NOTE ON THE IDENTIFICATION OF A GULF-STREAM SPIN-OFF EDDY FROM EULERIAN DATA

The variability of currents and hydrography along the outer continental shelf of the South Atlantic Bight is occasionally dominated by Gulf Stream frontal spin‐off eddies. These eddy events have been recognized as an important mechanism for water mass, nutrient and larvae exchange on the outer shelf. Recent efforts to characterize the dynamics of these events from moored recording current meter data have considered a detection scheme based on a Lagrangian viewpoint, i.e., that the eddy events are cold core with the velocity vector at a fixed point rotating counterclockwise with time in the horizontal plane. However, as we show in this paper, the horizontal velocity vector at a fixed point can rotate either clockwise or counterclockwise depending on whether the mooring is located to the right or to the left of the center of the eddy as it is advected past the mooring and is independent of sense of rotation of the eddy as viewed by an observer moving with it. Further, depending on the shelf hydrographic season, the eddy event could either warm or cool the shelf locally. Therefore, conventional eddy detection schemes using moored instrument data are lacking in perspective. Copyright 1979 by the American Geophysical Union.