Dataset: Thermal stratification in a small lagoon in the windward reef flat of Davies Reef, central Great Barrier Reef


Stratification and flushing of a small lagoon in the windward reef flat of Davies Reef in the central Great Barrier Reef was examined in 1980/1981 using three complementary experiments. \n \nIn the first experiment, salinity-temperature-depth (STD) profiles were taken each 0.5 hr for 2 days (25-27th April, 1980). On the 27th April at low tide (1400hrs), the resident bottom water of the lagoon was marked with fluorescein dye. The dye was sampled with Niskin bottles, at 2m intervals from and including the bottom every 4 hours until the dye could not be detected. STD profiles were taken concurrently. Dye sampling commenced at 1630hrs, to avoid photodegradation, and fluorescence was measured on an Amico-Bowman spectrophotofluorometer. STD and dye experiments were repeated from the 2-5th November, 1980. Rhodomine dye was used on this occasion to allow daylight sampling and dye profiles were taken at 30 minute intervals. \n \nIn the second experiment, 7 Aanderaa RCM4 current meters were deployed from the 15th June to 15th July 1980, in a vertical string, with a spacing of 2.7m in a position where the water depth was 20m below the reef flat. Temperature, pressure and vector-current profiles were recorded every 10 minutes. This array functioned as a thermistor string, as currents in the lagoon were near the determination limit of the current meters. An additional Aanderaa RCM4 current meter, measuring currents and water temperature was deployed midway between two lagoons, south west of the study site. Wind vectors were accessed from twice daily recordings at the weather station at the Cape Cleveland lighthouse. \n \nIn the third experiment temperatures at the top and bottom waters of the lagoon were recorded every 10 minutes between the 24th April 1980 and 21st March 1981. Wind measurements were taken from the weather station at the Cape Cleveland lighthouse.\n Experiments were undertaken to gain an understanding of thermal stratification and the trapping of bottom water in reef lagoons on three time scales by: \n1. using temperature and dyes to mark diurnal events \n2. studying currents on the reef flat and stratification in the lagoon for 1 month \n3. using temperature to infer events from a time series of approximately 1 year\n

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