A cyclonic eddy and shelf‐slope water exchange associated with a Gulf Stream warm‐core ring

Abstract

Warm‐core ring (WCR) 83D passed through a linear array of moored temperature, conductivity and velocity sensors during October 1983. Satellite‐derived thermal imagery combined with data from the moored sensors have revealed a cold‐core cyclonic eddy, of approximately 80‐km diameter, traveling in advance of ring 83D. This cyclone, whose angular momentum magnitude was about 1/3 that of the WCR, evolved either during or shortly after the WCR's formation. Hydrographic and moored sensor data suggest that the WCR brought about a subsurface exchange of shelf and slope water, with near‐surface slope water moving onshore and near‐bottom shelf water being drawn offshore and around the ring. Examination of 308 cross‐shelf hydrographic sections from the Middle Atlantic Bight has indicated that such exchange commonly occurs in the presence of a WCR. This apparent ring‐induced exchange may significantly affect the overall salt balance of Middle Atlantic Bight shelf water. As an example, the volume of slope water within a well‐surveyed intrusion, which lay onshelf of WCR 79B, was 16% of Wright's (1976) estimate of the annual slope water transport to the Middle Atlantic Bight shelf.