Seasonal changes in the distribution of Leeuwin Current waters of Southern Australia

Abstract

Three major water masses occur for all or part of the year within the shelf and slope region off southern Australia. A Leeuwin Current carries the warmest water mass of relatively low salinity into the region, principally along the shelf break as far east as 130ºE. This water mass first enters the western end of the region in May, disappears from the eastern end after July and from the western end by September-October. A warm and very high salinity water mass is present in the central and eastern half of the Great Australian Bight for most of the year. This central Bight water mass drifts to the south-east and occupies much of the shelf and slope region east of 135ºE., particularly in winter. A West Wind Drift cold water mass of lowest salinity is found throughout the year off the slope region of southern Australia and periodically intrudes into the shelf break, especially when the Leeuwin Current is weakly developed.

The central Bight waters, which provide a second source of warm waters in the eastern half of the region, greatly complicate the interpretation from satellite imagery of warm waters in that region as being derived solely from the Leeuwin Current. Adequate salinity data and sea surface temperatures derived from satellite imagery are required to determine more accurately the eastward extent of the Leeuwin Current.