The Problem of Gulf Stream Separation: A Barotropic Approach

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  • 1 Institut für Meereskunde an der Universität Kiel, Kiel, Germany
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Abstract

Inertial separation of a western boundary current from an idealized continent is studied in a homogeneous ocean circulation model. A number of processes are identified that either encourage or prevent separation at a coastal promontory in this model. For a single-gyre wind forcing a free-slip boundary condition forces the stream to follow the coastline, whereas the no-slip condition allows separation at a sharp corner. A prescribed countergyre to the north of the stream is not necessary to achieve separation if the no-slip condition is used. “Premature” separation occurs for wind fields that do not extend beyond the latitude of the cape. For a more realistic wind field and coastline two distinct states of the stream are found. At small Reynolds numbers the current fails to separate and develops a stationary anticyclonic meander north of the cape. Stronger currents separate and drive a recirculation in the lee of the continent.

Abstract

Inertial separation of a western boundary current from an idealized continent is studied in a homogeneous ocean circulation model. A number of processes are identified that either encourage or prevent separation at a coastal promontory in this model. For a single-gyre wind forcing a free-slip boundary condition forces the stream to follow the coastline, whereas the no-slip condition allows separation at a sharp corner. A prescribed countergyre to the north of the stream is not necessary to achieve separation if the no-slip condition is used. “Premature” separation occurs for wind fields that do not extend beyond the latitude of the cape. For a more realistic wind field and coastline two distinct states of the stream are found. At small Reynolds numbers the current fails to separate and develops a stationary anticyclonic meander north of the cape. Stronger currents separate and drive a recirculation in the lee of the continent.

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