Multi-Year Observation of Holloway Current along the Shelf Edge of North Western Australia

Analysis of multi-year current meter data across North West shelf of Australia identified various aspects of the mean flow in a macro-tidal environment. Main features of the flow appear to be a continuous alongshore south-westward flow, i.e., Holloway current located along the continental shelf edge in depth 100-200 m. Annually, the current transports similar to 1 Sv of lower salinity, higher temperature water from the tropical regions to North West Cape. The Holloway current is at its maximum intensity (up to 2 Sv) during autumn/winter (Apr-Jul) when the winds are either weak or the region is dominated by south-east trade winds. Unlike alongshore flow, cross-shore structure of the flow is fairly complex and shows variations with depth and season. A new mechanism is proposed to justify the observed intensification of the flow in austral autumn that is closely related to the seasonal cycle of sea level around Australia. Each year, due to the monsoon cycles there is a high sea level anomaly that peaks in February in the Gulf of Carpentaria in the upstream side of the Holloway current that manifests itself as southward progressive high sea level anomalies in the following months along the West Australian coastline. Observed onshore fluxes can also have some implications for the strength of the Holloway current.