either practial salinity (in which case temperature
and pressure must be provided) or an oce object
(in which case salinity, etc. are inferred from the object).
temperature
in-situ temperature [$^\circ$C]
pressure
pressure [dbar]
longitude
longitude of observation (only used if eos="gsw"; see
Details).
latitude
latitude of observation (only used if eos="gsw"; see
Details).
eos
equation of state, either "unesco" or "gsw".
Value
Value in 1/degC.
Details
If the first argument is a ctd object, then salinity,
temperature and pressure values are extracted from it, and used for
the calculation.
References
The eos="unesco" formulae are based on the UNESCO equation
of state, but are formulaed empirically by Trevor J. McDougall, 1987,
Neutral Surfaces, Journal of Physical Oceanography, volume 17, pages
1950-1964. The eos="gsw" formulae come from GSW; see references in
the swRho documentation.