On the seasonal variation of air-sea CO2 fluxes in the outer Changjiang (Yangtze River) Estuary, East China Sea
- 海洋环境－已发表论文 
Based upon seven field surveys conducted during April 2005 - April 2008, we examined the surface partial pressure of CO2 (pCO(2)) and dissolved oxygen (DO) in the outer Changjiang (Yangtze River) Estuary, on the inner shelf of the East China Sea (ECS). This area represents a most dynamic zone of the ECS where high pCO(2) riverine water meets with highly productive shelf waters, covering a 2 degrees x 3 degrees area, similar to 10% of the surface area of the entire ECS. Surface pCO(2) ranged 320 - 380 mu atm (average similar to 345 mu atm) in winter, 180 - 450 mu atm (average similar to 330 mu atm) in spring, 150 - 620 mu atm (average similar to 310 mu atm) in summer and 120 - 540 mu atm (average similar to 375 mu atm) in autumn. The seasonal variation pattern of surface DO generally mirrored that of pCO(2), ranging 95% - 105% in winter, 96% - 142% (average 110%) in spring, 73% - 192% (average 718%) in summer and 81% - 178% (average 102%) in autumn. The dynamics of pCO(2) drawdown and DO enhancement in the warm seasons (from April to October) appeared to be controlled by primary productivity and air - sea exchange, while mixing dominated the aqueous pCO(2) in the cold seasons (from November to March of the following year). This study showed that the outer Changjiang Estuary served as a moderate or significant sink of atmospheric CO2 in winter, spring and summer, while it turned to a net source in autumn. The integrated sea - air CO2 flux in the outer Changjiang Estuary was estimated as -1.9 +/- 1.3 mol m(-2) year(-1), which is double the recent sea-air CO2 flux estimation for the northern ECS. (C) 2009 Elsevier B.V. All rights reserved.