Northern sources of the Leeuwin Current and the “Holloway Current” on the North West Shelf

This paper reviews the northern sources of the Leeuwin Current and related circulation on theNorth West Shelf, north of where it consolidates into its well-known poleward boundary currentstructure off North West Cape, Australia.This review finds that relatively warm, low salinity waters enter the Indonesian-Australian Basinthrough two major remote northern sources. One is tropical Pacific Ocean water emanating fromthe South East Asian seas via the Lombok, Ombai and Timor Straits. The other is tropical northwestIndian Ocean water via the South Java Current within the 5–10° S zone off the Sumatra and Javacoasts.At the broadest scales, both sources undergo circuitous routes and associated evaporation andcooling before entering the head of the Leeuwin Current off North West Cape.It is largely unresolved as to how close to the North West Shelf coast the Leeuwin Current’s sourcewaters flow. However, earlier oceanographic studies, supported by more recently collected datapresented in this paper, indicate that at least during the low wind conditions of the SouthernHemisphere autumn, a reasonably well-defined, southwestward coastal flow occurs along the shelfand shelf break. An explanation previously suggested is that this current is driven by the stericheight gradient produced by local surface heating, and we propose here to name it the HollowayCurrent in honour of the late Dr Peter Holloway.