Abstract

The melting of Antarctic ice sheets is a major potential driving force for global sea-level rise. One process responsible for Antarctic ice sheet melt is the intrusion of warm circumpolar deep water (CDW) onto the continental shelf, triggering basal melt at the ice sheet grounding line. However, the mechanisms responsible for driving on-shelf CDW intrusions are not well understood. Here we examine how sea surface height (SSH) anomalies propagating around the Antarctic coastline as coastal-trapped waves can drive warm water intrusions through changes in bottom Ekman transport. A wind perturbation motivated by the recent intensification and poleward shift of the Southern Annular Mode (SAM) during its positive phase is applied over Eastern Antarctica between 20◦ E-120◦ E in two global ocean sea-ice models (1/4◦ and 1/10◦) and a single-layer shallow-water model. The changes in winds generate a drop in coastal SSH that propagates around Antarctica as a barotropic Kelvin wave. The SSH drop is accompanied by a barotropic flow which alters the bottom stress, generating an onshore transport of warm water wherever thermal gradients are favourable. We estimate the resulting anomalous bottom Ekman flow and use temperature gradients calculated from the Southern Ocean State Estimate (SOSE), along with the 1/4◦ and 1/10◦ models, to estimate the resultant anomalous temperature advection. We find an average anomalous subsurface warming of 0.1-0.7◦C in 1 year along the West Antarctic Peninsula.