Abstract :
Due to the excess of evaporation over rainfall, some regions of the coastal waters fringing the semi-arid zones of Australia are highly saline. At the head waters of Gulf St Vincent in South Australia, where there is virtually no river discharge, the salinity can increase to over 42 in summer when the rainfall is minimal. Based on the data available from a salinity monitoring programme over the northern regions of the Gulf, the seasonal variation of the salt balance has been reviewed. The component of the salt efflux due to the oscillatory vertical shear of the tidal current has been estimated by using an existing simple model. Based on this estimation, the seasonal variation of the salt efflux associated with the (lateral) general circulation has been calculated. Therefrom, the intensity of the general circulation is estimated at 1–2 cm s−1which agrees well with available current meter observations. Due to the large width to depth ratio of the region, the general circulation dominates over dispersion in the salt-flushing process, except in mid-winter when the two mechanisms contribute almost equally. The general circulation, which is maintained to a large extent by the horizontal density gradient and the wind stress, reverses itself at times, depending on the relative strength of these two factors.
