Models of Wind-Driven Currents on the Continental Shelf

Adjacent to the ocean shoreline, the continental shelves form regions of relatively shallow water for offshore distances that vary with geographical location, but are typically the order of 50-150 km. The sea floor slopes gently across the continental shelf from the coast to water depths of about 200 m, where an abrupt increase in slope generally occurs at the so-called shelf break. Seaward of the break, the continental slope extends down­ ward to the deep ocean floor over an additional horizontal distance of the order of 100 km. The motion of the oceanic waters over the continental shelf and slope is influenced by the earth's rotation, the density stratification, the offshore current regime, the sloping bottom topography, and the presence of a coastline. In particular, the topographic constraints of the coastline and shallow sloping bottom give the shelf flow field certain characteristics that differ from those typical of the deep ocean. 111 many instances, flow over the shelf may be considered independent of motions farther offshore. The physical oceanographic conditions on the shelf influence several important oceanic processes. For example, most of the biological primary productivity of the world's oceans takes place in the relatively fertile surface waters over the continental shelves. The biological phenomena involved there are highly dependent on the fluid mechanical processes on the shelf. Sediment transport and pollutant dispersion are other processes occurring over the shelf that are strongly affected by the properties of the fluid motion. Observational information on the nature of shelf flow fields has increased tremendously since the early 1970s with the development and