Rossby Wave Driven Eulerian Mean Flows Along Non-Zonal Barriers, with Application to the Hawaiian Ridge

Abstract

Abstract We show that the reflection of baroclinic Rossby waves from a non-zonal barrier generates a Eulerian mean flow along the barrier. In order to produce a mean current of realistic magnitude, friction (in the form of Rayleigh damping) has to be incorporated into the theory. However, the wave-induced mean flow still exists in the absence of friction; the key requirement for mean flow production is the non-zonality of the reflecting wall. The theory is applied to the Hawaiian Ridge where the incident Rossby wave field is known for the 5° square 20–25°N, 155–160°W (Magaard, 1983). The mean flow produced by this incident wave field consists of 1) a narrow eastward coastal jet ∼20 km wide, and 2) a band-structured flow of alternating directions beyond the coastal jet. The width of each band in 2) is ∼50 km, and the envelope of the current oscillations decreases (from a maximum surface value of ∼0.75 m s−1) exponentially with distance from the Hawaiian Ridge. In the region between the western side of Maui...