Improving the Dynamic Coupling of Sea-ice and Ocean Models

The separation of sea-ice and ocean models and the choice of coupling scheme can lead to a number of instabilities (e.g. inertial-stress instability, gravity-wave instability, and thermodynamic instability). Higher frequency coupling, which increases the computational cost of simulations, or artificially weakening the physical link between the sea-ice and ocean can often reduce the development of these instabilities. To fully address the fundamental tight dynamic coupling of ice floating in water a different coupling scheme that does not treat the sea-ice and ocean as separate components is needed. By integrating the sea-ice rheology and dynamics, which evolve on timescales of minutes, into the timestepping of the barotropic ocean dynamics, the pressure force of sea-ice on the ocean and the resulting gravity waves can be resolved. Evolving the sea-ice and barotropic ocean dynamics simultaneously is referred to as “embedded” coupling; the slower interactions between the sea ice and the ocean (such as melting and freezing) would remain coupled on the longer timescales. This coupling scheme will be described in relation to a concurrent coupling scheme and intermediate “interspersed” coupling scheme. The impacts of these coupling schemes in MOM6/SIS2 on the sea-ice and ocean state will be shown in idealized and regional Arctic simulations.