The soil of the vulnerable Thwaites Glacier favors its resistance

June 1 () –

The ground under Antarctica’s most vulnerable megaglacier, the Thwaites, has been mapped for the first time. which will help scientists better understand how climate change affects it.

published in magazine ‘Science Advances’analysis of the geology under the Thwaites Glacier in West Antarctica shows that there is less sedimentary rock than expected, a finding that could affect how the ice slides and melts for decades to come.

“The sediments allow for faster flow, like sliding over mud,” said Dr. Tom Jordan, a British Antarctic Survey (BAS) geophysicist, who led the study. “Now that we have a map of where they are the slippery sediments, we can better predict how the glacier will behave in the future as it recedes.”

The distribution of sedimentary rocks under the Thwaites Glacier is included in a new map of the region’s geology produced by the BAS researchers. The findings are important because the glacier, which is the size of Great Britain or the US state of Florida, It is one of the most rapidly changing ice-ocean systems in Antarctica.

The Thwaites Glacier’s contact zone with the seafloor has receded 14 km since the late 1990s. Much of the ice sheet is below sea level and is susceptible to rapid and irreversible ice loss that it could raise global sea level by more than half a meter in a matter of centuries.

The new analysis is based on aerial surveys carried out with planes equipped with radars capable of seeing rocks through ice, as well as sensors capable of mapping minute variations in gravity and magnetism hundreds or thousands of meters below ground and the seabed on which the glacier rests.

Researchers use these multiple data sources to compile a three-dimensional picture of the features, including the type and extent of the various rocks.

Jordan states that “the integrated nature of the aerial surveys was one of the keys to this investigation. Each sensor on the aircraft provided an important but incomplete part of the image, but by putting them all together we were able to provide the detailed map of the underlying geology.”

In doing so, the study turns back the geological clock to examine what happened when New Zealand was torn from Antarctica around 100 million years ago, long before the Thwaites Glacier formed.

Since the base of Thwaites Glacier lies well below sea level, the researchers expected that thick sediments would have been deposited there over the ensuing millions of years. Similar analyzes have been carried out on other Antarctic glaciers, who have shown that coarse sediments predominated in these systems.

But the data from the aircraft suggest that only a fifth of the ground under the glacier is sedimentary rock. It is a series of basins between 80 and 200 km long and about 30 km wide.

The remainder is made up of other types of geological bodies, such as granite peaks and other hard rocks. Scientists believe that these sedimentary basins were once much larger, but that the movement of the glacier has reduced them to bedrock.

It is not yet clear how this new understanding of subglacial geology will affect estimates of flow and ice loss from Thwaites and other glaciers. The study demonstrates that the geologic landscape has direct control over basal shear stress, which influences the rate at which ice can flow into the ocean.

Members of the research team will now carry out more detailed studies of these processes. Modelers will also be able to use the new data to make more reliable projections of future ice loss.

“We hope that by showing detailed geology, and how it correlates with basal friction, future models of glacial retreat will have less uncertainty, as the controls of basal processes will be better understood,” Jordan says.

And he adds that “no isolated scientific study can ever match the magnitude and challenge of climate change, but it is the incremental construction of all individual scientific studies like this one that allows us to understand and address that challenge.“.

For her part, Dr. Sarah Thompson, a glaciologist and co-author of the study, highlights that “the integrated approach used in this study has significant potential for its successful application elsewhere in Antarctica, allowing us to explore other potentially vulnerable regions.” where current knowledge is scant.