Topographic eddies in a stratified ocean

The generation of topographic eddies and wave wakes over low seamounts in vertically and horizontally sheared zonal currents is studied on the f- and beta-plane within the context of the baroclinic quasigeostrophic model. Water stratification and the vertical shear in velocity are shown to result in the joint effect of baroclinicity and a current velocity shift ('JEBACS'), which essentially transforms the manifestation of beta-effect on the beta-plane and can bring about pseudo beta-effect on the f-plane. Similar to the beta-effect, 'JEBACS' plays an important part in the generation of above- mountain topographic eddies and wave wakes. The spectrum of the Sturm-Liouville operator for vertical modes can have negative eigenvalues in the beginning of the spectrum not only on the beta-plane but also on the f-plane. The negative eigenvalues in the spectrum result in the appearance of wave modes in the respective Helmholtz operator. The wave modes account for wave wakes behind seamounts. Captured Rossby waves, which always appear in any homogeneous eastward flow behind a seamount on the beta-plane, may not appear in flows with vertical shear in velocity, even though these flows axe also directed eastward. In this context, it was shown that the use of averaged velocities with the aim to derive the conclusion regarding the generation of waves that form the wave wake can be incorrect in the case of flows with vertical shift. This is an important distinction of the flows with velocity shift from homogenous flow in the case of flows around seamounts.