Numerical study on the spatial and temporal characteristics of nonlinear internal wave energy in the Northern South China sea

Abstract The energy features of nonlinear internal waves (NLIWs) are relatively less known and should be an important term in the energy budget of the northern South China Sea (NSCS). In this paper, the spatial and temporal characteristics of NLIW energy across the NSCS basin are investigated using a realistic three-dimensional nonhydrostatic model. An anisotropic nature of the NLIW energy is revealed based on the depth-integrated kinetic energy and available potential energy within the waves. It is a result of the 3D wave dynamics which are not only associated with local shoaling topography but also affected by the 3D bathymetry of the basin in the course of wave propagation. A further investigation of the NLIW energy transportation suggests that the and have different patterns of transit but eventually will enter the shelf primarily through the right side of the Dongsha Atoll. By estimating the energy carried by NLIWs at different stages of propagation, it is found that it changes from a total of 111.98 TJ near the generation area to 43.49 TJ in the shelf region. This means more than half of the NLIW energy will be lost after the waves cross the basin. Finally, we are able to quantify the NLIW energy importation rate in three regions of the NSCS basin that are distinct in the dynamics of propagation. With a clearer view of the spatial and temporal characteristics of NLIW energy in the NSCS, this study stresses the importance and necessity to investigate the 3D nature of NLIWs in the NSCS.