Deep scattering layer investigation through multi-beam bathymetry

It has been suggested that perhaps a multi-beam sonar would be a useful tool for studying the reverberation contours of the biologically active plankton regions of the ocean known as the deep scattering layer, DSL. A brief experiment, utilizing the SASS multi-beam sonar on board the US Navy´s oceanographic survey ship USNS Tanner during sea trials in December 1992, was performed to evaluate this possibility. The results of an August 1993 analysis of the sonar data collected, and sound velocity profiles of the area, clearly indicated that SASS was capable of mapping the DSL. Having established SASS as a useful DSL investigative tool, more ambitious experiments were included in the Test Plan of the ocean survey ship USNS Wyman for its February 1994 sea trial period. In addition to collecting larger amounts of sonar data in different locations, observations of contour variations during the DSL´s vertical migrations at sunrise and sunset were also made. This paper describes the DSL measurement system, the data collection process, the results of the experiments, and presents examples of post processed data plots generated using Mathcad 4.0. The SASS System could, with some not-too-difficult software modifications to existing bathymetric/image processing and contour display techniques, be made to perform DSL/Water Column mapping in real time