News Source: 
UW Today
January 2, 2014

Pine Island Glacier is one of the biggest routes for ice to flow from Antarctica into the sea. The floating ice shelf at the glacier’s tip has been melting and thinning for the past four decades, causing the glacier to speed up and discharge more ice.

Understanding this ice shelf is a key for predicting sea-level rise in a warming world. A paper published Jan. 2 in the advance online version of the journal Science shows that the ice shelf melting depends on the local wind direction, which is tied to tropical changes associated with El Niño.

The study, led by author Pierre Dutrieux at the British Antarctic Survey, uses new data to show how winds and topography control how much warm water reaches the ice shelf. University of Washington co-authors provided atmospheric modeling expertise to help interpret the observations and show how they are related to climate conditions in the tropical Pacific Ocean.

“These new results show that how much melt the Antarctic ice sheet experiences can be highly dependent on climatic conditions occurring elsewhere on the planet,” said co-author Eric Steig, a UW professor of Earth and space sciences.

The Pine Island ice shelf has thinned nearly continuously since observations began in the 1970s. Earlier studies have shown that warm deep-ocean water is melting the ice shelf from below, suggesting that warming global oceans are gradually targeting the underside of the ice sheet.  But the picture is more complex, say authors of the new study.  The deep ocean has been getting warmer but, more importantly, more warm water has been reaching the ice shelf.