Signatures of tidal interference patterns in the South China Sea

Abstract

The formation of arc-type structures in the surface elevation and temperature fields due to internal tidal (IT) waves is studied in the region of the South China Sea (SCS) and Luzon Strait. It is demonstrated that these arc-type structures in the surface elevation and temperature at depth result from the merging of IT waves. Predictions of internal baroclinic tides are conducted with a nonlinear hydrostatic model, the Luzon Strait Nowcast/Forecast System, forced with tides, realistic surface forcing and stratification (Appendix 1). It is shown that IT waves generated by the undersea ridges near the Batan and Babuyan Islands in the Luzon Strait propagate westward and merge into arcs in the SCS. The superposition of IT waves is also investigated with a linear knife-edge model (Appendix 2). M2 and K1 tidal waves are considered. It is demonstrated that K1, M2 tidal waves from the Babuyan Islands combine with waves from the Batan Islands to form arc signatures in sea surface elevation and warm spots in the South China Sea. Possible modulation effects of K1 waves on M2 waves are shown. Dynamics of the nonlinear hydrostatic model shape the arc segments differently from the linear model. Arc lengths increase from the sources in nonlinear and linear models. The model-predicted merged IT waves are compared with SAR images.