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b_lumenkraft

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The Amery Ice Shelf Thread
« on: February 21, 2019, 04:14:14 PM »
Resuming conversation from

New clear Sentinel pics today.

Link >> https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=-71.61099038970809&lng=69.23789978027344&zoom=13&preset=CUSTOM&layers=B01,B02,B03&maxcc=20&gain=1.0&gamma=1.0&time=2018-08-01%7C2019-02-21&atmFilter=&showDates=false&evalscript=cmV0dXJuIFtCOEEqMSxCMDMqMSxCMDIqMV0%3D

Indeed the big melt pond is now frozen but with pretty blue cracks visible. I wonder if it's melting again. (pic1)

Upstream the melt ponds are still blue. (pic2)

Stephan

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Re: The Amery Ice Shelf Thread
« Reply #1 on: February 21, 2019, 06:07:44 PM »
Thanks for opening this thread. I think Améry should gain more attention than it received so far in this forum.
It is too late just to be concerned about Climate Change

b_lumenkraft

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Re: The Amery Ice Shelf Thread
« Reply #2 on: February 21, 2019, 06:13:25 PM »
Agreed Stephan. :)

Since Neven never opposed i just went for it! ;)

oren

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Re: The Amery Ice Shelf Thread
« Reply #3 on: February 22, 2019, 01:31:57 AM »
Thanks for opening this thread. I think Améry should gain more attention than it received so far in this forum.
+1, although I hope it stays calm and cool and loses attention...

maga

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Re: The Amery Ice Shelf Thread
« Reply #4 on: September 25, 2019, 09:11:07 PM »
Big claving at Amery!

blumenkraft

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Re: The Amery Ice Shelf Thread
« Reply #5 on: September 25, 2019, 09:27:00 PM »
Wow!  :o

Stephan

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Re: The Amery Ice Shelf Thread
« Reply #6 on: September 25, 2019, 10:05:40 PM »
Wow  :o
That is huge, and probably not seen there for a while ?!? [Haven't checked the calving history of this ice shelf]
It is too late just to be concerned about Climate Change

sidd

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Re: The Amery Ice Shelf Thread
« Reply #7 on: September 25, 2019, 11:08:17 PM »
I have been worried about Amery for a while. I have been seein sporadic reports of warm water offshore. The ice profile in that basin is concave upward and the thing is like a dagger pointed into the heart of antarctica.

sidd

oren

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Re: The Amery Ice Shelf Thread
« Reply #8 on: September 26, 2019, 03:46:50 AM »
A quick and dirty Worldview animation shows that the ice shelf forward progress since the year 2000 was less than half of the calve width, so I would say this sets back Amery ~40 years. Hopefully this is cyclical and the next 20 years will see Amery back to its year 2000 position.
If someone has access to older satellite images of the shelf this could be improved.

In addition, this article (linked from Wikipedia) says the following:
Quote
Australians to study giant Antarctic ice cracks
Updated 20 Dec 2006, 7:39am

Hobart scientists are heading to Antarctica to study the cause of enormous cracks forming in the Amery Ice Shelf.

The cracks began forming around a decade ago and are growing at three to five metres a day.

The fractures threatened to break off a 900-square-kilometre piece of the Amery Ice Shelf, which is about the size of Tasmania.

Scientists want to know what is causing these cracks, as the last recorded activity in this part of eastern Antarctica was in the 1960s.

The head of the research, Professor Richard Coleman, says there is not enough evidence to blame global warming.

"It may be in a 50- to 60-year cycle but we would need more data to say whether it's increasing in terms of calving events due to warming of the ice shelf," he said.

Professor Coleman says with the ice already floating, it will not increase ocean levels.

As the new calving is roughly 900 km2 (eyeballing maga's image), this could be the result of a very long process.

IceConcerned

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Re: The Amery Ice Shelf Thread
« Reply #9 on: September 26, 2019, 11:53:44 AM »
The speed of this calving is properly astonishing : I was having  alook from time to ime to the shelf, and the big cracks showed no really active propagation
For example see Sentinel image (from Polarview) on Sept.23 :
https://www.polarview.aq/images/105_S1jpgfull/S1A_IW_GRDH_1SSH_20190923T154447_5F29_S_1.final.jpg

blumenkraft

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Re: The Amery Ice Shelf Thread
« Reply #10 on: September 26, 2019, 07:11:03 PM »
And to make the collection complete, here is the Sentinel radar, 20. vs 25.


Stephan

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Re: The Amery Ice Shelf Thread
« Reply #11 on: September 26, 2019, 08:59:10 PM »
Thank you blumenkraft and Oren for these movies.
Compared to PIIS and Thwaites Amery seems to be at least half a tens potency slower.
It is too late just to be concerned about Climate Change

blumenkraft

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Re: The Amery Ice Shelf Thread
« Reply #12 on: September 26, 2019, 09:07:39 PM »
Welcome, Stephan. :)

vox_mundi

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Re: The Amery Ice Shelf Thread
« Reply #13 on: October 01, 2019, 06:34:17 AM »
Giant Iceberg Breaks Off East Antarctica
https://www.theguardian.com/world/2019/oct/01/giant-iceberg-breaks-off-east-antarctica

The tabular iceberg, officially named D-28, separated from the Amery ice shelf on 26 September. The iceberg is 1,636 square kilometres in size, or about 50 x 30km, the Australian Antarctic Division said.

