Thwaites Glacier Discussion

[Ajpope85]

Ice will tend to push any debris off what it rubs against; true, though, some rock debris is stuck to some icebergs. If I was between an iceberg and some bedrock, I wouldn’t bet on my survival, but the forces a mostly floating iceberg exerts on a pinning point must be much less then what the glacier exerts on the valley floor.

I agree. We are talking about massive forces though, so there must be some effect. It probably isn't significant, but maybe it is. Even the loss of a few centimeters might become significant with the compounding of rising seas levels and thinner icebergs, and suddenly an anchor point becomes a small speed bump, and a loss of a few centimeters becomes compounded into an effective loss of meters.

Unfortunately, we won't know until we know. I think it is a question worth investigating. Too bad funding for studies is so low.

[Chris83]

   Polarview is back online
   New damage is visible (and recent (last 4 days) ), with new cracks appearing quite far "inland".

  (Compare 29.12.2023 and 03.01.2024 on Polarview)

[baking]

New damage is visible (and recent (last 4 days) ), with new cracks appearing quite far "inland".

I assume this is the area you are talking about.  I should point out that today's image is darker due to seasonal melting on the upper surface of the snowpack.  It happens every year at this time and it causes some crevasses to appear wider.  It's not unusual to have crevasses near the grounding line here and they usually close up as the ice shelf moves forward, but this year they are unusually large.

[Chris83]

   Good morning Baking

  In fact , I was talking about this area . I cropped the photo for clarity

[IceConcerned]

THe long iceberg along the Eastern side of the TEIS has finally detached

[Chris83]

12.01.2024

A larger view is available today (polarview)
Lots of sea ice is still visible. Very different from 2023.
JAXA data shows ice loss is speeding up again. The forecast shows a "heatblob" coming the next 3 days in the area, but colder after that .

[baking]

12-day low-res GIF showing a lot happening in the sea ice surrounding Thwaites Eastern Ices Shelf (TEIS.)

[baking]

Today we have a new satellite, new to me anyway.  RadarSat Constellation Mission 3 or RCM3.  It uses side aperture radar, just like Sentinel-1, but more specifically designed to look at ice.  I haven't looked into the hows and whys, but today's image has better contrast in the sea ice.  I tried to line up the images for direct comparison.

[baking]

12-day hi-res GIFs of the Eastern and Western flanks of Thwaites Eastern Ice Shelf.

[baking]

2-day Worldview GIF of the fast sea ice West of Thwaites breaking up.

[baking]

5-day GIF from Worldview while we wait for hi-res SAR images through Polarview.  Not the long recently calved iceberg from the Eastern flank of TEIS sliding Eastward along the front.  Also a recently calved iceberg on the Western flank has also shifted position.

[baking]

1-day GIF from Worldview showing the Western flank of the grounded portion of TEIS is now ice free.  This happened on February 13 last year: https://forum.arctic-sea-ice.net/index.php/topic,1760.550.html

[baking]

7-day low-res radar image of iceberg movement near the flanks of Thwaites Eastern Ice Shelf (TEIS.)

[baking]

2-day Worldview GIF.  It's not a great image for today, but I will update it if the satellite makes another pass.  The only significant observation is the loss of some "fast" (stationary) sea ice in front of Thwaites Tongue.  The remaining fast ice is currently held behind a single iceberg that appears to be grounded.  It's an unusual place for icebergs to be grounded, but the bathymetry for the area says it is about 400 meters deep so not out of the question.

Edit:  Updated the GIF with a clearer image as promised.

[baking]

2-day low-res radar GIF showing a detail of the icebergs and sea ice moving in front of Thwaites Tongue.

[baking]

1-day GIF with late-in-the-day images from Worldview showing some of the fast ice in front of Thwaites Tongue breaking up behind the presumably grounded iceberg.  The area of interest is just below the center of the image.  Also, there is loose ice shifting around at the top and bottom of the image.

[IceConcerned]

Of interest too is that the fast ice in front of the eastern flank of the TEIS has detached, leaving this front open

[baking]

Blurry 1-day GIF from Worldview showing a detail of the fast ice in front of the Tongue breaking up.  Hoping for something clearer later today. 

[baking]

Here is an updated GIF from later in the day.

