Effect of Ocean Warming on West Antarctic Ice Streams and Ice Shelves

The Intergovernmental Panel on Climate Change (IPCC) has deemed the Western Antarctic Ice Sheet (WAIS) as very likely to have contributed to sea level rice over the past two decades, estimating a loss of 44 ±13 Gt/yr. Focus has shifted to the behavior and dynamics of the WAIS ice streams since ~90 % of the outward ice flux flows through the ice streams. The behavior and movement of the ice streams is directly coupled with the condition of the ice shelves they flow onto. Recent satellite radar altimetry observations have shown that the three main ice shelves in the Amundsen Sea have simultaneously decreased in elevation, pointing to warming oceans as the common cause. Warming oceans have increased basal melting at the bottom of the ice shelves, causing them to thin. Models have shown that the increased basal melting can produce perturbations at the grounding line that will cause upstream ice to thin at distances ~200 km from the grounding line. This additional coupling of the ice stream to inland ice has signified a potentially dangerous instability of the WAIS that could cause it to eventually enter a rapid " collapse " phase where it would contribute 60-120 cm of sea level rise for 5-7 centuries. In terms of anthropogenic forcing, increased precipitation accompanying rising global temperatures may have decreased the salinity of the surrounding oceans, decoupling the warm ocean surface with the colder deep waters. The result is the possible warming of the surface and subsurface waters, leading to the basal melting of the ice shelves. So far, computer models have not been able to fully implement all of the dynamic forces involved with the flow of the ice streams, so the stability issue of the WAIS is not fully resolved. Nevertheless, the combination of observations of ice shelf thinning and model predictions of inland thinning demand that more attention should be spent to modeling ice streams and monitoring ocean conditions.