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logicmanPatrick

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Shackleton Ice Shelf
« on: January 30, 2017, 09:15:01 AM »
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.

The 1st image below, from NSIDC shows the shelf ice as it was in February 2003.

The 2nd image, from the current Antarctic mosaic shows some interesting cracks and calvings.  The image was enhanced by reducing brightness and increasing contrast.

Please discuss, add info, etc.
« Last Edit: March 25, 2022, 09:33:22 AM by oren »
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dingojoe

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Re: Shackleton ice shelf
« Reply #1 on: January 30, 2017, 07:50:35 PM »
Welp, it's looks like the let side is ready to go, whether tomorrow or a few years from now.  The crack is definitely recent and in fact multiplying.

I've noticed in the past that the ice on the NE side of the ice shelf will fracture and push out when the wind is right, but then will settle right back into place.  A slight amount probably does join the loose ice moving counterclockwise but the flow does seem rather constricted here.  The whole SE quadrant of Antarctica (from 90E to 180) seems to be rife with similar choke points.

logicmanPatrick

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Re: Shackleton ice shelf
« Reply #2 on: February 03, 2017, 12:37:39 AM »
Welp, it's looks like the let side is ready to go, whether tomorrow or a few years from now.  The crack is definitely recent and in fact multiplying.

I've noticed in the past that the ice on the NE side of the ice shelf will fracture and push out when the wind is right, but then will settle right back into place.  A slight amount probably does join the loose ice moving counterclockwise but the flow does seem rather constricted here.  The whole SE quadrant of Antarctica (from 90E to 180) seems to be rife with similar choke points.

I have looked at some historical data and have created a new false-colour image which shows much more detail.

The image below is from my article on Amery and Shackleton.  Comments are welcome here or at science20.com.  Keep me honest!
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georged

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Re: Shackleton ice shelf
« Reply #3 on: February 03, 2017, 01:26:54 AM »
Thanks for posting this. Here's an interesting article on the morphology of the shelf-bed.

http://www.annalsofgeophysics.eu/index.php/annals/article/view/4563

It includes the following images:

https://www.researchgate.net/publication/50302070_Radio_echo_sounding_data_analysis_of_the_Shackleton_Ice_Shelf

https://www.researchgate.net/figure/50302070_fig1_Figure-1-Features-around-the-Shackleton-Ice-Shelf-and-its-location-in-Antarctica-The

I wasn't able to find much about the Scott (East Antarctica) Glacier, which suggests that it isn't a well studied glacier. It appears to be heavily buttressed by this shelf which it flows into.

logicmanPatrick

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Re: Shackleton ice shelf
« Reply #4 on: February 03, 2017, 09:59:30 AM »
Thanks for posting this. Here's an interesting article on the morphology of the shelf-bed.

http://www.annalsofgeophysics.eu/index.php/annals/article/view/4563

It includes the following images:

https://www.researchgate.net/publication/50302070_Radio_echo_sounding_data_analysis_of_the_Shackleton_Ice_Shelf

https://www.researchgate.net/figure/50302070_fig1_Figure-1-Features-around-the-Shackleton-Ice-Shelf-and-its-location-in-Antarctica-The

I wasn't able to find much about the Scott (East Antarctica) Glacier, which suggests that it isn't a well studied glacier. It appears to be heavily buttressed by this shelf which it flows into.

Thanks for the links and very interesting info.

btw, I'm moving house soon, so too busy to post much, but next article is scheduled to be about Petermann glacier.
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maga

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Re: Shackleton ice shelf
« Reply #5 on: February 04, 2017, 03:17:30 PM »
There is a mix of ice shelfs here: Only the first picture shows the Shackelton Ice Shelf, the others show the West Ice Shelf where a large ice berg is finally breaking apart after staying put for at least 25 years.

logicmanPatrick

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Re: Shackleton ice shelf
« Reply #6 on: February 04, 2017, 05:36:21 PM »
There is a mix of ice shelfs here: Only the first picture shows the Shackelton Ice Shelf, the others show the West Ice Shelf where a large ice berg is finally breaking apart after staying put for at least 25 years.

