Study On Ocean Acidification At The Chukchi Sea And The Nordic Sea

Since the industrial revolution, the CO2 has increased rapidly in the atmosphere, the ocean acidification occured by absorbing more atmospheric CO2. The ocean acidification is a global phenomenon, in the high latitude areas,the situation is even more severe. In the Arctic Ocean acidification the Arctic surface seawater has lower p CO2, lower temperature and sea-ice melting in summer, which could worsen the acidification.Based on the data from Chinese National Arctic Research Expedition and CARINA database, ocean acidification in the Nordic Sea and the Chukchi Sea was studied. Furthermore, the data was analysed by orthogonal partial least squares discriminant analysis(OPLS-DA). The outcomes are concluded as follows:(1) Ocean acidification in the Chukchi Sea happends. The surface water being exposed to high CO2 concentrations atmosphere for more time,with the Arctic sea ice retreated rapidly and the ice-free period extended. The waters at the north of the Chukchi Sea has been through aragonite unsaturated(Ωarag <1) in 2012. Two subsurface aragonite unsaturated water massses were found in the Chukchi Sea, one of them is at 100 meter depth at the shelf break and the other is at 200 meter depth at shelf slope. They were two distinct water masses in 1994, while they expanded and joined during the Chinese National Third Arctic Research Expedition in 2008 as well as in 2012. p Hin-situ in the Chukchi Sea also has a trend of declining from 1994 to 2012.(2) On the contrary, the ocean acidification in the Nordic Sea is not obvious. All the waters in the Nordic Sea is aragonite supersaturated. The lowest aragonite saturation observed in four cruises from 1993 to 2012 is 1.77. The deep water is mixed by many water masses, of which the deep water masses are almost the same and calcium carbonate saturation decreases with depth. Aragonite saturation compensation horizon is at about 2000 meter depth. Aragonite saturation compensation horizon has no change in these years. The surface water masses are extremely different since they have different sources. The Nordic Sea is a area without sea-ice melt water and river runoff. The carbonate system in Greenland coastal water would be only affected by ice melt water in early summer.(3) Biological factors, absorption capacity of the atmospheric CO2, temperature and salinity are the main controls on surface water ocean acidification in the two sea areas. High primary productivity in surface waters lead to high p H values and Ω, which meets the Phytoplankton Carbonate Saturation State model. The Chukchi Sea is affected by river runoff, sea-ice meltwater and snowmelt from surrounding mainland. Biologically production and freshwater dilution have much effect on the ocean acidification in the Chukchi Sea. Nordic Sea has stable water masses without river runoff, only the Greenland coastal waters suffered the effect of dilution.(4) Arctic sea-ice retreats as the Arctic Sea gets warm. The data of all these years observed in the Arctic indicate that the extent of ocean acidification and Arctic sea-ice conditions of the same has a significant correlation. The Chukchi Sea suffered the worst ocean acidification in the summertime of 2008 and 2012, when Arctic sea ice retreated most ever since 1980.