Large linear structures (tens of meters by several meters) have been observed recently in seafloor imagery and bathymetry collected with both synthetic aperture sonar (SAS) and multibeam echosounder (MBES) systems. It has been suggested [Hansen, et al., IEEE J. Oceanic Eng., 40, 621-631 (2015)] that this phenomenon is not due to the true morphology of the seafloor, but is caused by water column features related to breaking internal waves. Changes observed in acoustic intensity and bathymetry estimates are caused by a focusing of the acoustic field which results in structures that appear to be true seabed topography. In terms of seafloor mapping, these topography-mimicking features will impact the interpretation of imagery, may complicate the production of mosaics, and have the potential to cause bathymetric uncertainties exceeding International Hydrographic Organization standards. In this talk we will show that these water-column caused features may not be uncommon using examples of data collected with several different SAS and MBES systems in a variety of experimental locations.
Lyons, A. P., Hansen, R. E., Prater, J., Connors, W. A., Rice, G., & Pailhas, Y. (2017). Internal wave effects on seafloor imagery and bathymetry estimates. Journal of the Acoustical Society of America, 141(5), 4004. https://doi.org/10.1121/1.4989187