Fluctuations in the Florida Current, summer 1970

Abstract

Abstract Four-month thermistor array and tide gauge records from either side of the Florida Current indicate fluctuations at semidiurnal, diurnal, near-inertial, several-day, weekly, fortnightly, and monthly time scales. Most of the subtidal frequency temperature variance was associated with two or three vertical modes. The surface geostrophic velocity and the 30 m-relative-to-210 m (baroclinic) geostrophic velocity were coherent and in-phase for several period bands between several-day and fortnightly time scales. For time scales of several days to monthly, the oceanographic fields were strongly coupled to the local wind stress. The fluctuating north-south wind stress did work on the fluctuating surface current at a significant rate. Multiple coherence calculations indicate a high degree of predictability for oceanographic fields from two or three other (temperature, sea level, meteorological, or acoustic phase) fields for time scales longer than a day. Both the semidiurnal and diurnal temperature fluctuations were, on the average, out-of-phase across the Florida Straits as expected for the gravest internal seiche modes. The internal tides had fortnightly and monthly (or longer) modulation time scales. The internal tides contained as much energy as the surface tides, suggesting that the Straits may serve as a significant trap for surface tidal energy. Near-inertial motions were affected by the horizontal shear of the mean Current.