A new density relation for pure and saline water

An equation has been developed for the density of pure and saline water. It contains only one term in temperature, as an expansion around the temperature at the density extremum. The salinity and pressure effects appear in the equation in an ordered way. The density variation is fitted in the temperature, salinity and pressure ranges to 20°C, 40%, and 1000 bars abs. The most accurate form is in agreement with the pure water correlation of Fine and Millero (Journal of Chemical Physics, 59, 5529-5536, 1973) to an r.m.s. difference of 3.5 ppm. For saline water it agrees to 10.4 ppm with the data of Chen and Millero (Deep-Sea Research, 23, 595-612, 1976). The overall r.m.s. difference, for both pure and saline water, is 9.0 ppm. Inferences concerning the inherent accuracy of the data arise from the comparisons. Our results also suggest the pressure effect on the extremum temperature, for both pure and saline water. The equation is also separately fitted to the 1-atm correlation of Fofonoff and Bryden (Journal of Marine Research, 33, 69-82, 1975) to 2.5 ppm, over the salinity range from 8 to 40%, and from 0 to 20°C.