# gsw_SA_CT_plot

plots Absolute Salinity - Conservative Temperature profiles on a SA-CT diagram including freezing line and selected potential density contours.(75-term equation)

## Contents

## USAGE:

gsw_SA_CT_plot(SA,CT,p_ref,isopycs,title_string)

## DESCRIPTION:

Produces a plot of Absolute Salinity - Conservative Temperature profiles. The diagram also plots the Conservative Temperature freezing point for p = 0 dbar assuming the seawater is completely saturated with dissolved air and user defined potential density contours. 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".

## INPUT:

SA = Absolute Salinity [ g/kg ] CT = Conservative Temperature [ deg C ] p = sea pressure [ dbar ] ( i.e. absolute pressure - 10.1325 dbar )## Optional:

p_ref = reference sea pressure for the isopycnals [ dbar ] (i.e. absolute reference pressure - 10.1325 dbar) If it is not suppled a default of 0 dbar is used. isopycs = isopycnals, can be either an array of isopynals or the number of isopynals to appear on the plot. If it is not supplied the programme defaults to 5 isopynals. title_string = title text to appear at the top of the plot.

SA & CT need to have the same dimensions. p_ref should be a scalar, (i.e. have dimensions 1x1). isopycs can be either 1x1 or 1xN or Mx1

## EXAMPLE:

SA = [34.7118; 34.8915; 35.0256; 34.8472; 34.7366; 34.7324;] CT = [28.8099; 28.4392; 22.7862; 10.2262; 6.8272; 4.3236;] p = [ 10; 50; 125; 250; 600; 1000;] p_ref = 1000 isopycs = [24:0.5:33];

gsw_SA_CT_plot(SA,CT,p_ref,isopycs,'\it{S}\rm_A - {\Theta} diagram')

## AUTHOR:

Rich Pawlowicz [ help@teos-10.org ] Note. This function was extracted and adapted from Rich Pawlowicz's ocean toolbox.

Modified:

Paul Barker & Trevor McDougall

## VERSION NUMBER:

3.05 (21st May, 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.

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 and P.M. Barker, 2015: Accurate polynomial expressions for the density and specific volume of seawater using the TEOS-10 standard.Ocean Modelling,90, pp. 29-43. http://dx.doi.org/10.1016/j.ocemod.2015.04.002

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