Observations of acoustic scattering from turbulent microstructure in Knight Inlet

Calibrated echo-sounder surveys were conducted on the backscatter from turbulent microstructure within internal lee-waves at a sill in Knight Inlet, B.C. Volumetric scatter strengths in the range $−90$ to $−75 dB$ $(re 1 m−1)$ were observed within narrow (1 to 10 m thick) layers at three frequencies (38, 120, and 200 kHz). The observed acoustic scattering levels were in reasonable agreement with published models for microstructure scattering. A new volumetric multi-beam sonar was used to image the spatial structure of the turbulent billows.