Synchronous terminus change of East Antarctic outlet glaciers linked to climatic forcing

Abstract

In recent years there has been a growing trend of acceleration, thinning and retreat of ocean-terminating outlet glaciers in both the Greenland and West Antarctic Ice Sheets, resulting in an increasing contribution to sea level rise. Similar changes in glacier elevation have been observed in major marine basins of the much larger East Antarctic Ice Sheet, but there are few measurements of glacier terminus positions. In this study, the frontal position of 175 marine terminating glaciers along a 5,400 km stretch of the East Antarctic coastline is analysed. Overall, between 1974 and 2010 there was little change in glacier frontal position (median: 0.7 m a-1). However, strong decadal trends have been observed, from 1974 to 1990, the majority of glaciers retreated (63%), whereas between 1990 and 2000, most glaciers advanced (72%), a pattern which dropped to fewer glaciers advancing (58%) in the most recent decade (2000 to 2010). The patterns in glacier frontal position change are consistent with a rapid and coherent response to atmospheric and oceanic/sea-ice forcing, which are ultimately driven by the dominant mode of atmospheric variability in the Southern hemisphere, the Southern Annular Mode. This indicates that the East Antarctic Ice Sheet may be more vulnerable to climate change than previously recognised. However, unlike in Greenland, there appears to be no clear link between recent changes in glacier elevation and frontal position, possibly due to the unconstrained (~90%) nature of the majority of glaciers in the study area.