Ocean acoustic tomography

The western North Atlantic showing the locations of two experiments that employed ocean acoustic tomography. AMODE, the "Acoustic Mid-Ocean Dynamics Experiment" (1990-1), was designed to study ocean dynamics in an area away from the Gulf Stream, and SYNOP (1988-9) was designed to synoptically measure aspects of the Gulf Stream. The colors show a snapshot of sound speed at 300 metres (980 ft) depth derived from a high-resolution numerical ocean model. One of the key motivations for employing tomography is that the measurements give averages over the turbulent ocean.

Ocean acoustic tomography is a technique used to measure temperatures and currents over large regions of the ocean.[1][2] On ocean basin scales, this technique is also known as acoustic thermometry. The technique relies on precisely measuring the time it takes sound signals to travel between two instruments, one an acoustic source and one a receiver, separated by ranges of 100–5,000 kilometres (54–2,700 nmi). If the locations of the instruments are known precisely, the measurement of time-of-flight can be used to infer the speed of sound, averaged over the acoustic path. Changes in the speed of sound are primarily caused by changes in the temperature of the ocean, hence the measurement of the travel times is equivalent to a measurement of temperature. A 1 °C (1.8 °F) change in temperature corresponds to about 4 metres per second (13 ft/s) change in sound speed. An oceanographic experiment employing tomography typically uses several source-receiver pairs in a moored array that measures an area of ocean.

  1. ^ Munk, Walter; Peter Worcester; Carl Wunsch (1995). Ocean Acoustic Tomography. Cambridge: Cambridge University Press. ISBN 978-0-521-47095-7.
  2. ^ Walter Sullivan (1987-07-28). "Vast Effort Aims to Reveal Oceans' Hidden Patterns". New York Times. Retrieved 2007-11-05.