The specific volume of seawater at high pressures

Abstract The high pressure specific volumes of seawater (relative to pure water and 1 atm) have been measured from 0 to 40°C, 0 to 1000 bars and 5 to 40 ‰ salinity with a high pressure magnetic float densimeter ( Millero, Knox and Emmet , Journal of Solution Chemistry , 1 , 173–186, 1972). The results of the measurements have been fitted to a secant bulk modulus ( K ) equation of state K = V 0 P/(V 0 − V P ) = K 0 + AP + BP 2 , where V 0 and V P are the measured specific volumes of seawater at applied pressure zero and P , respectively, K 0 = 1/β o , the reciprocal of the isothermal compressibility at atmospheric pressure, A and B are all salinity- and temperature-dependent parameters. The specific volumes have been fitted to this equation with a standard deviation of 7 ppm (on the measurement residuals) over the entire salinity, temperature and pressure range. The fitted relative specific volumes ( V P − V 0 ) are in excellent agreement (within ±5ppm ) with the sound-derived data of Wang and Millero ( Journal of Geophysical Research , 78 , 7122–7128, 1973) over the oceanographic range of salinity, temperature and pressure. The derived P-V-T properties have been compared with the experimental work of Ekman ( Publications de circonstance. Conseil permanent international pour l'exploration de la mer , 43 , 1–47, 1908); Wilson and Bradley ( Deep-Sea Research , 15 , 355–363, 1968); Bradshaw and Schleicher ( Deep-Sea Research , 17 , 691–706, 1970; personal communication 1974); Duedall and Paulowich ( Review of Scientific Instruments , 44 , 120–127, 1973); Emmet and Millero ( Journal of Geophysical Research , 79 , 3463–3472, 1974) and the sound-derived data of Wang and Millero (1973); Fine, Wang and Millero ( Journal of Marine Research , 32 , 433–456, 1974).