The Effect of the Amundsen Sea Freshwater Balance on Ocean Melting of the West Antarctic Ice Sheet

The Amundsen Sea has some of the highest thinning rates of ice shelves in Antarctica. This is thought to be caused by increased ocean melting due to warm Circumpolar Deep Water (CDW) intrusions onto the continental shelf in the region, with these intrusions having a large inter-annual variability. The resulting changing fresh water balance in the region could affect the currents and mixing, due to density being strongly dictated by salinity in the Polar Regions. However, a clear understanding of the sources and sinks of fresh water in the region is lacking. Therefore a MITgcm model of the Amundsen Sea region, with passive freshwater tracers, is used to investigate the relative magnitudes and climatological spatial distributions of the different freshwater components. An analysis of the freshwater components’ inter-annual variability is presented, along with their effects on the variability of ice shelf melting. The effect of including grounded icebergs and their fresh water flux is studied in detail. The presence of icebergs increases CDW intrusions that reach the base of ice shelves. This provides a possible feedback mechanism whereby more icebergs induce greater ice shelf melting and hence more icebergs. However the strength of this feedback is found to be dependent on the poorly constrained sea ice atmosphere drag parameter.