SCOR/IAPSO WG127

SCOR/IAPSO Working Group 127 was established in 2005, charged with taking into account the spatial variations of the composition of seawater and with providing accurate algorithms for evaluating seawater properties.

Contact

Trevor J McDougall
CSIRO Marine & Atmospheric Research,
Hobart, Tasmania, Aust.
Phone:
+61 3 6232 5250

[Email]

Attachment

This site provides links to papers describing a new thermodynamic formulation, TEOS-10, for the properties of seawater and to codes implementing this new approach. TEOS-10 has been adopted by the Intergovernmental Oceanographic Commission at its 25th Assembly in June 2009 to replace EOS‐80 as the official description of seawater and ice properties in marine science.

TEOS-10 is a new thermodynamic description of seawater based on a Gibbs function from which all thermodynamic properties of seawater can be derived in a physically consistent manner. The seawater Gibbs function is the sum of a pure water component Feistel (2003) and a saline component Feistel (2008), that has also appeared as IAPWS Release (2008).

A significant change from present practice is the use of Absolute Salinity as opposed to Practical Salinity (which is essentially a measure of the conductivity of seawater). Absolute Salinity, and the reference composition of standard seawater that underlies it, are defined in Millero, Feistel, Wright and McDougall (2008).

Absolute Salinity (g/kg) is an SI unit of concentration. The thermodynamic properties of seawater, such as density and enthalpy, are naturally functions of Absolute Salinity rather than functions of the conductivity of seawater. The spatial variations of the composition of seawater means that Absolute Salinity is not simply proportional to Practical Salinity.

A computer algorithm that provides an estimate of the Absolute Salinity of a seawater sample (for given values of Practical Salinity, pressure, longitude and latitude) is described in McDougall, Jackett and Millero (2009). This algorithm exploits the observed correlation between silicate and the density differences due to spatial variation in the composition of seawater. This correlation is used together with a global hydrographic atlas of silicate data to provide an estimate of Absolute Salinity given the sample's Practical Salinity.

A detailed explanation of the TEOS-10 thermodynamic description of seawater can be found in the TEOS-10 Manual which is being published by IOC, SCOR and IAPSO.