

Also gerontocrat has his theory that increased melting of the Antarctic ice sheet causes increased sea ice formation but there's probably not much melting going on there at this time of year, perhaps thats more of a factor in the southern hemisphere summer.

nukefix

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Re: What's new in Antarctica ?
« Reply #615 on: October 21, 2020, 10:38:28 AM »

Alphabet Hotel

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Re: What's new in Antarctica ?
« Reply #616 on: October 21, 2020, 04:45:18 PM »
New paper today in JCLI. Open access, full text at link.

Multidecadal Warming and Density Loss in the Deep Weddell Sea, Antarctica
https://doi.org/10.1175/JCLI-D-20-0271.1

ABSTRACT

The World Ocean is estimated to store more than 90% of the excess energy resulting from man-made greenhouse gas–driven radiative forcing as heat. Uncertainties of this estimate are related to undersampling of the subpolar and polar regions and of the depths below 2000 m. Here we present measurements from the Weddell Sea that cover the whole water column down to the sea floor, taken by the same accurate method at locations revisited every few years since 1989. Our results show widespread warming with similar long-term temperature trends below 700-m depth at all sampling sites. The mean heating rate below 2000 m exceeds that of the global ocean by a factor of about 5. Salinity tends to increase—in contrast to other Southern Ocean regions—at most sites and depths below 700 m, but nowhere strongly enough to fully compensate for the warming effect on seawater density, which hence shows a general decrease. In the top 700 m neither temperature nor salinity shows clear trends. A closer look at the vertical distribution of changes along an approximately zonal and a meridional section across the Weddell Gyre reveals that the strongest vertically coherent warming is observed at the flanks of the gyre over the deep continental slopes and at its northern edge where the gyre connects to the Antarctic Circumpolar Current (ACC). Most likely, the warming of the interior Weddell Sea is driven by changes of the Weddell Gyre strength and its interaction with the ACC.

AbruptSLR

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Re: What's new in Antarctica ?
« Reply #617 on: October 21, 2020, 05:44:46 PM »
So why are Antarctic sea ice losses running so slow this year?

Well the temperature anomalies for Antarctica have been 1.5 to 3 Celsius colder than average for months now. That could be one reason. Maybe the La Nina has some effect as well?

Also gerontocrat has his theory that increased melting of the Antarctic ice sheet causes increased sea ice formation but there's probably not much melting going on there at this time of year, perhaps thats more of a factor in the southern hemisphere summer.

First, icebergs and the basal side of Antarctic ice shelves melt year round, and the first linked reference about HadGEM3-GC3.1 projections related to climate responses from the modeled increasing Antarctic iceberg and ice shelf melt.  Key identified issues include that:

- Increased meltwater is increasing (temporarily) sea ice extent while reducing AABW production; both of which contribute to a slowing of the MOC.

- Increase snowfall at lower latitudes of Antarctica is applying more driving force on key marine glaciers; which will cause both ice velocities and iceberg calving to increase; and increased snow that falls directly into the ocean also contributes to both a slowdown of the MOC and increased advection of warm CDW towards key marine glacier grounding lines.

Shona Mackie; Inga J. Smith; Jeff K. Ridley; David P. Stevens and Patricia J. Langhorne (2020), "Climate response to increasing Antarctic iceberg and ice shelf melt, J. Climate 1–70; https://doi.org/10.1175/JCLI-D-19-0881.1

https://journals.ametsoc.org/jcli/article/doi/10.1175/JCLI-D-19-0881.1/353964/Climate-response-to-increasing-Antarctic-iceberg

Abstract: "Mass loss from the Antarctic continent is increasing, however climate models either assume a constant mass loss rate, or return snowfall over land to the ocean to maintain equilibrium. Numerous studies have investigated sea ice and ocean sensitivity to this assumption and reached different conclusions, possibly due to different representations of melt fluxes. The coupled atmosphere-land-ocean-sea ice model, HadGEM3-GC3.1, includes a realistic spatial distribution of coastal melt fluxes, a new ice shelf cavity parametrization and explicit representation of icebergs. This makes it appropriate to revisit how increasing melt fluxes influence ocean and sea ice, and to assess whether responses to melt from ice shelves and icebergs are distinguishable. We present results from simulated scenarios of increasing meltwater fluxes and show that these drive sea ice increases and, for increasing ice shelf melt, a decline in Antarctic Bottom Water formation. In our experiments, the mixed layer around the Antarctic coast deepens in response to rising ice shelf meltwater, and shallows in response to stratification driven by iceberg melt. We find similar surface temperature and salinity responses to increasing meltwater fluxes from ice shelves and icebergs, but mid-layer waters warm to greater depths and further north when ice shelf melt is present. We show that as meltwater fluxes increase, snowfall becomes more likely at lower latitudes, and Antarctic Circumpolar Current transport declines. These insights are helpful for interpretation of climate simulations that assume constant mass loss rates, and demonstrate the importance of representing increasing melt rates for both ice shelves and icebergs."

