A Description of Local and Nonlocal Eddy-Mean Flow Interaction in a Global Eddying State Estimate

Wednesday, 17 December 2014
Carl I Wunsch1,2, Ru Chen3 and Glenn Flierl1, (1)Massachusetts Institute of Technology, Cambridge, MA, United States, (2)Harvard University, Cambridge, MA, United States, (3)Scripps Institution of Oceanography, La Jolla, CA, United States
The assumption that local baroclinic instability dominates eddy-mean flow interactions is tested on a global scale using a dynamically consistent eddying state estimate. Interactions are divided into local and nonlocal. If all the energy released from the mean flow through eddy-mean flow interaction is used to support eddy growth in the same region, or if all the energy released from eddies through eddy-mean flow interaction is used to feed back to the mean flow in the same region, eddy-mean flow interaction is local; otherwise, it is nonlocal. Different regions have different characters: in the subtropical region studied in detail, interactions are dominantly local. In the Southern Ocean and Kuroshio and Gulf Stream Extension regions, they are mainly nonlocal. Geographical variability of dominant eddy-eddy, and eddy-mean flow processes is a dominant factor in understanding ocean energetics. This work points out the prevalence of eddy energy nonlocality and indicates the need of using nonlocal eddy parameterization schemes.