Modelling Sea Ice in the Changing Arctic: A Combined Elastic-Viscous-Plastic and Collisional Rheology for Sea Ice

Exposure of large, previously ice-covered areas of the Arctic Ocean to the wind and surface ocean waves results in the Arctic pack ice cover becoming more fragmented and mobile, with large regions of ice cover evolving into the Marginal Ice Zone (MIZ). The need for better climate predictions, along with growing economic activity in the Polar Oceans, necessitates climate and forecasting models that can simulate fragmented sea ice with a greater fidelity. Current models are not fully fit for the purpose, since they neither model surface ocean waves in the MIZ nor include sea ice rheology that represents MIZ ice dynamics. We present initial results from a global ocean model NEMO (Nucleus for European Modelling of the Ocean) coupled to the Los Alamos sea ice model CICE. The model setup implements a novel rheological formulation for sea ice dynamics, accounting for ice floe collisions and effects of the ice floe size distribution, thus offering a seamless framework for pack ice and MIZ simulations. In the multidecadal model integrations we examine MIZ and basin scale sea ice and oceanic responses to the changes in ice rheology and floe size distribution. We analyse model sensitivities and attribute them to key sea ice and ocean dynamical-thermodynamical mechanisms. The results suggest that to make more accurate sea ice predictions in the changing Arctic, models need to include MIZ dynamics and physics.