Process-oriented modeling studies of the 5500-km-long boundary flow off western and southern Australia

The seasonal and daily wind-forcing experiments highlight both the seasonal and interannual variability of this complex current system. The Leeuwin Current along the western coast is slightly stronger in winter (July) than summer (January). There is much greater mesoscale activity in January when the opposing winds are strongest. The results also show that, although upwelling has been observed only in the summer in the Capes Current region, upwelling occurs intermittently in the 2001 winter but not in the 2001 summer. This illustrates that, depending on the strength of the forcing mechanism, such as strong equatorward winter 2001 winds, features such as upwelling on the west coast, usually thought to exist in the summer but only intermittently, can occur in different seasons. Along the southern coast, a gyre forms intermittently in the Great Australian Bight in summer, but the flow is constantly eastward across the entire shelf in winter. The production of upwelling in the Great Australian Bight during the 2000 summer but not during the 2001 summer is an indication of the importance of interannual variability. Overall, the results of this process-oriented study compare well with available observations off western and southern Australia.