GULF-STREAM AND WIND-INDUCED CURRENT VARIABILITY ON THE NORTHEASTERN FLORIDA CONTINENTAL-SHELF

Subtidal current fluctuations on the continental shelf off northern Florida and their relationship with local wind and Gulf Stream forcing were examined for a 3-month period from February to May 1980. The depth of the main thermocline, determined by acoustic travel time and bottom pressure measurements on the upper slope, was used as an indicator of Gulf Stream displacement. At mid-shelf stations (28 and 40 m isobaths), along-shelf wind stress influenced along-shelf current at all frequencies. With increasing depth in the water column, there was increasing partial coherence and time lag (up to 10 h) between wind and current. At the outer-shelf (75 m) station, significant partial coherence was limited to the 4- to 6-day band with a similar time lag observed towards the bottom. Throughout the water column, at the outer-shelf and, to a lesser extent, the mid-shelf stations, Gulf Stream influences on along- and across-shelf currents, and across-shelf wind influences on along-shelf currents, were strong at ∼4-day periods. Compared with results from an earlier study off northern Georgia, these data show greater influence of the Gulf Stream at the 40 m isobath, and a shorter period (4 days instead of 12 days) associated with this influence. Baroclinic instability calculations suggest that the shorter period may be associated with stronger vertical shear. © 1990.