Mixed layer thermodynamics of the Southern South China Sea

Seasonal and inter-annual variability of the mixed layer temperature in the Southern South China Sea (SSCS) is investigated using a regional ocean circulation model simulation. The mixed layer depth (MLD) over the SSCS exhibits a strong seasonal signal with deeper MLDs during the northeast and southwest monsoons. The main factor that drives the mixed layer temperature variation in the SSCS is the air-sea heat fluxes, with vertical ocean processes acting as a relatively weak negative feedback. In general, the budget analysis demonstrates a net balance between the vertical ocean processes and surface heat flux during the pre-monsoon and southwest monsoon. Northeast monsoon period is noted by an offsetting of surface heat flux, horizontal and vertical ocean processes. The first dominant mode of mixed layer temperature inter-annual variability in the SSCS shows significant correlation (0.34) with the El Nino phenomenon in the Pacific Ocean and is best correlated (0.67) with a lag of 5 months.