All of the above images show the Shackleton ice shelf.  The West ice shelf lies between Amery and Shackleton and is not shown above.  Please see the image below.

The ice island in Shackleton is sometimes known as Pobeda ice island: it is mentioned in my article The Amery Zig-Zags.
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maga

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Re: Shackleton ice shelf
« Reply #7 on: February 04, 2017, 10:29:29 PM »
Dear Patrick,

the map is correct. Now you just have to go to the NSIDC webpage that you linked and look at the different ice shelfs.

http://nsidc.org/data/iceshelves_images/index_modis.html

logicmanPatrick

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Re: Shackleton ice shelf
« Reply #8 on: February 04, 2017, 11:20:01 PM »
Dear Patrick,

the map is correct. Now you just have to go to the NSIDC webpage that you linked and look at the different ice shelfs.

http://nsidc.org/data/iceshelves_images/index_modis.html

OOps!  My bad!  :-[

I checked the images on my computer and I have mislabelled some.

The map of shelves also misled me into seeing West as a different shape to Shacleton, whereas they are very similar.  I've coloured in the missing blue bit in the image below.

I'm off now to write out 100 times: "I must not rush to post information until I have re-checked it."  ;D
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prokaryotes

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Re: Shackleton ice shelf
« Reply #9 on: July 30, 2020, 03:41:54 PM »
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.
Where can I find more info on this?
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prokaryotes

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Re: Shackleton ice shelf
« Reply #10 on: July 30, 2020, 07:23:47 PM »
1913
Quote
This image shows the SY Aurora, a ship owned by the Australasian Antarctic Expedition, anchored at the Shackleton Ice Shelf in eastern Antarctica. The photograph was taken by Frank Hurley, the expedition’s official photographer.

Ships like the Aurora, with their strong wooden hulls, reinforced bows and reliable steam engines, were fundamental to Antarctic exploration at the time of the Australasian Antarctic Expedition. Classified as a steam yacht, the Aurora measured 50.3 by 9.3 by 5.7 metres and weighed 386 tonnes. Originally built as a sealer, it was bought by Mawson and refitted for the expedition in 1910.

Western Base, where this image was taken, was established by the expedition on the edge of the Shackleton Ice Shelf, about 2000 kilometres away from Main Base. 8 people were stationed there. They carried out valuable scientific work and charted large areas of the coastline.

The large Shackleton Ice Shelf was also explored and named by members of the expedition.
https://www.naa.gov.au/learn/learning-resources/learning-resource-themes/australia-and-world/antarctica/sy-aurora-edge-shackleton-ice-shelf-antarctica
« Last Edit: July 30, 2020, 07:59:07 PM by prokaryotes »
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FredBear

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Re: Shackleton ice shelf
« Reply #11 on: March 09, 2022, 03:23:19 AM »
Just down from the Shackleton (away from the Amery ice shelf) on Worldview is an island connected to Antarctica by marked permanent ice. This ice has been eroding away in recent years and I notice that the last of the old marked ice connection has now calved away, but this leaves the islands still connected by fast ice outside the marked area.
I attach Worldview image showing the ice blocks in the peninsular area, and also with the general area (Shackleton at the top, eroding peninsular at the bottom) from March 08 2022.

be cause

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Re: Shackleton ice shelf
« Reply #12 on: March 09, 2022, 09:01:15 AM »
HMS Endurance has endured . Near perfect 'wreck' at 3000m .
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 + 1 .. it's 2022 !

  don't panic  ..   life's not organic !

