The role of ice-ocean inertia in representing the impact of storms on sea ice in fully coupled Earth System Models
Tuesday, 16 December 2014: 10:35 AM
We present results from the first fully coupled ice-ocean inertial resolving simulations of the Community Earth System Model (CESM) using coupling techniques developed within the Regional Arctic System Model (RASM). RASM is a fully coupled pan-Arctic climate model that uses the same ocean, sea ice and coupling infrastructure as CESM, and is configured at a resolution of 1/12° for the ice-ocean models and 50 km for the atmosphere-land model components. However, we have changed the standard coupling configuration in RASM from the CESM standard daily oceanic coupling, so that each component model is coupled at the same sub-hourly interval, and satisfies important ice-ocean inertial stability criteria. These criteria result from representing combined ice-ocean Ekman transport as a system of two coupled oscillators within the sea ice and ocean models, respectively. If the coupling criteria are not satisfied, chaotic and potentially unstable ice-ocean motion may ensue. In RASM, this new coupling configuration produces sea ice inertial oscillations that closely match observed Arctic high-frequency drift. Applied to 1º CESM, this coupling configuration causes a significant reduction in pre-industrial Antarctic sea ice extent, and increases the seasonally averaged ice-ocean inertial speed up to an order of magnitude greater than for the standard CESM case. This work suggests that significant sea ice extent and thickness biases may exist in Earth System Model simulations where the sea ice response to storms is not fully resolved.