Frictionally Modified Continental Shelf Waves and the Subinertial Response to Wind and Deep-0cean Forcing

Abstract

Analytic solutions am obtained for the barotropic shelf circulation caused by wind and deep-ocean forcing at subinertial frequencies. An Inclined beach model of the continental shelf is used and only situations in which bottom friction is important are considered. Three different alongshore forces are considered: pressure gradients and currents (maintained by the deep ocean) at the shelf break and wind stress, over the shelf. In each case the model is formulated as a boundary value problem in which the boundary conditions are determined by the forcing mechanism. In general, a damped resonant response occurs when the forcing function has the same longshore velocity as an unforced continental shelf wave and is most significant for the fim mode. In the case of forcing by an alongshore pressure gradient at the edge of the shelf, this leads to the amplification of the pressure signal toward the coast. The model frequencies and structures are determined for various frictional values. When friction is small the results are consistent with those of Brink and Allen in that phase speeds remain unchanged and cross-shelf phase differences are introduced. At larger frictional values, however, phase speeds are reduced, and the model structures and cross-shelf phase differences are further altered.