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grixm

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Re: Thwaites Glacier Discussion
« Reply #300 on: September 22, 2020, 10:49:40 AM »
Overview of the whole Thwaites glacier back in March before the sun set, and now.

solartim27

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Re: Thwaites Glacier Discussion
« Reply #301 on: September 22, 2020, 04:55:23 PM »
From Peter Neff @icy_pete
Today is the first day of the #WAIS2020 West #Antarctic glaciology workshop! 🇦🇶❄️

If you registered, you can attend any session over the next two weeks. Zoom links in your inbox. 📬

Today: Grounding zones & ice shelves, Session 7
3-5pm Eastern
https://t.co/v3HfBXL0Tp https://t.co/IDzzmQhQ43

All sessions are recorded and available on YouTube  from @MinesGlaciology
https://www.youtube.com/channel/UC-nSFKCeciZh5KQtEgrJqmg
FNORD

baking

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Re: Thwaites Glacier Discussion
« Reply #302 on: September 26, 2020, 05:09:38 PM »
Another piece of Iceberg B22-A broke off from the older (Western) end earlier this month and floated off this week.  Click on the GIF below.  You can also see the amount of movement of B22-A.

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« Last Edit: November 25, 2020, 03:09:22 AM by AbruptSLR »
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baking

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Re: Thwaites Glacier Discussion
« Reply #304 on: November 25, 2020, 04:15:07 AM »
I've been keeping a close eye on the sea ice off of Thwaites.  The Tongue is in such rough shape that I fear it could be devastated if the sea ice retreats much during this upcoming warm season.  It was protected by the fast ice it last year, but the year before it was very bad.  I am worried that it could be even worse this year.

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Re: Thwaites Glacier Discussion
« Reply #305 on: November 25, 2020, 03:36:16 PM »
I've been keeping a close eye on the sea ice off of Thwaites.  The Tongue is in such rough shape that I fear it could be devastated if the sea ice retreats much during this upcoming warm season.  It was protected by the fast ice it last year, but the year before it was very bad.  I am worried that it could be even worse this year.

I concur :(

Edit: For comparison the first image is from Sentinel-1 on Nov 27, 2017; while the second image is from Sentinel-2 on Nov 17 2020.
« Last Edit: November 25, 2020, 03:56:10 PM by AbruptSLR »
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baking

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Re: Thwaites Glacier Discussion
« Reply #306 on: November 25, 2020, 04:28:47 PM »
I think this morning's Sentinel-1 image illustrates the threat of open water (in black) reaching the Tongue.

gerontocrat

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Re: Thwaites Glacier Discussion
« Reply #307 on: November 25, 2020, 05:36:45 PM »
Thwaites is becoming a hot potato. For someone like me, (i.e. too old, tired and lazy to understand the science) the linked article does help as it shows that the scientists are unsure of what the future holds except for one thing:- if GHG emissions are not reduced, by a lot, then it's whoops for sure.

https://yaleclimateconnections.org/2020/11/can-shearing-of-thwaites-glacier-slow-or-stop-if-humans-control-greenhouse-gas-emissions/
Can shearing of Thwaites glacier slow or stop if humans control greenhouse gas emissions?

Runaway sea-level rise resulting from retreat of Antarctica's Thwaites glacier depends on humans' substantially cutting GHG emissions.

Quote

Scripps Institution of Oceanography scientist Jeffrey Severinghaus opens the video pointing to someone’s gradually rolling a large round boulder down a hill: Stop pushing a few moments, and the boulder may pause, may sit in place. But in time, the pushing gets to the point that the boulder sets apace on its own. Severinghaus calls that a “runaway positive feedback,” something to be avoided. Is that runaway prospect inevitable? he asks rhetorically. “We are possibly in a collapse right now,” he says. “but I would say it’s not very likely.” There’s a “but” coming, as Severinghaus adds “but we can’t completely rule it out either.”

