Towards ocean model simulations of the Southern Ocean and Antarctic ice shelf cavities forced by CMIP historical climate data

Ocean-driven melting of ice shelves is the primary cause of ice loss in Antarctica, ultimately leading to global sea-level rise. However, there is still much uncertainty over the interactions between physical processes that lead to this ocean-driven melting, such as the role of climate-driven wind changes, increasing air temperatures and changes in freshwater fluxes, such as precipitation and ice sheet runoff. The timescales over which the ice loss will occur and the subsequent potential for sea-level rise are also areas of uncertainty in need of further investigation. At present, many ocean models that provide data to drive ice sheet models, such as those in CMIP, do not accurately represent ocean conditions around Antarctica, for example due to low model resolution or a very simplified representation of ice shelves. Ice sheet models then use empirical schemes based on remote offshore ocean temperatures to estimate the ice shelf melt from CMIP models. As such, predictions of potential sea-level rise that depend on these simulations may in turn not be accurate. Improving the representation of ocean water masses and circulation on the continental shelves and underneath the ice shelves around Antarctica would therefore be a key improvement for forcing ice sheet models that are used for predicting ice loss related sea-level rise.

We present the results from a 1/4º resolution circum-Antarctic ocean model with a representation of ice shelf cavities and ice shelf melt, run over the historical period of 1850-2020, forced with UKESM 1.2 CMIP6 outputs. These historical outputs, alongside simulations to be run with projected SSP5-8.5 forcing, will aim to provide a better representation of water masses around Antarctica to force ice sheet models. Using these, we plan to further our understanding of the physical processes that drive ocean-driven melt, and derive climate transfer functions that can bridge the gap between ice sheet models and coarse resolution general circulation models.