The Evolution Of The Control Mechanism Of Surface Water PCO₂ In The Yellow Sea In Spring And Summer

Nowadays, the study on the transfer and end-result of carbon dioxide including the ocean's ability in absorbing and transferring the atmospheric carbon dioxide, the cycle mechanism of carbon dioxide in oceans et al. has been an important content in many international marine scientific research plans, such as JGOFS,LOICZ and IGBP, especially in the Surface Ocean and Lower Atmosphere Study (SOLAS).In combination with the cogredient datas of hydrology, chemistry and biology, the dates of surface water CO₂ partial pressure (pCO₂) at grid stations in the Yellow Sea(YS),in the three cruises of SOLAS , the first cruise of"908"and the cruise in July,2001,are served to discuss the distribution of the pCO₂ and the mechanisms by which the whole sea could sustain such level of pCO₂.The main results are following: The magnitude of pCO₂ of early spring showed that the YS acted as a source of CO₂ for the atmopher. Mainly because the vertical mixing was remain prominent hydrographic feature in early spring, so that the water with high concentration of CO₂ at the bottom layer could transport to the surface layer. In spring, the pCO₂ is high in the northern YS and the coastal area due to influences of vertically homogeneous structure. As far as the offshore of the southern YS which influenced by Yellow Sea Cold Water, is concerned, pCO₂ is lower than atmosphere pCO₂. The significant hydrology feature of the southern YS is the emergence of the thermal stratification, and the surface water could not get high pCO₂ supplement from the bottom so that pCO₂ is lower there than others. Meanwhile, due to the spring stratification, the nutriment is abundance for which the biological activity is intense, so the photosynthesis has caused a decrease of pCO₂ in the middle SYS. In May, the Yangzte freshwater, Northern Jiangsu Coastal Water, the upwelling water bring about the high value of pCO₂ in the southwestern SYS. In summer, The pCO₂ is high in the northern of 35°N and the coastal area, due to the physical factors. The southern of 35°N pCO₂ is low due to influences of Yangzte freshwater. During the diffusing of Yangzte freshwater to NE, it generates a plume front which can expand to 35°N, and the pCO₂ decrease with Chl-a. That because the plume front contains abundant nutrients which result in significantly enhanced biological activities, and thus lead to pronouncedly increased consumption of CO₂.Using three gas exchange coefficients calculated from the Wanninkhof (1992), Tans(1990), McGillis(2001)and the instantaneous wind speed, to calculate the monthly and seasonally flux of the Yellow Sea. In March, the whole YS as a source, can release 2.98×10⁶tC to the atmosphere. The flux of April and July releases about tenth of the March. But in May, the SYS becomes a sink, and it can absorbs 0.90×10⁶tC. Overall, the region is a sink in spring and summer, and it releases 3.54×10⁶tC to the atmosphere in all.