East Australian current adjacent to the Great Barrier Reef

Abstract

Hydrographic data from a series of cruises during 1980-1981 are used to determine the circulation in the western Coral Sea region immediately adjacent to the Great Barrier Reef. The data show flow westward towards the Great Barrier Reef, bifurcating just north of 18�S. During the monsoon season (December to February), the bifurcation point moves north to at least 14�s. The geostrophic westward flow has a subsurface maximum at a depth of about 150 m. South of the bifurcation point, the flow is south-eastward on the upper continental slope and north-eastward offshore. North of the bifurcation point, the surface flow and transport (relative to 900 dbar) are northward. However, there is sometimes a south-eastwards near-surface shear. Near the bifurcation point, the surface currents are weak and variable. All of these features of the surface flow are reflected in the paths followed by satellite-tracked drifters. Although the drifters were fixed infrequently, the drifter data indicate the possible presence of small cyclonic eddies in the region of the bifurcation. All of the satellite-tracked drifters went aground in the Great Barrier Reef within 30 days of entering the region offshore from the Reef. The data are consistent with recent models of the wind-driven circulation in the South Pacific that propose that the westward flow bifurcates at about 20�S., with 17 x 106 m3 s-1 flowing through the Indonesian Archipelago from the Pacific Ocean to the Indian Ocean.