Application of an atmospheric boundary layer model to a large-scale coupled sea-ice-oceanic mixed-layer model for the Southern Ocean
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A coupled sea-ice-oceanic mixed-layer model for the Southern Ocean is forced with daily atmospheric variables from the global analyses of the European Center for Medium Range Weather Forecasts (ECMWF). Using the analyses of the lowest level in the calculations of the turbulent heat fluxes and stresses with the appropriate bulk formulae, the simulation results resemble earlier ones with climatological forcing. In order to avoid a predetermination of the simulated sea-ice conditions from the (climatological) specification of the surface boundary conditions in the atmospheric general circulation model (AGCM), the sea-ice model is coupled additionally to a one-dimensional atmospheric boundary layer model. Using the global ECMWF-analyses as before, the coupled model is now forced from the geostrophic level (850 hPa). Without any changes of the original model parameters and physics, the results are rather poor in that the ice extent as well as the ice velocities are generally too low and that the ice thickness distribution resembles the results of a pure thermodynamic sea-ice model. The results with the forcing from the higher level are more realistic when snow and mixed-layer effects are neglected, thus resembling those of Koch (1988) in the Weddell Sea. This indicates that the parameterizations in the atmospheric boundary layer model have to be readjusted in order to interact realistically with the snow-sea-ice-oceanic mixed-layer model. Additionally, it will be demonstrated that the pattern of the wind field, whether from the geostrophic or the surface level, has a significant influence on the sea-ice model results.
