John Marshall

Cecil and Ida Green Professor of Oceanography, MIT

EDDY-MEAN-FLOW INTERACTION IN A BAROTROPIC OCEAN MODEL

EDDY-MEAN-FLOW INTERACTION IN A BAROTROPIC OCEAN MODEL.

(MARSHALL, JC), QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, vol. 110, no. 465, pp. pages, 1984.

Abstract

The role of eddies in the maintenance of idealized, antisymmetrically forced double gyres is studied using a barotropic ocean circulation model. A diagnosis in terms of q, the quasi-conserved absolute vorticity, enables an understanding of the effect of the eddies on the time-mean flow. The unstable model Gulf Stream, partitioning counter-rotating gyres, is the confluence region where q contours from widely differing latitudes become concentrated, interwoven and irreversibly deformed. Here there is a strong enstrophy cascade, large eddy fluxes and eddy flux divergences, and significant driving of mean flow by the eddies. This barotropic instability of the internal jet results in a lateral transfer of vorticity sufficient to balance the net forcing of the subtropical gyre by the wind-stress curl. The separation of the eddy flux into non-divergent ‘advection’ and divergent ‘conversion’ contributions, using the eddy enstrophy equation as a dynamical reference, makes transparent the sense of the local eddy q flux and its systematic effect on time-mean flow.

doi = 10.1002/qj.49711046502