Observations of the Leeuwin Current off Western Australia

Abstract

Shipboard observations made in May 1982 showed a definite poleward surface flow (the Leeuwin Current) over the West Australian shelf from 22°S to 28°S. The surface current was relatively fresh, warm, low in dissolved oxygen concentration, and high in nutrients. The current flowed against a strong wind. Only a small portion of its flux of 4 × 106 m3 s−1 came from the Northwest Shelf. There was a subsurface equatorward current at a few hundred meters depth which was salty, high in oxygen concentration and low in nutrients. Observations from previous cruises show a surface geopotential gradient that could drive the surface current. It is suggested that winter deepening of the mixed layer may allow the geopotential gradient to overcome the wind stress. Abstract Shipboard observations made in May 1982 showed a definite poleward surface flow (the Leeuwin Current) over the West Australian shelf from 22°S to 28°S. The surface current was relatively fresh, warm, low in dissolved oxygen concentration, and high in nutrients. The current flowed against a strong wind. Only a small portion of its flux of 4 × 106 m3 s−1 came from the Northwest Shelf. There was a subsurface equatorward current at a few hundred meters depth which was salty, high in oxygen concentration and low in nutrients. Observations from previous cruises show a surface geopotential gradient that could drive the surface current. It is suggested that winter deepening of the mixed layer may allow the geopotential gradient to overcome the wind stress.