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Abstract. 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. In this study we investigate the seasonal evolution of sea ice over the Labrador shelf with a coupled ice-ocean model. Our objective is to assess the capability of the model in simulating the evolution of the ice cover and to identify model deficiencies. We examine the processes that limit the ice extent.Labrador sea ice has been the subject of a number of studies with numerical models.

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This paper investigates the formation and maintenance of the North Water Polynya, Baffin Bay in winter using a multi-category sea-ice model coupled with the Princeton ocean model. Monthly climatological atmospheric data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis provides the forcing. An objectively-analysed climatology provides the initial ocean temperature and salinity. Wind stress drives the ice in a cyclonic gyre around northern Baffin Bay. Localized regions of thin ice form where wind drives ice away from coastlines or fast ice. The regions of thin ice are characterized by enhanced ice growth, exceeding 1.2 m mo -1 . In the regions of thin ice, surface ocean heat flux is also enhanced and is between 30-60 W m -2 . Surface heat flux is, in part, attributable to convective mixing and entrainment driven by ice growth. The surface heat flux reflects advection of the warm West Greenland Current. Heat and salt balances show that horizontal advective exchange counterbalances surface fluxes of heat and salt. RÉSUMÉ [traduit par la rédaction] Cet article examine la formation et le maintien de la polynie des eaux du Nord dans la baie de Baffin en hiver au moyen d'un modèle de glace de mer multicatégorie couplé au modèle océanique de Princeton. La nouvelle analyse des données climatologiques mensuelles de l'atmosphère faite par les National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) fournit le forçage. Une climatologie analysée objectivement fournit la température et la salinité initiales de l'océan. La poussée du vent soumet la glace à une circulation cyclonique dans le nord de la baie de Baffin. De la glace mince se forme par endroits, là où le vent éloigne la glace des côtes ou de la banquise côtière. Les régions de glace mince sont caractérisées par un fort taux de croissance de la glace dépassant 1,2 m par mois. Dans les régions de glace mince, le flux de chaleur en provenance de la surface de l'océan est également accru et se situe entre 30 et 60 W m -2 . Le flux de chaleur en surface est en partie attribuable au mélange convectif et à l'entraînement causé par la croissance de la glace. Ce flux de chaleur reflète l'advection du courant groenlandais de l'Ouest chaud. L'équilibre de chaleur et de salinité montre que des échanges advectifs horizontaux font contre-partie aux flux de chaleur et d'humidité en surface.