Abstract

An inertial multi-layer model of the recirculation gyres surrounding a separated boundary current is presented. The boundary current is defined to be separated when the upper layer thickness vanishes. The strong eastward flow found at the outcrop causes the circulation to extend to the bottom through baroclinic instability. In order to decrease the vertical shear responsible for the instability, the deep flow must also have maximum eastward velocity at the outcrop latitude. Thus the deep flow to the north of the outcrop (where no upper fluid is present) must move so as to keep velocity continuous. The eastward flowing deep water is returned in a westward flow to the south and north of the separation latitude. Thus in the upper layer we find a single anticyclonic gyre bounded by the outcrop latitude to the north, while the deep circulation is characterized by two almost antisymmetric counterrotating gyres. The recirculating gyres are defined as regions in which the flow conserves potential vorticity and Bernoulli function, and are surrounded by motionless fluid. The model predicts the location of the separation latitude and of the gyres' boundaries, together with the flow inside the gyres, as functions of the potential vorticity and Bernoulli function in each layer.

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