&

Second, the second linked reference indicates that some of the recent high Antarctic sea ice extents have been due to both natural variability and to recent changes in wind-driven sea ice transport that move sea ice northward into the Southern Ocean.

Zhang, L., Delworth, T. L., Cooke, W., & Yang, X. (2018). Natural variability of Southern Ocean convection as a driver of observed climate trends. Nature Climate Change. doi:10.1038/s41558-018-0350-3, https://doi.org/10.1038/s41558-018-0350-3

https://www.nature.com/articles/s41558-018-0350-3

Abstract: "Observed Southern Ocean surface cooling and sea-ice expansion over the past several decades are inconsistent with many historical simulations from climate models. Here we show that natural multidecadal variability involving Southern Ocean convection may have contributed strongly to the observed temperature and sea-ice trends. These observed trends are consistent with a particular phase of natural variability of the Southern Ocean as derived from climate model simulations. Ensembles of simulations are conducted starting from differing phases of this variability. The observed spatial pattern of trends is reproduced in simulations that start from an active phase of Southern Ocean convection. Simulations starting from a neutral phase do not reproduce the observed changes, similarly to the multimodel mean results of CMIP5 models. The long timescales associated with this natural variability show potential for skillful decadal prediction."

Extract: "However, we cannot conclude that internally generated SO deep convection is the only driver, even in recent observations. The SO deep-convection change could work together with various other mechanisms identified in earlier studies, such as wind-driven ice transport and cold/warm-temperature advection, and anthropogenic surface freshening due to an amplified hydrological cycle and ice-sheet melting. As mentioned above, the surface wind trend favours warm SST and decreasing sea ice over the Antarctic Peninsula through warm advection and over the Amundsen– Bellingshausen seas through enhanced vertical mixing caused by anomalous negative wind stress curl. Our model also shows that the long-lasting westerly winds over the SO induce upwelling and a spin-up of the AABW cell, which in turn generates the warm SST.  The surface freshwater changes due to shifted storm tracks and melting ice sheet in future may slow down the SO MOC, which also cannot be excluded. It is also possible that melting of land-based ice sheets, a process usually not included in climate models, could cause surface freshening and the subsequent suppressed convection and SST cooling."
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Gerntocratis#1

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Re: What's new in Antarctica ?
« Reply #618 on: October 21, 2020, 09:44:21 PM »
So why are Antarctic sea ice losses running so slow this year?

Well the temperature anomalies for Antarctica have been 1.5 to 3 Celsius colder than average for months now. That could be one reason. Maybe the La Nina has some effect as well?

Also gerontocrat has his theory that increased melting of the Antarctic ice sheet causes increased sea ice formation but there's probably not much melting going on there at this time of year, perhaps thats more of a factor in the southern hemisphere summer.

First, icebergs and the basal side of Antarctic ice shelves melt year round, and the first linked reference about HadGEM3-GC3.1 projections related to climate responses from the modeled increasing Antarctic iceberg and ice shelf melt.  Key identified issues include that:

- Increased meltwater is increasing (temporarily) sea ice extent while reducing AABW production; both of which contribute to a slowing of the MOC.

- Increase snowfall at lower latitudes of Antarctica is applying more driving force on key marine glaciers; which will cause both ice velocities and iceberg calving to increase; and increased snow that falls directly into the ocean also contributes to both a slowdown of the MOC and increased advection of warm CDW towards key marine glacier grounding lines.

