The Wind-Driven Ocean Circulation with an Isopycnal-Thickness Mixing Parameterization

James C. McWilliams National Center for Atmospheric Research, Boulder, Colorado

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Peter R. Gent National Center for Atmospheric Research, Boulder, Colorado

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Abstract

Numerical solutions are examined for the nearly adiabatic, large-scale ocean circulation in a midlatitude, rectangular domain with steady wind driving. The model used is the balance equations and its various subsets; hence, dynamical effects at finite Rossby number are included. The solutions are steady ones, and the necessary transports by the missing mesoscale eddies are parameterized, in part, using the authors’ previous proposal for isopycnally oriented mixing of tracers and isopycnal thickness or static stability. This yields qualitatively credible, quasi-adiabatic solutions for realistic magnitudes for the subgrid-scale transport coefficients. Among these solutions are ones with nearly homogeneous fields of potential vorticity on upper-thermocline isopycnal surfaces, even though the parameterized eddy mixing does not act directly to this end.

Abstract

Numerical solutions are examined for the nearly adiabatic, large-scale ocean circulation in a midlatitude, rectangular domain with steady wind driving. The model used is the balance equations and its various subsets; hence, dynamical effects at finite Rossby number are included. The solutions are steady ones, and the necessary transports by the missing mesoscale eddies are parameterized, in part, using the authors’ previous proposal for isopycnally oriented mixing of tracers and isopycnal thickness or static stability. This yields qualitatively credible, quasi-adiabatic solutions for realistic magnitudes for the subgrid-scale transport coefficients. Among these solutions are ones with nearly homogeneous fields of potential vorticity on upper-thermocline isopycnal surfaces, even though the parameterized eddy mixing does not act directly to this end.

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