Baroclinic Structure of the Abyssal Circulation and the Role of Meridional Topography

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  • 1 Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
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Abstract

A simple linear model of the abyssal circulation is studied in which a north-south topographic slope influences the interior and boundary-layer flow. As in an earlier study, the reversals of the meridional velocity in the abyssal interior are related to the longitudinal variation of upwelling into the main thermocline.

When the topography slopes in the anti-β sense (down to the north in the northern hemisphere) an eastern boundary current appears regardless of the magnitude of the slope. If the slope is weak, the eastern boundary current is broad and bottom trapped. As the slope becomes steeper, the current narrows and stretches vertically. At a critical value of the slope, for which the barotropic potential vorticity gradient changes sign, the eastern boundary current metamorphoses into a modified Munk layer.

For all values of the slope, a system of broad, baroclinic western boundary currents exist whose effects reach rather far into the interior.

Abstract

A simple linear model of the abyssal circulation is studied in which a north-south topographic slope influences the interior and boundary-layer flow. As in an earlier study, the reversals of the meridional velocity in the abyssal interior are related to the longitudinal variation of upwelling into the main thermocline.

When the topography slopes in the anti-β sense (down to the north in the northern hemisphere) an eastern boundary current appears regardless of the magnitude of the slope. If the slope is weak, the eastern boundary current is broad and bottom trapped. As the slope becomes steeper, the current narrows and stretches vertically. At a critical value of the slope, for which the barotropic potential vorticity gradient changes sign, the eastern boundary current metamorphoses into a modified Munk layer.

For all values of the slope, a system of broad, baroclinic western boundary currents exist whose effects reach rather far into the interior.

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