ABSTRACT: The South China Sea (SCS) exhibits strong variations on seasonal to interannual time scale, and the changing Southeast Asian Monsoon has direct impacts on the nutrients and phytoplankton dynamics, as well as the carbon cycle. A Pacific basin-wide physi-cal-biogeochemical model has been developed and used to investigate the physical variations, ecosystem responses, and carbon cycle consequences. The Pacific basin-wide circulation model, based on the Regional Ocean Model Systems (ROMS) with a 50-km spatial resolution, is driven with daily air-sea fluxes derived from the National Centers for Environmental Prediction (NCEP) reanalysis between 1990 and 2004. The biogeochemical processes are simulated with the Carbon, Si(OH) 4 , Nitrogen Eco-system (CoSINE) model consisting of multiple nutrients and plankton functional groups and detailed carbon cycle dynamics. The ROMS-CoSINE model is capable of reproducing many observed features and their variability over the same period at the SouthEast Asian Time-series Study (SEATS) station in the SCS. The integrated air-sea CO 2 flux over the entire SCS reveals a strong seasonal cycle, serving as a source of CO 2 to the atmosphere in spring, summer and autumn, but acting as a sink of CO 2 for the atmosphere in winter. The annual mean sea-to-air CO 2 flux averaged over the entire SCS is +0.33 moles CO 2 m –2 year –1 , which indicates that the SCS is a weak source of CO 2 to the atmosphere. Temperature has a stronger influence on the sea-sonal variation of pCO 2 than biological activity, and is thus the dominant factor con-trolling the oceanic pCO 2 in the SCS. The water temperature, seasonal upwelling and Kuroshio intrusion determine the pCO 2 differences at coast of Vietnam and the north-western region of the Luzon Island. The inverse relationship between the interannual variability of Chl-a in summer near the coast of Vietnam and NINO 3 SST (Sea Sur-face Temperature) index in January implies that the carbon cycle and primary pro-ductivity in the SCS is teleconnected to the Pacific-East Asian large-scale climatic variability.
Journal of Oceanography 01/2009; 65:703-720. · 1.23 Impact Factor