The Leeuwin Current

The Leeuwin Current is a warm-water current of tropical origin that flows southwards down the Western Australian coast, most strongly in autumn and winter, which maintains much higher sea temperatures off our coast than occur off the west coasts of Southern Africa and South America.

It has two effects on our coastal waters - it transports tropical marine larvae down from more northern latitudes, and it also raises winter water temperatures to enable many of these organisms to survive at Rottnest Island.

Satellite images have revealed some of the complex current patterns associated with the Leeuwin Current. The accompanying images show the Leeuwin Current in red (often enveloping the Island in warm water), with the coolest water in blue.

Average temperatures derived from the satellite data have shown that the coastal waters near the eastern end of the Island vary from about 23°C in summer to 19°C in winter. Thanks to the Leeuwin Current, this is a much smaller temperature range than occurs near the mainland coast, where the temperature falls to about 15°C in winter.

Acknowledgement: Satellite imagery provided by Alan Pearce, CSIRO Marine Research (courtesy of WASTAC).

N9/50190: Satellite image showing the Leeuwin Current (in red) flowing southwards down the Western Australian coast in September 1994. The black line marks the edge of the continental shelf (approximately the 200 m depth contour), and the mottled-white areas towards the top of the image are clouds. Note the large eddy west of Cape Leeuwin carrying the warm water offshore into the much cooler (blue) oceanic waters, as well as the relatively cool water in Geographe Bay at this time of year.

N11/1097: In December, the Leeuwin Current (in red) is weaker and in this image has in fact almost "turned back on itself" to form a very large anticlockwise eddy. The cool Capes Current (blue) is evident flowing northwards from Geographe Bay towards Rottnest Island, and there is a narrow band of warm water along the coast.

For more information, please visit the CSIRO website.