Instability and eddy pairs on the Leeuwin current south of Australia

Abstract

Infra-red images taken by the Advanced Very High Resolution Radiometer onboard NOAA7 reveal much of the surface structure of the Leeuwin Current along the south coast of Australia during spring of 1982. Between Cape Leeuwin and Cape Arid, large eruptions from the outer edge of the current temporarily blocked the flow of warm water along the coast and diverted it into unstable baroclinic waves. The waves had zero phase speed relative to the coast. They also led to formation of cyclone-anticyclone eddy pairs, a phenomenon previously discovered in laboratory experiments with density fronts and buoyancy driven boundary currents. The dimensions, separation distances, growth-rates and life-times of the waves and eddies indicate that these structures were the result of baroclinic instability. Although some eddy pairs carried a large volume of warm water away from the current, tentative estimates of heat transport resulting from baroclinic instability show only a small net heat loss from the current.