Tidal Mixing in the South China Sea: An Estimate Based on the Internal Tide Energetics

Abstract

Abstract By taking into account the contributions of both locally and remotely generated internal tides, the tidal mixing in the Luzon Strait (LS) and the South China Sea (SCS) is investigated through internal-tide simulation and energetics analysis. A three-dimensional nonhydrostatic high-resolution model driven by four primary tidal constituents (M 2 , S 2 , K 1 , and O 1 ) is used for the internal-tide simulation. The baroclinic energy budget analysis reveals that the internal tides radiated from the LS are the dominant energy source for the tidal dissipation in the SCS. In the LS, the estimated depth-integrated turbulent kinetic energy dissipation exceeds O (1) W m −2 atop the two subsurface ridges, with a dissipation rate of > O (10 −7 ) W kg −1 and diapycnal diffusivity of ~ O (10 −2 ) m 2 s −1 . In the SCS, the most intense turbulence occurs in the deep-water basin with a dissipation rate of O (10 −8 –10 −6 ) W kg −1 and diapycnal diffusivity of O (10 −3 –10 −1 ) m 2 s −1 within the ~2000-m water column above the seafloor as well as in the shelfbreak region with a dissipation rate of O (10 −7 –10 −6 ) W kg −1 and diapycnal diffusivity of O (10 −4 –10 −3 ) m 2 s −1 . These estimated values are consistent with observations reported in previous studies and are at least one order of magnitude larger than those based solely on locally generated internal tides.