Measurements of the turbulent microstructure of a buoyant salinity plume using acoustics

A study has been undertaken to examine the nature of acoustic scattering from salinity fluctuations. A theoretical relationship between acoustic backscattering and salinity fluctuation has been developed. This relationship is expressed in terms of measurable oceanographic variables, namely the turbulent kinetic energy dissipation rate, epsiv, and the salinity gradient variance rate, chi_s. Acoustic and oceanographic data taken from an autonomous underwater vehicle, the SMAST T- REMUS, operating in a naturally occurring freshwater plume was used to compare theoretical and observed backscattering strengths. Observations were found to be in qualitative agreement with predictions.