TOPOGRAPHIC INFLUENCES ON RECIRCULATION IN THE DEEP WESTERN BOUNDARY CURRENT - RESULTS FROM RAFOS FLOAT TRAJECTORIES BETWEEN THE BLAKE-BAHAMA OUTER RIDGE AND THE SAN-SALVADOR GATE

Over a period of several years, RAFOS floats were launched into three levels of the deep western boundary current (DWBC) east of the norther n Bahamas in order to identify and study any local recirculations that might be present in addition to the thermohaline-driven component of the current. These float trajectories reveal the presence of recircula tions that are clearly caused by features of the lateral and bottom to pography. In particular, the San Salvador Spur exerts a major influenc e on the paths of these floats. Although the floats exhibit a complica ted set of motions, some order is imposed by relating periods when flo ats move directly along the boundary versus periods when they leave th e launch site ''anomalously'' (i.e., to the east or northeast) due to motions of the DWBC core. Comparison to current meter records along 26 degrees 30'N near the launch site shows that floats in the latter gro up were deployed when the DWBC core was located offshore. The ''erupti on'' of floats into the interior recirculation at the San Salvador Spu r causes a reduction (by a process similar to what elsewhere has been termed ''arrested dispersion'') in the mean rate at which the floats, and presumably other tracers, move southward along the boundary. The ' 'effective southward spreading rate'' of these floats is estimated as 1.97 cm s(-1), in reasonable agreement with analogous results from tra cer studies in the same region.