The observations Icefin made of the seafloor and ice around the grounding zone supply more information on the picture of how melting differs underneath the ice shelf. They found the staircases, called balconies, as well as crevasses in the ice base are melting rapidly.
BAS team deploying the hot water drill at Thwaites Glacier consisting of Paul Anker, Keith Nicholls, James Smith and Peter Davis. Credit: Icefin/ITGC/Schmidt
So, although the vertical melting along the base of the ice rack was less than expected, melting along sloped ice in these terraces and cracks is much greater and might be a substantial factor in ice loss across Thwaites Glacier, specifically as major rifts are advancing across the ice rack and might become the primary trigger for ice shelf collapse.
Image of Icefin operating under the sea ice near McMurdo Station. Credit: Icefin/NASA/PSTAR RISE UP/Schmidt/Lawrence
Dr. Britney Schmidt, whos an Associate Professor at Cornell University and lead author of the 2nd study, states:
” These brand-new ways of observing the glacier permit us to understand that its not simply how much melting is happening, but how and where it is happening that matters in these hot parts of Antarctica. We see crevasses, and most likely terraces, throughout warming glaciers like Thwaites. Warm water is entering the cracks, assisting use down the glacier at its weakest points.”
MELT and Icefin teams on the sea ice in front of NSF USAP McMurdo station in November 2019. Credit: Icefin/ITGC/Dichek).
Recommendations:.
” Heterogeneous melting near the Thwaites Glacier grounding line” by B. E. Schmidt, P. Washam, P. E. D. Davis, K. W. Nicholls, D. M. Holland, J. D. Lawrence, K. L. Riverman, J. A. Smith, A. Spears, D. J. G. Dichek, A. D. Mullen, E. Clyne, B. Yeager, P. Anker, M. R. Meister, B. C. Hurwitz, E. S. Quartini, F. E. Bryson, A. Basinski-Ferris, C. Thomas, J. Wake, D. G. Vaughan, S. Anandakrishnan, E. Rignot, J. Paden and K. Makinson, 15 February 2023, Nature.DOI: 10.1038/ s41586-022-05691-0.
” Suppressed basal melting in the eastern Thwaites Glacier grounding zone” by Peter E. D. Davis, Keith W. Nicholls, David M. Holland, Britney E. Schmidt, Peter Washam, Kiya L. Riverman, Robert J. Arthern, Irena Vanková, Clare Eayrs, James A. Smith, Paul G. D. Anker, Andrew D. Mullen, Daniel Dichek, Justin D. Lawrence, Matthew M. Meister, Elisabeth Clyne, Aurora Basinski-Ferris, Eric Rignot, Bastien Y. Queste, Lars Boehme, Karen J. Heywood, Sridhar Anandakrishnan and Keith Makinson, 15 February 2023, Nature.DOI: 10.1038/ s41586-022-05586-0.
The MELT team melted large amounts of snow to create the hot water to drill through Thwaites Glacier to reach the grounding line. Credit: Peter Davis
A layer of fresher water in between the bottom of the ice shelf and the underlying ocean, slows the rate of melting along flat parts of the ice rack. However the authors were shocked to see the melting had actually formed stair-case-like topography across the bottom of the ice rack. In these areas, as well as in fractures in the ice, rapid melting is happening.
Thwaites Glacier is one of the fastest altering glaciers in Antarctica: the grounding zone– the point where it meets the seafloor– has pulled away 14 km because the late 1990s. Much of the ice sheet is listed below water level and prone to fast, irreparable ice loss that could raise worldwide sea-level by over half a meter within centuries.
The new data were collected as part of the MELT project, one of the jobs in the UK-US International Thwaites Glacier Collaboration, among the biggest worldwide field campaigns ever carried out in Antarctica. The MELT team undertook observations of the grounding line (where the ice initially satisfies the ocean) beneath the Thwaites Eastern Ice Shelf in order to understand how the ice and ocean interacts in this critical region.
Icefin at Kamb Ice Stream after having been pulled from the water, showing icicles that have grown on the car. Credit: Icefin/NASA/PSTAR RISE UP/Schmidt/Lawrence
Dr. Peter Davis of the British Antarctic Survey (BAS) took ocean measurements through a 600m deep borehole around two kilometers from the grounding line, created by a warm water drill in late 2019. These measurements were compared to melt rate observations taken at 5 other sites beneath the ice shelf. Over a nine-month duration, the ocean near the grounding line ended up being warmer and saltier however the melt rate at the ice base balanced 2-5 m annually: less than formerly modeled.
Borehole drilling website on Thwaites Glacier 2022. Credit: Peter Davis– British Antarctic Survey
Dr. Peter Davis, whos an oceanographer at BAS and lead author on among the research studies, says:
” Our results are the glacier however a surprise is still in difficulty. The ice coming off the continent will match the amount of ice being lost through melting and iceberg calving if an ice shelf and a glacier are in balance. What we have found is that regardless of percentages of melting there is still rapid glacier retreat, so it appears that it doesnt take a lot to press the glacier out of balance.”
Obviously, the quick retreat of Thwaites Glacier in West Antarctica is driven by various processes under its floating ice shelf than scientists previously understood. Unique observations from where the ice gets in the ocean reveal that while melting beneath much of the ice shelf is weaker than anticipated, melting in crevasses and cracks is much quicker. A layer of fresher water between the bottom of the ice rack and the underlying ocean, slows the rate of melting along flat parts of the ice rack. If an ice shelf and a glacier are in balance, the ice coming off the continent will match the amount of ice being lost through melting and iceberg calving. The observations Icefin made of the seafloor and ice around the grounding zone offer more detail on the photo of how melting differs underneath the ice shelf.
The icefin robot under the ice near McMurdo research station, operated by the US Antarctic Program. Credit: Rob Robbins USAP
New information from an international expedition and underwater robotic Icefin underneath the remote Thwaites Glacier, nicknamed the Doomsday Glacier, in Antarctica. It is one of the most important glaciers in West Antarctica, and its prospective collapse might trigger a substantial increase in water level, which might have catastrophic effects for seaside neighborhoods worldwide.
Apparently, the rapid retreat of Thwaites Glacier in West Antarctica is driven by different processes under its floating ice rack than researchers formerly understood. Unique observations from where the ice goes into the ocean show that while melting below much of the ice shelf is weaker than anticipated, melting in crevasses and fractures is much quicker. Regardless of the suppressed melting the glacier is still retreating, and these findings provide a crucial advance in understanding the glaciers contribution to future sea-level increase.
Thwaites Glacier in Antarctica is very remote and difficult to get to. Credit: Britney Schmidt
Two documents in the journal Nature today (February 15, 2023) supply a clearer image of the changes happening under the glacier, which is the size of Great Britain or the US state of Florida and is one of the fastest-changing ice-ocean systems in Antarctica. Results reveal that although melting has increased beneath the drifting ice rack, today rate of melting is slower than lots of computer system designs presently approximate.
