Sensitivity of Antarctic Basal Melt Rates to Precipitation

Ocean-driven melting of Antarctic ice shelves remains poorly understood and challenging to simulate, despite its importance for ice sheet stability and global sea level rise. As we seek to improve model representation of Antarctic melt, both over the historical period, and for future projections, we need to better understand how biases and uncertainty in forcing can affect the simulated ice shelf melt. In particular, climate models differ in the magnitude and spatial patterns of precipitation over the Southern Ocean and near the Antarctic coast. Biases in precipitation can have significant impact on the shelf water mass properties, sea ice production, convection and sub-ice shelf melt rates.

In this study, we examine the transient response of basal melt rates to precipitation, using a 5km-resolution pan-Antarctic ROMS configuration with thermodynamically coupled (static) ice-shelf cavities. We examine the impact of using a historical precipitation climatology derived from a climate model (ACCESS1.3 downscaled by MAR) vs. observations (Global Precipitation Climatology Project). We perform additional sensitivity experiments covering the spread of CMIP5 historical precipitation, providing insight on the processes governing the transient response of ocean properties, sea ice, and basal melt, as well as the timescales associated with these responses.