February 26, 2024

Currently stable parts of East Antarctica may be closer to melting than previously thought

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Collecting ground-based radar data to image kilometers of ice with electromagnetic waves. Credit: Eliza Dawson

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Collecting ground-based radar data to image kilometers of ice with electromagnetic waves. Credit: Eliza Dawson

In a warmer climate, Antarctic meltwater is expected to contribute significantly to rising seas. For the most part, however, research has focused on West Antarctica, in places like the Thwaites Glacier, which has undergone significant melting in recent decades.

In an article published on January 19 in Geophysical Research LettersStanford researchers have demonstrated that the Wilkes Subglacial Basin in East Antarctica, which contains enough ice to raise global sea levels by more than 3 meters, may be closer to runaway melting than previously thought.

“There haven’t been a lot of analyzes in this region — there’s a huge volume of ice there, but it’s been relatively stable,” said Eliza Dawson, a Ph.D. geophysics student at Stanford and first author on the paper. “We are looking for the first time at the temperature at the base of the ice sheet and how close it is to potential melting.”

The Wilkes Subglacial Basin is about the size of California and empties into the Southern Ocean through a relatively small section of coastline. Dawson and his colleagues found evidence that the base of the ice sheet is close to melting. This raises the possibility that this coastal region, which holds ice within the entire Wilkes Subglacial Basin, may be sensitive to even small changes in temperature.

A mix of frozen and thawed

Previous research has shown that because the land in this region is below sea level and slopes downward away from the ocean, the Wilkes Subglacial Basin could be particularly vulnerable to irreversible melting if warming seawater passes downward. of the ice sheet. Dawson and his colleagues are the first to analyze how current temperatures at the base of the region’s ice sheet may contribute to this vulnerability.

The researchers collected data from existing radar surveys conducted by planes flying over the glacier. The planes record reflections of electromagnetic signals that have traveled through the ice sheet and bounced off the ground beneath it. Dawson and his colleagues developed a new technique to analyze this data, transforming cross-sectional images of ice and rock into information about temperature conditions at the base of the ice sheet.

“Ice temperature affects how much radar is reflected in several ways, so a single measurement is ambiguous,” said Dustin Schroeder, associate professor of geophysics and electrical engineering. “This statistical approach essentially involved choosing regions that could be assumed to be frozen or thawed and comparing other radar signatures to them. It allowed us to tell whether other areas of the ice sheet were definitely frozen, definitely thawed, or difficult to identify. identify.”


The LC-130 Hercules picks up scientists at McMurdo Station in Antarctica at the end of the field season, bound for Christchurch, New Zealand. Credit: Eliza Dawson

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The LC-130 Hercules picks up scientists at McMurdo Station in Antarctica at the end of the field season, bound for Christchurch, New Zealand. Credit: Eliza Dawson

The researchers found large areas of frozen and thawed ground interspersed throughout the region, but most of the area could not be definitively classified as one or the other. In some cases, this may be due to changes in the geometry of the ice sheet or other complications in the data, but it may also mean that large sections of ground beneath the ice sheet are close to melting or are made up of closely intermixed frozen layers. . and thawed areas. If this is true, the Wilkes Subglacial Basin glaciers could reach a tipping point with just a small increase in temperature at the base of the ice sheet.

“This suggests that glacial retreat may be possible in the future,” Dawson said. “This part of East Antarctica has been largely ignored, but we need to understand how it could evolve and become more unstable.

Best predictions for East Antarctica

Different models predicted very different futures for the Wilkes Subglacial Basin and its impact on sea level rise because there simply wasn’t enough data about the region. The researchers are planning to integrate their radar-based temperature observations into an ice sheet model to improve predictions about how the region will evolve under various climate scenarios.

They hope their work highlights the importance of examining this and other areas of East Antarctica that have seemed stable but could play a significant role in our future.

“This area has conditions that we could imagine changing,” Schroeder said. “And if warm ocean water gets there, it will ‘turn on’ an entire sector of Antarctica that we don’t normally think of as a contributor to sea level rise.”

Schroeder is a senior fellow at the Stanford Woods Institute for the Environment and an affiliate faculty at the Stanford Institute for Human-Centered Artificial Intelligence. Additional co-authors are from the Georgia Institute of Technology, the Alfred Wegener Institute for Polar and Marine Research, Ludwig Maximilian University Munich, and Dartmouth College.

More information:
Eliza J. Dawson et al, Heterogeneous basal thermal conditions underpinning the Adélie-George V coast, East Antarctica, Geophysical Research Letters (2024). DOI: 10.1029/2023GL105450

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