The Carbon Dioxide System In Seawater Of North Yellow Sea And Qingdao Coast

As the biggest carbon reservoir on the earth surface, oceans play a dominant role in the natural regulation of CO2 in the atmosphere, thus exerting a powerful influence on the climate and marine ecosystem. The study of carbon dioxide including the ocean's ability of absorbing and transferring the atmospheric carbon dioxide has become an important content. The coastal seas only account for a small fraction of ocean but they contribute a disproportionately large fraction of oceanic primary production and strongly affect the global carbon cycle. However, it has been unsure whether the coastal seas act as sinks or sources of atmospheric CO2. The reason is that there has been lack of field data on the spatial and temporal variability of dissolved inorganic carbon (DIC) and partial pressure of CO2 (pCO2) in coastal oceans. Another question of carbon dioxide system research is that the scale of pH is still inconsistent. It is a goal to use identical pH scale in the natural water in the future. Yellow Sea is one of the most typical marginal seas in the world, but the study of carbon dioxide system in North Yellow Sea is scarcely reported untill now, especially the study of DIC and pHSWS in seawater of North Yellow Sea.In this article two typical marginal seas, namely north Yellow Sea and Qingdao Coast, are investigated. Field observations were carried out in North Yellow Sea and Qingdao Coast. Data on the distribution of dissolved inorganic carbon (DIC) are obtained from three cruises. And pH is translated from pHNBS into pHSWS. Carbonate parameters are calculated by DIC, pHSWS, temperature, salinity and dissociation constants of carbonic acid in seawater. The distribution difference is discussed between DIC and normalized total CO2 (NTCO2) in north Yellow Sea and Qingdao Coast. Air–sea CO2 fluxes are calculated using Liss&Merlivat method, Tans method and Wanninkhof method. The average of the air–sea CO2 fluxes is estimated by arithmetic mean and 0.5°×0.5°grid, and the results suggest that both North Yellow Sea in October, 2007, and Qingdao Coast in October, 2007 and November, 2008 are potential source of atmospheric CO2.The main achievements are following: 1.pH is translated from pHNBS into pHSWS and applied to North Yellow Sea and Qingdao Coast.①According to the carbonic acid dissociation constant (pK1) in the sea water, pH is translated from pHNBS into pHSWS, and pHSWS is applied to North Yellow Sea and Qingdao Coast.②There is a reverse trend of pHSWS distribution in upper layer and lower layers in North Yellow Sea in October, 2007. pHSWS in upper layer increases from the shelf to the centre of North Yellow Sea, whereas pHSWS in lower layers decreases from the shelf to the centre of North Yellow Sea.③There is no obvious distribution trend of pHSWS in Qingdao Coast in October, 2007. pHSWS decreases southward in Qingdao Coast in November, 2008. Except 20m layer, there is an obvious minus relationship between pHSWS and DIC in North Yellow Sea in October, 2007. pHSWS and DIC in Qingdao Coast in October 2007 and November, 2008 is no obvious relationship.2. The distributions of DIC and normalized total CO2 (NTCO2) are researched in North Yellow Sea in October, 2007 and in Qingdao Coast in October, 2007 and November, 2008.①There is a reverse trend of distribution of NTCO2 in upper layer and lower layers in North Yellow Sea in October, 2007. NTCO2 in upper layer decreases from the shelf to the centre of North Yellow Sea, whereas NTCO2 in lower layers increases from the shelf to the centre of North Yellow Sea and South Yellow Sea. The distribution of DIC and NTCO2 is reverse at Yalu River estuary in upper layer in North Yellow Sea in October, 2007. It is found that the high DIC areas are consistent with the areas of Yellow Sea Cold Water Mass.②In Qingdao Coast, DIC decreases from Jiaozhou Bay to offshore then increases gradually in open sea, and the lowest DIC area lies between JB and open sea, whereas NTCO2 decreases gradually from Jiaozhou Bay to open sea in October, 2007; DIC and NTCO2 decrease gradually from Jiaozhou Bay to open sea in November 2008. 3.The distributions of carbonate and pCO2(SW) in seawater are researched in North Yellow Sea in October, 2007 and in Qingdao Coast in October, 2007 and November, 2008.①The distributions of HCO3- and CO32- are respectively similar with the distributions of DIC and pHSWS in the researched area.②In North Yellow Sea, pCO2(SW) in surface seawater decreases from the shelf to the centre of North Yellow Sea in October, 2007, except Yalu River estuary where pCO2(SW) in surface seawater increases from the shelf to the centre of North Yellow Sea.③In Qingdao Coast, pCO2(SW) in surface seawater increases southward in October, 2007 and November, 2008.4.The air–sea CO2 flux is calculated by Liss&Merlivat method, Tans method and Wanninkhof method with in situ speed of wind and monthly mean wind speed in North Yellow Sea in October,2007 and Qingdao Coast in October 2007 and November, 2008. Both North Yellow Sea in October 2007 and Qingdao Coast in October, 2007 and November, 2008 are potential source of atmospheric CO2.①The averages of the air–sea CO2 flux of North Yellow Sea is 0.0365 mol·m-2·a-1 ~ 0.2279 mol·m-2·a-1 in October, 2007, which suggests that North Yellow Sea in October, 2007 is a potential source of atmospheric CO2.②The averages of the air–sea CO2 flux of Qingdao Coast is 0.4023 mol·m-2·a-1~ 0.8915 mol·m-2·a-1,0.3020 mol·m-2·a-1 ~ 0.4270 mol·m-2·a-1 in October, 2007 and November, 2008 respectively which suggests that Qingdao Coast in October, 2007 and November, 2008 respectively is a potential source of atmospheric CO2.