Rossby Wave-Induced Secondary Flows near Barriers, with Application to the Hawaiian Ridge

Abstract

We restudy the reflection of baroclinic Rossby waves from a nonzontal barrier. We add lateral friction to an earlier study by Mysak and Magaard to obtain a more realistic secondary flow near the barrier. Contrary to the earlier study, we not only calculate the Eulerian mean flow but also the Stokes drift associated with the incident and reflected waves. We apply our theory to the Hawaiian Ridge where the incidence wave field is known. Compared to the case of vanishing lateral friction, the Eulerian mean flow now shows smaller current speeds and wider current bands. The narrow eastward jet in the immediate neighborhood of the ridge is now replaced by a much weaker, broader eastward flow. The subsequent western boundary current and eastward countercurrent are now shifted farther away from the ridge in better agreement with White's analysis of historical temperature data. The Lagrangian mean flow is stronger than the Eulerian mean flow. Within the first 100 km off the ridge the two flows are mostly in opposite directions.