George VI, Wilkins, Bach and Stange Ice Shelves

[paolo]

Calving of the Wilkins Ice Shelf.
Attached is a map to locate the event and an animation with two S1 (low resolution) images from 09/01 and 21/01
There was no discussion topic related to the Ice shelves in this area, hence the creation of this new topic

Click to enlarge and animate

[oren]

Thanks for this, paolo.
For the less-knowledgeable and lazier-minded folks among us, which I represent quite well, it would be helpful to include a map of Antarctica showing the general location.

[paolo]

Oren, I add a map with the four Ice Shelves (indicated with a red circle)

click to enlarge

[oren]

Thank you paolo. I'll add an even larger map  for completeness.

[FredBear]

In the oren map above Wilkins is still attached to Charcot Island but in the 1st paolo map Charcot Island is separated by Attenborough Strait.

I remember seeing items on the break-up of Wilkins and a quick look with google brings up NASA  Earth Observatory articles from 2008, 2009 and 2013:-


https://earthobservatory.nasa.gov/images/8931/wintertime-disintegration-of-wilkins-ice-shelf
https://earthobservatory.nasa.gov/images/37806/wilkins-ice-bridge-collapse
https://earthobservatory.nasa.gov/images/81174/breakup-continues-on-the-wilkins-ice-shelf

[paolo]

A calving at the George VI Ice Shelf on the south side, the area involved is about 31 km2
Below is an animation with information and a map of the area

Click twice to animate and enlarge the image completely

PS: I have just noticed that the information was wrong, my apologies and I guarantee that I had not been drinking. The total area is 20.1 km2

For the animation with the correct information see https://forum.arctic-sea-ice.net/index.php/topic,3733.msg331923.html#msg331923
 

[IceConcerned]

And another one at the rear of the sound...

[paolo]

Good point,
I add:
> the animation with the information,
> a map with the indication of the two calvings: today's and yesterday's.

Regarding yesterday's calving, I just noticed that the information was wrong, my apologies and I guarantee that I had not been drinking.

I therefore add the corrected animation of this calving (with the right information 

Click to animate and enlarge the images

[FredBear]

There were numerous melt ponds visible on the eastern section of the George VI ice shelf on Feb.12 but it has been more cloudy since then. I don't think they will cause major disruption because they are not close to the ends of the shelf but they show that this shelf is not very secure against global warming.

[paolo]

Iceberg ballet
Just a curiosity: the two icebergs, coming from two different places, turning one 120° and the other 225° while exchanging positions, end up as a couple next to each other.

[paolo]

New small calvings in the George VI ice shelf:
The first one to the south of about 4.8 km2 (including the biggest piece of 3.4 km2 and several pieces, already farther south-east) and a calving further north of about 2.4 km2 (that there was a calving is almost certain)
The feeling is that the big calving (well expected on this forum) should not be long in coming

Click to animate and enlarge

[IceConcerned]

Yes I too have been watching the area for some time now, but the big cracks do not seem to expand that much. It feels more like a slow erosion wherever it is possible (more could be identified a little south, between the pinning points/ice rises)
Nothing really spectacular but a clear trend discharging rhe Is month by month

[paolo]

What I said is being confirmed
Information in the animation

Click to animate and enlarge

Animation update (corrected information)

[paolo]

George VI, Southern Front
The crumbling continues (even if in the last 12 days we only had minor calvings)...
Attached :
> a long animation with 4 high resolution S1 images (1px =20m; overall size 44 x 30 km) covering 36 days: from 01/02/2022 to 09/03/2022.
> The image of 01/02/2022 on which I have transferred the front to 09/03/2022. You can see that small calvings have occurred everywhere

Click to animate (twice to enlarge the animation completely, as well as the image)

[paolo]

Very small calving on the south side of the George VI Ice shelf

Animation with images from 20/05 and today, click to animate and click a second time to enlarge completely

[paolo]

Wilkins Ice Shelf 04/07/2022

Even if this iceberg is still attached with its northern tip to the ice shelf, I wanted to present it to you before it breaks into several pieces (the southern tip is already fractured).

Indeed it seems to me that it deserves to be immortalized in all its strangeness: 50 km long and less than 1.4 km thick (and almost everywhere less than 1 km)

Very large image (1900x2700 px), click twice to see it fully enlarged

[Stephan]

Very interesting.
If it were to calve completely would it be large enough to be given an official number? Its length should be enough for that... 

[paolo]

For the longest axis, no problem, but the surface is too small, it should be at least 20 sqNM and the very approximate value of the surface of this iceberg is about 15 sqNM (but it is not too far!   ).
Moreover it seems inevitable that it will break into a lot of pieces

[IceConcerned]

Well, it did indeed break into pieces.
In the meantime, the erosion of the shelf on the north is going on and the agglomerate of semi-detached icebergs that were static for many years have decided to move out

[FredBear]

Lots of melt ponds on George VI sound and Bach Ice Shelf on Worldview (24.01.2023), often happens at this stage of the season and will probably not cause a collapse?
The Wilkins Ice Shelf connection to Rothchild Island has narrowed this year, good image Worldview 23.01.2023 (69^o44'S,72^oW).
Various edges of ice shelves around the Bellinghausen Sea have retreated slightly, others slightly advanced but no new passages through the ice.
Most of the pack ice has drifted off west towards the Amundsen Sea.

