A NUMERICAL STUDY OF DENSE WATER FORMATION AND TRANSPORT ON A SHALLOW, SLOPING CONTINENTAL-SHELF

The circulation and transport of dense water generated by an idealized coastal polynya is studied using a three-dimensional primitive equati on model. Starting with a homogeneous, quiescent ocean, a constant neg ative buoyancy flux is imposed at the surface over a half-elliptical r egion adjacent to the coastal boundary on a gently sloping continental shelf. The flow response can be divided into the following three phas es: geostrophic adjustment, instability, and offshore eddy transport. During geostrophic adjustment the fluid within the forcing region beco mes denser and the flow at the edge of the forcing region accelerates in response to the strong density gradient there. Eventually, the flow at the leading edge of the forcing region (relative to Kelvin wave pr opagation) becomes unstable and a train of counterrotating eddies deve lops. These eddies then form a complex three-dimensional flow field an d rapidly transport dense water offshore, across isobaths. The density within the forcing region reaches a maximum which remains fairly cons tant after the eddies begin to transport the dense fluid offshore. The results are qualitatively insensitive to weakening of the negative bu oyancy forcing and to changing the bottom slope. Eddy scales and veloc ities are consistent with observations in the Arctic. The results sugg est that instability processes and eddy fluxes are important in transp orting dense water off continental shelves and into marginal seas.