Severinghaus shares with climate scientist Eric Rignot, of the University of California, Irvine, a concern that so little is known about the underlying topography of the Antarctic ice sheets. “We know more about the topography of Mars than we know about the topography beneath Antarctic Ice,” he says. Rignot agrees, pointing to “not enough observations.”

“The accident of where it is, is that Thwaites can cause tremendously more sea-level rise by itself than these others can,” says Penn State climate scientist Richard Alley. He notes that some models show the unending shearing and collapse of Thwaites ice “keeps going,” but says other models hold that the shearing can be constrained – and the resulting sea-level rise kept “small, slow, and expected” – if greenhouse emissions can be substantially reduced, and soon.
That’s a point Twila Moon, scientist with the National Snow and Ice Data Center, fully buys into. “All of these different elements of the cryosphere” in the future will look “dramatically different if we are taking very strong action to reduce GHG emissions, versus if we are following a path like today.”


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AbruptSLR

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Re: Thwaites Glacier Discussion
« Reply #308 on: November 25, 2020, 06:26:52 PM »
Thwaites is becoming a hot potato. For someone like me, (i.e. too old, tired and lazy to understand the science) the linked article does help as it shows that the scientists are unsure of what the future holds except for one thing:- if GHG emissions are not reduced, by a lot, then it's whoops for sure.

https://yaleclimateconnections.org/2020/11/can-shearing-of-thwaites-glacier-slow-or-stop-if-humans-control-greenhouse-gas-emissions/
Can shearing of Thwaites glacier slow or stop if humans control greenhouse gas emissions?

Runaway sea-level rise resulting from retreat of Antarctica's Thwaites glacier depends on humans' substantially cutting GHG emissions.

Quote

Scripps Institution of Oceanography scientist Jeffrey Severinghaus opens the video pointing to someone’s gradually rolling a large round boulder down a hill: Stop pushing a few moments, and the boulder may pause, may sit in place. But in time, the pushing gets to the point that the boulder sets apace on its own. Severinghaus calls that a “runaway positive feedback,” something to be avoided. Is that runaway prospect inevitable? he asks rhetorically. “We are possibly in a collapse right now,” he says. “but I would say it’s not very likely.” There’s a “but” coming, as Severinghaus adds “but we can’t completely rule it out either.”

Severinghaus shares with climate scientist Eric Rignot, of the University of California, Irvine, a concern that so little is known about the underlying topography of the Antarctic ice sheets. “We know more about the topography of Mars than we know about the topography beneath Antarctic Ice,” he says. Rignot agrees, pointing to “not enough observations.”

“The accident of where it is, is that Thwaites can cause tremendously more sea-level rise by itself than these others can,” says Penn State climate scientist Richard Alley. He notes that some models show the unending shearing and collapse of Thwaites ice “keeps going,” but says other models hold that the shearing can be constrained – and the resulting sea-level rise kept “small, slow, and expected” – if greenhouse emissions can be substantially reduced, and soon.
That’s a point Twila Moon, scientist with the National Snow and Ice Data Center, fully buys into. “All of these different elements of the cryosphere” in the future will look “dramatically different if we are taking very strong action to reduce GHG emissions, versus if we are following a path like today.”



I am not very good at graphics but hopefully the three attached images will give readers a better appreciation that the calving front for icebergs from the base of the Thwaites Ice Tongue is rapidly approaching the southern face of the subglacial cavity in the Thwaites Gateway leading down into the BSB (Byrd Subglacial Basin).  The first image is from the Peter Sinclair video you linked to of an image from the austral 2017-18 summer season showing the location of the subglacial cavity at the base of the Thwaites Ice Tongue circa 2017, with only initial fracturing of the ice over the subglacial cavity (which I have previously termed the 'Big Ear', inside the zone called T1 in the image).  The second image created by baking shows a Sentinel-1 image from May 21, 2020 showing that the calving front has moved close to the southern side of the Big Ear subglacial cavity.  The third image from Sentinel-2 on November 17, 2020 shows that the icebergs floating over the top of the Big Ear subglacial cavity while still constrained from floating way when the local sea ice melts, but are much less constrained than they were in May 2020.  Once the icebergs floating over the Big Ear subglacial cavity do float away, they will likely expose a bare ice cliff face that is subject to a MICI-type of failure leading directly into the BSB.

