gsw package

Subpackages

• gsw.gibbs package
  • Submodules
  • gsw.gibbs.constants module
  • gsw.gibbs.conversions module
  • gsw.gibbs.density_enthalpy_48 module
  • gsw.gibbs.density_enthalpy_48_ct module
  • gsw.gibbs.density_enthalpy_ct_exact module
  • gsw.gibbs.derivatives module
  • gsw.gibbs.earth module
  • gsw.gibbs.freezing module
  • gsw.gibbs.geostrophic module
  • gsw.gibbs.geostrophic_48 module
  • gsw.gibbs.isobaric module
  • gsw.gibbs.library module
  • gsw.gibbs.neutral_nonlinear_48 module
  • gsw.gibbs.practical_salinity module
  • gsw.gibbs.steric module
  • gsw.gibbs.thermodynamics_from_t module
  • gsw.gibbs.water_column_48 module
  • Module contents

Module contents

gsw.gibbs(ns, nt, npr, SA, t, p)

Calculates specific Gibbs energy and its derivatives up to order 2 for seawater. The Gibbs function approach allows the calculation of internal energy, entropy, enthalpy, potential enthalpy and the chemical potentials of seawater as well as the freezing temperature, and the latent heats of freezing and of evaporation. These quantities were not available from EOS-80 but are essential for the accurate accounting of heat in the ocean and for the consistent and accurate treatment of air-sea and ice-sea heat fluxes.

Parameters:

ns : int

order of SA derivative [0, 1 or 2 ]

nt : int

order of t derivative [0, 1 or 2 ]

npr : int

order of p derivative [0, 1 or 2 ]

SA : array_like

Absolute salinity [g kg ^-1]

t : array_like

in situ temperature [\(^\circ\) C (ITS-90)]

p : array_like

pressure [dbar]

Returns:

gibbs : array_like

Specific Gibbs energy or its derivatives. Gibbs energy (ns=nt=npr=0) has units of: [J kg ^-1] Absolute Salinity derivatives are output in units of: [(J kg ^-1) (g kg ^-1) ^-ns] Temperature derivatives are output in units of: [(J kg ^-1) K ^-nt] Pressure derivatives are output in units of: [(J kg ^-1) Pa ^-npr] The mixed derivatives are output in units of: [(J kg ^-1) (g kg ^-1) ^-ns K ^-nt Pa ^-npr]

Notes

The Gibbs function for seawater is that of TEOS-10 (IOC et al., 2010), being the sum of IAPWS-08 for the saline part and IAPWS-09 for the pure water part. These IAPWS releases are the officially blessed IAPWS descriptions of Feistel (2008) and the pure water part of Feistel (2003). Absolute Salinity, SA, in all of the GSW routines is expressed on the Reference-Composition Salinity Scale of 2008 (RCSS-08) of Millero et al. (2008). The derivatives are taken with respect to pressure in Pa, not withstanding that the pressure input into this routine is in dbar.

References

[R1]	Feistel, R., 2003: A new extended Gibbs thermodynamic potential of seawater Progr. Oceanogr., 58, 43-114.

[R2]	Feistel, R., 2008: A Gibbs function for seawater thermodynamics for -6 to 80 \(^\circ\) C and salinity up to 120 g kg -1, Deep-Sea Res. I, 55, 1639-1671.

[R3]	IAPWS, 2008: Release on the IAPWS Formulation 2008 for the Thermodynamic Properties of Seawater. The International Association for the Properties of Water and Steam. Berlin, Germany, September 2008, available from http://www.iapws.org. This Release is referred to as IAPWS-08.

[R4]

IAPWS, 2009: Supplementary Release on a Computationally Efficient Thermodynamic Formulation for Liquid Water for Oceanographic Use. The International Association for the Properties of Water and Steam. Doorwerth, The Netherlands, September 2009, available from http://www.iapws.org. This Release is referred to as IAPWS-09.

[R5]	IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. See section 2.6 and appendices A.6, G and H.

[R6]	Millero, F. J., R. Feistel, D. G. Wright, and T. J. McDougall, 2008: The composition of Standard Seawater and the definition of the Reference-Composition Salinity Scale, Deep-Sea Res. I, 55, 50-72.