Observed Deep Circulation in the Luzon Strait

Three mooring systems were deployed at the Bashi Channel (BS), Luzon Trough (LT) and off the east coast of Batan Island (BI), respectively, to examine the deep circulation around the Luzon Strait (LS). Our analysis suggests that semidiurnal and diurnal tidal signals dominate the fluctuation of the deep flow. Subinertial flow is basically from Pacific to the South China Sea (SCS) and controlled by topography, with maximum of 0.35m/s and a 30-day oscillation. Correlation analysis is conducted between velocity of upstream and downstream, as well as between velocity and potential temperature. The subinertial flow at BS and LT reveals the existence of a remarkable seasonal variability that the deep flow is much stronger in winter than in summer, which is consistent with the potential density difference between deep Pacific and SCS. In addition, decomposition of velocity at BI shows that the meridional component along the topography is much larger, which also vibrates with seasonal signal, basicly flowing to the south in summer and north in winter.