West Antarctic Surface Melt: Recent Drivers, Future Directions

Surface melting on ice sheets and ice shelves is a physical threshold of much climatic and geophysical significance. Wetting reduces albedo and encourages additional melt, runoff may contribute to ice-sheet mass loss, and penetration of meltwater to the glacier bed can lubricate faster flow and thereby increase mass loss by calving. Meltwater is also a major factor in ice-shelf collapse through wedging open of crevasses.

While fringing ice-shelf collapse along the Antarctic Peninsula is probably the best known example of the cryospheric response to a warming atmosphere (and ocean), surface melting is also present in inland portions of West Antarctica. In addition to potentially contributing to ice sheet dynamics, surface melt occurrence is a valuable proxy for changing atmospheric temperature conditions.

Combining satellite remote sensing with atmospheric modeling, we examine the 1988-2008 austral melt season to diagnose the meteorological conditions associated with melt events. In particular, we look at the December 1991/January 1992 surface melt event on the Ross Ice Shelf, the most extensive and longest such event in the period 1987-2008. Through this case study, we examine the utility and skill of our meteorological datasets (reanalyses, Polar WRF, selected CMIP5 GCMs) in the development of diagnostic tools for identifying surface melt as observed by satellite and simulated by regional and global models.

To assess GCM model skill in the recent, and to better appraise imminent work on future predictions, we compare warm-season climatologies derived from several CMIP5-class model simulations against observations and the ERA-Interim reanalysis. Sub-daily temperatures are compared where both model output and in-situ observations are available. Trends in the surface climate for the historical period are also examined in order to assess which models simulate the most realistic changes. Selected GCMs are used with Polar WRF for comparison with contemporary ERA-Interim-based results and future GCM-based simulations.

GCM projections, and downscaled simulations driven by them, will be used to assess the probability of melt on the Antarctic ice sheet and ice shelves in a changing climate. Recent glaciological work reveals that several ice shelves in the Peninsula and West Antarctica are already vulnerable to unusual summer warmth, as occurred in Greenland in summer 2012. Results from this project will help us understand where these trends are going in a warming world.