Currently stable parts of East Antarctica may be closer to melting than we imagine

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

In an article published on January 19 in Geophysical research lettersStanford researchers have shown that East Antarctica’s subglacial Wilkes Basin, which contains enough ice to raise sea levels more than 10 feet, may be closer to melting uncontrolled than we thought.

“There hasn’t been a lot of analysis in this area: there’s a huge volume of ice there, but it’s relatively stable,” said Eliza Dawson, a Ph.D. student in geophysics at Stanford and first author of 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 possible 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 about to melt. This raises the possibility that this coastal region, which holds ice throughout the Wilkes subglacial basin, may be sensitive to even small temperature changes.

A mixture of frozen and defrosted

Previous research has shown that because the soil in this region lies below sea level and extends away from the ocean, the Wilkes subglacial basin could be particularly vulnerable to irreversible melting if the Warming seawater was expected to pass beneath the ice sheet. Dawson and his colleagues are the first to examine how the current temperature at the base of the region’s ice sheet could increase this vulnerability.

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

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

Researchers found large areas of frozen and thawed ground scattered throughout the region, but the majority of the area could not be definitively classified as one or the other. In some cases, this may be due to changes in ice sheet geometry or other complications in the data, but it could also mean that large sections of soil beneath the ice sheet are either about to melt , or made up of closely mixed frozen earth. and thawed areas. If the latter hypothesis is true, glaciers in the Wilkes Subglacial Basin could reach a tipping point with only a slight increase in temperature at the base of the ice sheet.

“This suggests that glacier retreat may be possible in the future,” Dawson said. “This part of East Antarctica has been largely neglected, but we need to understand how it might evolve and become more unstable. What would need to happen to start seeing mass loss?”

Better forecasts 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 on the region. The researchers plan to integrate their radar-based temperature observations into an ice sheet model to improve predictions of how the region will evolve under various climate scenarios.

They hope their work will highlight the importance of examining this and other areas of East Antarctica that appear stable, but could play an important role in our future.

“This region has conditions that we could imagine changing,” Schroeder said. “And if warm ocean water gets there, it will ‘activate’ a whole sector of Antarctica that we don’t normally think of as contributing to sea level rise.”

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