Broadband Acoustic Mapping of Physical Processes, Bubbles, Suspended Sediment, and Fish in Highly Stratified Estuaries

Broadband acoustic scattering techniques can be used to complement traditional sampling techniques, such as CTDs, ADCPs, and microstructure measurements, with the goal of imaging and quantifying physical processes, bubbles, suspended sediments, and biological scatterers in highly stratified and dynamic estuaries. Broadband acoustic scattering techniques can be a valuable tool in helping to understanding these dynamic estuarine environments across the broad range of spatial and temporal scales that characterize their variability. Data collected over a series of field campaigns in two salt-wedge estuaries, the Connecticut River (2008-2012) and Columbia River (2015) estuaries, are presented, contrasting the different dominant scatterers and highlighting the importance of understanding the underlying scattering mechanisms to effectively and accurately interpret the acoustic images. Highlights of these field campaigns are presented, including the quantification of the structure and evolution of shear instabilities, mixing induced by shear instabilities, the acoustic manifestation of fronts, and the impact of physical processes, such as fronts and shear instabilities, on fish distribution.