A fine resolution model of the Leeuwin Current System off western and southern Australia

Abstract

To investigate the role of wind forcing, bottom topography and thermohaline gradients in the Leeuwin Current System (LCS) off western and southern Australia, several experiments are conducted with a sigma coordinate primitive equation model on a beta-plane. Results show that off the west (southern) coast the LCS is an anomalous eastern boundary current system that generates a coastal poleward (eastward) current, an equatorward (westward) undercurrent, and highly energetic mesoscale features such as meanders and eddies. Off the west coast, thermohaline forcing, wind forcing and bottom topography all play important roles: Thermohaline gradient effects are shown to be the primary mechanism in the generation of the poleward current, equatorward undercurrent, eddies and meanders. Inshore of the poleward surface flow, next to the coast, wind forcing also plays an important role in generating an equatorward coastal current and upwelling. Bottom topography is responsible for strengthening and trapping currents near the coast, intensifying eddies off capes and in preventing the undercurrent from becoming the dominant surface flow. Bottom topography is also shown to play a dominant role off the southern coast in trapping the eastward Leeuwin Current and the westward Flinders Current over the shelf break and slope, respectively. Overall, the results of the study compare well with available observations and previous studies of the LCS.