The speed of sound in
seawater is by no means
constant, depending on the water's
density (and therefore on
temperature,
depth and
salinity) but can be
calculated approximately with the following
equation:
c(D,S,t) = c(0,S,t) + (16.23 + 0.253t)D + (0.213-0.1t)D2 + [0.016 + 0.0002(S-35)](S - 35)tD
where
c(0,S,t) = 1449.05 + 45.7t - 5.21t2 + 0.23t3 + (1.333 - 0.126t + 0.009t2)(S - 35)
and
t = T/10 where T = temperature in degrees Celsius
S = salinity in parts per thousand
D = depth in kilometers
Range of validity: temperature 0 to 35 degrees Celsius, salinity 0 to 45 parts per thousand, depth 0 to 4000 m
This equation was developed by one Dr. A.B. Coppins in 1981 and published in the Journal of the American Society of Acoustic Sciences.