Estimating the Energy Flux of Internal Tides in the Northern South China Sea Using Underwater Gliders

The character of internal tides energy flux in the northern South China Sea (SCS) is explored through an analysis of a fleet of underwater gliders. It is found that the lower mode diurnal internal tides with ~300 km wavelength in the middle basin originate predominantly at the Luzon Strait (LS) and propagate over 1000 km to the western SCS. The semidiurnal internal tides, however, originate from multiple regions, including the LS, the continental shelf, and the islands in the west part. The energy flux of the mode-1 diurnal internal tides attenuated rapidly within 450 km of the LS and was less pronounced after that. The estimated dissipation rate based on the mode-1 energy flux is about 10-8 W/kg, underling the significant role of mode-1 diurnal internal tides in bolstering far-field mixing. This study provides a unique view of the spatial pattern, energy flux, and energy sink of the internal tides in the northern SCS, which could supplement the altimetry-based results and improve the parameterization in ocean models.