Edit: The fourth image is a Landsat photo from 2018 showing growing crevasse-damaged areas near the grounding line of the Thwaites Ice Tongue base; with much less crevasse-damage than shown in the third image of a Sentinel-2 photo from Nov 2020.
« Last Edit: November 25, 2020, 10:44:34 PM by AbruptSLR »
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Stephan

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Re: Thwaites Glacier Discussion
« Reply #309 on: December 27, 2020, 09:18:38 PM »
New calving at Thwaites Glacier.

Comparing the EOSDIS pictures from Nov 26 and Dec 25 a new rift (approx. 6 km long) is visible close to the grey line which once represented the grounding line. I painted a green line right to this new rift.

To be further examined on Sentinel images.

See attached picture. Might need a click for magnification.
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baking

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Re: Thwaites Glacier Discussion
« Reply #310 on: December 27, 2020, 10:05:31 PM »
Just a quick and dirty GIF of the calving front versus almost 2 years ago.  Not seeing much a retreat.

baking

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Re: Thwaites Glacier Discussion
« Reply #311 on: January 10, 2021, 07:06:24 AM »
I've noticed a recent increase in movement of Iceberg B22-A recently, so I thought I would give an update.  I post about B22-A here instead of the Iceberg thread because it is still close enough to Thwaites to affect the sea ice that helps to stabilize Thwaites to some extent.

The GIF below shows the movement of B22-A over the past 22 months.  It can be separated into three phases: 1) March 2019 to April 2020, Northward Movement; 2) April 2020 to October 2020, Westward movement (with calving from the western end); and 3) October 2020 to January 2021, Northward movement again.  All three phases resulting in approximately the same distance moved, so you can see that the velocity just about doubled between each phase (12 months to 6 months to 3 months.)  It is this increase in speed that is most concerning.

There is some rotation during this movement, but it hasn't resulted in a pattern yet.  Alternating between clockwise and counter-clockwise rotation, the orientation hasn't changed much over time.

The second image shows three areas of shallow water that tend to keep B22-A in place.  A peak on the eastern end, shallows on the western end, and another shallow to the Southwest near Bear Peninsula.  One concern is that the recent calving from the older Western end of the iceberg may allow it to rotate away from the shallows.  Of course, further movement to the West could also free it from the Eastern Peak.

The bathymetry under B22-A has never been accurately mapped, so it is hard to make predictions.  But observing the motion over time give us clues to where the iceberg is grounding and how it might float off, or at least float far enough away to change the sea ice off of Thwaites and neighboring glaciers.

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Re: Thwaites Glacier Discussion
« Reply #312 on: January 10, 2021, 01:08:53 PM »
I was just looking at b22 A movement. It is clearly moving more and I suspect that process will continue. I conjecture the reason is probably bottom melt. I am not sure we will know. My guess is it will continue move northward this year but will escape next southern melting season.

baking

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Re: Thwaites Glacier Discussion
« Reply #313 on: January 10, 2021, 04:06:04 PM »
Below is a 3-day GIF of the land-fast sea ice off of Thwaites Tongue.  There had been no significant change since late November.  The next two months will be critical for this season.  Remember the glacier tongue is constantly pushing on the sea ice so that helps to weaken it.  The Tongue has been weakened by many fractures over the past two years and exposure to open water would be very destructive.

Stephan

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Re: Thwaites Glacier Discussion
« Reply #314 on: January 10, 2021, 06:58:56 PM »
Thank you baking, for this update.
I noticed two bigger icebergs from the sea south of B-22 were flushed towards the bottleneck at the SW edge of B-22 (where the shallow sea is). I am curious whether they can make it through this gateway or whether they will ground there, making ice flow out through the bottleneck more difficult than it already is.
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baking

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Re: Thwaites Glacier Discussion
« Reply #315 on: January 10, 2021, 07:13:53 PM »
As a comparison with last year, here is the land-fast sea ice off of Thwaites Tongue from March 23-25, 2020, with the discussion at:
https://forum.arctic-sea-ice.net/index.php/topic,1760.msg256340.html#msg256340

As it turns out, the sea ice began refreezing in early April 2020, so nothing significant came from that break-up.

