In the framework of the Bremerhaven Regional Ice Ocean Simulations a coupled sea ice-ocean model, based on a dynamic-thermodynamic sea ice model and the S-coordinate Primitive Equation Model, has been developed. The model is run on a circumpolar grid that is focused on the Weddell Sea. It includes the major Antarctic ice shelves; ice shelf-ocean interaction is described by the sea ice model's thermodynamic component. Numerical simulations are forced with 6 hourly data of the European Centre for Medium-Range Weather Forecasts reanalysis of the period 1985--1993 and validated against observations of hydrography as well as sea ice extent, thickness, and drift. Qualitatively and quantitatively, a good agreement with observations is achieved. The basin-wide circulation features a double-cell structure of the Weddell Gyre with maximum transports close to recent observations. Summer sea ice coverage is underestimated, but winter ice extent, as well as sea ice thickness and drift, is well reproduced.