Observations of Water Mass Mixing in the Luzon Strait

A vertical water mass structure was observed from temperature and salinity in the Luzon Strait. The corresponding shear velocity and turbulent dissipation rate were observed by an acoustic Doppler current profiler (ADCP) and a microstructure instrument (TurboMAP–L). Temperature and salinity at two stations (21ºN, 120ºE and 19.5ºN, 121ºE) changed sharply at 80- and 120-m depths. Interestingly, the turbulent dissipation rates and the eddy diffusivity had two peaks at these depths with values of O(10^-6)Wkg^-1 and O(10^-3)m²s^-1. Notable shear instabilities with critical Richardson number were captured at these depths. It is suggested that the two peaks of dissipation rate and eddy diffusivity were induced by strong shear instability between the interfaces of different water masses in the Luzon Strait.