The hydraulics of local separation applied to middle layer upwelling at the exit of Shelikof Strait, northwest Gulf of Alaska

Oceanic upwelling/downwelling is generally understood from the viewpoint of ageostrophic current divergence. However, this theory does not explain the middle layer (120–200 m) upwelling around the southern coast of the Shelikof Strait exit, northwest Gulf of Alaska. Hence, the present study investigates the mechanism of this internal upwelling. An analysis of the simulation results for the climatological January mean indicates that this middle layer upwelling coexists with a barotropic geostrophic current, which crosses the iso-depth of an inclined isopycnal surface. This upsloping flow (upsloping relative to a geopotential surface) is represented by the Montgomery stream function on the isopycnal layer at $$\:1025.62\pm\:0.01\:\text{kg/}{\text{m}}^{\text{3}}.$$ Regarding the formation of the barotropic flow which crosses isopycnal depth contours, hereinafter referred to as the barotropic cross-isopycnal-depth current, the mean current separation when moving from a straight coastline to a convex coastline is solved in the second shelf mode of the coastal hydraulics; this forms a recirculation, which crosses the depth contours of the isopycnal surface downstream from the separation.