The East Antarctic Ice Sheet repeatedly melted back several hundred miles inland during several warming periods 3 million to 5 million years ago in the Pliocene Epoch, according to a new study in the journal Nature Geoscience.
While most of the West Antarctica and Greenland ice sheets are thought to have melted during this time, the East Antarctic Ice Sheet was considered more stable due to its larger size and higher elevation. The study shows that the East Antarctic ice sheet is also vulnerable to substantial melting under warmer climates than today.
During the Pliocene, seas are thought to have risen up to 70 feet higher than today due to the melting ice sheets, about half of which may have come from East Antarctica. It is not well know how fast sea levels rose, but it is currently understood to take millennia.
The research team say understanding this glacial melting during the Pliocene Epoch may give us insights into how sea levels could rise as a consequence of current global warming. This is because the Pliocene Epoch had carbon dioxide concentrations similar to now and global temperatures comparable to those predicted for the end of this century.
“We suspected from the sea level estimates that East Antarctic ice was at risk from warming, but this is the first good evidence from East Antarctica itself that the ice on low-lying areas melted back repeatedly during the Pliocene,” said study coauthor Trevor Williams, a marine geologist at Columbia University’s Lamont-Doherty Earth Observatory.
Roughly the size of Australia, the East Antarctic Ice Sheet is the largest ice mass on Earth. Its size has ebbed and flowed from its formation 34 million years ago to about 14 million years ago, when scientists believe the ice sheet stabilized. But the study results suggest that the East Antarctic Ice Sheet was more sensitive to Pliocene warming than previously thought. Carbon dioxide levels at the time were roughly the same as they are today, at 400 parts per million, while temperatures were 3 to 5 degrees F higher—within the range projected for 2100.