Tor Bejnar

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Re: Shackleton ice shelf
« Reply #13 on: March 09, 2022, 10:39:44 PM »
read about the Shackleton's Endurance (ship) in New in Antarctica thread.
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

paolo

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Re: Shackleton ice shelf
« Reply #14 on: March 13, 2022, 06:58:55 PM »
Regarding the calving announced by FredBear :
The eastern part of the Shakleton Ice Shelf is gone, only the Tongue of the Glenzer and Conger glaciers remain without any support (they just lost the one with Bowman Island) and the rest is just fast ice.
We can also mention further west the discharge point of the Kiselëva glacier with a very small Tongue and to the east that of the Angarskij glacier.
You will find attached :
> a USGS map from 1956 (with the front line in 1947)
> an AADC map from 2012 (with front line in 2012)
> an animation with S1 images (1px 80m: overall dimensions 148 x 106 km)

Click twice to animate and enlarge

FredBear

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Re: Shackleton ice shelf
« Reply #15 on: March 16, 2022, 06:29:53 PM »
Just down from the Shackleton (away from the Amery ice shelf) on Worldview is an island connected to Antarctica by marked permanent ice. This ice has been eroding away in recent years and I notice that the last of the old marked ice connection has now calved away, but this leaves the islands still connected by fast ice outside the marked area.
I attach Worldview image showing the ice blocks in the peninsular area, and also with the general area (Shackleton at the top, eroding peninsular at the bottom) from March 08 2022.
Oops - the Bowman Island has now lost its "fast ice" link to the mainland (even at this stage of the melt season!).

paolo

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Re: Shackleton ice shelf
« Reply #16 on: March 16, 2022, 09:48:24 PM »
More than the fast ice, what is interesting is that the Tongue of the Glenzer and Conger glaciers seems to have completely broken up!

paolo

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Re: Shackleton ice shelf
« Reply #17 on: March 17, 2022, 07:41:51 PM »
Update with S1 images
Please find attached the animation with S1 images from 21/02, 05/03 and today (1px ≈ 127m; overall dimensions ≈ 95 x 89 km)
Indeed things went very fast and not only the East Shackleton Glacier platform is no more, but also the Tongue of the Glenzer and Conger glaciers is disentegrated

Click to animate

Phil.

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Re: Shackleton ice shelf
« Reply #18 on: March 18, 2022, 04:56:53 PM »
Update with S1 images
Please find attached the animation with S1 images from 21/02, 05/03 and today (1px ≈ 127m; overall dimensions ≈ 95 x 89 km)
Indeed things went very fast and not only the East Shackleton Glacier platform is no more, but also the Tongue of the Glenzer and Conger glaciers is disentegrated


The images show 2021 dates not 2022, which are right?

paolo

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Re: Shackleton ice shelf
« Reply #19 on: March 18, 2022, 05:38:01 PM »
?????
The dates of the three images are 21/02/2022, 05/03/2022 and 17/03/2022 and it is these dates that appear in the images!

PS: Perhaps you opened the animation in a very small format and the 2 of 2022 does not appear clearly because of Bowman Island, click a second time to display it in the right format!

PS2: Moreover in the title of the animation there are the dates of the first and last image
« Last Edit: March 18, 2022, 05:50:30 PM by paolo »

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Re: Shackleton ice shelf
« Reply #20 on: March 20, 2022, 10:31:06 PM »
1) The eastern part of the Shackleton Ice Shelf is small and completely separate from the rest. In addition, some articles about the Shackleton Ice Shelf contain maps that show only the western (main) part.
I am therefore looking for confirmation that the eastern part is officially part of the Shackleton Ice Shelf:
> An extensive ice shelf fronting the coast of Antarctica for about 240 mi (95E to l05E); projecting seaward about 90 mi in the W portion and 40 mi in the east. The existence of this ice shelf was first made known by the USEE under Wilkes who mapped a portion of it from the Vincennes in February 1840. It was explored by the AAE under Mawson (1911-14) who named it for Sir Ernest Shackleton. The extent of the ice shelf was mapped in greater detail in 1955; using aerial photography obtained by USN Operation HighJump; 1946-47. Further mapping by the Soviet Expedition of 1956 showed the portion eastward of Scott Glacier to be a part of this ice shelf.
(Citation SCAR-Composite Gazetteer of Antarctica-Place names)
> Shackleton Ice Shelf is an extensive ice shelf fronting the coast of East Antarctica from 95° E to 105° E. It extends for an along-shore distance of about 384 km (239 mi), projecting seaward about 145 km (90 mi) in the western portion and 64 km (40 mi) in the east. It occupies an area of 33,820 square km (13,058 sq mi).
(Citation WikipediA)
> Shackleton Ice Shelf is an ice shelf in Eastern Antarctica, on the coast of Queen Mary Land (or Queen Mary Coast) and Wilkes Land, between 95° and 105° E long. The Shackleton Ice Shelf measures 440 km from west to east and 170 km from south to north. It has an area of 37,400 sq km and is 180–200 m thick. The thick Scott and Denman outlet glaciers feed into the middle parts of the shelf. Individual ice domes rise 250–300 m above the ice surface.
(Citation from The Great Soviet Encyclopedia (1979)


