Home Glaciers The Antarctic glacier may be more stable than initially feared

The Antarctic glacier may be more stable than initially feared


Ice cliff – credit Rob Larter, British Antarctic Survey

New international study sheds light on the future of the massive Thwaites Glacier and other ice caps.

The world’s largest ice caps may be at less risk of sudden collapse than expected, according to new findings led by the University of Michigan, in partnership with the University of St Andrews as part of the International Thwaites Glacier Collaboration.

The team of international researchers simulated the disappearance of one of the world’s largest and most unstable glaciers, the Thwaites Glacier in West Antarctica. The team of scientists modeled the collapse of varying heights of ice cliffs, almost vertical formations that occur where glaciers and ice shelves meet the ocean, and found that instability does not always lead to rapid disintegration.

The Thwaites Glacier covers 192,000 square kilometers (74,000 square miles), the size of the US state of Florida or Great Britain, and is particularly sensitive to climate change.

Over the past 30 years, the overall rate of ice loss from Thwaites and its neighboring glaciers has more than quintupled. Already, the ice flowing from Thwaites into the Amundsen Sea accounts for about four percent of global sea level rise. A precipitous collapse of the glacier could cause a significant rise in sea level of about 65 cm (25 inches) and scientists want to know if or when this could happen.

The new findings, published in Science (Friday, June 18, 2021), add a nuance to a previous theory called sea ice cliff instability, which suggested that if the height of an ice cliff reaches a certain threshold, it may suddenly disintegrate under its own weight in a chain reaction of ice fractures. The Thwaites Glacier in Antarctica, sometimes referred to as the “Doomsday Glacier”, is approaching this threshold.

Researchers combined for the first time the variables of ice breakage and ice flow, finding that stretching and thinning of ice, as well as strengthening of trapped chunks of ice, can moderate the effects of l instability of the sea ice cliff induced by the fracture.

Principal Investigator, Associate Professor Jeremy Bassis, University of Michigan, said: “What we found is that over long time scales, ice behaves like a viscous fluid, kind of like a pancake spreading out in a frying pan. Thus, the ice spreads and thins faster than it can break, which can stabilize the collapse. But if the ice can’t thin out fast enough, then you have the possibility of a rapid glacier collapse. “

Ship the Nathaniel B Palmer to Thwaites Glacier credit Alex Mazur

The research team also found that icebergs that crack and fall from the main glacier during a process known as “iceberg calving” can prevent, rather than contribute to, catastrophic collapse. If the chunks of ice get stuck on outcrops on the ocean floor, they can put back pressure on the glacier to help stabilize it.

But Bassis notes that even if the glacier does not collapse catastrophically, the exposure of a high cliff could still trigger a retreat of a few kilometers per year, or the equivalent of the length of about 20 lots. football and resulting in a significant contribution to future sea level rise.

While it is clear that Thwaites and other glaciers are melting, the speed of their disappearance is of great interest to coastal areas as they develop strategies to adapt and build resilience. But predicting the retreat of glaciers is an incredibly complex matter, as they are affected by the interplay of many factors: the stress and strain of billions of tons of moving ice, changes in air and temperature. water and the effects of liquid water flowing over ice, to name a few. As a result, predictions of the collapse of the Thwaites Glacier range from a few decades to several centuries. The new study is an important step towards producing accurate and actionable predictions.

Bassis explains: “There is no doubt that sea levels are rising, and that this will continue for decades to come. But I think this study offers hope that we’re not approaching a complete collapse – that there are measures that can ease and stabilize things. And we can always make a difference by making decisions about things like energy emissions, methane, and CO2.

The article’s co-author, Dr Anna Crawford, of the School of Geography and Sustainable Development at the University of St Andrews, added that the results of the study will also be useful in predicting the fate of other glaciers and ice formations in the Arctic and Antarctic: “This important information will inform future research on the retreat of the Thwaites Glacier and other large outlet glaciers from the West Antarctic ice sheet that are vulnerable to retreat by rupture of ice cliffs and instability of sea ice cliffs.

“They highlight the conditions that facilitate recoil, demonstrate the potential for restabilization of the terminal, and show how sea ice can actually slow down the collapse process.”

The research team is already working to further refine their models by incorporating additional variables that affect glacial retreat, including how the shape of individual glaciers affects their stability and the interaction between glacial ice and the liquid ocean that l ‘surrounded.

Bassis adds: “The ocean is still there, sort of tickling the ice in a very complex way, and we’ve only known for a decade or two how important it is, but we’re starting to understand. that this is driving a lot of the changes we’re seeing, and I think this will be the next big frontier in our research.

The article Transition to Marine Ice Cliff Instability Controlled by Ice Thickness Gradients and Velocity by JN Bassis, B. Berg, AJ Crawford and D. Benn is published in the journal Science.

Please ensure that the article’s DOI 10.1126 / science.abf6271 is included in all online stories and social media posts and that Science is credited as the source.

This study is part of the International Thwaites Glacier Collaboration, one of the objectives of which is to provide critical observations of the past and present behavior of Thwaites in order to better test the models and predict with more certainty the future fate of the glacier.

The research was supported by the DOMINOS project, a component of the International Thwaites Glacier Collaboration, and by the National Science Foundation (grant number 1738896) and the Natural Environment Research Council (grant number NE / S006605 / 1).

The International Thwaites Glacier Collaboration (ITGC) is a five-year, joint US and UK $ 50 million mission to learn more about Thwaites Glacier, its past and what the future holds. Significant research contributions also come from Sweden, Germany and South Korea. The ultimate goal of the project is to predict to what extent Thwaites will contribute to global sea level rise and how soon a transition to faster ice retreat could occur. ITGC is funded by the National Science Foundation (NSF) of the United States and the Natural Environment Research Council (NERC) of the United Kingdom.

Pack ice is a large floating shelf of ice that forms where a glacier or ice cap flows to a shoreline and across the ocean surface. Ice shelves are found only in Antarctica, Greenland, Canada and the Russian Arctic.

The ice cap, also known as the continental glacier, is a mass of glacial ice that covers the surrounding terrain and measures over 50,000 km2 (19,000 square miles).

The glacier is a huge mass of ice that moves slowly across the land. The term “glacier” comes from the French word glace (glah-SAY), which means ice. Glaciers are often called “rivers of ice”.

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