The previous year, 2019, was a different story.  The earliest image I have from February 16, 2019, shows the area almost completely free of sea ice.  Shortly afterwards, most of the icebergs at the lower right side of the image floated off en masse.

It sure looks like 2021 will be worse than 2020 (at least in this part of the Antarctica) but too soon to say if comparisons with 2019 are warranted.

Stephan

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Re: Thwaites Glacier Discussion
« Reply #316 on: January 21, 2021, 09:03:13 PM »
Micro calving at the eastern flank of the Thwaites Eastern Ice Shelf.

A small iceberg (ca. 2*1 km) has detached from the ice shelf, close to a larger calving in the same area (reported here in this thread a while ago), and not too far away from Cork, which lies still grounded since the large PIIS calving last spring.

See attached picture. The new iceberg is marked in a green quadrangle. May need a click to enlarge.
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baking

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Re: Thwaites Glacier Discussion
« Reply #317 on: April 10, 2021, 03:16:32 AM »
First published results I've seen from some of the 2019 fieldwork.  This from robotic submarines measuring water temperatures under the ice shelf.

"Pathways and modification of warm water flowing beneath Thwaites Ice Shelf, West Antarctica"
https://advances.sciencemag.org/content/7/15/eabd7254

and from Earther:

"First-Ever Observations From Under Antarctica’s ‘Doomsday Glacier’ Are Bad News"
https://earther.gizmodo.com/first-ever-observations-from-under-antarctica-s-doomsd-1846650385

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Re: Thwaites Glacier Discussion
« Reply #318 on: May 17, 2021, 12:31:01 AM »
Here's a link to a Science News article about under-ice exploration baking cited above

https://www.sciencenews.org/article/climate-thwaites-glacier-under-ice-shelf-risks-warm-water

It's a bit short on details about the results, but did mention one unexpected finding that folks might find interesting, that the water flowing under Thwaites Glacier is coming from Pine Island Bay. The article also includes a couple more citations

S.H.R. Rosier et al. The tipping points and early warning indicators for Pine Island Glacier, West Antarctica. The Cryosphere. Vol. 15, March 25, 2021, p. 1501. Doi: 10.5194/tc-15-1501-2021.

P. Milillo et al. Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica. Science Advances. Published online January 30, 2019. doi: 10.1126/sciadv.aau3433.

baking

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Re: Thwaites Glacier Discussion
« Reply #319 on: May 26, 2021, 04:38:12 PM »
A late season sea ice break up caused a shift in the iceberg melange off of Thwaites and Crosson Ice Shelves including about half of Thwaites Tounge.  This 6-day GIF was scaled down and is still huge.  Click to enlarge.
« Last Edit: May 26, 2021, 05:57:50 PM by baking »

Stephan

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Re: Thwaites Glacier Discussion
« Reply #320 on: May 26, 2021, 08:28:28 PM »
Thank you for that information.
Hopefully the large icebergs from Crosson find their way out into the open sea and will not get grounded as B-22 did.
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baking

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Re: Thwaites Glacier Discussion
« Reply #321 on: May 26, 2021, 09:55:55 PM »
Thank you for that information.
Hopefully the large icebergs from Crosson find their way out into the open sea and will not get grounded as B-22 did.
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oren

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Re: Thwaites Glacier Discussion
« Reply #322 on: May 26, 2021, 11:01:14 PM »
My thoughts exactly, best if they become grounded rather than float away. Not that Thwaites cares what I wish for.

