Effects of bottom topography and density stratification on variations of western boundary currents caused by periodic change in wind stress

Abstract

Variations of the western boundary currents induced by a periodic change in wind stress are studied in a two-layer model with a continental slope along the western boundary. The variation of the total transport of the western boundary current over the continental slope shows a considerable phase lag with the wind stress and a decrease in amplitude compared with for the flat bottom ocean, though the interior barotropic response is to adjust almost instantaneously to the wind stress. The total transport variation of the western boundary current is well approximated by the upper layer transport variation. That is, almost complete separation of the upper- and lower-layer flows takes place over the slope, and only the upper layer flow contributes to the change in total transport of the western boundary current. Contributions of the interior barotropic and baroclinic responses to the upper layer transport variation depend on the forcing period. With decrease in the forcing period, the barotropic response becomes relatively important for determining the upper layer transport variation although the amplitude of the variation is smaller.