East Antarctic ice may be more vulnerable to global warming than previously thought

Science : Because the East Antarctic Ice Sheet (EAIS) lies mostly on land, it had been thought to be less vulnerable to global warming than either Greenland or Antarctica’s western ice sheet, which lies mostly over water. However, Carys Cook of Imperial College London and colleagues, who have been studying deep sediment core samples collected by the Integrated Ocean Drilling Program, have found that during the Pliocene period some 3 million to 5 million years ago, when Earth was undergoing warming and carbon dioxide concentrations similar to today’s, parts of the Wilkes Land Subglacial Basin were ice free. In addition, some data suggest that sea levels were as much as 22 m higher than they are today, which would also indicate that significant portions of the EAIS had melted. Despite computer-modeling predictions that the eastern ice sheet has been relatively stable, it may actually have alternated between ice-free periods and glacial periods. How quickly it alternated—whether over hundreds or millions of years—has yet to be determined.