The study sheds light on the future of the great Thwaites glacier.
New findings from the University of Michigan reveal that the world’s largest ice sheet may be less at risk of sudden collapse than previously thought.
Studies published in Science, including simulating the demise of the Thwaites Glacier in West Antarctica, one of the largest and most stable glaciers in the world. The researchers modeled the collapse of ice cliffs at different heights – the near-vertical formations that occur when glaciers and ice sheets meet the ocean. They found that instability does not necessarily lead to rapid disintegration.
“What we found was that over a long period of time, ice behaved like a thick liquid, like pancakes spread across a frying pan,” said Jeremy Pacis, professor of climate and space science and engineering at the University of Michigan. . “So the ice is spreading and diminishing faster than it can fail and that could prove an avalanche. But if the ice doesn’t recede fast enough, then you have the potential for the glacier to collapse quickly.”
The researchers combined ice collapse and ice flow variables for the first time, and found that ice expansion and loosening, as well as support from trapped ice chunks, could reduce the effects of sea ice sheet instability caused by fracture.
The new findings add nuance to an earlier theory called sea ice sheet instability, which suggested that if the ice sheet height reached a certain threshold, the ice sheet could suddenly disintegrate under its own weight in a chain reaction of ice fractures. The Thwaites Glacier in Antarctica—sometimes referred to as the “Apocalypse Glacier”—is close to this threshold and could contribute about 3 feet to sea level rise in the event of a complete collapse. At 74,000 square miles, roughly the size of Florida, it is highly vulnerable to climate and ocean changes.
Gletser Thwaites. Kredit: NASA/James Youngle
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The research team also found that icebergs cracking and falling off major glaciers in a process known as “glacier birth” could actually prevent rather than contribute to catastrophic destruction. If ice blocks stick to outcrops on the ocean floor, they can put back pressure on the glacier to help stabilize it.
Pacis notes that even if the glaciers don’t collapse catastrophically, exposing the towering cliffs could cause a retreat of several kilometers per year — equal to the length of about 20 football fields — making a significant contribution to future sea level rise.
How fast is sea level rising?
While Thwaites and other glaciers are clearly melting, their speed of death is of great interest to coastal areas as they develop strategies for adaptation and building resilience. But estimating the retreat of glaciers is a very complex business, as it is affected by the interplay of various factors – the pressure and tension of billions of tons of moving ice, changes in air and water temperatures, and the effects of liquid water flows. On ice, to name a few.
As a result, predictions of the collapse of the Thwaites glacier range from several decades to several centuries. Pacis said the new study was an important step towards producing accurate and actionable predictions.
Gletser Thwaites. credit: NASA
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“There is no doubt that sea levels are rising, and that will continue for decades to come,” Basis said. But I think this research offers hope that we’re not near total collapse – that there are steps that can ease and stabilize things. And we still have a chance to change things by making decisions about things like energy emissions – methane and carbon dioxide. “
The fate of the Antarctic and Greenland ice sheets
In addition to Pacis, the research team of postgraduate research assistants includes Brandon Berg, Anna Crawford and Doug Penn of the University of St Andrews.
Crawford said the results would also be useful in predicting the fate of glaciers and other ice formations in the Arctic and Antarctic.
“These important insights will guide future research into the retreat of the Thwaites Glacier and other large glaciers in the West Antarctic Ice Sheet that are prone to retreat by ice sheet collapse and sea ice slope instability,” he said. “This highlights the conditions that facilitate retreat, demonstrates the potential for re-stabilization of the station and shows how sea ice can actually stop the collapse process.”
The research team is already working to improve their model further by incorporating additional variables that affect glacier retreat, including how the shape of individual glaciers affects their stability and interactions between glacial ice and the surrounding molten ocean, Pacis said.
“The ocean has always been there, tickling the ice in very complex ways, and we’ve only known for a decade or two how important that is,” he said. “But we’re starting to understand that this is driving a lot of the changes we’re seeing, and I think that’s going to be the next big frontier in our research.”
Reference: “Transition to sea ice sheet instability controlled by gradient and velocity ice thickness” by JN Pacis, B. Berg, AJ Crawford and De Penn, 18 June 2021, Available here. Science.
DOI: 10.1126 / science.abf6271
This study is part of the Thwaites Glacier International Collaboration. This research was supported by the DOMINOS project, a component of the Thwaites Glacier International Collaboration, by the National Science Foundation (grant number 1738896) and the Natural Environment Research Council (grant number NE/S006605/1).
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