Distribution And Controlling Factors Of Surface Seawater Partial Pressure Of CO₂ In The Northern Yellow Sea During Autumn

Because of the unique geographical structure of the shelf sea and the adjacent land, subject to the impact of human activities, the source/sink mechanism of CO₂ is more complex. But for the Chinese area the carbon cycle and its mechanism are still relatively weak. Distribution and controlling factors of surface seawater partial pressure of CO₂ (pCO₂) were determined in the northern Yellow Sea during autumn based on the data obtained using continuous underway measurements of pCO₂ and related parameters in hydrology, chemistry and biology during October 2007.The results show that in autumn the pCO₂ ranged from 354μatm to 435μatm, with an average of 395μatm. The Liaonan coastal area acted as a source of atmospheric CO₂. But in the coastal area north of Shandong Peninsula, both sources and sinks of the atmospheric CO₂ exist: the pCO₂ was oversaturated in the area strongly influenced by the input of Bohai Sea coastal water and terrestrial materials, whereas it was undersaturated in the area with strong biological activity. Because of the strong biological activity, the central region occupied with the Yellow Sea Mixing Water acted as a large sink of atmospheric CO₂ during autumn. On the whole, the northern Yellow Sea acted as a weak source of atmospheric CO₂ during autumn.During autumn the pCO₂ was mainly controlled by the biological activity. Higher temperature and higher DIC concentration in response to higher pCO₂, respectively higher Chl a level associated with lower pCO₂. Especially, in the central region the pCO₂ was significantly affected by the intense biological activity, and the pCO₂ of the coastal region located in the north of Shandong Peninsula which hosted high turbidity was mainly controlled by higher DIC level and terrestrial influence.The northern Yellow Sea is a source of the atmospheric CO₂, and the carbon flux at the sea-atmosphere interface is about 2.27×10³tC in autumn. The area influenced by Bohai Sea coastal water account for 10% of the source although its area reach 0.4×10⁴km². Because of biological activity the area influenced by the Yellow Sea Mixing Water acted as a sink of atmospheric CO₂ and it accounted for 99%.