The US Antarctic Program's icefin robot near McMurdo research station. Photo: Rob Robbins USAP
Utilizing a underwater robot Icefin, we can see the melting beneath the Antarctic Glacier from a close up view.
Researchers have concluded that the rapid retreat of Thwaites Glacier in West Antarctica was influenced by different mechanisms than previously assumed. They show that while melting beneath much of the ice shelf is weaker than expected, melting in cracks and crevasses is much slower. Significantly, the glacier is still retreating, according to the researchers.
"A greater and more complete picture of the glacier's interaction with the world ocean is emerging by including in new observations," says David Holland, director of New York University's Fluid Dynamics Laboratory and NYU Abu Dhabi's Center for Global Sea Level Change. "The melt rates on the western side of Antarctica are the highest to date, suggesting the glacier may be in retreat."
The findings, which were published in two papers in the Nature journal, are a significant step forward in understanding how the glacier, which is the size of Florida, is causing future sea level rise.
The melting of flat sections of the ice shelf is slowed by a layer of fresher water between the bottom of the ice shelf and the underlying ocean. Surprisingly, however, the melting had formed a staircase-like topography across the bottom of the ice shelf. The melting is happening in these areas as well as in cracks in the ice.
Britney Schmidt's photograph is from Thwaites Glacier in Antarctica.
Thwaites Glacier is one of Antarctica's fastest-changing glaciers: its grounding zone has retreated 14 kilometers, or more than eight miles, since the late 1990s. Much of the ice sheet is below sea level and vulnerable to rapid, irreversible ice loss that might raise global sea-level by more than half a meter in centuries.
The new information was collected as part of the MELT project, one of the many international field trips undertaken in Antarctica by the MELT team. The MELT team began observations along the Thwaites Eastern Ice Shelf in order to better understand how the ice and water interact in this critical region.
Thwaites Glacier in 2022: A borehole drilling site
The melting rate at the ice base averaged 2-5 meters per year, according to Peter Davis of the British Antarctic Survey (BAS).
"Our findings are disappointing, but the glacier is still in danger," says Davis, the lead author of one of the Nature papers. "If an ice shelf and a glacier are in balance, the amount of ice coming off the continent will match the amount of ice being lost as a result of melting and iceberg calving."
Paul Anker, Keith Nicholls, James Smith, and Peter Davis are among the members of the BAS team performing the hot water drill at Thwaites Glacier. Credit: Icefin/ITGC/Schmidt
Britney Schmidt, a member of Cornell University's Astronomy and Earth and Atmospheric Sciences, and a team of scientists and engineers guided Icefin through a 600-meter-deep borehole. The vehicle is designed to locate grounding areas that were previously difficult to survey.
As water flows through them, heat and salt can be transferred into the ice, causing the crevasses and rifts to collapse. Although the vertical melting along the bottom of the ice shelf was smaller than anticipated, melting along sloped ice in these cracks and terraces is much higher and may be a major contributor to ice loss across Thwaites Glacier.
The MELT crew melted large amounts of snow to create hot water to drill through Thwaites Glacier to reach the 'grounding line.'
Schmidt, the lead author of one of the Nature papers, believes that it's not just how much melting is happening, but how and where it is happening in these very hot areas of Antarctica. Warm water is breaking through the cracks, helping to weaken the glacier at its weakest points.
Icefin working under sea ice near McMurdo Station. Credit: Icefin/NASA/PSTAR RISE UP/Schmidt/Lawrence
Holland, a professor at New York University's Courant Institute of Mathematical Sciences and a co-author of the Nature papers, assembled a group of researchers from five universities and sent them to the Thwaites Eastern Ice Shelf in January 2020. They discovered relatively little melting, but returned two years later aboard the South Korean icebreaker Araon.
See Also: The Doomsday Glacier Is "In Trouble."
B. E. Schmidt, P. Washam, K. W. Nicholls, J. D. Lawrence, A. Spears, A. J. G. Dichek, A. D. Mullen, E. Clyne, B. Yeager, P. Anker, M. R. Meister, B. C. Hurwitz, E. S. Quartini, J. Wake, D. G. Vaughan, S. Anandakrishnan, J. Pad
Peter E. D. Davis, Keith W. Nicholls, Britney E. Schmidt, Irena Vaková, Clare Eayrs, Andrew D. Mullen, Justin D. Meister, Elisabeth Clyne, Aurora Basinski-Ferris, Eric Rignot, Sridhar Anandakrishnan, and Keith Makinson, 15 February 2023, Nature. DOI: 10.1038/s41586-022-05586-0
The project, which was established in 2018, is part of the International Thwaites Glacier Collaboration (ITGC), a five-year $50 million collaboration between the United States and the United Kingdom to understand the Thwaites Glacier's past and what the future holds.
The Natural Environment Research Council of the United Kingdom and the National Science Foundation of the United States supported the study (1739003, 1929991).