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Re: Thwaites Glacier Discussion
« Reply #323 on: May 27, 2021, 01:43:54 PM »
You both are right. From the perspective of a "as slow as possible" disintegration of Thwaites (and Crosson) ice shelves as much sea ice, fast ice and icebergs have to be retained in that area. And - looking at the bathymetry - the probably thick icebergs from Crosson will very likely ground somewhere in that area.
On the other hand a fastened decay of both ice shelves (hopefully acknowledged in greater public) may point our global attention to the problem of the WAIS instability in the long run in general. Maybe an earlier onset of the decay can act as another "wake-up call" for us all.
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Tor Bejnar

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Re: Thwaites Glacier Discussion
« Reply #324 on: May 27, 2021, 04:25:45 PM »
I'm "woke" already!  :o ::)  Now can we keep the ice all bottled up and thickening so I can focus on my sore muscles?
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baking

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Re: Thwaites Glacier Discussion
« Reply #325 on: May 30, 2021, 04:54:38 PM »
Huge shift in Iceberg B22-A in today's 6-day GIF.  Scaled down 10X.

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Re: Thwaites Glacier Discussion
« Reply #326 on: May 30, 2021, 06:03:59 PM »
Is this the follow-up of the break-up of the fast ice/ice mélange in front of Crosson you reported about one week ago?
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Tor Bejnar

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Re: Thwaites Glacier Discussion
« Reply #327 on: May 30, 2021, 06:24:25 PM »
Huge shift in Iceberg B22-A in today's 6-day GIF.  Scaled down 10X.
Great gif!
A pinning point appears to be near the top of the gif (as presented).  A gif over a longer period might tell us how consistent this point is.  Maybe there were 'two' pinning points and now there is only one.  As melting (and rock-on-ice abrasion) continue, we'll either see the iceberg break or watch a pendulum swing back and forth for a while.  (Or maybe it'll get stuck on a 'new' 2nd pin.)
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baking

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Re: Thwaites Glacier Discussion
« Reply #328 on: May 30, 2021, 06:47:43 PM »
Is this the follow-up of the break-up of the fast ice/ice mélange in front of Crosson you reported about one week ago?
Probably unrelated.   Fast ice release was due to smaller icebergs shifting off of another, nearby, underwater peak.

baking

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Re: Thwaites Glacier Discussion
« Reply #329 on: May 30, 2021, 06:57:54 PM »
Huge shift in Iceberg B22-A in today's 6-day GIF.  Scaled down 10X.
Great gif!
A pinning point appears to be near the top of the gif (as presented).  A gif over a longer period might tell us how consistent this point is.  Maybe there were 'two' pinning points and now there is only one.  As melting (and rock-on-ice abrasion) continue, we'll either see the iceberg break or watch a pendulum swing back and forth for a while.  (Or maybe it'll get stuck on a 'new' 2nd pin.)
B22-A is grounded/restrained at three points.  An underwater peak in the top left (Northeast), as you noted, and shallows at the bottom (West) and bottom left (Southwest.)  It moved back and forth a lot in 2020, although not as much so far most of this year, but is pretty hemmed in and doesn't seem likely to escape anytime soon.  However it has rotated quite a bit clockwise over time and it lost its Southwest corner last year so may be less constrained than before.  If it continues to rotate, all bets are off.

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Re: Thwaites Glacier Discussion
« Reply #330 on: May 31, 2021, 01:41:14 AM »
It has been slowly twisting and sliding further out the last year or two. Before that I don't think it moved very often. I have not followed it for more than two years so if I am wrong please correct me.

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Re: Thwaites Glacier Discussion
« Reply #331 on: May 31, 2021, 02:48:56 AM »
My main point was the gif showed that, during the two frames, B-22A pivoted around a single point.  Any other grounding points were (at least temporarily) non-effective at immobilizing the iceberg.  (And it's been pretty stable for years.)
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Re: Thwaites Glacier Discussion
« Reply #332 on: May 31, 2021, 04:05:57 AM »
My main point was the gif showed that, during the two frames, B-22A pivoted around a single point.  Any other grounding points were (at least temporarily) non-effective at immobilizing the iceberg.  (And it's been pretty stable for years.)
Then I am wrong in thinking it has been moving more in the last year or two?

