Remote Sensing of Temperature and Salinity Microstructure in Rivers and Estuaries Using Broadband Acoustic Scattering Techniques

Abstract

Abstract : To measure and understand high-frequency broadband acoustic scattering in rivers and estuaries characterized by strong temperature and salinity gradients and intermittent, high dissipation rates of turbulent kinetic energy. To use these measurements and understanding to develop a remote sensing tool for quantifying the structure of stratified turbulence. The primary objective is to measure high-frequency broadband acoustic backscattering in highly stratified, energetic, estuarine environments, where there is significant salinity stratification, high shear, and high dissipation rates of turbulent kinetic energy. In order to validate these measurements, and support their interpretation, it is necessary to perform coincident, direct measurements of turbulence parameters at similar scales to the acoustic measurements. Estuaries provide an excellent environment to quantify stratified turbulence and its influence on acoustic backscattering, as these environments provide a broad range of stratification and turbulence intensities within a single tidal cycle. Testing the validity of existing microstructure scattering models, determining the range of conditions under which these scattering models are valid, and quantifying the contribution to scattering from salinity versus temperature variance over a broad frequency range, are secondary objectives of this work.