A Gibbs function for seawater thermodynamics for −6 to 80 °C and salinity up to 120 g kg–1

The specific Gibbs energy of seawater is determined from experimental data of heat capacities, freezing points, vapour pressures and mixing heats at atmospheric pressure in the range −6 to 80 °C in temperature and 0–120 g kg–1 in absolute salinity. Combined with the pure-water properties available from the 1996 Release of the International Association for the Properties of Water and Steam (IAPWS-95), and the densities from the 2003 Gibbs function of seawater, a new saline part of the Gibbs function is developed for seawater that has an extended range of validity including elevated temperatures and salinities. In conjunction with the IAPWS 2006 Release on ice, the correct description of concentrated brines by the new formulations permits an accurate evaluation of sea ice properties down to salinity saturation temperatures. The new Gibbs function is expressed in terms of the temperature scale ITS-90. Its input variable for the concentration is absolute salinity, available from the new Reference-Composition Salinity Scale of 2008.