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Antarctica's grounding lines are retreating across the seafloor

"Our study provides clear evidence that retreat is happening across the ice sheet due to ocean melting at its base," said researcher Hannes Konrad.

By Brooks Hays
Antarctica's grounding lines are retreating across the seafloor
The first-ever complete map of Antarctica's grounding line. Photo by Hannes Konrad et al./University of Leeds

April 2 (UPI) -- The grounding lines of Antarctica are on the retreat on the ocean floor. According to a new study by scientists at the University of Leeds, warm ocean water is shrinking Antarctica's underwater footprint.

According to the new data, published this week in the journal Nature Geoscience, the Southern Ocean melted 565 square miles of underwater ice between 2010 and 2016.

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Antarctica's glaciers have been retreating at an average rate of 82 feet per year. But the rate retreat of the grounding lines of eight of the ice sheet's 65 largest glaciers is five times greater, roughly 410 feet per year.

The most dramatic rates of grounding line retreat were measured along the coast of West Antarctica.

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"Our study provides clear evidence that retreat is happening across the ice sheet due to ocean melting at its base, and not just at the few spots that have been mapped before now," lead researcher Hannes Konrad said. "This retreat has had a huge impact on inland glaciers, because releasing them from the sea bed removes friction, causing them to speed up and contribute to global sea level rise."

Scientists relied on data collected by the European Space Agency's CryoSat-2 to conduct their study. The satellite measures changes in ice sheet elevation. With knowledge of glacier and sea floor geometry, as well as the Archimedes principle of buoyancy, scientists can use the data to estimate the horizontal motion of the ice sheet's grounding line.

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"We were delighted at how well CryoSat-2 is able to detect the motion of Antarctica's grounding lines," said Andy Shepherd, professor of environmental science at Leeds. "They are impossible places to access from below, and usually invisible on the ground, so it's a fantastic illustration of the value of satellite measurements for identifying and understanding environmental change."

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Despite the alarming rates of grounding line retreat in West Antartica, scientists found evidence that Pine Island Glacier's groundling line has halted its losses. Until recently, the Pine Island Glacier was one of the ice sheet's fastest retreating glaciers.

"These differences emphasize the complex nature of ice sheet instability across the continent, and being able to detect them helps us to pinpoint areas that deserve further investigation," Konrad said.

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