Remote Topographic Forcing of a Baroclinic Western Boundary Current: An Explanation for the Southland Current and the Pathway of the Subtropical Front East of New Zealand*

Abstract

Abstract The Southland Current is a western boundary current adjacent to the South Island of New Zealand and flows along a segment of the Southern Hemisphere subtropical front (STF). The physical mechanisms that govern the behavior of this current and other portions of the STF and subantarctic front (SAF) are investigated using one regional and three global ocean simulations. The three global ocean simulations used in this study are a 1½-layer reduced-gravity linear simulation, a six-layer nonlinear flat-bottom simulation, and a six-layer nonlinear simulation that incorporates vertically compressed, but otherwise realistic, bottom topography confined to the abyssal layer. All three simulations have horizontal spacings of ⅛° and are forced with climatological-mean monthly wind stress data. The regional simulation has a horizontal spacing of ½° and contains two layers, with an idealized bottom topography. The only forcing is supplied by inflow and outflow ports. The pathway of the SAF is shown to be strongl...