On the Dynamics of β Plumes

Abstract

The dynamics of zonal recirculating flows (? plumes) driven by a source of potential vorticity, or a sink of mass, located at the eastern boundary of an ocean basin are investigated using analytical solutions of the barotropic, linear, steady quasigeostrophic equation with bottom and lateral friction. By scaling the ratio of the strength of the recirculation to that of the sink by that from the inviscid solution, the regimes are identified in which friction becomes a dominant factor. The primary new finding of this study is that the recirculating flow component disappears due to frictional effects when the meridional extent of the sink becomes small. Unlike for the zonal extent of the sink, which affects the recirculating component only if it is on the order of the frictional boundary layer scale, the deviation of the recirculating flow strength from that given by the inviscid solution is apparent for meridional sink scales, which are much larger than the frictional boundary layer scale. Also, location of the maximum recirculation and westward penetration distance of the plumes are quantified. Finally, a stability analysis is conducted to determine the parameter regime in which the ? plumes are candidates for instability.