Impacts of Stratification Variation on the M2 Internal Tide Generation in Luzon Strait

ABSTRACT Topographic features, stratification, and barotropic tidal currents are three factors that determine internal tide (IT) generation. However, the mechanism of the impacts of stratification variation on IT generation in Luzon Strait (LS) has not been extensively explored. A three-dimensional high-resolution model is used to simulate the M2 ITs in the northern South China Sea (SCS) under different stratification conditions. The model is run with idealized topographies where the east or west ridge of LS is removed. Results indicate that both the M2 conversion rate and energy fluxes in the northern SCS show seasonal variations that are site dependent. By analyzing all the results from the simulations, we find that stratification variation changes IT generation in LS mainly through two mechanisms. First, the impact of stratification variation on the bottom pressure perturbation is caused by barotropic tidal currents flowing over topographic features, which directly affects the conversion. Second, stratification variation changes the wavelength of ITs and, hence, the interference of ITs within the double ridges, which finally changes the conversion in LS. The second mechanism is found to be the dominant one for seasonal variation of the M2 IT generation in LS.