# gsw_mlp

mixed-layer pressure (75-term equation)

## Contents

## USAGE:

mlp = gsw_mlp(SA,CT,p)

## DESCRIPTION:

Calculates the mixed-layer pressure based on de Boyer Montégut et al. (2004), however this programme calculates the mlp as 0.3 g/kg greater than the surface density. The mlp is always deeper than 20 dbar, if the initial estimate of the mlp is less than 20 dbar, the temperature and salinity of the bottles in the top 5 dbar are set to that of the bottle closest to 5 dbar. This removes the effect if a thin layer of fresh water, such as that from a river outflow or from rain.

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 (ITS-90) [ deg C ] p = sea pressure [ dbar ] (ie. absolute pressure - 10.1325 dbar)

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

## OUTPUT:

mlp = mixed-layer pressure [ dbar ]

## EXAMPLE:

SA = [34.7118; 34.8915; 35.0256; 34.8472; 34.7366; 34.7324;] CT = [28.7856; 28.4329; 22.8103; 10.2600; 6.8863; 4.4036;] p = [ 10; 50; 125; 250; 600; 1000;]

mlp = gsw_mlp(SA,CT,p)

mlp =

50

## AUTHOR:

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

## VERSION NUMBER:

3.06.12 (15th June, 2020)

## REFERENCES:

de Boyer Montégut, C., G. Madec, A.S. Fischer, A. Lazar and D. Iudicone 2004: Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology,J. Geophys. Res.,109, http://dx.doi.org/10.1029/2004JC002378

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

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