Melting Glaciers in East Antarctica Are More Vulnerable to Global Warming Than We Thought

Adelie penguins cross the ice at Cape Denison, in Commonwealth Bay in East Antarctica, on January 6, 2010. The melting of the Aurora Basin in East Antarctica could cause a sea level rise of 10 to 15 feet. Reuters

Enough water is frozen into the East Antarctic ice sheet that if all of it melted, it could raise sea levels nearly 174 feet. The ice sheet was previously believed to be much more stable, especially in comparison with its cousins: the West Antarctic and Greenland ice sheets. But a study published last Wednesday in Nature found it's more vulnerable than scientists thought.

As with much of climate science, a window into the past can reveal clues to our climate future. Ice cores document hundreds of years of snowfall history, revealing rapid snowfall increases seen in parts of the world today. A strange period in history of megadroughts helps us understand the likelihood of widespread drought today. And now, the history of East Antarctica's glaciers gleaned from mud samples, ancient pollen and marine seismic technology shows us the potential instability of the glaciers' future.

"It turns out that for much of the East Antarctic ice sheet's history, it was not the commonly perceived large stable ice sheet with only minor changes in size over millions of years," Sean Gulick, lead author and geophysics and geological sciences researcher at the University of Texas at Austin, said in a statement. "Rather, we have evidence for a very dynamic ice sheet that grew and shrank significantly between glacial and interglacial periods. There were also often long intervals of open water along the Sabrina Coast, with limited glacial influence."

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Crevasses in ice are viewed from NASA’s Operation IceBridge research aircraft, in the Antarctic Peninsula region, above Antarctica, on October 31. A recent study showed that the East Antarctic ice sheet was not the large stable ice sheet commonly perceived but a dynamic one that grew and shrank. Getty

Scientists from several universities used marine seismic technology deployed from an icebreaker in order to reconstruct how glaciers have changed over the past 50 million years along the Sabrina Coast. They also collected mud samples from three to six feet below the seafloor and ancient pollen. Their findings revealed that the basin has been retreating and advancing multiple times throughout its history—at least 11 in the first 20 million years. Early in its life, the ice sheet also had more meltwater on its surface, which can cause "tunnel valleys," eroding into the rock below the ice. These markers of instability occurred when atmospheric levels of carbon dioxide were similar to or higher than today's carbon dioxide levels.

"We shouldn't view this as one ice sheet that suddenly grew to its present size, but rather one that was a transient ice sheet that expanded every couple million years or so," Gulick said.

With carbon dioxide levels on the rise causing global temperatures to increase, East Antarctic glaciers could return to their historically unstable state. The Aurora Basin, where the Sabrina Coast is, was the key area of the study. Warm, nearby oceans make glaciers in this area of the ice sheet susceptible to melting. The melting of the Aurora Basin alone could cause the sea level to rise 10 to 15 feet. Warm water is already melting the Totten Glacier—the largest glacier in East Antarctica.

"The past behavior and dynamics of the Antarctic ice sheet are among the most important open questions in the scientific understanding of how the polar regions help to regulate global climate," Jennifer Burns, director of the National Science Foundation's Antarctic Integrated Science System Program, which funded the study, said in a statement. "This research provides an important piece to help solve that massive puzzle."