The West Antarctic Ice Sheet

So far I have examined the recent climatic changes in the East Antarctic and Antarctic Peninsula, and the associated effects. The West Antarctic Ice Sheet (WAIS) tells yet another story.

Ice Shelves Matter!

Temperatures in West Antarctica, particularly in the Amundsen Sea region, have increased and glaciers have retreated in recent decades. The WAIS is inherently less stable than the East and vulnerable to anthropogenic climate change. As a Marine Ice Sheet (MIS) it is located mainly below sea level and its stability rests on the ice shelves which fringe its exterior. Ice shelves are floating tongues which act as a buttress to inland glaciers, but are vulnerable to rising ocean temperatures. 

Ice shelves buttress inland glaciers (Image: AntarcticGlaciers)

In fact the MIS instability hypothesis states that as ice shelves melt, grounding lines retreat and as a result the glacier rests on deeper water and the ice is thicker. This results in sustained ice losses in a positive feedback loop. (This complex process is well explained in the video below, fast forward to 2'30!)

In recent decades many ice shelves have thinned, leading to an increase in ice discharge. In the Amundsen Sea region studies have shown ice shelves are particularly vulnerable to warming oceans, which melt them from below. 

Channelised melt 

A recent study indicated that the Dotson, Crosson and Pine Island ice shelves have experienced rapid basal melting in recent decades, thinning by 2m per year on average. What is even more worrying is a channel which has recently been discovered under the Dotson ice shelf. Formed by Circumpolar Deep Water (CDW), this channel could cause the ice shelf to collapse in just 40 years, 170 years earlier than at current thinning rates. Similar channels are likely to be present beneath other ice shelves in the region, but few have been identified. This will have huge implications for WAIS stability. 

High resolution satellite data reveals a channel of high melt beneath the DIS (Image: Gourmelon et al., 2017)

Shrinking glaciers 

It is not just ice shelves which are vulnerable to climate change. A study of the Thwaites, Haynes, Smith and Kohler glaciers indicate retreat of 14km, 10km and 35km respectively between 1992 and 2011. These dramatic losses indicate that this section of the WAIS is starting to become more unstable. 

The implications of channelised melting, ice shelf collapse and the stability of the WAIS are closely linked. Recent studies suggest that the WAIS is indeed unstable and becoming more so. I will be examining the associated implications in a few weeks.