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Author Topic: The State of Wilkes Basin Glaciers  (Read 650 times)

prokaryotes

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The State of Wilkes Basin Glaciers
« on: July 27, 2020, 04:01:05 PM »
The Cook, Mertz and Ninnis Glaciers present an ice formation, preventing the irreversible retreat of what to appears to be the real 'doomsday glacier', this time located in East Antarctica. National Geographic headlines this new 2020 study,  'Biggest ice sheet on Earth more vulnerable to melting than thought'
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Greenland, West Antarctica, and other glaciers globally might contribute 30 feet of rise if they melted. Adding another 10 to 13 feet from the Wilkes Basin in East Antarctica “is completely consistent” with those estimates
https://www.nationalgeographic.com/science/2020/07/east-antarctic-ice-sheet-more-vulnerable-to-melting-than-thought/

Southern Ocean warming and Wilkes Land ice sheet retreat during the mid-Miocene
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Our results further confirm and may be taken to extrapolate recent monitoring observations of the East Antarctic ice sheet, which indicate the high sensitivity of the Wilkes subglacial basin to ocean warming.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5778126/

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The stability of the Wilkes marine ice sheet has not been the subject of any comprehensive assessment of future sea level. Using recently improved topographic data in combination with ice-dynamic simulations, we show here that the removal of a specific coastal ice volume equivalent to less than 80 mm of global sea-level rise at the margin of the Wilkes Basin destabilizes the regional ice flow and leads to a self-sustained discharge of the entire basin and a global sea-level rise of 3–4 m.
https://www.nature.com/articles/nclimate2226 pdf http://www.pik-potsdam.de/~anders/publications/mengel_levermann14.pdf

Cook Glacier
Velocity increases at Cook Glacier, East Antarctica, linked to ice shelf loss and a subglacial flood event

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The loss of the Cook West Ice Shelf is surprising given that the present-day ocean climate conditions in the region are not typically associated with catastrophic ice shelf loss. However, we speculate that a more intense ocean climate forcing in the mid-20th century may have been important in forcing its collapse. Since the loss of the Cook West Ice Shelf, the presence of landfast sea ice and mélange in the newly formed embayment appears to be important in stabilizing the glacier front and enabling periodic advances. We also show that the last calving event at the larger Cook East Ice Shelf resulted in the retreat of its ice front into a dynamically important portion of the ice shelf and observe a short-lived increase in velocity of Cook East between 2006 and 2007, which we link to the drainage of subglacial Lake Cook. Taken together, these observations suggest that the velocity, and hence discharge, of Cook Glacier is highly sensitive to changes at its terminus, but a more detailed process-based analysis of this potentially vulnerable region requires further oceanic and bathymetric data.
https://tc.copernicus.org/articles/12/3123/2018/

Mertz Glacier
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In February 2010 about half of the Mertz Glacier Tongue, a piece of ice about 78 kilometres (48 mi) long and 33–39 kilometres (21–24 mi) wide and protruding 100 kilometres (62 mi) out into the Southern Ocean, broke away from the main body of the Tongue. The separation occurred around the 12 or 13 February along two existing rift lines on opposite sides of the Tongue. The event was helped in part when the large Iceberg B-9B collided with it. Iceberg B-9B is a 97 kilometres (60 mi) long by 30 kilometres (19 mi) wide remnant of Iceberg B-9 which broke off the Ross Ice Shelf in 1987 and has recently ungrounded itself from Ninnis Bank to the east of the Tongue where it had been lodged for 18 years.

The newly formed iceberg has been named Iceberg C-28, because it is the 28th substantial iceberg to have broken off the Antarctic ice shelf, in the quadrant that faces Australia, since 1976. The iceberg is 400 metres (1,300 ft) high, has a surface area of 2,545 square kilometres (983 sq mi)and weights in at about 860 billion tonnes. According to Australian glaciologist Neal Young, such an event occurs once in 50 to 100 years. As the Tongue advances at 1 km per year this new iceberg represents about 70 years of glacier advance. Within 2 weeks the Mertz Iceberg rotated about the point of impact with B9-B and lay parallel with the coastline. The iceberg drifted westwards after the collision and in April 2010 hit a submerged peak which caused it to break into two pieces.