Shona Mackie; Inga J. Smith; Jeff K. Ridley; David P. Stevens and Patricia J. Langhorne (2020), "Climate response to increasing Antarctic iceberg and ice shelf melt, J. Climate 1–70; https://doi.org/10.1175/JCLI-D-19-0881.1

https://journals.ametsoc.org/jcli/article/doi/10.1175/JCLI-D-19-0881.1/353964/Climate-response-to-increasing-Antarctic-iceberg

Abstract: "Mass loss from the Antarctic continent is increasing, however climate models either assume a constant mass loss rate, or return snowfall over land to the ocean to maintain equilibrium. Numerous studies have investigated sea ice and ocean sensitivity to this assumption and reached different conclusions, possibly due to different representations of melt fluxes. The coupled atmosphere-land-ocean-sea ice model, HadGEM3-GC3.1, includes a realistic spatial distribution of coastal melt fluxes, a new ice shelf cavity parametrization and explicit representation of icebergs. This makes it appropriate to revisit how increasing melt fluxes influence ocean and sea ice, and to assess whether responses to melt from ice shelves and icebergs are distinguishable. We present results from simulated scenarios of increasing meltwater fluxes and show that these drive sea ice increases and, for increasing ice shelf melt, a decline in Antarctic Bottom Water formation. In our experiments, the mixed layer around the Antarctic coast deepens in response to rising ice shelf meltwater, and shallows in response to stratification driven by iceberg melt. We find similar surface temperature and salinity responses to increasing meltwater fluxes from ice shelves and icebergs, but mid-layer waters warm to greater depths and further north when ice shelf melt is present. We show that as meltwater fluxes increase, snowfall becomes more likely at lower latitudes, and Antarctic Circumpolar Current transport declines. These insights are helpful for interpretation of climate simulations that assume constant mass loss rates, and demonstrate the importance of representing increasing melt rates for both ice shelves and icebergs."

&

Second, the second linked reference indicates that some of the recent high Antarctic sea ice extents have been due to both natural variability and to recent changes in wind-driven sea ice transport that move sea ice northward into the Southern Ocean.

Zhang, L., Delworth, T. L., Cooke, W., & Yang, X. (2018). Natural variability of Southern Ocean convection as a driver of observed climate trends. Nature Climate Change. doi:10.1038/s41558-018-0350-3, https://doi.org/10.1038/s41558-018-0350-3

https://www.nature.com/articles/s41558-018-0350-3

Abstract: "Observed Southern Ocean surface cooling and sea-ice expansion over the past several decades are inconsistent with many historical simulations from climate models. Here we show that natural multidecadal variability involving Southern Ocean convection may have contributed strongly to the observed temperature and sea-ice trends. These observed trends are consistent with a particular phase of natural variability of the Southern Ocean as derived from climate model simulations. Ensembles of simulations are conducted starting from differing phases of this variability. The observed spatial pattern of trends is reproduced in simulations that start from an active phase of Southern Ocean convection. Simulations starting from a neutral phase do not reproduce the observed changes, similarly to the multimodel mean results of CMIP5 models. The long timescales associated with this natural variability show potential for skillful decadal prediction."

Extract: "However, we cannot conclude that internally generated SO deep convection is the only driver, even in recent observations. The SO deep-convection change could work together with various other mechanisms identified in earlier studies, such as wind-driven ice transport and cold/warm-temperature advection, and anthropogenic surface freshening due to an amplified hydrological cycle and ice-sheet melting. As mentioned above, the surface wind trend favours warm SST and decreasing sea ice over the Antarctic Peninsula through warm advection and over the Amundsen– Bellingshausen seas through enhanced vertical mixing caused by anomalous negative wind stress curl. Our model also shows that the long-lasting westerly winds over the SO induce upwelling and a spin-up of the AABW cell, which in turn generates the warm SST.  The surface freshwater changes due to shifted storm tracks and melting ice sheet in future may slow down the SO MOC, which also cannot be excluded. It is also possible that melting of land-based ice sheets, a process usually not included in climate models, could cause surface freshening and the subsequent suppressed convection and SST cooling."

Wow that is crazy to me that there is melting going on in Antarctica in -40 to - 50 temps but you learn something new everyday! Thanks for the info.

AbruptSLR

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Re: What's new in Antarctica ?
« Reply #619 on: October 21, 2020, 10:13:44 PM »
...

