The Leeuwin Current, eddies and sub-Antarctic waters off south-western Australia
G. R. Cresswell A B and D. A. Griffin AA CSIRO Marine Research, PO Box 1538, Hobart, Tasmania 7001, Australia.
B Corresponding author. Email: george.cresswell@csiro.au
Marine and Freshwater Research 55(3) 267-276 https://doi.org/10.1071/MF03115
Submitted: 8 August 2003 Accepted: 9 March 2004 Published: 19 May 2004
Abstract
Data from a research vessel cruise in late 1994 and several years of satellite observations revealed complex interactions of ocean features off south-western Australia. The ship measurements showed that the Leeuwin Current (LC) commonly ran at 0.5 m s–1 above the upper continental slope and extended down to approximately 250 m. South of the continent, a 200-km diameter anticyclonic eddy depressed the ocean structure in the upper 1000 m. The eddy showed influences of the LC, deep mixing in winter and summer heating. The sub-Antarctic water around the eddy was cooler, fresher and richer in nutrients and oxygen than both the eddy and the LC. Satellite thermal and topographic measurements showed that cyclonic eddies accelerated the LC along the southern upper continental slope, whereas anticyclonic eddies diverted it out to sea and then back again. The images suggested that weak eddies originating east of the Great Australian Bight migrate westward, first encountering the continental slope off the Recherche Archipelago. There, the anticyclonic eddies take on warm water from the LC and strengthen. Several anticyclonic eddies were followed westward beyond the archipelago for 18 months as they drifted at up to 5 km day–1 and interacted with the LC and with one another.
Extra keywords: ocean currents, salinity, subsurface temperature, TOPEX/Poseidon.
Acknowledgments
We thank the ship’s officers and crew and our CSIRO colleagues, particularly Chris Rathbone, who processed the satellite data. The drifter was part of a program managed by Ralph Roblee.
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