Study On Impacting Factors Of PCO₂ In The East China Sea In Winter

In the study of global carbon cycle, the continental margin, being considered one of the potential sinks of the missing term of carbon, has become the focus of researches in the past few decades. It is of great importance, for the discussion of global carbon cycle and for the consummation of the global carbon database, to study the CO2 flux over the East China Sea since it is one of the important marginal seas in Northwest Pacific.Based on the cruise carried out during Jan. and Feb. 2007 in the East China Sea (ECS), the hydrological, chemical and biological properties of surface water of ECS were studied. The data of surface water CO2 partial pressure (pCO2) and other related cogredient parameters were investigated to discuss the distribution of the pCO2 and the impacting factors by which the whole sea could sustain such level of pCO2.Surface pCO2 ranged from 237 to 507μatm in winter, Large pCO2 (values ? 400μatm) occurred in the northeast part of the study area. The relationship between pCO2 and water stability suggested that the amount of mixing and /or upwelling of CO2-rich water might be the important process controlling surface pCO2 levels. A negative linear between surface and Chla suggested that photosynthesis caused by plankton activity is another major factors controlling surface pCO2 distribution in spite of the low temperature of surface water in winter.Sea-air CO2 flux, based on the application of a Wanninkhof formula for gas transfer velocity (1992, Relationship between wind speed and gas exchange over the ocean) and a set of in situ instantaneous wind data was -0.71 mol C/m2 yr, the CO2 flux of source and sink area were +2.72 and -5.82 mol C/m2 yr respectively. During the winter, the study area is assumed to absorb about 1.85×106 t C from the atmosphere. That result suggests that the ECS is a net sink for atmospheric CO2 in winter.