We use a multicategory sea ice model coupled to the Princeton ocean model, which is driven by monthly climatological atmospheric forcing, to study the seasonal variation of ice cover in the Labrador Sea. Initial ocean conditions are derived from a gridded, objectively analyzed temperature-salinity data set that provides improved resolution of gradients in the vicinity of the shelf break. The model produces a realistic seasonal variation of sea ice. There is ice growth over the inner shelf and ice melt over the outer shelf and slope. Over the inner shelf, advection and diffusion decrease the ice mass; over the outer shelf, advection and diffusion increase the ice mass, which maintains the location of the ice edge. Near the offshore ice edge the melt rate exceeds 1 m per month, and the heat to melt ice together with the heat lost to the atmosphere exceeds 500 W m-2. The heat lost at the ocean surface is compensated for by advection of heat from an offshore convective region. The dominant heat source for the spring retreat of ice in the south is shortwave radiation over the open water fraction. ¿ 2000 American Geophysical Union