Diurnal and semidiurnal internal tide energy flux at a continental slope in the South China Sea

Abstract

Barotropic (surface) and baroclinic (internal) tides were measured at four mooring sites during a field investigation of acoustic propagation characteristics and physical oceanography in the northern South China Sea. The mooring positions were in a line moving up the shallow portion of a continental slope at water depths between 350 and 85 m. Using time series of temperature and velocity, at several depths, 1-month series of semidiurnal and diurnal species internal tidal energy flux vectors were computed for three sites, with a 14-day series computed for the fourth (shallow) site. The internal tides had a temporal signature that was not in complete accord with the barotropic tides, showing an enhancement of diurnal internal tides with respect to semidiurnal. Bathymetric slope, barotropic tidal fluid particle trajectories, and scale of generation site versus internal tide wavelength are investigated as possible causes of the differing response of the species.