13 Jul 2023
 | 13 Jul 2023

A Thermodynamic Potential of Seawater in terms of Conservative Temperature

Trevor John McDougall, Paul Barker, Rainer Feistel, and Fabien Roquet

Abstract. A thermodynamic potential is found for seawater as a function of Conservative Temperature, Absolute Salinity and pressure. From this thermodynamic potential, all the equilibrium thermodynamic properties of seawater can be derived, just as all these thermodynamic properties can be found from the TEOS-10 Gibbs function (which is a function of in situ temperature, Absolute Salinity and pressure). Present oceanographic practice in the Gibbs SeaWater Oceanographic Toolbox uses a polynomial expression for specific volume (and enthalpy) in terms of Conservative Temperature (as well as of Absolute Salinity and pressure), whereas the relationship between in situ temperature and Conservative Temperature is based on the Gibbs function. This mixed practice introduces (numerically small) inconsistencies and superfluous conversions between variables. The proposed thermodynamic potential of seawater, being expressed as an explicit function of Conservative Temperature, overcomes these small numerical inconsistencies, and in addition, the new approach allows for greater computational efficiency in the evaluation of sea surface temperature from Conservative Temperature.

Trevor John McDougall et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1568', Anonymous Referee #1, 31 Jul 2023
  • RC2: 'Comment on egusphere-2023-1568', Stephen M. Griffies, 06 Aug 2023
  • CC2: 'Comment on egusphere-2023-1568', Remi Tailleux, 07 Sep 2023

Trevor John McDougall et al.

Trevor John McDougall et al.


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Short summary
A thermodynamic potential is derived with the temperature argument being Conservative Temperature. All thermodynamic quantities can be derived from this new thermodynamic potential function, and it enables the accurate (to computer machine precision) calculation of the in situ temperature and entropy of seawater. This new thermodynamic potential function provides fundamental thermodynamic justification to the adoption of Conservative Temperature in oceanography in 2010.