Interannual and decadal variability of the ice-shelf basal melting in the Amundsen region, West Antarctica - Focus on the oceanic factors

Abstract:

Following observations of a drop in the West Antarctic Ice Sheet (WAIS) mass balance over the last few decades with the possibility to reach a tipping point leading to ineluctable glaciers outlets instability in the region, understanding the driving processes has become a priority. In particular, the Circumpolar Deep Water (CDW) intrusion in the Amundsen Sea is, nowadays, in the spotlight, and gathers the attention of both the observers and the modellers of the region. This modelling study presents the analysis of a 1/12°simulation of the Amundsen Sea sector focusing on the interannual and decadal variability. The development of a methodology to study the ocean dynamics and properties in the reference frame of the continental shelf break enables us to distinguish a western fresh shelf zone and an eastern warm shelf zone in the region, for which we characterize the ocean dynamics and properties, and suggest mechanisms driving the CDW inflow onto the continental shelf. In addition, connecting the ice shelves basal melt rates variability in the region with the ocean fluctuations at the shelf break as well as the global oceanic circulation in the Amundsen Sea, we propose key elements, which could drive the melt activity on the shelf. In particular, we draw attention to the sea ice effect in terms of Ekman pumping to the left of the eastward current along the shelf break, and we point out the possible initiation of a southern Antarctic Circumpolar Current (ACC) branch to the south-east of the Ross Gyre, which could control part of the variability along the Amundsen Sea shelf.