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Re: Thwaites Glacier Discussion
« Reply #333 on: May 31, 2021, 05:44:07 AM »
My main point was the gif showed that, during the two frames, B-22A pivoted around a single point.  Any other grounding points were (at least temporarily) non-effective at immobilizing the iceberg.  (And it's been pretty stable for years.)
Then I am wrong in thinking it has been moving more in the last year or two?
I don't have any specific information from more than about two years ago, but I don't think it is possible that this rate of movement has been going on for much more than two years given the distance it has traveled.

Here is a two year GIF made up of three images, one from March 2019, another from May 2020, and the last from May 26, before the recent move.  It doesn't prove much except that total movement during the 2019-20 and 2020-21 seasons were  about the same.

The main thing you should see is that most of the movement was probably due to the loss of ice from the older Western end of the iceberg, although it is possible that it is also getting thinner and grounding further west in the shallows.

I should also point out the rotational moves are not uncommon, but obviously they have been balancing out over time since there has been no long-term rotation over the past two years.  Also, it has been remarked that there has been relatively little motion in early 2021 and there were a couple of notable shifts before the recent one.

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Re: Thwaites Glacier Discussion
« Reply #334 on: May 31, 2021, 06:48:57 AM »
For your discussions on B22A an animation from 15/06/2017 to 25/05/2021 (the interval between images being 360 days)

Click to animate and enlarge

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Re: Thwaites Glacier Discussion
« Reply #335 on: May 31, 2021, 08:07:58 AM »
Thank you baking and paolo for the short gifs.
My bet for the future is that the movement direction will continue in the next year(s), maybe with increasing speed until B-22 has reached less shallow waters and may then be freely floating with the currents.
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Re: Thwaites Glacier Discussion
« Reply #336 on: May 31, 2021, 04:02:16 PM »
Thank you baking and paolo for the short gifs.
My bet for the future is that the movement direction will continue in the next year(s), maybe with increasing speed until B-22 has reached less shallow waters and may then be freely floating with the currents.
The question is, will it ride over the shallows to the West or slip Northward past the underwater peak.  I can't really see it going completely over the shallows in the next few years, so sliding past the underwater peak seems to be the most worrisome scenario, and if it were to rotate by 90 degrees, that would seem to be a lot more likely.

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Re: Thwaites Glacier Discussion
« Reply #337 on: June 01, 2021, 04:09:33 AM »
thanks for the gifs and responses

grixm

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Re: Thwaites Glacier Discussion
« Reply #338 on: June 11, 2021, 10:13:25 AM »
More movement of B-22 and surroundings between June 6th and 11th

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Re: Thwaites Glacier Discussion
« Reply #339 on: June 11, 2021, 01:07:54 PM »
If it keeps moving like this it may make it out to the open ocean within a year.

baking

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Re: Thwaites Glacier Discussion
« Reply #340 on: June 11, 2021, 05:06:08 PM »
Wow!  Look at the effect this had on Thwaite's Tongue.  This is not the first time this has happened:

https://forum.arctic-sea-ice.net/index.php/topic,1760.msg230715.html#msg230715

It helps me see B22-A as a giant cork holding back the melange.

EDIT: Alignment is a little bit better.
« Last Edit: June 12, 2021, 01:11:26 AM by baking »

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Re: Thwaites Glacier Discussion
« Reply #341 on: June 11, 2021, 05:25:52 PM »
Wow!  Look at the effect this had on Thwaite's Tongue.  This is not the first time this has happened:

https://forum.arctic-sea-ice.net/index.php/topic,1760.msg230715.html#msg230715

It helps me see B22-A as a giant cork holding back the melange.
Ok, I am a complete dumbo on stuff like this, but my immediate thought was the opposite, i.e. Look at the effect of the split in the ice tongue on B22-A.

or Who's in charge - the melange or the berg?
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baking

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Re: Thwaites Glacier Discussion
« Reply #342 on: June 11, 2021, 06:03:18 PM »
There seems to be an alignment issue with the GIF above.  I will try to fix it.  Meanwhile, enjoy this detail from the end of Thwaites Tongue.


