The Southern Ocean, generally taken to be the ocean south of 60◦S, is of critical importance for global climate. Connecting three major ocean basins, it plays a major role in global ocean circulation via sea ice formation and is responsible for a large majority of global ocean heat and carbon uptake. Encircling the Antarctic continent, the Southern Ocean drives melt of the Antarctic ice sheet, which contains 60 m of potential global sea level rise—a major threat to societies around the world. Changes in the Southern Ocean may also impact the climate of other regions via atmospheric teleconnections. Antarctic climate variability arises as result of the tightly-coupled interactions between the Southern Ocean, its overlying atmosphere, the AIS and Antarctic sea ice and the response of these components to external forcing, which make this a highly complex system.

At its winter maximum, sea ice covers much of the Southern Ocean. Antarctic sea ice plays an important role in strong feedback loops with the ocean and atmosphere. From the beginning of the satellite era in the late 1970s, Antarctic sea ice expanded to a maximum in 2014. This puzzling behaviour is not captured by global climate models, casting doubt on global climate projections. Over the past decade, Antarctic sea ice has since decreased dramatically. It is unclear to what extent the changes are driven by internal variability versus the forced response to greenhouse gases, ozone and aerosols.

We aim to improve understanding of the Antarctic climate system and Southern Ocean sea ice on timescales relevant for modern climate. Working with state-of-the-art Earth system models, we will test the impact of different physical processes and model resolution. We are motivated to work towards improving earth system modelling for the polar regions and to provide societally-relevant climate information on expected changes this coming century.