2) I searched the recent scientific literature to see if anything had been published about the Eastern Shackleton Ice Shelf and found only this paragraph (in which, by the way, it does not mention the Eastern Shackleton Ice Shelf, but the Glenzer Glacier).
"A strong retreat within the second decade occurred also at Glenzer Glacier next to Wilkes Land. The retreat is not yet mentioned in the literature, but satellite imagery reveals that
an important pinning point was lost in 2004, and a rift started to propagate and led to a breakup event in April 2020. We suggest that the initial destabilization and loss of the pinning
point were caused by an increase in zonal winds (+0.32 m/s) as well as enhanced surface melt (up to +0.4 mm w.e. per day) during the first decade. Increased zonal winds persisted
during the second decade (+1.23 m/s), indicating further ocean forcing. Nevertheless, the more recent calving event in April 2020 occurred due to a rift that developed over several years. Whether environmental drivers played a role or whether the rift developed due to ice flow acceleration initiated by the previous lost pinning point requires further investigation."
(Citation "Environmental drivers of circum-Antarctic glacier and ice shelf front retreat over the last two decades" 2021)


3) Images and animations of this post:
> Image S1 from yesterday: It's confirmed, there is nothing left, the Conger Tongue is completely detached, it's broken into three pieces and it's rapidly moving away (top left)

> Follow-up of calving events between 2018 and today with animation based on the following S1 images:
03/03/2018, (followed by a calving in spring 2018, after 03/03/2018)
05/03/2019, (followed by a calving in spring 2019, after 05/03/2019)
04/04/2020, 11/04/2020, 16/04/2020, 28/04/2020 (calving in spring 2020),
22/02/2021, 28/02/2021, 30/03/2021 (calving in spring 2021),
09/12/2021, 12/12/2021 (calving in winter 2021),
23/02/2022, 05/03/2022, 07/03/2022 and 17/03/2022 (final calving)

> Image from WorlView-MEaSUREs InSAR-Based Antarctica Ice Velocity Map, Version 1(2011):
Kiselëva Angarskij Glacier 150 m/yr
Glenzer Glacier 135 m/yr
Conger Glacier 265 m/yr
Angarskij Kiselëva Glacier 265 m/yr
These data are not the most recent, but they were immediately available (I will give more recent data later)

> Image from SCAR-ADD Map Viewer-Bed elevation (BedMachine)
These data are not the most recent, but they were immediately available (I will give more recent data later)

> Animation based on:
A recent S2 image (22/02/2022) and the S2 mask image on which I drew an approximate grounding line to allow a calculation of the surface of this ice shelf

4) Provisional findings:
This ice shelf was fed by four glaciers: Kiselëva Angarskij , Glenzer, Conger and Angarskij Kiselëva, with the Glenzer Glacier Tongue providing support on the pinning point corresponding to Bowman Island, the Conger Glacier Tongue providing strong support on the western side (and the major ice contribution to the ice shelf) and the other two providing external support to the bases of the two central Tongues.
It is noticeable that the Glenzer Tongue has a lower velocity than the two Tongues next to it, which must have caused some tension.
To the west no more pinning point (Unnamed Island), no more Kiselëva Angarskij Glacier Tongue (completely disrupted also in its eastern part), the fate of the Glenzer Glacier Tongue was signed and it was only a matter of time.
What I find a bit surprising is the very rapid and complete break-up of the Conger Glacier Tongue.
5) Final remark:
I have the impression that this calving has gone unnoticed outside this forum

