Description Usage Arguments Value Implementation Note Caution References Examples

Gibbs Energy of Seawater, and its Derivatives

1 |

`ns` |
An integer, the order of the |

`nt` |
An integer, the order of the |

`np` |
An integer, the order of the |

`SA` |
Absolute Salinity [ g/kg ] |

`t` |
in-situ temperature (ITS-90) [ degC ] |

`p` |
sea pressure [dbar], i.e. absolute pressure [dbar] minus 10.1325 dbar |

Gibbs energy [ J/kg ] if `ns`

=`nt`

=`np`

=0. Derivative of energy
with respect to `SA`

[ J/kg/(g/kg)^ns ] if `ns`

is nonzero and `nt`

=`np`

=0,
etc. Note that derivatives with respect to pressure are in units with Pa, not dbar.

This R function uses a wrapper to a C function
contained within the GSW-C system as updated 2021-03-27
at https://github.com/TEOS-10/GSW-C
with git commit 'f7bfebf44f686034636facb09852f1d5760c27f5'.
In turn, that 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 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 2021-0706, 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.

The TEOS-10 webpage for `gsw_gibbs`

does not provide test values, so
the present R version should be considered untested.

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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | ```
library(gsw)
p <- seq(0, 100, 1)
SA <- rep(35, length(p))
t <- rep(-5, length(p))
## Check the derivative wrt pressure. Note the unit change
E <- gsw_gibbs(0, 0, 0, SA, t, p)
# Estimate derivative from linear fit (try plotting: it is very linear)
m <- lm(E ~ p)
print(summary(m))
plot(p, E)
abline(m)
dEdp1 <- coef(m)[2]
# Calculate derivative ... note we multiply by 1e4 to get from 1/Pa to 1/dbar
dEdp2 <- 1e4 * gsw_gibbs(0, 0, 1, SA[1], t[1], p[1])
## Ratio
dEdp1 / dEdp2
``` |

Embedding an R snippet on your website

Add the following code to your website.

For more information on customizing the embed code, read Embedding Snippets.