AIR-SEA INTERACTIONS OVER TERRA-NOVA BAY DURING WINTER - SIMULATION WITH A COUPLED ATMOSPHERE-POLYNYA MODEL

A preliminary simulation of the Terra Nova Bay polynya has been perfor med with a coupled atmosphere-polynya model. The atmospheric model is a hydrostatic primitive equations model that has been validated previo usly by a simulation of the strong katabatic winds observed in that ar ea. The polynya model includes a representation of the free drift of f razil ice and simple sea-ice dynamics and thermodynamics. Two and thre e-dimensional experiments have been performed under polar night condit ions. Two-dimensional experiments show that an open (warm) water area influences significantly the atmospheric circulation in the antarctic coastal zone: an additional ice-breeze effect is simulated and is resp onsible for the strenghthening of the katabatic winds near the coast. Because of the important temperature difference between the continenta l air and the ice-free ocean (up to 40 degrees C), strong surface heat fluxes are simulated over the polynya. Finally, a three-dimensional e xperiment has been performed. The integration domain includes Terra No va Bay. The polynya observed in that region is well simulated. It is f ound that heat losses from the polynya surface are stronger than previ ously thought but are probably constrained by the idealized representa tion of frazil ice, which is assumed to be uniform in each grid box. T his stresses the need for having a better knowledge of frazil ice evol ution in large polynyas.