ACES · Antarctic Cyclones: Expression in Sea Ice

The Amundsen Sea Low (ASL) is an atmospheric low pressure system that sits over the Pacific sector of the Southern Ocean. Variations in the position and strength of the ASL have a strong influence on Antarctic climate change, controlling both Antarctic sea-ice trends and ocean melting of the Antarctic Ice Sheet. However, the classical view of the ASL as a large, smooth region of low pressure is misleading. The ASL is an average of many short-lived atmospheric cyclones, and the effect of the ASL on local climate is the highly non-linear net effect of these cyclones. ACES will investigate the role of the individual cyclones and their net effect on the changing climate of West Antarctica by achieving three main objectives:(1) Characterise the physics of cyclones by tracking them with machine learning algorithms in atmospheric re-analysis data and sea ice drift satellite observations. Elucidate cyclone-sea ice-ocean interactions using a model of individual cyclones.(2) Use the new understanding to improve a circum-Antarctic ice-ocean model, determining the effect of cyclone dynamics on hindcasts of ice shelf basal melting in West Antarctica.(3) Assess climate model representations of cyclone-sea ice-ocean interactions, enabling them to better represent past and future sea ice extent and future ice shelf basal melt rates.ACES will be the first attempt to comprehensively characterise the role of individual cyclones over sea ice. It will generate a solid physical understanding of cyclone-sea ice-ocean interactions, as well as improve past estimates of ice shelf basal melt rates and provide important feedback on the capability of climate models to represent Antarctic sea ice trends and ice shelf basal melt rates.