Larsen Ice Shelves A, B, D, E, F, G

[paolo]

BIG calving at Larsen D !

Large image, click to animate

[gerontocrat]

BIG calving at Larsen D !

Scale? please pretty please

[paolo]

The scale was displayed at the bottom left, next to the date, in the second image (post-calving image: 12/11).

[Stephan]

The scale is only visible when the picture is zoomed.

It is a real massive calving event. Did anyone of us have it on his agenda?

Thank you paolo for sharing this information with us.

[paolo]

Here is the history of the front lines of 06/11 and 12/11. I have differentiated a part that probably is not part of the ice shelf and is simply very thick sea ice (multi-year). I added the estimate of the area that calved.

click to enlarge

[interstitial]

Here is the history of the front lines of 06/11 and 12/11. I have differentiated a part that probably is not part of the ice shelf and is simply very thick sea ice (multi-year). I added the estimate of the area that calved.

click to enlarge

all of the grey is not ice shelf but multiyear sea ice but thanks for the update.

[paolo]

Interstitial,
Thank you, I had doubts myself, but it must be very thick, and almost simulates the appearance of an ice platform.
So I applied a very strict criterion, and I find a line parallel to the blue-coloured part in the Sentinel1 image (the displacement corresponding to the advance of the ice shelf).
Below is the result and you can see that this calving remains very impressive.

Click to enlarge

[interstitial]

Interstitial,
Thank you, I had doubts myself, but it must be very thick, and almost simulates the appearance of an ice platform.
So I applied a very strict criterion, and I find a line parallel to the blue-coloured part in the Sentinel1 image (the displacement corresponding to the advance of the ice shelf).
Below is the result and you can see that this calving remains very impressive.

Click to enlarge

It is an impressive calving and you can't really tell from the satellite image how thick they are. This calving was predicted by the same scientist who predicted the last one that occurred a bit north of this one. She didn't give an exact time table but I believe this was within her predicted time. Thanks for pointing this out. They seem to do nothing for so long I stop checking then BAM! something happens.

The ice shelf does advance from the blue boundary. I just wish I knew when the boundary was created so I can estimate how fast some of those glaciers are moving. The Ronne ice shelf has extended well beyond its boundary but I don't think it is moving very fast. It may have already calved too. IDK

[oren]

For the sake of less knowledgeable readers, whom I represent quite well, here is the short text from Wikipedia about Larsen D, and a map of the locations of the various Larsen ice shelves.
I would greatly appreciate if anyone can match the animation location relative to the map, or if anyone can post an overview image showing the regions surrounding the calving area.

The Larsen D Ice Shelf is between Smith Peninsula in the south and Gipps Ice Rise. It is considered to be generally stable. Over roughly the past fifty years it has advanced (expanded) whereas comparable George VI, Bach, Stange, and Larsen C ice shelves have retreated (to a much greater net extent). The most recent survey of Larsen D measured it at 22,600 km2. There is fast ice along the entire front. This makes it difficult to interpret the ice front because the semi-permanent sea ice varies in thickness and may be nearly indistinguishable from shelf ice.

[FredBear]

Earlier this year (July) iceberg A69 broke off from the extreme northern edge of Larsen D, just south of the "island' at the end of Larsen C.This 'berg then quickly broke into two named parts:-
https://www.natice.noaa.gov/doc/PR%20-%2020200708%20-%20Iceberg%20A-69A-B.pdf

The new breakage is offshore & south of the peninsular embedded in the ice shelf just south of the Larsen "D" tag on the previous map but nothing has been given the "A-70" iceberg tag yet. This indicates that the break-out is not significant enough to merit naming an individual big iceberg (although some of the 'bergs look as big as the bits of A69, some ice is likely to be accumulated sea ice)?

[paolo]

Oren,
You will find enclosed :
> An animation with the two Sentinel1 images in their integrality with the scale and the indication lof two landmarks
> A simplified image of the Antarctic Peninsula with the two landmarks
> A detailed map of the Antarctic Peninsula

Click to enlarge and to animate the first image (very large images, to enlarge them completely click twice)

[oren]

Thank you paolo.

