either salinity [PSU] (in which case
temperature and pressure must be provided) or
a ctd object (in which case salinity,
temperature and pressure ar
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" [1,2] or "gsw"
[3,4].
Value
Sound speed [m/s].
Details
If the first argument is a ctd or section object, then
values for salinity, etc., are extracted from it, and used for the
calculation, and the corresponding arguments to the present function are
ignored.
If eos="unesco", the sound speed is calculated using the formulation
in section 9 of Fofonoff and Millard (1983). If eos="gsw", then the
gsw_sound_speed function from the gsw package is
used.
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.)