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Re: Thwaites Glacier Discussion
« Reply #343 on: June 11, 2021, 06:16:38 PM »
Wow!  Look at the effect this had on Thwaite's Tongue.  This is not the first time this has happened:

https://forum.arctic-sea-ice.net/index.php/topic,1760.msg230715.html#msg230715

It helps me see B22-A as a giant cork holding back the melange.
Ok, I am a complete dumbo on stuff like this, but my immediate thought was the opposite, i.e. Look at the effect of the split in the ice tongue on B22-A.

or Who's in charge - the melange or the berg?
I will admit to being quite confused the first time I saw this, but having watched B22-A more closely after the past two years and seeing it move many many times in all directions I am quite confident in saying that it doesn't need Thwaite to push it around.

Of course B22-A probably didn't pull all that ice with it either.

The most likely mechanism is a combination of some pushing and pulling and wind and current acting on all the ice simultaeously.  It is probably better to think of it as a sequence of shifts where B22-A moved and freed up some patch of ice behind it which freed up another patch etc.  We only see snapshots so we don't know how quickly this happened, but the movement doesn't appear to be completely uniform over the 100 or so km from end to end so that seems to be the best explanation.  And if so, it has to occur offshore first and free up ice as it approaches the ice sheet.  (Edit:  Because the offshore ice is least constrained.)

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Re: Thwaites Glacier Discussion
« Reply #344 on: June 12, 2021, 08:37:32 AM »
Thank you baking for this report on B-22A and Thwaites.
Would it be possible to make a comprehensive gif of that area over the last months? Maybe from that we can conclude whether pulling or pushing factors might have played a more important role?
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Re: Thwaites Glacier Discussion
« Reply #345 on: June 14, 2021, 07:38:27 AM »
Would it be possible to make a comprehensive gif of that area over the last months? Maybe from that we can conclude whether pulling or pushing factors might have played a more important role?
Here is a large-scale GIF over the last three months.  What I found interesting while putting this together is that, at least in this sequence, the first shift of the melange occurred between May 13 and May 25, (the third and second images from the end) but B2-A didn't move between those two dates.  The second shift of the melange occurs after the end of this sequence.

Finding a good sequence of images taken at the same angle and covering the whole area of interest limits the dates you have to choose from.  I will try to update it on June 18.

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Re: Thwaites Glacier Discussion
« Reply #346 on: June 14, 2021, 10:08:44 AM »
Interesting that some of the smaller white 'bergs in the above sequence are moving diagonally down  before exiting towards the lower left in the image - the same 'bergs having looked grounded during the summer? B22A also wriggles back & forth a little before the final frame, looks pinned at the top, around the 74S line.
Thanks baking, looking forward to updates.

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Re: Thwaites Glacier Discussion
« Reply #347 on: June 14, 2021, 03:57:59 PM »
Here is an animation from 07/01/2020 to 06/06/2021, one image every 12 days, excluding the image of 29/07/2020 which is missing.

Click to animate

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Re: Thwaites Glacier Discussion
« Reply #348 on: June 14, 2021, 08:36:10 PM »
Thank you for the animations.
From them I can say that B-22 is not completely grounded but it may be pinned a little bit at its eastern end. The shift northward in the last frame has shown that it can move as a whole.
The bottle neck at its SW end (S of 74°, W of 110°) has now opened; one of the larger icebergs has been flushed through it (last frame). When this northward move goes on a larger portion of sea ice and (smaller) icebergs will be able to leave the sea south of B-22.
Please also note a little calving at the southern part of the western tip of B-22.
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Re: Thwaites Glacier Discussion
« Reply #349 on: June 17, 2021, 02:46:17 PM »
It rotated back the way it came! 11th vs 17th