The flow of icebergs from the calved glacier tongue has reduced the effectiveness of the polynya west of Mertz Glacier that acted as one of Antarctica's major areas for the formation of dense Antarctic Bottom Water. The calving could affect future thermohaline circulation around Antarctica
https://en.wikipedia.org/wiki/Mertz_Glacier

Collision Calves Iceberg from Mertz Glacier Tongue, Antarctica
https://earthobservatory.nasa.gov/images/42819/collision-calves-iceberg-from-mertz-glacier-tongue-antarctica
« Last Edit: July 28, 2020, 11:55:15 AM by prokaryotes »
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AbruptSLR

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Re: The State of Wilkes Basin Glaciers
« Reply #1 on: July 27, 2020, 07:13:42 PM »
Regarding what is the real 'doomsday glacier', the IPCC’s SROCC says that “Thwaites Glacier is particularly important because it extends into the interior of the WAIS, where the bed is >2000m below sea level in places”. 

Although, the SROCC also notes that while MISI requires a retrograde bed slope to occur, MICI could even happen on a flat or seaward-inclined bed where combined with hydrofracturing (see the first attached image from the SROCC).  So a key question regarding the Wilkes MICI stability is when will the local coastal surface temperatures (say at EL +100m) be high enough to induce frequent ice surface melting in the January to February timeframe; which is a function of both TCR and ECS (see the second image from E3SMv1 which includes the influence of a slowdown of the MOC due to projected freshening of the North Atlantic and Southern Ocean surface waters).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

prokaryotes

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Re: The State of Wilkes Basin Glaciers
« Reply #2 on: July 28, 2020, 01:53:58 AM »
A new study suggests that the East Antarctica Ice Sheet in the Wilkes Basin may have completely disappeared around 400,000 years ago. Currently the Wilkes Basin is only hold back by the Cook, Mertz, and the Ninnis glacier - the Cook Glacier shelf has already collapsed. There is also the Totten Glacier farther to the east, part of the Aurora Basin, also prone to warmer water at the grounding line, elevation has changed, though the topography is not favorable for rapid retreat in this case. Nevertheless, observations remain scarce, and the Wilkes Basin ice sheet may be the real elephant in the room.

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wili

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Re: The State of Wilkes Basin Glaciers
« Reply #3 on: July 28, 2020, 03:45:24 AM »
Thanks, prok. Glad to see that  you are still at it

In case anyone doesn't know, prok has, as far as I have seen, the best collection of AGW related videos on the internets, at climatestate

(I am ashamed that I remember the name partly because I think of it as 'prokstate'  :-[ ::) ;D )
"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."

prokaryotes

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Re: The State of Wilkes Basin Glaciers
« Reply #4 on: July 28, 2020, 04:11:48 AM »
Thanks, prok. Glad to see that  you are still at it

In case anyone doesn't know, prok has, as far as I have seen, the best collection of AGW related videos on the internets, at climatestate

(I am ashamed that I remember the name partly because I think of it as 'prokstate'  :-[ ::) ;D )
Thanks!  8) Unfortunately there was an incident at YouTube, they claimed that my content was not by me and that it doesn't matter if I have permissions or use public domain content. So I deleted roughly 900 videos from the channel, though most videos were outdated, just bad, but also a lot of great stuff. The great stuff is in large part now hosted at Vimeo (see link in my signature).
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prokaryotes

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Re: The State of Wilkes Basin Glaciers
« Reply #5 on: July 28, 2020, 10:38:39 AM »
Added something on Mertz Glacier, an event happened there in 2010, considered to only happen once every 50-100 years.
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