Edit: I stand corrected. The collapse was of the sea ice tongue, not the ice stream tongue, which is further north. Twitter User twitter.com/… provided the clarification. However, this is still fast-paced, devastating news.
Sad news: the Thwaites sea ice tongue has disintegrated, confirmed by satellite imagery. When the clouds cleared enough, the collapse was visible. That part of the ice stream was in danger after Iceberg B22a, melting from below by warming waters, freed itself in December of 2022 and floated away from a shoal it had been lodged on for twenty years. B22a protected the glacier stream at the surface and depth. The loss of B22a enabled southern ocean storms with monster waves to batter the tongue badly eroded from upward cavities carved into the ice by warm currents.
As I shared yesterday, the Thwaites Eastern Ice Shelf is rapidly disintegrating, as confirmed by Polar View imagery and its pinning points stressed. It may have been spring tides that finally took the sea ice tongue down off the eastern shelf. The entire eastern shelf is now exposed to the ocean.
The western shelf has remained relatively stable until today. The break took much of the melange (icebergs and sea ice).
Note the floating glacial tongue is still intact but threatened.
This study from January 2023 explains one of the processes that may lead to the collapse of the glacier’s tongue.
Abstract
The stability and dynamics of Thwaites Glacier depend on the structural properties of its marine terminus; however, the relationship between these variables on the floating ice tongue is poorly understood. Here we present a six-year record of ice speed, derived from satellite observations starting in 2015, showing two large-magnitude (approximately 30–45%) and prolonged (approximately one to two years) cycles of speed variation across the ice tongue. Using an automated, deep learning-based method of extracting high-resolution fracture maps from satellite imagery, we detail periods of increasing fracture development and subsequent reconsolidation in the ice tongue shear margin that coincide with the observed speed changes. Inverse modelling using the BISICLES ice-sheet model indicates that the variation in ice speed can be accounted for by these observed changes to the spatial pattern of fracturing. This study provides further evidence of direct coupling between fracturing and dynamic variability in West Antarctica but indicates that increased fracturing and associated speed changes are reversible on one- to two-year timescales. We suggest that fracturing does not necessarily lead to positive feedback with glacier acceleration on these timescales and that damage process modelling is important for accurately predicting the evolution of the Antarctic Ice Sheet.
Faster than predicted.
NATURE BRIEFING 15 December 2021 Daily briefing: Thwaites Glacier closer to collapse
Giant fractures in the floating ice of Antarctica’s massive Thwaites Glacier could shatter part of the shelf within five years. If that happens, the glacier could release an armada of icebergs and begin flowing much faster into the ocean. That would funnel ice that had been resting on land into the sea, where it would contribute to sea-level rise. If Thwaites were to collapse completely, it would raise sea levels by 65 centimetres. “We have been expecting that ice shelf to fail, and that’s one of the reasons that there has been such a coordinated international effort to study Thwaites — it’s big and important, but it’s also been clearly poised on the brink of change,” says geophysicist Kirsty Tinto.Interesting post from the Arctic Sea Ice Forum on the above and other satellite images
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.
Cover the kiddie's ears.