Wow that is crazy to me that there is melting going on in Antarctica in -40 to - 50 temps but you learn something new everyday! Thanks for the info.

The ice is currently melting in the water, where the temperature is above freezing, while the temperatures that you cite are air temperatures.
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oren

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Re: What's new in Antarctica ?
« Reply #620 on: October 22, 2020, 12:31:28 AM »
Yes, ice shelves reach depths of hundreds of meters, where they are melted by the CDW, water that can be at 2C.
For example, read this:
http://www.antarcticglaciers.org/glaciers-and-climate/changes-circumpolar-deep-water/

FredBear

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Re: What's new in Antarctica ?
« Reply #621 on: October 23, 2020, 10:29:38 PM »
I kept wondering why some islands to the east of the tip of the Antarctic Peninsular looked as if they were melting long before the surrounding sea ice and other islands. Now the "melting" can be seen tracking across the ice on Worldview - think it must be penguin poo!?

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Re: What's new in Antarctica ?
« Reply #622 on: November 05, 2020, 01:44:38 PM »
This is about arctic, but I put here cause this phenomenon could potentially concern Antarctica?
Saw this paper this morning, it relates to two recent discussions, the first was about how water absorbs energy from the sun (the conclusion was that infrared radiation was absorbed readily by water, while visible light was mostly absorbed by particulates such as algae and their remains), and the second discussion was about Arctic Amplification and how ever more open water leads to a warmer Arctic and ever more open water in a true positive feedbac.

This article points out another potentially powerful positive feedback: The more open water there is to receive insolation, the more algae and the more particulates will be found, leading to more absorbtion of insolation in the upper layers, leading to more Arctic amplification.

Amplified Arctic Surface Warming and Sea Ice Loss Due to Phytoplankton and Colored Dissolved Material


Plain language summary:
Quote
The amount of microalgae and colored dissolved organic material in the ocean determines how much light is absorbed in the surface waters and how much can reach greater depths. The vertical distribution of energy affects the upper ocean temperature and general circulation. Here, we use a numerical ocean model with biogeochemistry and sea ice, in which the individual effects of microalgae and colored dissolved organic matter can be turned on and off separately. When both effects are turned on, the summertime surface temperatures in the Arctic are larger and consequently more sea ice melts, so that the sea ice season is shorter by up to one month. We find that, to a large extent, the colored dissolved material is responsible for these changes. An increase of this material due to climate change will amplify the observed Arctic surface warming. For better projections of climate change, new models should account for the effect of these light‐absorbing water constituents.
Very interesting, thank you
It also reminds me of Antarctica, because it is there that are the clearest waters on the planet, from memory a visibility of 80 m and very high purity.
If this happened there, this phenomenon would certainly have to be taken into consideration so
Sorry, excuse my bad english

vox_mundi

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Re: What's new in Antarctica ?
« Reply #623 on: November 11, 2020, 09:28:31 PM »
Atmospheric Rivers Help Create Massive Holes in Antarctic Sea Ice
https://phys.org/news/2020-11-atmospheric-rivers-massive-holes-antarctic.html

Warm, moist rivers of air in Antarctica play a key role in creating massive holes in sea ice in the Weddell Sea and may influence ocean conditions around the vast continent as well as climate change, according to Rutgers co-authored research.



Scientists studied the role of long, intense plumes of warm, moist air—known as atmospheric rivers—in creating enormous openings in sea ice. They focused on the Weddell Sea region of the Southern Ocean near Antarctica, where these sea ice holes (called polynyas) infrequently develop during the winter. A large hole in this area was first observed in 1973 and a hole developed again in the late winter and early spring of 2017.

In the first study of its kind, published in the journal Science Advances, scientists found that repeated strong atmospheric rivers during late August through mid-September 2017 played a crucial role in forming the sea ice hole. These rivers brought warm, moist air from the coast of South America to the polar environment, warming the sea ice surface and making it vulnerable to melting.

Under projected future climate change, atmospheric rivers are predicted to become more frequent, longer, wider and more effective in moving high levels of water vapor toward the Antarctic Ocean and continent, along with increasing the intensity of precipitation.

"On the crucial role of atmospheric rivers in the two major Weddell Polynya events in 1973 and 2017 in Antarctica" Science Advances (2020)
https://advances.sciencemag.org/content/6/46/eabc2695

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