Continental shelf currents near the Abrolhos Islands, Western Australia

Abstract

Recording current meters were used to identify features of the circulation of the continental shelf near the Abrolhos Islands and Rottnest Island in 1973-75. In summer, from November to March, there was a mean northward drift of 0.1 m s^-1; in winter, from April to August, the mean flow was southward at 0.2 m s^-1, possibly due to the spread of the Leeuwin Current onto the shelf. In all seasons, the current records had superimposed upon them a variability with period from days to weeks. The several- day period variability in the along shore currents had peaks of up to 0.5 m s^-1 and was strongly correlated with sea level and with phase-lagged alongshore wind at the nearby port of Geraldton. In summer, strong southerly wind events associated with the eastward passage of highs produced sea-level troughs and northward current pulses. In winter, northwesterly storms from lows passing over Cape Leeuwin produced sea-level crests and southward current pulses. Satellite drifter tracks confirmed the summer and winter behaviour revealed by the current meter records and, further, showed that the winter behaviour extended north of the Abrolhos Islands to 26ºS.