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Introduction

The Australian North West Shelf (NSW) is known for large-amplitude internal tides and internal solitary-like waves (ISWs, or internal solitons)^1),3). Since strong currents induced by ISWs are an important factor in structural design and operation for the Australian oil and gas industry, there has been strong interests in 3D ISW modelling. When I was at CSIRO, RPS MetOcean approached me to collaborate on testing the feasibility of 3D ISW modelling for engineering purposes.

Methods

We used MITgcm²⁾ for our 3D ISW modelling. We made our model configuration as realistic as possible, and used realistic topography, stratification, and tidal forcing with full non-hydrostatic and Coriolis effects.

Results

The modelled ISWs (Fig. 1) were consistent with our understanding from previous studies and the mooring observation by RPS MetOcean in some aspects. For example,

• The ISWs are generated by the steepening of internal tides excited around ~200 m depth;
• The ISWs propagate toward SSE-SE on the rear-face of internal tides; and

However, there were other aspects that were not modelled well. For example, the modelled amplitudes were considerably smaller than the observations. This deficiency appeared to be particular in shallow water, because our MITgcm ISW modelling in the Andaman Sea (deep water) did not appear to show such deficiency.

Concluding remarks

This study was a short research project (~half a year in total) to confirm the feasibility of 3D ISW modelling on a continental shelf. Since then, I have improved the modelling methodology to apply 3D ISW modelling for engineering purposes.

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