A VARIETY OF TRANSFORMATIONS OF NONLINEAR INTERNAL TIDAL WAVES ON THE NORTH-WEST AUSTRALIAN SHELF

Abstract

Highly non-linear internal waves at the continental margin on the northwest shelf of Australia are discussed using detailed velocity and temperature time series recorded from moored current meters. The region has a vigorous semidiurnal inland tide that propagates towards the shore along the shelf. In this area, there is an increase in the internal tide and the formation of bore-like formations, often accompanied by internal solitary waves. In this paper, the emphasis is on the analysis of the shape and properties of the internal tide. The frequency spectrum of internal waves is presented, calculated from the records of the current component directed along the normal to the coast. Five different types of waves are distinguished, which consist of burrs on the front or back side of the wave, “square” waveforms with a bores on both the front and back sides of the wave at the same time, as well as linear waves of small and large amplitude. The statistics of transformations of the types of internal tides during their propagation along the section of the route from the slope to the shelf is given. The main types of waves passing without transformation and waves with a short lifetime, which include “square” tidal waves and waves with bores on the back slope of the wave, are revealed. In general, the analysis showed a real picture of the ongoing nonlinear transformations of tidal internal waves occurring on the north-west shelf of Australia.