either salinity [PSU] (in which case t and p
must be provided) or a ctd object (in which case
S, t and p are determined from the object, and
must no
t
in-situ temperature [$^\circ$C]
p
pressure [dbar]
Value
Sound speed [m/s].
Details
If the first argument is a ctd object, then salinity,
temperature and pressure values are extracted from it, and used for
the calculation.
The sound speed is calculated using the formulation in section 9 of
Fofonoff and Millard (1983).
References
Fofonoff, P. and R. C. Millard Jr, 1983. Algorithms for
computation of fundamental properties of seawater. Unesco
Technical Papers in Marine Science, 44, 53 pp. (See section
9.)