Mooring observations of tidal currents in the Jailolo Strait of the Indonesian seas

Abstract

The vertical structure of internal tidal currents in the Jailolo Strait of the Indonesian seas is studied using the year-long mooring observations with two Acoustic Doppler Current Profiler instruments looking upward and downward, respectively, coving the full depth of the strait. The barotropic tides are extracted from the full-depth current profile measurements, showing the dominant M₂, K₁, and O₁ tidal currents with amplitudes of 13.5 cm s⁻¹, 11.0 cm s⁻¹ and 7.6 cm s⁻¹, in nearly reciprocating movement in the direction of 34.5°, 63.1°, and 75.2° clockwise from due north. The internal tidal currents in the Jailolo Strait contributing to about 50% of the total kinetic energy are found to be dominated by the low baroclinic modes, with M₂ tide as the most dominant tidal constituent. High-frequency internal tides of D₃ and D₄ are observed, with baroclinic structure similar to that of M₂ tides, and are suggested to be stimulated by nonlinear processes. The complicated vertical structure of tidal currents in the Jailolo Strait is disclosed for the first time in history. Its potential impact on vertical turbulent mixing suggests its importance in global ocean circulation and climate.