Abstract: An ADCP mooring system was placed at a depth of 4000m southwest of the Luzon Strait in August 2008. Upper-ocean currents at high frequency were measured for about one month. Using different data processing methods, the authors analyze the current records to obtain the vertically averaged currents, tidal currents at each depth, and frequency distributions of the baroclinic currents. The main tidal components in this area are irregular diurnal tidal currents, and their ellipses are spiraling with depth. The power spectrum indicates that the tidal energy reaches the maximum near the thermocline and then decreases with depth. The analysis of the current frequency also shows that the currents have significant near-inertial oscillations. These observations provide first-hand data for studying tidal currents, near-inertial oscillations and water exchange between the South China Sea and the Pacific nearby the Luzon Strait.

Key words: ADCP observation, ADCP observation, Luzon Strait, Luzon Strait, tidal current, tidal current, near inertial oscillations, near inertial oscillations