Propagation characteristics of coastally trapped waves on the Australian Continental Shelf

Abstract

Coastally trapped waves (CTWs) are investigated around the Australian coast based on their signature in the sea surface height (SSH) field, using independent data from coastal tide gauge observations and the Bluelink ocean forecasting system from 2009. A high correlation (correlation coefficients from 0.6 to 0.9) between the model and observational data is demonstrated for locations between Hillarys, in the south‐west of the continent, and Cape Ferguson, in the north‐east. This justifies the use of Bluelink data for the rest of the investigation and enables coastal locations between tide gauge stations to be included. Spectrum analysis shows that CTWs have periods of between 10 and 25 days, with the 10 day period dominating along the south coast, and greater energy around the 20 day period on the east coast. The greatest spectral power is located around the Great Australian Bight. After filtering to isolate these CTW frequencies, phase speeds are estimated using two methods and are consistent with earlier studies. There is a close correlation between the standard deviation of the filtered SSH data and the width of the continental shelf, indicating that CTW amplitudes are strongly modulated by the local shelf width. Contrary to earlier studies, a complex empirical orthogonal function analysis shows that the majority of the variance propagates as continuous features between the south‐west and north‐east, and although modulated by the shelf width, it is unaffected by the sharply changing coastline orientation, shallow Bass Strait, or wind forcing regions.