It is the first major calving event on the Amery ice shelf since 1963-64.

“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― anonymous

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

blumenkraft

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Re: The Amery Ice Shelf Thread
« Reply #14 on: October 01, 2019, 06:47:51 AM »
Actually, it broke off between 24th and 25th, not 26.

Also, the morphing thingy the Guardian did with their GIF is weird. Gives a wrong impression of what happened.

With ASIF you get a timely and correct reporting with accurate GIFs.  :P

sidd

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Re: The Amery Ice Shelf Thread
« Reply #15 on: October 07, 2019, 02:15:38 AM »
Last year, Alley et al. (doi: 10.1016/j.rse.2018.03.025 )  valued antarctic ice shelf vulnerability to hydrofracture. The measure of vulnerability is the fraction of ice saturated firn.

Amery is disquieting, The first figure attached shows the Amery Shelf in panel a (panel b is the Roy Baudouin shelf)

Today ASLR informs of Stokes et al. (doi : 10.1038/s41598-019-50343-5 ) who superpose supraglacial lake images on those vulnerable areas. Amery is even more disquieting. The second figure attached shows Amery in panel b.
The lakes are in black, the grounding lines in red.

sidd



blumenkraft

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Re: The Amery Ice Shelf Thread
« Reply #16 on: February 09, 2020, 07:01:53 PM »
Bit off-topic: Much less pooled water higher up the ice-shelf in this catchment area this year - the lowest big pool in particular is missing!

I noticed the same. I suspected it could have drained. It was very big and must have been very deep. I can't imagine it to freeze solid during one winter.

FredBear

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Re: The Amery Ice Shelf Thread
« Reply #17 on: January 07, 2021, 11:08:02 AM »
Much less "blue" melt water this year on the whole ice shelf so far - probably less than any year since 2002. Amery's biggest melt years  by Jan.7 were 2004-6, 2015, 2019 (on Worldview) with big pools of blue water.

vox_mundi

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Re: The Amery Ice Shelf Thread
« Reply #18 on: June 26, 2021, 07:03:38 AM »
Antarctic Lake Suddenly Disappears
https://phys.org/news/2021-06-antarctic-lake-suddenly.html



A global team of scientists including several from Scripps Institution of Oceanography at the University of California San Diego discovered the sudden demise of a large, deep, ice-covered lake on the surface of an Antarctic ice shelf.

This rare event, chronicled in a study published today in the journal Geophysical Research Letters, occurred during the 2019 Antarctic winter on Amery Ice Shelf in East Antarctica, and it is estimated that 600-750 million cubic meters (21-26 billion cubic feet) of water, about twice the volume of San Diego Bay, were lost to the ocean.

Study authors used images from a radar satellite which can "see" during the polar night to pin the event's timing down to a week or less in June. After drainage, in place of the lake, there was a crater-like depression in the ice shelf surface, covering about eleven square kilometers (4.25 square miles). This surface depression, known as an ice "doline," contained the fractured remains of the ice cover.

The hydrofracture process has been implicated in the collapse of smaller ice shelves in the Antarctic Peninsula, where meltwater forms on the surface of ice shelves during austral summer, but it is not often seen driving through ice as thick as the 1400 meters (4,590 feet) at this location on Amery Ice Shelf.

Repeat orbits of ICESat-2 on the exact ground tracks before and after the lake drainage revealed the vertical scale of the disruption. The ice surface fell as much as 80 meters (260 feet) in the doline cavity, even though the loss of the water load made the floating ice shelf lighter and ocean pressure caused it to flex upwards, with the lake's immediate surroundings rising as much as 36 meters (118 feet).

The team also used surface elevation maps generated by the Polar Geospatial Center (PGC) at the University of Minnesota to show that the disruption modified the regional landscape across 60 square kilometers (23 square miles).

The uplift of the lake created a new lake out of a shallow arm of the original one. During the next melt season this lake filled within a few days at more than a million cubic meters per day and overflowed into the doline cavity. When ICESat-2 crossed the doline again a few days later, the team was able to measure a meltwater channel 20 meters (65 feet) wide, freshly cut into the doline, detecting the water surface at three meters depth, and photons scattered from the stream bed a further three meters below.

The amount of water lost to the ocean was calculated using the volume of the cavity and the extent of uplift. While Amery Ice Shelf does have many melt-lakes and streams in austral summer, the amount of water lost when the lake drained was many times the annual meltwater input to it.

"This abrupt event was apparently the culmination of decades of melt-water accumulation and storage beneath that insulating lid of ice," said co-author Jonathan Kingslake, professor at Lamont Doherty Earth Observatory at Columbia University, who aided in the measuring of the surface meltwater.

The future of the newly formed doline is uncertain. It may accumulate meltwater again or drain to the ocean more frequently. It appears that the fissure reopened briefly in the 2020 melt season. It is certain that scientists will now be watching.

Roland C. Warner et al, Rapid formation of an ice doline on Amery Ice Shelf, East Antarctica, Geophysical Research Letters (2021).
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL091095
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― anonymous

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

oren

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Re: The Amery Ice Shelf Thread
« Reply #19 on: June 26, 2021, 11:00:28 AM »
Amazing.