Ocean Acoustic Tomography

Ocean acoustic tomography infers interior ocean temperature and current from the travel times of sound transmitted across an array of source-receiver paths, proposed by Walter Munk and Carl Wunsch in 1979 as an acoustic analogue of medical CT. A 1 degree C temperature change shifts sound speed about 4 m/s, so measured travel-time changes along multiply-refracted SOFAR-channel rays invert to range-averaged temperature over megameter paths. Reciprocal transmission separates the current component from the temperature component. The technique gives basin-scale, depth-integrated heat-content monitoring that point sensors cannot, and it underlies acoustic thermometry experiments such as ATOC.