[paolo]

Interstitial,
I looked in Worldview which gives the speeds, but relative to 30/12/2011 and I find a maximum speed of 400 m/yr in the middle between Steele Island and Butler Island and 160 m/yr between Butler Island and Cape Mackintosh

"https://worldview.earthdata.nasa.gov/?v=-1795024.1235806216,913897.3490050219,-1598416.1235806216,1006313. 3490050219&p=antarctic&t=2011-12-30-T18%3A25%3A07Z&l=Coastlines,MEaSUREs_Ice_Velocity_Antarctica,MEaSUREs_Ice_Velocity_Greenland,Reference_Labels(hidden), Reference_Features(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor(hidden)"

I checked the speed of a point between Steele Island and Butler Island, for which Worldview gives a speed of 280 m/yr in 2011, using the Sentinel2 images from 23/10/2019 and 17/10/2020 and I find, for the same point, a speed of 340 m/yr (± 12 m/yr taking 2 px as error).

Even if the oldest Sentinel1 image of the zone dates only from 09/07/2020 (120 days before the one of 06/11/2020), which makes a too narrow base to calculate speeds of a few hundred meters per year, I wanted to make a test anyway and, for this same point, I find a speed of 365 m/yr (happy coincidence, an error of only one pixel corresponds to an error of 60 m/yr!).

We can conclude that, at least for this point, there was a significant acceleration (25%).

For the moment no more detailed analysis, this sector does not fit, for the moment, in my schedule.

[interstitial]

If I did not make a mistake the letters are the snow covered rises that look like snow covered boulders too me. A is not sure B is Dolleman I. C is Steele I. D is Ewing I. The numbers are the calving's. #1 is A68a the long skinny one that is still mostly intact and some speculate that it will crash into an Island soon. #2 is A69 #3 Just happened. I made images too but the image files are too big.                                                                                                               

[interstitial]

Thanks paolo. That is a lot slower than PIG. I knew it would be I just wanted the comparison.

[FredBear]

More breakouts of ice today from the Larsen D ice shelf where the 70° south line crosses it - rather cloudy so not very clear (might possibly be mistaken??) - but a continuation of this years fraying of that shelf?

[Tor Bejnar]

Wikipedia image:


Attached composite image from PolarView shows icebergs (circled in green).  Larsen C & D are circled in red.  Two selected frames have preview images.

Go to the PolarView link, select the frame of interest, then under the Image preview (it will be on the left), select a Product download (I use "variable" or "full resolution" to look at detail.)  Larsen D icebergs enlarged below.  [click to enlarge]

[paolo]

FredBear,
There has been no new calving, the icebergs, which you saw in Worldview (and the image is actually a bit foggy) are simply moved away from the coast (along with the sea ice). Below is an animation

[paolo]

My apologies, I responded by looking at the image of Tor Bejnar, but in reality FredBear, as he pointed out, was referring to a calving further north and this one is real.
There is no Sentinel1 image from yesterday and today, so I am posting an animation based on the Sentinel1 image from 14/12 and the Worldview image.

Click to animate

Update: in the commented image I had inverted the "old rift" and "new rift" labels. It is corrected

Update two: my apologies for French

[Tor Bejnar]

Good eye, Paolo!

There are some curious long rectangular icebergs (less bright than others - floes?) around 74S in this Dec. 14 PolarView image.  There are a couple of places they look like they may have come from (near orange bars).  They might be old (thick) fast-ice floes rather than icebergs from an ice shelf.

[RobertM]

Is this March 24 calving of Larsen F significant? It's very far south (74º 08'), right at the SE corner of the peninsula. https://twitter.com/usnatice/status/1376208662985854976

[interstitial]

Is this March 24 calving of Larsen F significant? It's very far south (74º 08'), right at the SE corner of the peninsula. https://twitter.com/usnatice/status/1376208662985854976

I think so but maybe move it to the Antarctic iceberg thread. Maybe group the Larsen  threads together? IDK
It is not a huge calving. It shows a progression of calving's southward on all of the Larsen ice shelfs.

[oren]

Good point interstitial, moved here.

Hello again RobertM.

[paolo]

Small animation about the A75 iceberg (images from 21/02, 17/03 and 29/03)
Dimensions: 16 km x 6.5 km

Click to animate and enlarge

[oren]

Oren,
You will find enclosed :
> A detailed map of the Antarctic Peninsula

Can you point the location of the new calving (and Larsen F) on this detailed map?

[paolo]

Attached:
> The Sentinel1 image with notations
> An extract from 'Ellsworth Land to Palmer Land' USGS Map
> A map of the Antarctic Peninsula

Click to enlarge

[oren]

Thanks a lot!

