LAUSR

The complex influences of the East Australian Current (EAC) and winds on the waters of the continental shelf were addressed with a ship survey, moored and drifting instruments, satellite images and wind and sea level measurements. The study revealed intrusions of continental slope water reaching the inner continental shelf when the EAC was near the shelf edge and wind stress was near zero or upwelling favourable (northerly). The process was the onshore movement of a southward flowing stream of water originally from the continental slope. One event was captured near Cape Byron and Evans Head when these waters upwelled to the surface. When the wind stress turned northward, it reversed the inner shelf current and drove downwelling. Variations in the wind stress also modulated the strength of the EAC out across the shelf to the upper slope. The strength of the EAC per se varied with a time scale of 2–3 months; these variations decreased in amplitude westward until they were undetectable at the inner shelf. The EAC had a subsurface speed maximum of up to 1.6ms–1 at 100–150-m depth above the continental slope and was seen to accelerate with both time and distance southward along the 190-km length surveyed by the ship.