Gulf Stream Dynamics. Pad II: Eddy Energetics at 73°W

Abstract

Pointwise energy balances in the Gulf Stream System at 73°W (downstream of Cape Hatteras) are examined. Five current meter moorings obtained verlocity and temperature data at four different depths for approximately one year. These data were used to estimate eddy kinetic and potential energy flux divergences and the rates of energy conversion between the eddy and mean fields in both the Gulf Stream and the Deep Western Boundary Current. Based on our results and those of others, we argue that (i) the Gulf Stream is on average baroclinically unstable in this region, although energy release from the horizontal shear dominates near the surface; (ii) eddy pressure work is an important component of Gulf Stream eddy energetics and acts as a sink of eddy energy at 73°W; (iii) the Deep Western Boundary Current appears to be baroclinically unstable; (iv) Gulf Stream eddies are affected by the ?far-field"; and (v) the eddy-field at 73°W is significantly different in its effects on the Gulf stream than that upstream on Hatteras or that at 68°W, although the interaction rates are of comparable magnitude. We propose a hypothesis of eddy field dynamics in the vicinity of the Gulf Stream from the Florida Straits through the Gulf Stream extension.