As there is a limit of 4 images, the fifth one will be posted in the suite
Click twice to animate and fully expand the images


Correction : In the map with the speeds, as well as in the text, there was an inversion between the two names : Kiselëva and Angarskij.
Now it is fixed


« Last Edit: March 21, 2022, 02:42:29 PM by paolo »

paolo

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Re: Shackleton ice shelf
« Reply #21 on: March 20, 2022, 10:32:05 PM »
Suite (last image)

oren

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Re: Shackleton ice shelf
« Reply #22 on: March 20, 2022, 11:13:39 PM »
Wow. That's some serious disappearing act. The whole tongue just crumbled in a few years.

Carex

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Re: Shackleton ice shelf
« Reply #23 on: March 21, 2022, 01:13:20 PM »
The US Defense mapping agency (USDMA) Antarctic map of 1985 (compiled 1970) shows this "East Shackleton" ice shelf as contiguous with the main shelf.  I have not found any other name for it so "East Shackleton" makes sense to me.  The 2004 pinning point appears to be off of the western most glacier in the group (Kiseleva or Angarskij? the names are reversed between the "worldview speed.png" image and the "S2.gif" image) which is called Tracy Glacier on this USDMA map.
The area under the current worldview mask, reaching out to the "unnamed island", appears to have broken up about 2010 (I looked yesterday and didn't write down the dates).
It does not seem to be an area that has recieved much attention.

paolo

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Re: Shackleton ice shelf
« Reply #24 on: March 21, 2022, 02:05:46 PM »
Thank you very much Carex,
Indeed when editing the map with the speeds there was an inversion of name between the two glaciers (Kiselëva and Angarskij) and afterwards in the post
In the animation the names were correct (as well as in the animation published on 13/03.
I corrected the post

paolo

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Re: Shackleton ice shelf
« Reply #25 on: March 21, 2022, 02:37:21 PM »
Carex,
1) This ice shelf was located around 104E and in the SCAR-Composite Gazetteer of Antarctica-Place names, it is clearly stated that the extension of the Shackleton Ice Shelf is from 95E to l05E). So for me the question was already solved
2) I had a Modis image from 23/02/2009 and indeed it seems that a bridge still exists between the East Shackleton Ice Shelf and the Unnamed Island (error in the article quoted in my post or does it perhaps refer to another pinning point actually lost in 2004?)


Click twice to enlarge the image completely

PS: Currently the problem is how the Glenzer Glacier and Conger Glacier will react: will there be an increase in speed?
To be followed


PS2 : And of course I wonder if the debacle of the East Shackleton Ice Shelf is not the announcement of other calving in the West Shackleton Ice Shelf
« Last Edit: March 21, 2022, 02:59:54 PM by paolo »

Phil.

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Re: Shackleton ice shelf
« Reply #26 on: March 21, 2022, 04:34:20 PM »
?????
The dates of the three images are 21/02/2022, 05/03/2022 and 17/03/2022 and it is these dates that appear in the images!

PS: Perhaps you opened the animation in a very small format and the 2 of 2022 does not appear clearly because of Bowman Island, click a second time to display it in the right format!

PS2: Moreover in the title of the animation there are the dates of the first and last image

Yes it was the dates on the images that appeared to be contradictory, as you suggest it may have been the format and my old eyes!  It's clear now, thanks.

paolo

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Re: Shackleton ice shelf
« Reply #27 on: March 21, 2022, 06:40:36 PM »
I present an image edited with Quantarctica containing the Coastline and Grounding Line information of several bases of datas, as well as the MEaSURE v2 speeds.

