Annual and interannual variations of the Leeuwin Current at 32°S -: art. no. 3355

In this study, the annual and interannual variations of the Leeuwin Current at 32degreesS off the Western Australian coast are investigated. The mean annual cycle and the El Nino and La Nina composites of the Leeuwin Current temperature structures are obtained by linearly fitting a Taylor expansion to historical upper ocean temperature data. A temperature-salinity relationship is used to derive the salinity field and geostrophy is assumed to calculate the current velocity. The downward tilting of the isotherms toward the coast and the strength of a near-surface core of the low-salinity water indicate the seasonal variation of the Leeuwin Current. Seasonally, the Leeuwin Current has the maximum poleward geostrophic transport of 5 Sv (10(6) m(3) s(-1)) during June-July. Interannually, the Leeuwin Current is distinctly stronger during a La Nina year and weaker during an El Nino year. The annual average poleward geostrophic transports in the mean, the El Nino and La Nina years are 3.4, 3.0, and 4.2 Sv respectively. Variations of the Leeuwin Current structure on annual and interannual timescales are coastally trapped. A linear relationship between the coastal sea level deviation at Fremantle and the Leeuwin Current transport is derived, which justifies and calibrates the usage of the Fremantle sea level as an index for the strength of the Leeuwin Current.