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], defined on
the ITS-90 scale.
pressure
seawater 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
Specific heat $J kg^{-1}\,^\circ C^{-1}$
Details
If the first argument is a ctd object, then salinity, etc, are
extracted from it, and used for the calculation.
References
Millero et. al., J. Geophys. Res. 78 (1973), 4499-4507