Shelf edge tide correlated eddies along the southeastern United States

Abstract

High frequency radar observations in the Southeastern United States have revealed sequences of small short-lived cyclonic eddies along the shoreward edge of the Gulf Stream, that spin up as the local tide turns alongshelf antiparallel to the Stream. Eddies propagate equatorward along the shelf edge, sometimes progressing shoreward before dissipating one to three hours later. They are distinctly different from Gulf Stream meander eddies, which propagate poleward. In this article, radar and mooring data are used to establish three important aspects of these new eddies: they represent an instability process operating at a previously unidentified frequency, scale, and cross-Stream position; they contribute to shoreward momentum fluxes, defining a link between Gulf Stream and outer shelf subtidal variability and illustrating a mechanism to justify locally large horizontal eddy viscosity estimates; and they transport properties across the shelf edge, importing nutrients onto the shelf and transferring heat between the Gulf Stream and the coastal ocean. © 2010 by the American Geophysical Union.