Studies of nontidal circulation in estuaries and coastal lagoons

A 175-day time series of currentspeed and direction from a study sitein the interior of Florida's IndianRiver lagoon is used to show how advancesin computer technology and recordinginstrumentation over the pasttwo decades have permitted the explorationof low-frequency nontidal physicalprocesses in estuaries. Spectralanalysis confirms the importance oflow-frequency variations in the currentrelative to the ebb and flood ofthe tide. Hourly measurements of currentspeed and direction are convertedto cumulative net displacement for theentire study period, and then forshorter time intervals of up to 88days. Cumulative histograms are computedto show how the net flow at thestudy site is distributed for a giventime interval. A portion of the seasonalcycle emerges in the form of atransition from a net north-to-southflow during midwinter months to aperiod of little net flow from latewinter through late spring.