Using data recorded and made available by Network Canada, the fluctuations in the bottom high-frequency acoustic backscatter from a node in the Strait of Georgia was observed over a period of 11 days, along with other environmental factors, including hydrostatic pressure, temperature, and salinity. The bottom backscatter was observed using an Imaginex rotating sonar operating at a frequency of 1 MHz. The likely original purpose of the instrument was to observe bottom sediment pulses driven by tidal currents, but correlation between other environmental parameters and bottom backscatter are also evident. Due to the relatively shallow depth of 41 m, there should be sufficient sun light penetration for photosynthesis, which affects backscatter due to bubble generation by microorganisms in the sediment, as reported by Holliday et al. J. Acoust. Soc. Am. 2003, 114, 2317. Indeed, a small sun light correlation coefficient was found, with a periodicity of 1 day. Larger correlation coefficients were found with salinity and temperature variations, with longer periodicities. The temperature and salinity of the water were correlated, suggestive of the movement of two distinct bodies of water, in the manner of SPICE. Work supported by the US Navy’s Office of Naval Research, Code 322OA, grant N00014-23-1-2522.
Nicholas P. Chotiros (Wed,) studied this question.