[baking]

Large-scale 12-day GIF of radar images (low-res and scaled down) showing the underlying icebergs and sea ice in the region of the Thwaites Eastern Ice Shelf (TEIS) and Thwaites Tongue.  There is still some sea ice in front of the Tongue, but not much.  However, the Melange between TEIS and the Tongue is starting to move.

[baking]

3-day Worldview GIF.

[baking]

Today's 1-day Worldview GIF showing a detail of more ice slip-sliding away.

[Stephan]

Thank you for posting these daily animations. I'd like to see a week, 10 days or fortnight comparison to see the whole effect of what is breaking away there.

[baking]

Thank you for posting these daily animations. I'd like to see a week, 10 days or fortnight comparison to see the whole effect of what is breaking away there.

Worldview is pretty darn easy to use and most days since January 13 have had pretty good visibility.  Check it out at https://worldview.earthdata.nasa.gov/ and if you need help I can certainly give you some tips.  You want to use the Antarctic Projection and there is a comparison tool that can swipe between any two dates.  And it has better resolution than the images I can download from there.  You can also do comparisons to prior years.

I would prefer to use the 12-day Sentinel-1 radar images, but things have been happening more quickly than they can keep up with.

[baking]

Early 1-day GIF today from Worldview.  I will update with clearer images if we get them. [Updated]

Now most of the Western Flank of Thwaites Eastern Ice Shelf (TEIS) is ice free and it appears that some of the grounded icebergs in front of TEIS may have shifted due to the loss of sea ice around them.

[oren]

The good news is that the sea ice melting season should end in about 3 weeks.
The bad news is that 3 weeks is a long time, even then the new ice is still useless for buttressing icebergs, and for now the prevailing forces of wind and current seem to be straight out to sea, a bad setup.

[baking]

The good news is that the sea ice melting season should end in about 3 weeks.
The bad news is that 3 weeks is a long time, even then the new ice is still useless for buttressing icebergs, and for now the prevailing forces of wind and current seem to be straight out to sea, a bad setup.

Also, this is about the same a last year, but last year was pretty drastic.  Without Iceberg B22-A holding back the sea ice, this may become a regular occurrence.

[baking]

Very large 24-day high-resolution Sentinel-1 radar GIF today.  The latest change of note is the group of icebergs leaving the Western flank of the grounded portion of Thwaites Eastern Ice Shelf (TEIS) leaving it exposed to more calving.

[baking]

5-day low-res GIF showing the remaining melange has started to move.

[baking]

2-day low-res GIF showing the tip of the Tongue breaking up and another piece of the fixed portion of Thwaites Easter Ice Shelf (TEIS) floating away.

[baking]

2-day Worldview GIF covering the same time period in the Sentinel-1 images above, but slightly later in the day so showing more ice breaking up.

Posting this for reference because we expect no more Sentinel-1 images until Friday and will have to rely on Worldview and hope for no clouds before then to to keep an eye on the Tongue.

Edit:  Added a slightly clearer image from later in the day.

[baking]

1-day GIF from Worldview showing drifting ice but no new calving.

Edit: Update with fewer clouds.

[baking]

A beautiful cloud-free day over the mostly ice-free Amundsen Sea.  You can even see iceberg B22-A on its way to Cape Dart.

https://worldview.earthdata.nasa.gov/?v=-2899626.738627611,-1303867.6232526833,-278186.7386276112,-142651.62325268332&p=antarctic&t=2024-02-14-T14%3A14%3A34Z

Meanwhile, today's 1-day GIF shows two small icebergs breaking away from the fixed portion of Thwaites Eastern Ice Shelf (TEIS) near the shear margin.  The remaining Tongue and the nearby fast ice is unchanged over the past two days.

[baking]

3-day low-res Sentinel-1 GIF today.

[baking]

A large 12-day high-res Sentinel-1 GIF showing the loss of sea ice, the rest of the Melange, and pieces of the Tongue and parts of TEIS.  Take a close look at the movement along the shear margin of TEIS.  I'm thinking about making a longer-term closeup of that area with my thoughts about the future.

[baking]

Here is a GIF of the Thwaites Eastern Ice Shelf (TEIF) since the beginning of the year.  The shear margin is at the top of the image.

[RoxTheGeologist]

Baking: Let's have your thoughts! Is buttressing a thing of the past?

