A numerical investigation of the transport process of dense shelf water from a continental shelf to a slope

Abstract

We investigate the offshore transport process of dense shelf water, using a three‐dimensional, primitive equation model. We focus on the effects of bottom topography, in particular, inclination of a bottom slope from a continental shelf to a deep basin. For the numerical domain we use an idealized bottom topography in which the bottom deepens gradually from a shallow continental shelf region to a steep slope region. In the continental shelf region we use a salt flux which represents the typical brine rejection in a coastal polynya. Results of the numerical experiments show that dense shelf water is transported offshore by eddy flux and a dense plume. The transport by eddy flux occurs mainly over a continental shelf, while that by the dense plume occurs over a continental slope. A boundary between the regions where the above two processes are dominant corresponds locally to a shelf break. A salinity front is developed in the boundary over the shelf break, separating the dense shelf water from the offshore water. We also investigate the stability of the surface westward current over the shelf break front, using a simple analytical model. The analytical model investigation shows that shelf break topography plays an important role in determining a neutral point of the stability of the shelf break current and preventing dense shelf water from being transported farther offshore by eddy flux. We suggest that eddy activity on a continental shelf contributes not only to the development of the shelf break front but also to the water exchange between a continental shelf and a slope region.