[paolo]

I'm adding a map I just created with the names of the Larsen Ice Shelves

Click to enlarge

[paolo]

A large calving (about 317 km2) in January, which we missed, in what remains of Larsen B.

Oren: can you change the title of the thread to "Larsen A, B, C, D, E, F and G Ice Shelves Discussions"?
I propose to keep a single thread for all these ice shelves (described in the map in the previous post)

Click to animate and expand

[oren]

We currently have 3 Larsen threads. Besides this one, we have an old one for Larsen B, but also a large and often updated thread about Larsen C.
Tracking Larsen B remnants can be done in this thread, but I think Larsen C deserves its own thread.
How about "Smaller Larsen Ice Shelves A, B, D, E, F, G"?
And I'll rename the other one to "Larsen C Ice Shelf".

BTW, nice catch.

[paolo]

it's ok and thank you

PS: LarsenD is not so small!

PS2: Wikipedia gives LarsenC 44,200 km² and LarsenD 22,600 km²

[oren]

Done and noted.

[paolo]

A small calving (13 km2) at the Gipps Ice Rise, which is between the Larsen C and Larsen D (the calving is on the Larsen C side)
It happened on 03/02 and I mention it because this Ice Rise is very important for the stability of the Larsen C and Larsen D and this point is to be watched.
The animation is made with S1 images from 02/02, 03/02 and 07/02, as well as a zoom of the iceberg with its measurements. In the image from 07/02, we can see that the iceberg had already moved about 20 km away from the starting point.
I add a map of the area

Click to animate and enlarge

[paolo]

This is an old calving, which I just detected today, related to the Edgeworth Glacier in the ex-Larsen A area; indeed the remains of the calving were still lying around in the bay and they intrigued me.
I am attaching two maps (the second is a zoom of the first) to locate this glacier
There were several successive calving events (at least two), but I limit myself to presenting two S2 images: one before the start of calving and one after, and more precisely the images of 20/10/2021 and 28/01/2022 (1 px = 16.4 m; scale displayed on the bottom right left)
The area concerned by the calving, calculated from two fronts is 17.2 km2, but, taking into account the displacement of the glacier (between the two images 100 days ago), I added 2.3 km2 (for the velocity of the Edgeworth glacier, as well as its tributary, I used Worldview-Ice velocity Antarctica), which leads us to a total area of 19.5 km2.

For this glacier it is a big calving

Click to animate and to enlarge the images

[Stephan]

well spotted, paolo.
Tell me, are you a detective in real life?

[paolo]

A major calving has just occurred in Larsen D (global area 162 km2, 35.8 x 6.4 km)
Animation based on S1 high resolution images (1px = 20m) from 17/02/2022 and 01/03/2022
I also add a map to position the calving

Click to animate (twice to enlarge completely)

[oren]

Considering the recent activity it would be interesting to compare the Larsen D situation to 2008, when it was measured as stable/slightly advancing, 22600 km2, and considered the Antarctic Peninsula ice shelf which was farthest from risky average annual temperatures isotherms.
Interestingly, it appears recent activity is where the shelf was somewhat retreating in previous decades, while elsewhere it was advancing, if I read the diagram correctly.

Source: https://www.researchgate.net/figure/Larsen-D-Ice-Shelf_fig5_26848412

[paolo]

As can be seen, in this animation based on the high resolution S1 images (1px 20m; overall dimensions 24 x 26 km) of 16/02, 28/02 and today, the calving of the Edgeworth Glacier System continues, even if the areas are smaller.

In reality it is a complex of three glaciers: Dinsmoor, Bombardier and Edgeworth which I have indicated in the last image of the animation.

Click twice to animate and enlarge completely

[oren]

So first the Dinsmoor front has disconnected from the other glaciers (as shown in the "old calving" post upthread), and now it appears that Bombardier and Edgeworth fronts might be disconnected from each other soon. Every such disconnect case causes the glacier to lose support, helping to accelerate and destabilize the front.