Information relative to the bases of datas :
MEaSURE Coastline & Grounding Line (yellow)
Maps of Antarctic ice shelves, the Antarctic coastline and Antarctic basins. The maps are assembled from 2008-2009 ice-front data from ALOS PALSAR and ENVISAT ASAR data acquired during International Polar Year, 2007-2009 (IPY), the InSAR-based grounding line data (MEaSUREs Antarctic Grounding Line from Differential Satellite Radar Interferometry), augmented with other grounding line sources, the Antarctic ice velocity map (MEaSUREs InSAR-Based Antarctica Ice Velocity Map), and the Bedmap-2 DEM.

SCAR- ADD (Antarctic Digital Database) Coastlines v7.0 (Coastline & Grounding Line, orange)
Seamless dataset for Antarctic coastline applicable to all zoom levels. Data is a compendium of three line/polygon datasets which should display well at all zoom levels.
Highest resolution data were prepared by Cooper A.P.R BAS 2011 from various sources. For the line data, each segment is attributed with metadata concerning its source, updater and update time.
Last updated January 2013, by Fretwell P, BAS from remote sensing imagery dating from 2011. Main areas of update: Antarctic Peninsula and South Orkney Islands. This is the most accurate vector data for land south of -60 degrees.

UNIRC-ANTARTIC Shelf 2019: Coastline and Grounding Line (red)
This polygon shapefile depicts year-round ice shelves and ice tongues in Antarctica. Data does not include seasonal ice which extends much farther around the entire continent, and that can vary considerably day to day. Land data is included for context. Ice edges were manually digitized from high resolution satellite-based images from a variety of sensors, including MODIS, Sentinel, and RADARSAT-2, by experienced sea ice analysts at the US National Ice Center in Washington, DC, USA.

BAS-ADD (Antarctic Digital Database) Coastlines v7.3 2020 (blue)

SCAR-ADD (Antarctic Digital Database) Coastlines v7.4 2020 (black)

ASAID (Antarctic Surface Accumulation and Ice Discharge project)-Grounding line (purple)
High-resolution image-derived grounding line position for the Antarctic Ice Sheet. The data are derived using customized software to combine data from Landsat-7 imagery and Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry, which were primarily collected between 1999 to 2003. The data were developed as part of the Antarctic Surface Accumulation and Ice Discharge (ASAID) project.

MEaSUREs InSAR-based Antarctica Ice Velocity Map, version 2
It is assembled from multiple satellite interferometric synthetic-aperture radar systems. Data was largely acquired during the International Polar Year 2007 to 2009, as well as between 2013 and 2016. Additional data acquired between 1996 and 2016 was used as needed to maximize coverage.
This dataset is part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Program.

Note:
> The speeds given in the post (#20) refer to MEaSURE v1 and to the speeds upstream of the grounding line, hence the differences
> In the case of this Ice Shelf the information of ADD Coastlines versions 7.3 and 7.4 coincide almost completely and for this reason only one line is visible.

Click twice to enlarge completely

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Re: Shackleton ice shelf
« Reply #28 on: March 25, 2022, 09:33:03 AM »
Cross-posted from What's New thread.

Satellite Data Shows Entire Conger Ice Shelf Has Collapsed In Antarctica
https://www.theguardian.com/world/2022/mar/25/satellite-data-shows-entire-conger-ice-shelf-has-collapsed-in-antarctica

An ice shelf about the size of Rome has completely collapsed in East Antarctica within days of record high temperatures, according to satellite data.

The Conger ice shelf, which had an approximate surface area of 1,200 sq km, collapsed around 15 March, scientists said on Friday.

