OBSERVATIONS OF CIRCULATION AND EXCHANGE PROCESSES IN JERVIS BAY, NEW-SOUTH-WALES

This paper discusses oceanographic observations obtained in and near J ervis Bay, a small coastal embayment of approximately 124 km2 situated on the New South Wales coast, during a series of measurement programm es spanning three years. Various mechanisms that drive water circulati on within the bay and water exchange between the bay and the adjacent continental shelf are discussed. Current-meter data from within the ba y show surprisingly little correlation with the wind. Currents are cha racterized by persistent flows in one direction for periods of months, and it is suggested that influences from the shelf are responsible fo r driving the bay circulation. Flow through the bay entrance is weakly correlated with the wind at a period of around eight days, with near- surface inflow on the southern side of the entrance being in phase wit h deeper outflow on the northern side and vice versa. The shelf waters are well known for their coastally trapped waves. These have the pote ntial to oscillate vertically the density surfaces on the shelf on a t ime scale of around eight days, and observations indicate that these w aves are an additional mechanism driving circulation in the bay. The s helf waters are influenced by the warm East Australia Current and its eddies, and this appears to maintain a density contrast between the ba y and the shelf for most of the year, with the shelf waters being less dense, which may be an additional mechanism driving bay circulation. Current-meter data from the bay entrance show a persistent northward c urrent component in contrast to the strong southward flow of the East Australia Current on the shelf. Conductivity-temperature-depth data re veal cold, dense water flowing out of the bay during periods of strong winter cooling and the effects of warm eddies pushing warm water into the bay and displacing cold deeper water away from the bay. The heati ng/cooling cycle of the bay appears to be influenced by advection proc esses on the shelf as well as by air/sea heat and radiation exchanges.