Strong and Stable: The East Antarctic Ice Sheet

Discussing climatic changes across the Antarctic continent as a whole can be misleading as the nature of the effects are spatially heterogeneous and complex. Last week, I examined the evidence for climate change in the Antarctic Peninsula and the associated effects. 

The East Antarctic Ice Sheet

Today, I will look more closely at the East Antarctic Ice Sheet (EAIS), which has received  less attention than the West Antarctic Ice Sheet (WAIS) in recent decades.  The EAIS is very very cold (-94.7°C has been recorded) and very very large (if it were to melt completely global sea level would rise by 53m).

The WAIS has thinned in recent decades. On the other hand, the EAIS has remained relatively stable and is growing in thickness, especially in interior areas, at a rate of 0.3cm a year. It is more stable because it rests on bedrock and has experienced less dramatic change in temperatures than the WAIS. 

A warm climate increases the moisture-carrying capacity of the air. Thus, higher temperatures have enhanced snow fall in East Antarctic and this trend matches the thickening throughout the interior. In fact, between 1992 and 2003 modelled data indicates a linear correlation of 0.41 (p<0.01) between snowfall and elevation change in East Antarctica. The size of East Antarctica means that even small increases in accumulation could have a huge effect on global sea level change, and could even balance out losses from the WAIS.

Elevation changes in Antarctica between 1992 and 2003, positive (red) and negative (blue) (Image: Davis et al., 2005)

However, Winkelmann et al., 2012 postulate that as the ice sheet grows under a warmer climate, dynamic ice losses could increase. This is perhaps counter intuitive, but the authors argue that increases in elevation (caused as snow accumulates) could cause more ice to be lost. Simply, as snow falls and ice sheets become thicker, the surface gradient near the grounding line becomes steeper, which increases driving stress on the ice flow. 

Enhanced snowfall under global warming (blue) leads to comparatively higher elevation and driving stresses on ice compared to a warming only scenario (red). Elevations remain constant on the ice shelf, as it floats, but increase on the ice sheet (Image: Winkelmann et al., 2012)

Across the EAIS many glaciers are in equilibrium or growing. However, in coastal area there are cases where glaciers are shrinking and accelerating. Pritchard et al., 2012 present evidence that ice shelf glaciers, including Totten, West Shackleton and the Holmes glacier, are shrinking through basal and surface melt. The Totten Glacier reportedly thinned by 10m between 1996 and 2012. 

Not that strong and stable then (sounds like someone else we know!)

Compared to the WAIS and Antarctic Peninsula the EAIS is relatively stable, yet it is not immune to climatic changes. Coastal areas in particular are experiencing the effects of our changing climate, but these are complex and difficult to predict.