Eddy-Mean Flow Interactions in Western Boundary Current Jets

Motivated by involvement with the Kuroshio Extension System Study (KESS), a large-scale observational program of the Kuroshio Extension with the goals of understanding the processes that govern the jet's variability and the interactions between the Kuroshio jet and its recirculation gyres, we have studied the role of eddy-mean flow interactions in the dynamics of a baroclinic unstable boundary-forced jet in an idealized QG model.

We show that in this idealized configuration in a parameter regime relevant to the Kuroshio Extension and the Gulf Stream, eddy fluxes play important roles in both stabilizing the jet as it evolves downstream and driving recirculations through the mechanism of an up-gradient PV flux that occurs downstream of jet stabilization. We also find that the properties of the eddy-driven time-mean circulation (the strength of the time-mean jet and the strength and extent of the time-mean recirculations) can be predicted given the stability properties of the upstream jet that was the source of the eddy variability.

Initial results from the KESS observations to begin to test the relevance of these idealized results to actual oceanic western boundary current jets will also be presented.