Estimation & Analysis For CO₂ Flux Of Yellow Sea

Ocean plays an important role in global carbon cycle, and it is the major absorb tank for the CO2 in the atmosphere. An accurate quantitative estimation for marine carbon budget is meaningful to evaluate and predict the content of CO2 in atmosphere, the change of global climate and the influence to the marine ecological environment.The carbon exchange of the whole ocean depends on wind, temperature, speed of ocean circulation, biological pump and lots of other factors, while the carbon exchange between atmosphere and ocean can only occur in surface layer water. There are various funtions for computing gas transfer velocity, however, their huge differences lead to different CO2 flux results, which produces confusion to our quantitative estimation for carbon budget. In this thesis, our computation is based on Yellow Sea voyage in situ data collected by University of Xiamen during 13th-31st May 2005 and 16th-30th April 2006, the wind history data of the National Basic Research Program (also called 973 Program) of China, and the SWAN wave model results. Under the same difference of partial pressure between air and sea, the air-sea CO2 fluxs calculated according to the different parameterization gas transfer velocity functions are compared..The functions base on wind include the forms given by Wanninkhof (1992) Wanninkhof & McGillis(1999), Nightingale et al (2000b) and Sweeny et al (2007),while the functions base on sea surface conditions include Woolf(2005) and Zhao & Xie(2010) forms which focus on wave breaking effect, and the Zappa et al(2007) and Lorke & Peeters (2006) formulas that take the turbulent kinetic energy dissipation as the impact factor. The function for computing turbulent kinetic energy dissipation rate isε=0.604(Dissip/(ρw·Hsign), whereρw is the density of ocean, Dissip is the total energy dissipation, Hsign is significant wave height, which are all from the result of SWAN model.The values of gas transfer velocity can be totally different, and air-sea CO2 flux sensitively depends on the choice of gas transfer velocity, too. The models consider wind speed only is not appropriate or efficient to describe the effect on gas transfer. The function base on turbulent kinetic energy dissipation rate can avoid the monotonic dependence of wind speed, which still gets moderate gas transfer velocity even under low wind speed.The major souce of CO2 flux lies in western and southern part of South-Yellow Sea, where along the coastal area of Jiangsu Province, while the sink is in eastern and middle of South-Yellow Sea. The net CO2 flux for May of 2005 is negative, which is considered as the sink. The net CO2 flux for April of 2006 is positive, which is considered as the source.