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 andEmmet, 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 = V⁰P/(V⁰ − V^P) = K⁰ + AP + BP², where V⁰ and V^P are the measured specific volumes of seawater at applied pressure zero and P, respectively, K⁰ = 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 − V⁰) are in excellent agreement (within ±5ppm) with the sound-derived data ofWang andMillero (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 andBradley (Deep-Sea Research,15, 355–363, 1968);Bradshaw andSchleicher (Deep-Sea Research,17, 691–706, 1970; personal communication 1974);Duedall andPaulowich (Review of Scientific Instruments,44, 120–127, 1973);Emmet andMillero (Journal of Geophysical Research,79, 3463–3472, 1974) and the sound-derived data ofWang andMillero (1973);Fine, Wang andMillero (Journal of Marine Research,32, 433–456, 1974).