A global ocean general circulation model has been coupled with a dynamic
thermodynamic sea-ice model. This model has been spun-up in a 1000 year
integration using daily atmosphere model data. Main water masses and
currents are reproduced as well as the seasonal characteristics of the ice
cover of the Northern and Southern Hemispheres. Model results for the
Southern Ocean, however, show the ice cover as too thin, and there are large
permanent polynyas in the Weddell and Ross Seas. These polynyas are due to a
large upward oceanic heat flux caused by haline rejection during the
freezing of sea ice. Sensitivity studies were performed to test several ways
of treating the sea-surface salinity and the rejected brine. The impact on
the ice cover, water-mass characteristics, and ocean circulation are
described.