In the spring of 2002, a large chunk of the Larsen B ice shelf (LIS-B) on the Antarctic Peninsula broke off and tumbled into the Weddell Sea. A new analysis published today in the journal Nature suggests that the more than 3,200 square kilometer area that collapsed signifies an unprecedented loss in the past 10,000 years and can be attributed to accelerated climate warming in the region.

Eugene Domack of Hamilton College and his colleagues studied six sediment cores collected from the area around the ice shelf as well as other data, such as temperature and salinity measurements of the Weddell Sea. The results indicate that LIS-B has been stable since the Late Pleistocene to Holocene transition, which occurred 11,500 years ago. The ice shelf had been thinning slowly, however, which was evidenced by a change in the oxygen isotopes present in plankton preserved from the underlying water column. The team calculates that the glacier thinned by a few tens of meters over the course of thousands of years.

Local temperatures on the Antarctic Peninsula, meanwhile, have risen by about two degrees Celsius over the past 50 years, an increase that is more pronounced than in other regions of the world. The authors write that their observation that the modern collapse of the LIS-B is a unique event supports the hypothesis that the current warming trend in the northwestern Weddell Sea is longer and bigger than past warm episodes. Together with the slow thinning, it was this prolonged period of warming that led to LIS-B's collapse, they conclude.