Preliminary research on shoaling internal solitary waves with a trapped core in the Dongsha region, South China Sea by seismic reflection data

Based on seismic oceanography data, the relationship between the shoaling process of internal solitary waves, energy dissipation and mixing enhancement can be better analyzed by combining their waveform structure and the spatial distribution of mixing parameters. On a seismic section in the Dongsha area, we observed two internal solitary wave packets in the deep water area (500 similar to 1000 m) and shallow water area (300 similar to 400 m) of the upper slope respectively, which have obviously different waveform characteristics. Three internal solitary waves of the internal solitary wave packet in shallow water region are complex, showing chaotic reflection characteristics in the wave core, which may be the internal solitary waves with trapped vortex core. The estimated dissipation rate and diffusivity rate are O (10(-5)) W . kg(-1), O (10(-2.5)) m(2) . s(-1) respectively. There is a mode-2 internal solitary wave ahead of the internal solitary wave packet. Although the waveform of internal solitary waves in the packet in deep water is relatively simple, the induced turbulent mixing intensity is also strong, forming zones of high dissipation rate and diffusion rate within internal solitary waves development and a region with a thickness of 200m above the continental slope. In the deep and shallow water areas of the upper slope of the Dongsha area, the internal solitary waves continuously dissipate energy and enhance the turbulent mixing.