Abstract
The currents observed over the shelf and slope during the Australian Coastal Experiment (ACE) are used to determine the amplitudes (as functions of time) of the first three coastal-trapped wave (CTW) modes at three locations along the southeast coast of Australia. A statistical “eddy” mode is included to minimize contamination of the coastal-trapped wave currents from East Australian Current eddies. The first three CTW modes account for about 65% of the observed variance in the alongshelf currents on the shelf and slope at Cape Howe, about 40% at Stanwell Park, but only about 24% at Newcastle. Currents associated with the East Australian Current dominate the observations offshore from Newcastle. CTWs account for all but 10%, 37% and 27% of the currents observed at the most nearshore locations on the shelf at Cape Howe, Stanwell Park and Newcastle. The first two coastal-trapped wave modes propagate at close to the appropriate theoretical phse speeds, but the third coastal-trapped wave mode and the eddy mode are not coherent between the three current meter sections along the coast. Surprisingly, mode 2 carries a greater fraction of the coastal-trapped wave energy than does mode 1 at two of the sections. Modes 1 and 2 are coherent with each other at the 95% significance level. The major energy source for the CTWs is upstream (in the CTW sense) of the first line of current meters.
