Estimating the Absolute Salinity of China Offshore Seawater Using Nutrients and Inorganic Carbon Data

Abstract. In June 2009, the Intergovernmental Oceanographic Commission of UNESCO released the international thermodynamic equation of seawater – 2010 (TEOS-10 for short) (IOC et al, 2010) to define, describe and calculate the thermodynamic properties of seawater. Compared to Equation of Ocean State-80 (EOS-80 for short), the most obvious change of TEOS-10 is taking Absolute Salinity as salinity argument, replacing the Practical Salinity used in ocean society for 30 years. Due to lack of observation data, Absolute Salinity algorithm the applicability in the offshore and semi-closed sea is not very clear to date. Based on the Marine Integrated Investigation and Evaluation Project of China Offshore, other relevant data together with Pa08 model, we obtain the magnitude, distribution characteristics and formation mechanism of Absolute Salinity in China offshore. As the main composition anomaly relative to SSW, calcium carbonate, originating from terrestrial input of high calcium carbonate content and re-dissolution of sediment of China offshore, raises the Absolute Salinity Anomaly δS_A as high as 0.20 g kg^-1 and increases the Practical Salinity about 0.025 at most comparing to the chlorinity-based salinity. Moreover, both of them show obvious seasonal variation. Finally, relevant suggestions are proposed for the accurate measurement and expression of Absolute Salinity of the China offshore.