Summer surface circulation on the Gascoyne continental shelf

As part of a multidisciplinary investigative effort to establish an understanding of the relatively unstudied coastal waters off the Gascoyne region, 11 cross-isobath transects, spanning latitudes of 21/spl deg/S -28/spl deg/S off the West Australian coast were made during 13-27 November 2000. This paper examines CTD and ADCP data that were gathered aboard the RV Franklin, along with concurrent satellite SST imagery, to provide a description of the summer surface circulation on the Gascoyne continental shelf. The Leeuwin Current has generally been depicted as an eastern boundary current carrying warm, low salinity water poleward along the West Australian continental shelf break. This study reveals details of the Leeuwin Current ageing from its warm (24.85/spl deg/C), relatively fresh (34.92 psu) nature, to a cooler (21.21/spl deg/C), more saline (35.44 psu) condition, as it journeyed along its meandering path southward, encountering (I) the Ningaloo Current and an anticyclonic recirculation pattern south of Point Cloates, (II) hypersaline outflow from Shark Bay, (III) the Capes Current, (IV) offshore eddies, and (V) drastically varying shelf widths. Evidence was also seen of persistent ´common shelf water´ south of Shark Bay, with a very distinct 35.2 psu salinity signature.