# gsw_SA_from_rho

Absolute Salinity from density (75-term equation)

## Contents

## USAGE:

SA = gsw_SA_from_rho(rho,CT,p)

## DESCRIPTION:

Calculates the Conservative Temperature of maximum density of seawater. This function returns the Conservative Temperature at which the density of seawater is a maximum, at given Absolute Salinity, SA, and sea pressure, p (in dbar). This function uses the computationally- efficient 75-term expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Note that the 75-term equation has been fitted in a restricted range of parameter space, and is most accurate inside the "oceanographic funnel" described in McDougall et al. (2003). The GSW library function "gsw_infunnel(SA,CT,p)" is avaialble to be used if one wants to test if some of one's data lies outside this "funnel".

Click for a more detailed description of calculating the Absolute Salinty from density. |

## INPUT:

rho = density of a seawater sample (e.g. 1026 kg/m^3) [ kg/m^3 ] Note. This input has not had 1000 kg/m^3 subtracted from it. That is, it is 'density', not 'density anomaly'. CT = Conservative Temperature (ITS-90) [ deg C ] p = sea pressure [ dbar ] ( i.e. absolute pressure - 10.1325 dbar )

rho & CT need to hve the same dimensions. p may have dimensions 1x1 or Mx1 or 1xN or MxN, where SA is MxN.

## OUTPUT:

SA = Absolute Salinity [ g/kg ]

## EXAMPLE:

rho = [1021.8482; 1022.2647; 1024.4207; 1027.7841; 1029.8287; 1031.9916;] CT = [ 28.7856; 28.4329; 22.8103; 10.2600; 6.8863; 4.4036;] p = [ 10; 50; 125; 250; 600; 1000;]

SA = gsw_SA_from_rho(rho,CT,p)

SA =

34.712080120418108 34.891723808488869 35.026202257609505 34.847160842234572 34.736398269039945 34.732228881079742

## AUTHOR:

Trevor McDougall & Paul Barker [ help@teos-10.org ]

## VERSION NUMBER:

3.05 (16th February, 2015)

## REFERENCES:

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. Available from the TEOS-10 web site. See section 3.42 of this TEOS-10 Manual.

McDougall, T.J., D.R. Jackett, D.G. Wright and R. Feistel, 2003: Accurate and computationally efficient algorithms for potential temperature and density of seawater. J. Atmosph. Ocean. Tech., 20, pp. 730-741.

Roquet, F., G. Madec, T.J. McDougall, P.M. Barker, 2015: Accurate polynomial expressions for the density and specifc volume of seawater using the TEOS-10 standard. Ocean Modelling.

The software is available from http://www.TEOS-10.org