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FrostKing70

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Denman Glacier
« on: March 23, 2020, 07:03:30 PM »
Interesting article about a deep trench and potential 5 feet of sea level rise:

https://www.washingtonpost.com/climate-environment/2020/03/23/denman-glacier-climate-change/

kassy

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Re: Denman Glacier
« Reply #1 on: March 24, 2020, 11:59:57 AM »
BBC also has a story on it:

Climate change: Earth's deepest ice canyon vulnerable to melting

https://www.bbc.com/news/science-environment-52007637
Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

Tor Bejnar

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Re: Denman Glacier
« Reply #2 on: March 24, 2020, 09:26:00 PM »
See also "Ice Apocalypse" thread: research paper shared by ASLR.
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

iwantatr8

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Re: Denman Glacier
« Reply #3 on: May 13, 2020, 11:49:16 AM »

prokaryotes

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Re: Denman Glacier
« Reply #4 on: July 30, 2020, 03:46:02 PM »
Cross post from Shackleton ice shelf https://forum.arctic-sea-ice.net/index.php/topic,1863.0.html

2017 study
Quote
Significant changes have taken place on Denman Glacier and Shackleton Ice Shelf, which hold a 149-cm SLE (basin C-C′). Denman sped up 16% since the 1970s and the ice shelf sped up by 33% in 1957–1996 and 43% in 1957–2016. The glacier is 10% out of balance. Its neighbor Scott decelerated by 16% in 1957–1996 and 22% in 2000–2008 and sped up by 18% in 2016.
https://www.pnas.org/content/116/4/1095

2018
Quote
We find that the glacier grounding line experiences a complex pattern of migration with several kilometers retreat at its center, in contrast to a small retreat of the neighboring glaciers, e.g. Scott glacier. The floating section of the glacier experiences vigorous ice melt in contact with the ocean, which suggests the presence of Circumpolar Deep Water (CDW). However, there is no historical oceanographic data near the glacier. The marked increase in ice shelf velocity observed in recent decades could result from the grounding line migration associated with enhanced ice shelf melt. Alternatively, it can be symptomatic of a complex interaction between the fast-moving glacier tongue (Shackleton Ice Shelf) and the surrounding slower moving ice shelves; similarly, to the case of Stancomb-Wills Ice Shelf or Thwaites Ice Shelf.
https://ui.adsabs.harvard.edu/abs/2018AGUFM.C31C1526B/abstract

Some time ago the Denman Glacier ice tongue broke off but remained embedded in the Shackleton ice shelf.  That tongue fragment has recently calved a large part.
Appears to be 1974, see my next reply.
« Last Edit: July 30, 2020, 09:51:14 PM by prokaryotes »
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prokaryotes

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Re: Denman Glacier
« Reply #5 on: July 30, 2020, 09:04:28 PM »
Quote
Denman Glacier is one of the largest in East Antarctica, with a catchment that contains an ice volume equivalent to 1.5 m of global sea-level and which sits in the Aurora Subglacial Basin (ASB). Geological evidence of this basin’s sensitivity to past warm periods,combined with recent observations showing that Denman’s ice speed is accelerating, and its grounding line is retreating along a retrograde slope, have raised the prospect that it could contribute to near-future sea-level rise.

The recent changes in the Denman system are important because Denman’s grounding line447 currently rests on a retrograde slope which extends 50 km into its basin (Morlighem et al.,448 2019; Brancato et al., 2020), suggesting clear potential for marine ice sheet instability. Given449 the large catchment size, it has potential to make globally significant contributions to mean sea450 level rise in the coming decades (1.49 m; Morlighem et al., 2020). Crucial to assessing the451 magnitude of any future sea level contributions is improving our understanding of regional452 oceanography, and determining whether the observed changes at Denman are the consequence453 of a longer-term ocean warming. This is in addition to monitoring and understanding the454 potential impact of any future changes in the complex Shackleton/Denman ice shelf system.455 In a wider context our results add to the growing body of evidence that some major East456 Antarctic outlet glaciers, with multi-meter sea-level equivalent catchments have responded to457 changes in ocean-climate forcing over the past 100 years and, therefore, will be sensitive to458 projected future warming.
https://tc.copernicus.org/preprints/tc-2020-162/

« Last Edit: July 30, 2020, 09:40:42 PM by prokaryotes »
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prokaryotes

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Re: Denman Glacier
« Reply #6 on: July 30, 2020, 10:01:06 PM »

Mt Sandow, in the background Denman Glacier.


Somewhere in the region, perhaps Shackleton Ice Shelf or Denman Glacier front


Quote
Mt Sandow nunatak (alt 1380m) 450km west of Casey Station; almost enveloped by the Denman Glacier flowing from the East Antarctic Ice Sheet to the Shackleton Ice Shelf 150km away. Discovered by Mawson’s Western Base Party led by Frank Wild in 1912, pic Greg Barras
@AusAntarctic
https://twitter.com/AntarcticReport/status/974863428484386816
« Last Edit: July 30, 2020, 10:39:50 PM by prokaryotes »
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prokaryotes

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Re: Denman Glacier
« Reply #7 on: August 01, 2020, 04:49:49 PM »
There is now a video summary
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gerontocrat

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Re: Denman Glacier
« Reply #8 on: October 14, 2022, 07:06:07 PM »
Some scientists have had another look at the Denman Glacier, The paper (linked) adds weight to other papers suggesting that this glacier could be an accident waiting to happen.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2022GL100460
Vulnerability of Denman Glacier to Ocean Heat Flux Revealed by Profiling Float Observations
Quote
Abstract
Denman Glacier, which drains a marine-based sector of the East Antarctic Ice Sheet with an ice volume equivalent to 1.5 m of global sea level rise, has accelerated and undergone grounding line retreat in recent decades. A deep trough and retrograde bed slope inward of the grounding line leave this glacier prone to marine ice sheet instability. The ocean heat flux to the ice shelf cavity is a critical factor determining the susceptibility of the glacier to unstable retreat.

