Earth Sciences and Ecology Question #372

Larry King, a 39 year old male from the Internet asks on April 20, 1998,

How can you measure the energy of an ocean wave? Is there a reasonably simple equation that describes the energy in water waves?

viewed 14733 times

The answer

Fred Dobson answered on April 20, 1998

You should realize all this was worked out in the 1800's by people like Lord Kelvin and Lord Rayleigh - we're dealing with good solid physics that has stood the tests of time. In deep water (wavelength > 4xdepth) a wave with trough-to-crest height H = 2A (A is called amplitude), the total energy of a wave per unit area of sea surface is (Rho g A^2) / 2, where Rho is the density of water (1,000 kilos/cubic meter), g is the acceleration due to gravity (about 9.8 meters/sec^2) and A^2 means "A squared". The area to use is simply the crest-to-crest distance (the wavelength) times the desired along-wave distance. The energy is equally divided between kinetic and potential energy. If you want to read lots and lots about waves, you should find Wind Waves: Their Generation and Propagation on the Ocean Surface by Blair Kinsman, Prentice-Hall 1965, 676 pp. It's a wonderful book - a lot of mathematics, but in between are the desired formulae.

Add to or comment on this answer using the form below.

Note: All submissions are moderated prior to posting.

If you found this answer useful, please consider making a small donation to