Clement Rousset and Marie-Noelle Houssais, LODYC, Universite Paris VI, Paris, France
The thermohaline circulation in the North Atlantic is partly fed by the dense water overflow through the Greenland-Scotland Ridge. The dense waters originate upstream in the Arctic Ocean or in the GIN (Greenland-Iceland- Norwegian) seas through the coupling between a convective basin and a warm boundary current from the Atlantic Ocean. The exact composition of the dense water outflow is however not well known, nor is its long-term variability well understood. The above questions are addressed based on two approaches. First, using a large-scale coupled ice-ocean model, the interannual variability of the convection in the Greenland Sea is analysed together with its possible link to the Denmark Strait overflow variability. In a second step, the relation between the dense water outflow and the transformation processes upstream in the GIN seas will be examined based on a high resolution version of the Miami model, MICOM, implemented with idealized geometry and forcing representative of the GIN seas. Special attention will be paid to the interaction between the boundary current and the gyre interior in order to understand the formation, the pathway, and the export of the dense water over the exit sill.