Northern Sources of the Leeuwin Current and the 'Holloway Current' on the North West Shelf

摘要

This paper reviews the northern sources of the Leeuwin Current and related circulation on the North West Shelf, north of where it consolidates into its well-known poleward boundary current structure off North West Cape, Australia. This review finds that relatively warm, low salinity waters enter the Indonesian-Australian Basin through two major remote northern sources. One is tropical Pacific Ocean water emanating from the South East Asian seas via the Lombok, Ombai and Timor Straits. The other is tropical northwest Indian Ocean water via the South Java Current within the 5-10° S zone off the Sumatra and Java coasts. At the broadest scales, both sources undergo circuitous routes and associated evaporation and cooling 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 source waters flow. However, earlier oceanographic studies, supported by more recently collected data presented in this paper, indicate that at least during the low wind conditions of the Southern Hemisphere autumn, a reasonably well-defined, southwestward coastal flow occurs along the shelf and shelf break. An explanation previously suggested is that this current is driven by the steric height gradient produced by local surface heating, and we propose here to name it the Holloway Current in honour of the late Dr Peter Holloway.