Temperature at a mooring in Northern South China Sea and its connection with surface heat flux, wind and eddies

Abstract:

Twenty-two month temperature profile (from surface to z = -500m) at a mooring located west-southwest about 450 km from the Luzon Strait in northern South China Sea (NSCS) is analyzed in conjunction with altimetry, CCMP wind, and mixed-layer model forced by the NCEP surface heat flux. EOF [Kutzbach 1967 J. App. Met], SVD [Bretherton et al 1992, J. Clim] and EMD [Huang et al 1998, Proc. Roy Soc] methods are used to separate and identify different physical processes and mechanisms. The dominant fluctuation at the mooring is shown to be seasonal, caused (1) by seasonal surface fluxes and local Ekman pumping (on the f-plane) by the wind stress curl, (2) by eddies emanated west of the Luzon Strait spun up by wind stress curl west of Luzon, and (3) by Rossby waves due to Kuroshio path fluctuations in the Strait. Meso-scale eddies are embedded in the seasonal variation and they are shown to be locally generated by baroclinic instability and penetrate through the entire depth of the mooring.