Numerical study of the response of the Southern Ocean and its sea ice to a CO/sub 2/-induced atmospheric warming

A comprehensive coupled model of ocean circulation and sea ice has been developed to study a selected area of the Southern Ocean that includes the Weddell Sea and the Drake Passage. An existing general circulation model of the ocean was configured for the geometry of the Southern Ocean domain and then improved by including robust-diagnostic forcing and allowing for coupling to a sea-ice model. When the model was initially tested without coupling, the ocean circulation corresponded well with the observed circulation. In addition, a dynamic--thermodynamic model of sea ice was developed and tested with a constant upward oceanic heat flux. The results of two simulations made with the sea-ice model, with and without transport and dynamics, show that thermodynamics is insufficient to explain the large amplitude of the seasonal cycle of ice extent, and that the inclusion of transport and parameterized dynamics is essential for the reproduction of the observed cycle.