Thwaites Glacier Discussion

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https://www.pnas.org/doi/10.1073/pnas.2211711120

Synchronous retreat of Thwaites and Pine Island glaciers in response to external forcings in the presatellite era

Rachel W. Clark et al., February 26, 2024

Abstract

Today, relatively warm Circumpolar Deep Water is melting Thwaites Glacier at the base of its ice shelf and at the grounding zone, contributing to significant ice retreat. Accelerating ice loss has been observed since the 1970s; however, it is unclear when this phase of significant melting initiated. We analyzed the marine sedimentary record to reconstruct Thwaites Glacier’s history from the early Holocene to present. Marine geophysical surveys were carried out along the floating ice-shelf margin to identify core locations from various geomorphic settings. We use sedimentological data and physical properties to define sedimentary facies at seven core sites. Glaciomarine sediment deposits reveal that the grounded ice in the Amundsen Sea Embayment had already retreated to within ~45 km of the modern grounding zone prior to ca. 9,400 y ago. Sediments deposited within the past 100+ y record abrupt changes in environmental conditions. On seafloor highs, these shifts document ice-shelf thinning initiating at least as early as the 1940s. Sediments recovered from deep basins reflect a transition from ice proximal to slightly more distal conditions, suggesting ongoing grounding-zone retreat since the 1950s. The timing of ice-shelf unpinning from the seafloor for Thwaites Glacier coincides with similar records from neighboring Pine Island Glacier. Our work provides robust new evidence that glacier retreat in the Amundsen Sea was initiated in the mid-twentieth century, likely associated with climate variability.

[Open Access]

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12-day high-res GIF of Thwaites Tongue.  You can see how the center is running aground which tends to spit the Tongue into two.

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I noticed these new cracks in the Tongue in the high-res GIF above.  Probably related to motion against the grounded icebergs at the front.

[vox_mundi]

Massive Damage at Thwaites Glacier
https://www.dailykos.com/stories/2024/2/24/2225146/-Massive-damage-at-Thwaites-Glacier

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Massive Damage at Thwaites Glacier
https://www.dailykos.com/stories/2024/2/24/2225146/-Massive-damage-at-Thwaites-Glacier

I Know this is freshly published but March 2021 was a very long time ago for Thwaites glacier.

[baking]

Massive Damage at Thwaites Glacier
https://www.dailykos.com/stories/2024/2/24/2225146/-Massive-damage-at-Thwaites-Glacier

I Know this is freshly published but March 2021 was a very long time ago for Thwaites glacier.

I think this is a lot of confusion between Thwaites Eastern Ice Shelf (TEIS), Thwaites Western Ice Tongue (TWIT), and Crosson Ice Shelf.

[interstitial]

Massive Damage at Thwaites Glacier
https://www.dailykos.com/stories/2024/2/24/2225146/-Massive-damage-at-Thwaites-Glacier

I Know this is freshly published but March 2021 was a very long time ago for Thwaites glacier.

I think this is a lot of confusion between Thwaites Eastern Ice Shelf (TEIS), Thwaites Western Ice Tongue (TWIT), and Crosson Ice Shelf.

Yes in my mind I tend to bunch them together as one.

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12-day GIF of the Tongue.

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Here is a 1-year GIF from Worldview.  Thwaites Eastern Ice Shelf (TEIS) is looking pretty vulnerable.

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6-day low-res GIF showing movement of icebergs in front of Thwaites Eastern Ice Shelf (TEIS.)

[Mr. Ä]

What are the black outlines in Worldview images?

[Linus]

Coastal outline overlay. You can turn it off on the filter layers tool on the left side of the screen.

[baking]

What are the black outlines in Worldview images?

They are the grounding line and the extent of the ice sheet at some point in the distant past—usually 2011.

Compare with Figure 1 in this paper: https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2014gl060140

Edit:  2011 was a good guess.  Here is Worldview from January 8, 2011.

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3-day low-res GIF showing more iceberg movement off the front of Thwaites Eastern Ice Shelf (TEIS) and the tip of Thwaites Western Ice Tongue (TWIT.)

[gerontocrat]

Sea ice in the BellinghamAmundsen sea is late in refreezing this year, with lots of open water along the Thwaites / PIG coastline. Maybe fast sea ice & berg losses can continue for some time yet?

Image from latest Univ Bremen sea ice concentration.

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Today's 12-day high-res GIFs with details of Thwaites Eastern Ice Shelf (TEIS) and Thwaites Western Ice Tongue (TWIT.)

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1-day GIF from Worldview showing loss from the Melange but not clear how many icebergs are involved.

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Today's 2-day low-res GIF updating recent changes to the TEIS, the Tongue, and the Melange.

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1-day GIF from Worldview showing a breakup of some of the fast ice West of Thwaites Tongue.

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2-day low-res GIF of a few small calvings at the front of Thwaites Tongue.

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The first high-res image from Thwaites Eastern Ice Shelf (TEIS) in 24 days shows a new potential shear margin forming in the center.

The middle orange line in this post: https://forum.arctic-sea-ice.net/index.php/topic,1760.msg394891.html#msg394891

It was always a possibility, but now it is looking like a strong favorite.

[Stephan]

...and it looks that at the SW edge (right down corner) five new icebergs will soon calve...

[IceConcerned]

THere is more to it when we look at the general picture, and in particular the rear portion of hte ice sheet
The whole IS has got loose, we have indeed the creation of a shear zone that baking is indicating, but the whole sheet is moving in a north-north-east direction. The crack at its back has lengthened and hugely widened since first reported a little more than 2 years ago, and is now (purple cross section) about 2.3km wide.
At the same time, it is bound to end up in the open water separating the IS from the tongue, along one of the 2 main cracks underlined in green. the are currently growing fast, each hi-res pictures brings some change
And on the western side,  the orange crack are multiplying, leading most likely to another shear zone.

Definitely the event to follow in the coming months, or maybe even weeks.

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5-day low-res GIF showing some icebergs breaking away from the melange and an iceberg moving away from in front of TEIS.

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2-day low-res GIF showing some icebergs breaking away from the Tongue and one from the Melange.