Tidal and Long-Term Flow through two Tidal-Channels Connecting Southern Biscayne Bay and Card Sound with Atlantic Shelf Waters

Pitts, Patrick

Current meter data and local wind measurements from a 166-d study in 1996-97 are used to describe tidal and long-term flow through two tidal channels that connect southern Biscayne Bay and Card Sound with Atlantic shelf waters. Results indicate a quasi-steady, long-term outflow from the estuary through Caesar Creek and Angelfish Creek that averaged 12 cm s^-1 and 8 cm s^-1, respectively. Harmonic analysis indicates that the tides dominate the instantaneous flow through the channels, with diurnal and semi-diurnal tidal constituents accounting for 85-87% of the total variance. M2 amplitudes for Caesar Creek and Angelfish Creek are 72 and 52 cm s^-1 , respectively. Comparisons of local winds and along-channel currents indicate that wind stress plays the primary role in driving the nontidal flow through the channels. Spectral analysis shows high coherence between along-channel currents and a broad range of wind stress components over time scales of 2-16 d. Winds from the northern sector show particularly high coherence with along-channel flow through both creeks, accounting for 40-80% of the variance in nontidal along-channel flow over the low-frequency time scales. A close inspection of the seasonal and low-frequency wind stress pattern, however, suggests that the long-term outflow observed through the two channels is not due to wind stress alone. A comparison of freshwater flux in the bay with channel outflow indicated a marginal cause-and-effect relationship. Surface runoff and precipitation explain only 2-3% of the variance in outflow through the two channels.

Tidal and Long-Term Flow through two Tidal-Channels Connecting Southern Biscayne Bay and Card Sound with Atlantic Shelf Waters

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