In the frame of a project on transport of contaminants in the Arctic, the Hamburg shelf ocean model (HAMSOM) is applied to the Kara Sea. The HAMSOM system consists of a three-dimensional, baroclinic circulation model coupled to a thermodynamic and dynamic sea ice model. The Kara Sea model is forced with climatological winds, atmospheric heat fluxes, river runoff, and tides. The obtained results reveal no typical Kara Sea circulation that prevails throughout the year. Instead, the model showed a strong seasonal variability in circulation and hydrography due to winds, freshwater runoff, and ice formation. The circulation is weakest in spring when the wind speeds are low and horizontal density gradients are small. Fresh water from the rivers spreads toward the north and northwest rather than forming a coastally trapped current that flows to the east. In autumn, the circulation is significantly enhanced because of increasing wind speeds and strong horizontal density gradients. Good agreement was found between model results and recent observations. The classical cyclonic current pattern in the southern Kara Sea, however, was not reproduced by the model. ¿ 1999 American Geophysical Union