[Tealight]

Has anyone more information about the small hole in the Wilkins ice shelf? (-70.26,-71.37)

It is north of Dorsey Island and 10km² in size. Judging from the differences between 2017 and 2023 ice is definitively flowing into it and melting in this tiny area. I can only imagine ocean up-welling or volcanic heat to produce such melt rates.

Overall it is growing slightly. In oldest image from Google Earth in 1984 it was just 5 km². 40 years ago the ice to the north had the typical look of a glacier flowing against Dorsey Island, but today it looks like a flat ice sheet.

[paolo]

Tealight,
Nice shot, it's even indicated in the maps!
I checked a radar image in the middle of the southern winter (28/06/2022) and apparently it is still open.
You found a pool in Antarctica, you can open a balneare establishment
More seriously, as soon as I have some time, I'll look into it

[NotaDenier]

https://en.wikipedia.org/wiki/Dorsey_Island

Looks like there are pictures from the 40s and 70s also.

Figure 5c displays an area of 15 km2 open water between Dorsey Island and the 5 adjacent coast of Mozart Ice Piedmont. Open ocean in this form is only rarely found on ice shelves, and only where massive, fast flowing ice streams enter the ice shelf. Here,
the presence of a large ice rise acts to support the formation of open water.

 https://tc.copernicus.org/preprints/2/341/2008/tcd-2-341-2008-print.pdf

I think the study is saying the island has a steep slope to the ocean and the glacier flows quickly there.

[NotaDenier]

https://tc.copernicus.org/preprints/2/341/2008/tcd-2-341-2008-print.pdf

Abstract
The Wilkins Ice Shelf is situated along the Antarctic Peninsula, a region where seven ice shelves disintegrated between 1995 and 2002. This study combines various remote sensing data sets over Wilkins Ice Shelf, with the aim to detect its present and near-
5 past dynamics as well as recent changes. The survey includes structural mapping, ERS-1/2 SAR interferometry and analysis of ICESat GLAS ice surface elevation data. Ice front retreat rates from 1986 to 2008 showed distinct break-up events, including a recent event in February 2008, where 40% of a bonding of the ice shelf to two islands broke o. Surface elevations have been used to study tidal eects, crack formation and
10 to estimate the ice thickness over the floating area. The interferometric velocities cover the south-eastern part of the ice shelf as well as major tributaries and reveal maximum inflow speeds of up to 330 ma1. We show that drainage of melt ponds into crevasses were of no relevance for the break-up at Wilkins Ice Shelf. Buoyancy forces caused the rift formation before the break-up of February 2008. Additionally, the evolution of failure
15 zones of the order of tenths of kilometres in length in pre-conditioned locations at ice rises could be shown. Analysis of satellite image time series revealed that evolution and coalescence of failure zones coincides with major break-up events and is assumed to be triggered by them. Investigation of the current (April 2008) situation shows that about 38% at the northern Wilkins Ice Shelf is directly endangered, however, there is
20 no visible signature that the remaining 8000 km2 are at risk.

[NotaDenier]

http://www.sciencepoles.org/interview/the-future-of-the-wilkins-ice-shelf

The collapse of the ice bridge between Charcot and Latady Islands on the Wilkins Ice Shelf on April 1st marked an important milestone in the drama of the gradual disappearance of the ice shelf on the Antarctic Peninsula. Break-up events have been occurring on the Wilkins since1993; however since a major break-up event in February 2008, only a 40km-long ice bridge between had been holding the ice shelf in place. Between half a kilometre and a few kilometres wide, the ice bridge finally snapped at its narrowest point, succumbing to the enormous stresses it had been subjected to for over a year.

In light of this recent collapse, SciencePoles spoke again with Dr. Angelika Humbert from the Alfred Wengener Institute (AWI) and formerly of the Polar Geophysics Group at the University of Münster for some insight into the causes of this break-up and what might be in store for the ice shelf now that the ice bridge has snapped. Along with her colleague Dr. Matthias Braun from the Center for Remote Sensing at the University of Bonn, Dr. Humbert has been monitoring and modelling the Wilkins Ice Shelf for several years.

[kassy]

Nice interview.

In the best case scenario, the ice shelf will lose only 800 km2. In the worst case scenario it might lose up to 3,700 km2, leaving only about 8,000 km2 of ice shelf behind. This means a loss of about 30% of the current area of the ice shelf. That's quite a lot!

And even the worst case scenario is optimistic: It predicts that a new, stable ice front would form between Latady Island, the Petrie Ice Rise, Dorsey Island and the grounding line of the ice shelf in the east, which would require the build-up of a kind of arch of compressed stress.

We often only focus on images that show the northern part of the ice shelf, because this is where the ice bridge was. But in fact the Wilkins Ice Shelf has two large inlet areas and also a southern part, which is not often covered in the satellite images we're taking at the moment, because the southern part of the ice shelf looks stable at the moment.

We´ll see which way the numbers will go.

[paolo]

Kassy,
this is an interview from April 08, 2009 ....

[kassy]

Yeah but we are still somewhere on that path.