Recent Work and Thoughts on Eddy-Mean Flow Interaction,

In order to address the question of the roles of mesoscale eddies in the ocean general circulation it is necessary first to determine the ocean general circulation. Unless this circulation is known well enough to estimate the dominant terms in the mean heat, momentum and vorticity equations, it is not possible to evaluate the eddy turbulence terms--divergence of the eddy heat flux, divergence of the Reynolds stress tensor and curl of the divergence of the Reynolds stress tensor--and one can at best speculate on the basis of fragmentary data or theoretical concepts. Even if the detailed balances of the mean equations are known, it may not be simple to establish the roles of the eddies viz. the meteorological experience, but the task is almost exclusively inferential if the data are unavailable. As it is now clear that there is substantial low-frequency variability over most of the ocean, determining the general circulation will be an enormous task.