Importance of deformed ice in polar regions for climate models

Sea ice comes in a variety of sizes and shapes depending on the mechanical and thermodynamical events it has undergone. New ice offers little resistance to the winds and currents, while deformed ice contains hummocks and ridges that influence how heat and momentum are transferred at the atmosphere-ice-ocean interfaces. In most climate models, the surface fluxes are determined from "bulk formulas" with constant drag coefficients based on roughness length estimates. Therefore, these formulations do not account for the space-time variability of transfer coefficients due to variations in ice roughness. However, the ice roughness can be estimated from the models by quantifying the amount of deformed ice (Tsamados et al, 2013). To study the effect of ice deformation on the surface fluxes and the associated impact on the sea ice, we implement a tracer of deformed ice into the ocean-ice model NEMO-LIM3 v3.6 and modify the drag coefficients accordingly. From a run of NEMO-LIM3 between 1990 and 2010 at 1 degree resolution, we examine the spatial and temporal evolution of the drag coefficients in the Arctic and Antarctic regions. We investigate possible effects on the surface fluxes and impacts on the sea ice state. This study allows us to formulate an initial assessment on the importance of deformed ice variability for the current climate models.