Collapse Video: https://mobile.twitter.com/CapComCatWalk/status/1507137389432434739

https://mobile.twitter.com/icy_pete/status/1507196466699378691

East Antarctica saw unusually high temperatures last week, with Concordia station hitting a record temperature of -11.8C on 18 March, more than 40C warmer than seasonal norms. The record temperatures were the result of an atmospheric river that trapped heat over the continent



paolo

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Re: Shackleton Ice Shelf
« Reply #29 on: March 25, 2022, 10:00:07 AM »
> As far as speed of information is concerned, this forum has been the best (thanks to FreadBear)
> I'm still sticking to the SCAR: Composite Gazetteer of Antarctica Place names, which is the official bible of names. The fact that one encounters a plurality of names: "Grenzer Glacier" (in the only article found which, by the way, speaks of this area, but only in passing), "Conger Ice Shelf" in the references quoted by vox_mundi, is for me the sympthome of the almost complete disinterest in the past for this ice shelf, which makes that when they want to speak about it they don't even find the name and they quickly look for the first name which falls
« Last Edit: March 25, 2022, 04:03:32 PM by paolo »

paolo

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Re: Shackleton Ice Shelf
« Reply #30 on: March 25, 2022, 03:53:34 PM »
EShIS: East Shackleton Ice Shelf
> I made a second surface calculation based on the BedMachine v2 data (2020) and found a surface of 1370. This result is slightly higher than the one published in the documents published by vox_mundi because it was before the previous calvings of 2020 and 2021. But to evaluate the disappearance of this Ice Shelf it seems appropriate to me to take into account the area before these calvings.
Ice Shelfs                              km²  Percentage
East Shackleton                        1370   100,00 %
Shackleton                            33820     4,05 %
All outside of Ross Filchner-Ronne   646320     0,21 %
All                                 1541700     0,09 %
A74 (Calving Brunt 2021)               1270   107,87 %



> Named icebergs related to recent calvings :
C37 (8 x 3; Iceberg calved between 05/03 and 07/03) last piece of the joint with Bowman Island (last piece of the Glenzer Glacier Tongue to calve). See first image.
C38 (16 x 10; Iceberg calved between 12/03 and 17/03) Conger Glacier Tongue (last piece of the Est Shackleton Ice Shelf to calve). See second picture.

Click to enlarge

baking

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Re: Shackleton Ice Shelf
« Reply #31 on: March 25, 2022, 05:36:16 PM »
I don't pay much attention to East Antarctica, but I feel that I should point out that these are professional glaciologists calling it the Conger Ice Shelf, not amateurs or media members.

The Conger Glacier used to terminate into the eastern end of the larger Shackleton Ice Shelf but they became disconnected years ago and current papers discussing the Shackleton Ice Shelf do not include the Conger Glacier/Tongue/Shelf.

That said, if you wanted to grab the media's attention, saying that an "entire ice shelf" collapsed might do the job better than calling it a "disconnected portion" of a larger ice shelf or just a glacier tongue.

paolo

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Re: Shackleton Ice Shelf
« Reply #32 on: March 25, 2022, 06:46:04 PM »
In my post I was not questioning the scientific value of the people concerned, but the fact that this name was not an official name and that officially it is part of the Shackleton Ice Shelf and that its surface was well accounted for in it (the "SCAR: Composite Gazetteer of Antarctica Place names" is the organisation that deals with names and validates them and on this subject is very clear) or used in scientific communications while waiting for an official validation (this is not the case: a search with "Conger Ice Shelf" on Google Scholar does not give any result).

But on Google I found the description of a "MATLAB_Central" function linked to Bedmap2: "outlineashelf" (The outlineashelf function outlines the ice shelf 'shelf' on a map of Antarctica. Use of this function requires first running bedmap2_install. You'll also need the Antarctic Mapping Tools package).

In fact in the description we find the following list which I am publishing (it might be of some use):

