Generation of nonlinear internal waves on the northern continental shelf south of Hainan Island

Abstract

Nonlinear internal waves (NLIWs) are prevalent on the northern continental shelf south of Hainan Island in the South China Sea. However, our understanding of these NLIWs is still in a preliminary state. In the study, we take a step toward fully elucidating the generation and propagation process of the NLIWs on the northern continental shelf south of Hainan Island through a synergistic analysis of satellite observations, in situ measurements, and numerical simulations. Both mooring and satellite observations suggest that the Xisha Islands remotely generate the NLIWs on the northern continental shelf south of Hainan Island; moreover, more than one source exists in the Xisha Islands. Based on the realistic topography, stratification, and tidal forcing, two-dimensional numerical simulations using the MITgcm reveal that the NLIWs observed on the continental shelf can be generated from the Xisha Islands through the internal tidal beam regime. Furthermore, the internal tide energy flux estimation shows that the locally generated internal tides that arise from the continental shelf break mostly carry their energy toward the deep water and have little effect on the generation of NLIWs on the shelf.