Tidal, low-frequency and long-term mean transport through two channels in the Florida Keys

Current meter and water level data from two tidal channels in the Florida Keys are combined with acoustic Doppler profiler data to quantify tidal, low-frequency and long-term mean volume transport between Hawk Channel, on the Atlantic side of the Keys, and Florida Bay, on the Gulf side. Current meters in Long Key Channel and the Seven Mile Bridge channels were maintained for time periods of 279 and 259 days, respectively. During each study, shorter current records were obtained from additional study sites for channel calibration. In Long Key Channel, the combination of tidal and nontidal forcing produces inflows and outflows that occasionally exceed 8000 and −9000 m3 s−1, respectively. Maximum inflows and outflows through the Seven Mile Bridge channels can exceed 10,000 and −13,000 m3 s−1, respectively. The residual tidal transport through Long Key Channel is 27.7 m3 s−1 into Florida Bay, while the residual transport through the Seven Mile Bridge channels is −177.5 m3 s−1 into Hawk Channel. In Long Key Channel, the mean total transport from October 21, 1997 to July 27, 1998 was an outflow of −392 m3 s−1. The mean total transport in Seven Mile Bridge Channel from October 22, 1998 to July 8, 1999 was an outflow of −454 m3 s−1. Spectral analysis of volume transport and wind-stress quantifies low-frequency wind-forced exchanges. The Long Key Channel transport time series is highly correlated with wind stress over all time scales in excess of 3.5 days. High coherences were restricted to periodicities of 1–7 days in the Seven Mile Bridge channels. In both channels, highest correlation occurs when the along-channel axis lies 55° to the right of the wind-stress vector.