The Prediction of Wind-Forced Currents and Sea Level on the Southeast Australian Continental Shelf

Abstract

The Australian Coastal Experiment (ACE) in 1983–84 demonstrated the feasibility of using wind-forced coastal-trapped wave (CTW) theory to predict low-frequency alongshore currents and sea levels on the east Australian continental shelf. Moreover, it emphasized the importance of upstream boundary conditions for the CTW model to be of practical use. In ACE, the first three CTW modes at the upstream boundary of the model were obtained via an array of current meters across the continental shelf and slope. An alternative approach when such arrays are not available is to use the close relationship between the observed CTW modes in the southern ACE region and coastal sea level (or alongshore wind stress) in eastern Bass Strait to derive proxies for the modes from those readily obtainable variables. A CTW model that uses these revised modes as an upstream boundary condition is run for the ACE period, and predictions of alongshore current and sea level in the vicinity of Sydney compared with those from the standard model, as well as with the observed data. The respective hindcasts are qualitatively similar, though the revised model gives amplitudes that are about 10%–15% smaller than those from the standard model. An independent test of the scheme, made by running the revised model for the December 1984–April 1985 period, indicates predictions are in good agreement with the observed alongshore current record at a nearshore site some 400 km north of the model's upstream boundary.