Derivatives of Freezing Water Properties

Usage

gsw_t_freezing_first_derivatives(SA, p, saturation_fraction = 1)

Arguments

SA: Absolute Salinity [ g/kg ]. The valid range for most `gsw` functions is 0 to 42 g/kg.
p: sea pressure [dbar], i.e. absolute pressure [dbar] minus 10.1325 dbar
saturation_fraction: fraction of air in water [unitless]

Value

a list containing tfreezing_SA [ K/(g/kg) ], the derivative of freezing temperature with Absolute Salinity and tfreezing_p [ K/dbar ], the derivative with respect to pressure.

Implementation Note

This R function uses a wrapper to a C function contained within the GSW-C system as updated 2022-10-11 at https://github.com/TEOS-10/GSW-C with git commit `657216dd4f5ea079b5f0e021a4163e2d26893371`.

The C function uses data from the library/gsw_data_v3_0.mat file provided in the GSW-Matlab source code, version 3.06-11. Unfortunately, this version of the mat file is no longer displayed on the TEOS-10.org website. Therefore, in the interests of making GSW-R be self-contained, a copy was downloaded from http://www.teos-10.org/software/gsw_matlab_v3_06_11.zip on 2022-05-25, the .mat file was stored in the developer/create_data directory of https://github.com/TEOS-10/GSW-R, and then the dataset used in GSW-R was created based on that .mat file.

Please consult http://www.teos-10.org to learn more about the various TEOS-10 software systems.

References

http://www.teos-10.org/pubs/gsw/html/gsw_t_freezing_first_derivatives.html

Examples

SA <- c(               34.7118, 34.8915, 35.0256, 34.8472, 34.7366, 34.7324)
p <- c(                     10,      50,     125,     250,     600,    1000)
saturation_fraction <- c(    1,     0.8,     0.6,     0.5,     0.4,       0)
derivs <- gsw_t_freezing_first_derivatives(SA, p, saturation_fraction)
stopifnot(all.equal(derivs$tfreezing_SA,
    c(-0.056811800705787, -0.056856999671114, -0.056903079789292,
      -0.056904020028541, -0.056974588411844, -0.057082363270642)))
stopifnot(all.equal(derivs$tfreezing_p/1e-7,
    c(-0.748468312442338, -0.749793159537290, -0.752225023995510,
     -0.756170965034610, -0.767279572670040, -0.779936552091913)))