A circumpolar model for regional studies of the wind-driven and thermohaline circulation of theSouthern Ocean is described. A first series of numerical experiments focusses on the WeddellSea. The results of 20-year integrations are compared to observations. Artificial passive tracersand Lagrangian floats are used to determine the pathways and time scales of water massspreading in the model. The effect of the sub-ice shelf forcing on the water mass characteristicsis evaluated.