On the combined effects of surface heat and momentum fluxes on continental shelf baroclinic instability

Abstract

Idealized numerical experiments are used to study the effect of surface warming on wind-driven baroclinic instability over the continental shelf, i.e. where a coastal barrier and a sloping bottom are present. When winds, which are applied only for an initial period, are downwelling favorable, past results have shown that the primary instability occurs near the top of the bottom boundary layer, and so it is not surprising that sustained surface heating has little effect on instabilities in this case. When winds are upwelling favorable, the cold, relatively homogenous waters inshore of the upwelling front are warmed roughly uniformly, decreasing the density difference between upwelled and ambient waters. Thus, in this case, the ensuing Eddy Kinetic Energy is decreased (relative to the case with no heating) by up to more than 60% in the examples given. In addition, instability in the presence of combined upwelling favorable alongshore winds and modest surface cooling is also treated. Scalings are developed dealing these processes and are tested against model results.