[baking]

Baking: Let's have your thoughts! Is buttressing a thing of the past?

I always feel that my perspective might be biased because I'm only looking at satellite images and don't have information on what is going on under the ice, but I do have a strong sense that the shear margin is rapidly weakening and that other possible scenarios are just less likely to occur.

1) The oldest theory was that TEIS would thin out and lift off its pinning points at the northern end.

2) Then there was a Sept. 2021 paper that suggested "back-stress" from the pinning points could cause "rapid fragmentation" of TEIS: https://forum.arctic-sea-ice.net/index.php/topic,1760.msg322503.html#msg322503

3) And a Dec. 2021 press conference at AGU that announced a weakened area of TEIS that could potentially meet with growing transverse rifts that could cause a failure as early as 2024: https://forum.arctic-sea-ice.net/index.php/topic,1760.msg327945.html#msg327945

My current sense is that the shear margin is absorbing all these stresses making these scenarios less likely to occur.  The moving part of TEIS is no longer firmly attached to the pinned part making the first two scenarios unlikely, and for the same reason the transverse rifts are no longer growing making the third scenario less likely.

I am obviously concerned that this seems like an "easy answer" that also makes all the other options go away, but nonetheless it appears to be what is happening.

Below is a diagram of what I am seeing.  The "Zones of Destruction" (an old ASIF terminology) are areas where there is no longer any significant resistance in the shear margin.  All the resistance is in the center, assisted by to opposing "spurs" that have locked into each other.  The ultimate failure of the shear margin could occur along a number potential fault lines shown in orange.

Edit:  I updated the captions to differentiate between the old transverse rifts in the moving portion of TEIS and the new transverse rifts forming in the fixed portion.

[oren]

Seeing as the pinned part is shrinking over time, and quite rapidly at that, whatever buttressing remains is doomed in any case.
I don't expect Thwaites to do well in the next year/years, also adding the loss of B-22A which protected the flank (both at surface and at depth) for two decades.
The only possible semi-positive scenario is a calving so massive that it somehow manages to block the exits and stablize the region. This could only be many icebergs together, as producing another B-22 is now impossible. Not that I expect this scenario, it's more of a fantasy.
Btw many thanks for the continuous updates in this thread, though it would have been better if there was nothing to report.

[baking]

Well, PIG is growing bigger.  If that calves a large one and it doesn't break up, that might help.

[baking]

Subtle, yet massive, shift in the last remaining "fast" ice West of Thwaites Tongue in today's 2-day GIF from Worldview

[Stephan]

If this will break off ("calve" is probably wrong) an area of ca. 1400 km² of fast ice incl. mélange is lost. This loss will open new surfaces for further erosion...

[baking]

If this will break off ("calve" is probably wrong) an area of ca. 1400 km² of fast ice incl. mélange is lost. This loss will open new surfaces for further erosion...

This also happened last year in early February.  The question is how much of the pack of icebergs behind the fast ice will float away this season.  The sea ice will refreeze over the winter, but the icebergs will take longer to repopulate.  And of course, exposed ice shelves are also vulnerable.

[baking]

12-day GIF focused on the fast ice West of the Tongue.  Scaled down for size.

[baking]

Today's 5-day GIF.  The loose ice is continuing to break up.

[baking]

There was a small calving at the extreme Eastern end of Thwaites.  Something to watch out for because for the first time in years, the entire Eastern calving front is exposed to open water and the prevailing winds.

[baking]

Today's large-scale 2-day GIF.

[baking]

8-day GIF from Worldview.

[baking]

There has been some crazy talk about Thwaites Tongue on social media today.  This is a 24-day GIF made from Sentinel-1 radar images showing what has actually happened to Thwaites Tounge so far in February.

Thwaites Tongue is the fastest-moving part of Thwaites Glacier.  It is made up of tabular icebergs that calve and then move as a group.  Occasionally at this time of year, the surrounding sea ice breaks up and some of the older icebergs at the end of the Tongue float away.  This is what has happened so far this year.

Yes, there is a chance that more of the Tongue will break off, but it hasn't happened so far.  We will see about tomorrow.

[Click once to animate.  Click again to zoom.]

[baking]

Update on the Tongue with a 3-day GIF.

Note: The apparent motion in the lower right of the image is probably an artifact from comparing two different radar acquisition angles.