Measurements of acoustic correlation in the ocean with a high frequency echo-sounder

Abstract

Measurements in a British Columbia fjord, using a high frequency echo-sounder, have provided the basis for inferring both mean and random components of scatterer motion at ranges up to 100 m. The measurements demonstrate the potential for a novel technique of flow speed measurement using an echo-sounder and show the way in which the random component of scatterer motion decorrelates the resulting signal. The results indicate decorrelation times of several seconds, illustrating the passive behaviour of the scatterers. This behaviour makes the scatterers ideal targets for remote sensing of flow properties and represents a limiting example of the conditions in which such measurements can be made. The measurements provide a new source of information relevant to the study of Zooplankton behaviour; in more active oceanographic conditions the relative motion of passive acoustic targets may also provide a basis for inferring the corresponding water motions and in particular, turbulence.