Interannual-to-Multidecadal Responses of Antarctic Ice Shelf-Ocean Interaction and Coastal Water Masses during the Twentieth Century and the Early Twenty-First Century to Dynamic and Thermodynamic Forcing

摘要

Much attention has been paid to ocean-cryosphere interactions over the Southern Ocean. Basal melting of Antarctic ice shelves has been reported to be the primary ablation process for the Antarctic ice sheets. Warm waters on the continental shelf, such as Circumpolar Deep Water (CDW) and Antarctic Surface Water (AASW), play a critical role in active ice shelf basal melting. However, the temporal evolution and mechanisms of the basal melting and warm water intrusions throughout the twentieth century and the early twenty-first century have not been rigorously examined and are not fully understood. Here, we conduct a numerical experiment of an ocean-sea ice-ice shelf model forced with a century-long atmospheric reanalysis for the period 1900-2010. To begin with, we provide an assessment of the atmospheric conditions by comparing with available observation and show biases in warming and stronger westerly trends. Taking into account the limitation, we examine the interannual-to-multidecadal variability in the Antarctic ice shelf basal melting and the role of coastal water masses. A series of numerical experiments demonstrate that wind stress changes over the Southern Ocean drive enhanced poleward heat transport by stronger subpolar gyres and reduce coastal sea ice and cold-water formations, both of which result in an increased ocean heat flux into Antarctic ice shelf cavities. Furthermore, an increase of sea ice-free days leads to enhanced regional AASW contribution to the basal melting. This study demonstrates that changes in Antarctic coastal water masses are key metrics for better understanding of the ocean-cryosphere interaction over the Southern Ocean.