Ocean margins play an important role in the global oceanic carbon cycling.The South China Sea (SCS) is the world largest marginal sea located in the tropic and subtropical region.It is oligotrophic and our prior studies have shown that the northern SCS is a weak / moderate source for the atmospheric CO2 in spring,summer and autumn,while it is a moderate sink in winter.However,it is still lacking CO2 air-sea fluxes with reasonably spatial-temporal coverage of the northeastern South China Sea off Luzon.In December of 2006,we conducted a cruise in the SCS,covering the northeastern South China Sea off Luzon.During the cruise,the northeast monsoon burst out on the mid-December.Prior to the northeast monsoon,surface partial pressure of CO2 (pCO2) was measured as 360 – 390 μatm in the region.However shortly after the northeast monsoon beginning,pCO2 increased into 390 – 460 μatm,significantly high than atmospheric pCO2.This CO2 outgassing enhancement may attribute to the beginning of northeast monsoon induced upwelling in this region.In contrast to this winter upwelling region,the northern shelf region of the SCS had turned to uptake CO2 from the air,as revealed before.This result shows,there are more CO2 sources for the upper SCS than what has been revealed before.Much remains to be investigated in order to quantitatively evaluate the role of marginal seas in the global ocean carbon cycle.