LEEUWIN CURRENT OBSERVATIONS ON THE AUSTRALIAN NORTH-WEST SHELF, MAY-JUNE 1993

Observations of the Leeuwin Current, the poleward Row of warm, low salinity water off the west coast of Australia, are described from acoustic Doppler current profiler (ADCP), temperature and salinity (CTD) and moored current meter measurements from the Australian North West Shelf made in May and June 1993. Two cross-shelf and slope transects of ADCP and CTD measurements were completed at latitudes of approximately 17 and 19 degrees S. After the removal of the tidal signal, the ADCP measurements reveal the poleward Rowing Leeuwin Current. The current is broad (250 km at 17 degrees S), deep (at least 440 m) and relatively weak (typically 0.2 m s(-1)), but the poleward transport of approximately 4 x 10(6) m(3) s(-1) is similar to values reported in the literature for the more intense part of the Leeuwin Current, between approximately 22 and 35 degrees S, where a maximum of approximately 7 x 10(6) m(3) s(-1) has been observed. There is a significant flow reversal or undercurrent, of magnitude similar to the poleward transport, at the northern transect, but only a weak undercurrent is observed at the 19 degrees S transect. In the CTD data the current is also seen as a low salinity core with salinity less than 35.2 but also with patches less than 35.0, possibly a result of a series of eddies. A current meter record from mid-way along the 19 degrees S transect shows the poleward flow to be relatively persistent over all of May, but slightly stronger towards the end of May. There is only one significant reversal of flow towards the equator lasting a few days. Current meter data obtained between August 1983 and March 1985 from 120 m depth in the Timer Sea (approximately 12 degrees S) are also reported and reveal a weak poleward flow for much of the year and strongest from January to April. For some of this time (March-April) the poleward Row is supported by the South East Trade winds. However, the poleward current weakens and turns equatorward in May/June to flow into the persistent winds from the east. Simultaneous current meter measurements from the shelf at 20 degrees S show similar strength poleward flows from December to March.