Abstract: Seawater density is a key parameter for quality control of oceanographic observations and thermodynamic property calculations within the TEOS-10(thermodynamic equation of seawater 2010) framework. To address the limited availability of density measurements, theoretical density comparisons and uncertainty evaluations for Chinese standard seawater under the TEOS-10 framework, this study uses Chinese primary and series standard seawater as the main research objects, with IAPSO (international association for physical sciences of the ocean) Standard Seawater as a reference. Density measurements were conducted at 25℃ and atmospheric pressure using a DMA 5000M vibrating-tube densimeter and a pure-water substitution method. The Absolute Salinity range of the samples was 5.018–40.209g·kg−1. First, the Practical Salinity of Chinese standard seawater was converted to Absolute Salinity using sampling-location information, so as to unify the salinity input basis for TEOS-10 theoretical density calculation. Then, the measured densities were compared with the TEOS-10 theoretical densities, and the uncertainty of the density results was evaluated based on an uncertainty propagation model. The results show that the maximum absolute deviation between the measured densities and TEOS-10 theoretical densities for all samples was 0.0080kg·m−3, and the root mean square error was 0.0051kg·m−3. The root mean square error was 0.0061kg·m−3 for IAPSO Standard Seawater and 0.0040kg·m−3 for Chinese standard seawater, indicating similar deviation levels between the two groups. The expanded uncertainty of the density results was 0.0086kg·m−3 (k=2), and the maximum density deviation did not exceed the expanded uncertainty range. The equivalent density uncertainty converted from Absolute Salinity input and the measurement repeatability were the main sources of uncertainty in the density results. This study provides experimental evidence for density evaluation of Chinese standard seawater under the TEOS-10 framework, standard seawater value comparison, and quality control of oceanographic observations.

Key words: vibrating tube densitometer, substitution method, standard seawater, TEOS-10, measurement uncertainty