Profiling measurement of internal tide in the Bali Strait by reciprocal sound transmission

A reciprocal sound transmission experiment was carried out from 10 to 12 June 2015 along one-crossed-strait line in the Bali Strait with strong tidal current to measure the vertical section structures of range-averaged current and temperature at a 3 minutes interval. The five-layer structures of those parameters in the vertical sections were reconstructed by the regularized of travel time data for 2 rays. The hourly mean current showed a generation of nonlinear internal tide with amplitudes of (1.0—1.5)m/s and period of 6 hours, superimposed on semi-diurnal internal tide with amplitudes, decreasing from the upper to lower layer. The hourly mean temperature was characterized by variation with amplitude of (1.0-1.5) and period of 6 and 8 hours. Current variation revealed an out of phase relation between the upper and lower layer while temperature varied in phase for all five layers. The 2-day average current formed a stratified structure, varying from -0.6 to -0.1m/s and from 23.8 to 28, respectively. The five-layer current and temperature were significantly over the inversion errors. It is suggested that thermal stratification in the Bali strait was caused by intrusion of dense cold water from the Indian Ocean due to coastal upwelling.