[FredBear]

This is an old calving, which I just detected today, related to the Edgeworth Glacier in the ex-Larsen A area; indeed the remains of the calving were still lying around in the bay and they intrigued me.
I am attaching two maps (the second is a zoom of the first) to locate this glacier
There were several successive calving events (at least two), but I limit myself to presenting two S2 images: one before the start of calving and one after, and more precisely the images of 20/10/2021 and 28/01/2022 (1 px = 16.4 m; scale displayed on the bottom right left)
The area concerned by the calving, calculated from two fronts is 17.2 km2, but, taking into account the displacement of the glacier (between the two images 100 days ago), I added 2.3 km2 (for the velocity of the Edgeworth glacier, as well as its tributary, I used Worldview-Ice velocity Antarctica), which leads us to a total area of 19.5 km2.

For this glacier it is a big calving

The ice in front of the Edgeworth Glacier (60^o W line) on the edge of Larsen A had been consolidating but has recently broken down and started to disperse.
Recently ice has also been moving out from Larsen B bays - Vaughan Bay (north west) and Exasperation Inlet below it. The ice from Vaughan has been showing blue tints on Worldview (melting or old ice?). Image from 23 March.

[paolo]

At Larsen B in the last few weeks there has been a series of major calvings that have involved the Evans, Green and Hektoria Glaciers (EGH).

The first image is a map of the Larsen A and B where I have indicated the position of the new calving and I have recalled the positions of previous calvings: at the Scar Inlet (Larsen B) and at the DBE: the Dinsmoor, Bombardier and Edgeworth Glaciers (Larsen A)

The second is a zoom on the three glaciers

The third is an animation based on the S1 images of 28/02, 12/03, 24/03 and 05/04 (1px = 20m ; global dimensions 28x28 km) :
The image of 28/02 is the normal situation, before any modification, in the following image the mélange of icebergs and fast ice in face of the front of glaciers has totally disappeared, no more support and the break-up will start as we can see in the two following images.

Definitely an interesting year for Larsen A and B !

Click to enlarge the images completely and to animate the third image
Click again to enlarge the images completely

[oren]

Similar to the DBE situation, this is some serious calving and hastens the upcoming loss of support when the EGH glacier fronts lose contact with each other.

[grixm]

Is that record retreat for those glaciers?

[steve s]

Is that a retrograde bed collapse? Seems likely to me from the speed, the length of the retreat (beyond the obvious ice shelf) and the degree of fragmentation, but I don't have access to a bed map to check.

[Often Distant]

Green and Hektoria Glaciers continue the retreat.

[IceConcerned]

I recently reviewed the state of Larsen B : we can see a gradual erosion (follow the arrows) that has been going on slowly for some years now, but above all, a new longitudinal crack has apeared between the archipelago and the peninsula. It could have some dramatic consequences in the coming months.

[paolo]

A relatively large calving at Pederson Nunatak (between Larsen A and B).
And in this case it is a permanent loss (there will be no replacement)
The images are from 26/10 and 05/11

Click two four animate and enlarge completely (images 2000x1000 px)

[FredBear]

From:-  Antarctica / Re: What's new in Antarctica ?

Worldview is showing the fast ice in the old Larsen B embayment is continuing to break out for the first time since 2011, two months before the end of the melt season. It is peculiar how the ice builds up for years, then it all seems to break up at once? (There has been a lot of blue "melt" evident on this ice earlier in the season).

My post above shows the Larsen B area was being cleared of fast ice earlier this year, the noticeable effect was seeing breakouts from several glaciers in the area later in the season.
There were small breakouts from the Pederson Nunatak which were not noted but one of them may have been a key to the latest calving?
This melt season much of the ice in Larsen A has cleared already plus Larsen B has growing clear water now that it has lost its old fast ice. This makes for more solar heat absorption as well as lack of protection and back pressure from the old ice for all the remaining fast ice and glaciers in the area.
We should expect to see more losses of old irreplaceable ice in this area and further south as the planet warms up.

[FredBear]

The remaining Larsen A fast ice (+ice to the north) is showing blue "melt" tints on Worldview.
The Larsen B embayment has been clearing out pack ice but there has been a flush of (looks mushy?) finer blue ice from the area of Vaughan Bay (NW corner) drifting east recently.
The coastline around Exasperation Inlet has been losing fast ice and is more clearly defined now.
We can expect to see more losses soon?

[FredBear]

Another significant(?) break in the ice shelf today between 71^o-72^osouth, just west of 60^o west, around Odom and Hilton inlets.
It may be a continuation of the calving from March 1st (Reply 35 by paolo) but goes further south.