Profiling float observations show modified Circumpolar Deep Water as warm as −0.16°C reaches a deep trough extending beneath the Denman Ice Tongue. The ocean heat transport (0.77 ± 0.35 TW) is sufficient to drive high rates of basal melt (70.8 ± 31.5 Gt y−1), consistent with rates inferred from glaciological observations. These results suggest the Denman Glacier is potentially at risk of unstable retreat triggered by transport of warm water to the ice shelf cavity.
Plain Language Summary
The Denman Glacier is a vast river of ice that drains the East Antarctic Ice Sheet. The Denman holds a volume of ice equivalent to 1.5 m of global sea level rise, so changes in the glacier could have a large impact on future sea level rise. The vulnerability of the Denman Glacier to melting by warm ocean waters has been difficult to assess because very few oceanographic observations have been collected in the region. We use new profiling float measurements to show warm water reaches a deep trough that extends inland beneath the glacier, exposing the base of the ice to ocean-driven melting. We estimate that the amount of warm water entering the cavity is sufficient to melt 70.8 billion tons of ice each year. These observations suggest that the Denman Glacier is potentially at risk from unstable retreat driven by warm water flowing into the cavity and melting the ice from below.

4.Discussion and Conclusions

....................... The  observation  of  warm  water  in  the  deep  trough  adjacent  to  the  DIT  is  reminiscent  of  the  Totten  Ice  Shelf,  where  strong  inflow  of  warm  water  was  found  to  carry  sufficient  heat  transport  to  explain  high  rates  of  basal  melt inferred from satellite data (Rintoul et al., 2016). The similarity between the two systems extends further. The inflow of water warmer than −1.0°C is smaller at Denman (138 ± 65 mSv) than at Totten (220 ± 70 mSv), but the transport-weighted temperature is higher (−0.48°C at Denman vs. −0.81°C at Totten), resulting in ocean heat  transports  and  meltwater  production  rates  that  agree  within  error  bars  (ocean  heat  flux  sufficient  to  form  2.3 ± 1.0 mSv of meltwater at Denman, compared to 2.8 ± 0.9 mSv at Totten). The float measurements confirm that the Denman Glacier, like the Totten Glacier, is exposed to ocean heat transport sufficient to drive high rates of basal melt (70.8 ± 31.5 Gt y−1), as inferred from independent glaciological observations.

........................Estimates of the melt rate near the grounding line of the Denman Glacier are higher than for other glaciers in East Antarctica and rival melt rates of rapidly thinning glaciers in West Antarctica. Melt rates at the grounding line of 45 ± 4 m a−1 between 2011 and 2014 (Brancato et al., 2020) and 50 m a−1 between 2010 and 2018 (Liang et al., 2021) imply strong ocean thermal forcing.

..............................Glaciological  observations  have  documented  a  long-term  acceleration  of  the  Denman  Glacier.  For  exam-ple,  Rignot  et  al.  (2019)  estimated  a  16%  increase  in  flow  speed  of  the  glacier  since  the  1970's,  while  Miles  et al. (2021) found accelerations of 17 ± 4% (grounded portion) and 36 ± 5% (floating portion) between 1972 and 2017. For the recent short period between 2017 and 2021, no acceleration was found (Thompson et al., 2021). The grounding line of the Denman Glacier retreated by 5.4 ± 0.3 km between 1996 and 2017–2018 (Brancato et al., 2020). The changes in glacial flow may reflect an increase in ocean heat transport to the base of the glacier and/or ice dynamics (i.e., ice tongue thinning, changes in ice tongue structure following calving, or release from pinning points) (Miles et al., 2021; Rignot et al., 2019). While changes in ocean heat transport cannot be assessed with  available  observations,  recent  studies  have  documented  warming  of  waters  off  East  Antarctica  that  may  have increased ocean heat transport to the continental shelf (e.g., Herraiz-Borreguero & Naveira Garabato, 2022; Yamazaki et al., 2021).
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kassy

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Re: Denman Glacier
« Reply #9 on: October 17, 2022, 11:43:49 AM »
The glacier seems well on the move so the accident is happening already. It is human appreciation of the events that is lagging as usual.  ;)
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opensheart

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Re: Denman Glacier
« Reply #10 on: January 22, 2023, 05:48:29 PM »
When scientists tagged a curious seal, he led them to signs of a potential climate disaster

By Chris Mooney and Simon Ducroquet
 
Updated January 21, 2023 at 12:00 p.m. EST|Published January 20, 2023 at 6:00 a.m. EST

Quote
This is a story about a curious seal, a wayward robot and a gigantic climate change disaster that may be waiting to happen.

https://www.washingtonpost.com/climate-environment/2023/01/18/climate-change-glacier-antarctica/