Simulations of the annual sea-ice cover in the Weddell Sea

van Ypersele de Strihou, Jean-Pascal [UCL] Demuth, C.

A modelof sea-ice formation has been developed and applied to a sector of the Southern Ocean, including the Weddell Sea and the Drake Passage; it describes the annual cycle of sea-ice thickness and its spatial extent. This sea-ice model with leads consists of two parts: - the thermodynamical component which manages the freezing and melting processes due to energy fluxes between the atmosphere, ice and ocean. This component computes also the heat and salt transfers between mixed layer and deep ocean; - the dynamical component limited in the present version of the model to the computation of ice movement due to wind and surface current. The surface energy budget, heat and salt exchanges and momentum transfers are modelled and/or parameterised frorn monthly-averaged climatological data (wind, air temperature, dew point, cloudiness and snowfall) and annually- averaged values of temperature and salinity in the ocean. These data and the results of the sea-ice model, including ice thickness, temperature, mixed-layer depth and ice extent, are presented and discussed at specific points (offshore and coastal) and for the whole area. The sea-ice model has been applied to the Weddell Sea according to two methods: the "layer method" where the ocean depth is limited to a chosen value and the "robust-diagnostic method" where the obervations constrain the model with a short damping time. The results of both methods show good agreement with the observed amplitude for ice extent and the mean oceanic heat fluxes exchanged between ice and ocean. The sea-ice model using the robust-diagnostic method gives a smaller ice thickness than the layer method and better conserves salt and energy.