'abbot' Abbot Ice Shelf
'amery' Amery Ice Shelf
'bach' Bach Ice Shelf
'baudouin' Baudouin, Borchgrevink, & Lazarev Ice Shelves
'conger' Conger Ice Shelf
'cook' Cook Ice Shelf
'cosgrove' Cosgrove Ice Shelf
'crosson' Crosson & Dotson Ice Shelf
'dibble' Ice Shelf
'dotson' Crosson & Dotson Ice Shelf
'drygalski' Drygalski Ice Tongue
'fimbul' Fimbul (Fimbulisen), Atka, & Ekstrom Ice Shelf
'fris' Filchner-Ronne Ice Shelf
'george vi' George VI Ice Shelf
'getz' Getz Ice Shelf
'holmes' Holmes Glacier
'land' Land & Nickerson Ice Shelf
'larsen b' Larsen B Ice Shelf
'larsen c' Larsen C & Larsen D Ice Shelf
'larsen d' Larsen C & Larsen D Ice Shelf
'larsen e' Larsen E Ice Shelf
'mariner' Mariner Glacier Tongue
'mertz' Mertz Glacier Tongue
'muis' Moscow University Ice Shelf
'nansen' Nansen Ice Shelf
'nickerson' Nickerson & Land Ice Shelf
'ninnis' Ninnis Glacier Tongue
'nivl' Nivl (Nivilisen) Ice Shelf
'pig' Pine Island Glacier shelf
'prince harald' Prince Harald Ice Shelf
'publications' Publications Ice Shelf
'quar' Quarisen
'rayner' Rayner & Thyer Ice Shelf
'rennick' Rennick Bay Ice Shelf
'riiser' Riiser-larsen, Stancomb, & Brunt Ice Shelf
'ross' Ross Ice Shelf
'shackleton' Shackleton, Tracy/Tremenchus Ice Shelf
'stange' Stange Ice Shelf
'sulzberger' Sulzberger Ice Shelf
'swinburne' Swinburne Ice Shelf
'thwaites' Thwaites Glacier Tongue
'totten' Totten Glacier
'tracy' Tracy, Tremenchus, & Shackleton Ice Shelf
'venable' Venable Ice Shelf
'vigrid' Vigridisen or Vigrid Ice Shelf
'vincennes' Vincennes Bay Ice Shelf
'west' West Ice Shelf
'wilkins' Wilkins Ice Shelf
'all' equivalent to bedmap2('shelves')


It seems that the name "Conger Ice Shelf" comes from here  ;)

Correction: There were problems with the content of the list, fixed
« Last Edit: March 25, 2022, 06:55:56 PM by paolo »

oren

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Re: Shackleton Ice Shelf
« Reply #33 on: March 25, 2022, 07:12:19 PM »
The "good" news is the name no longer matters much, as that ice shelf (or part of an ice shelf) has disappeared.

NotaDenier

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Re: Shackleton Ice Shelf
« Reply #34 on: March 25, 2022, 09:47:46 PM »
Article regarding the collapse quoting woods hole.

A previously stable ice shelf, the size of New York City, collapses in Antarctica
https://www.npr.org/2022/03/25/1088840912/antarctica-ice-shelf-collapses

paolo

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Re: Shackleton Ice Shelf
« Reply #35 on: March 25, 2022, 11:10:57 PM »
I find the newspaper article very disappointing  >:(
Already the title: it was not a stable ice shelf!
This ice shelf had already entered a structural crisis in 2020 and the two calvings in the spring of 2020 and 2021 show it (see the animation above dedicated to the successive calvings). Moreover, these two calvings had completely destabilized it and what was left could not resist much longer. And the calving at the end of autumn was the death sentence! Moreover, the final calving started at the beginning of March, well before the wave of thermal anomaly, which has no link with this calving.
The end of this ice shelf was predictable, we just had to look at the right place at the right time.
What was probably less predictable was the destruction of the Conger Glacier Tongue immediately after the collapse of what remained of the Glenzer Glacier Tongue.


Returning to our analysis, I post an animation with the S1 images (1px = 20m; overall dimensions 34 x 58 km) to show in detail what currently remains of the three Tongues: Glenzer, Conger and Angarslij

Click to animate and, to see the details, click a second time

FredBear

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Re: Shackleton Ice Shelf
« Reply #36 on: March 26, 2022, 01:28:47 PM »
Paolo, what I find disturbing is the obvious fracturing of the ice tongues as they leave the edge of the continent in your 28-02-2022 image. To me this is indicating that there are weaknesses developing more recently that were just not happening earlier when the ice tongue that formed C38 grew. C38 is frayed and "toothed" round the edges - with more time we should discover if it has more integral weaknesses?