ACOUSTIC TRAVEL-TIME PERTURBATIONS DUE TO SHALLOW-WATER INTERNAL WAVES AND INTERNAL TIDES IN THE BARENTS-SEA POLAR FRONT - THEORY AND EXPERIMENT

During August 1992, a combined acoustics/physical oceanography experim ent was performed to study both the acoustical properties and the ocea n dynamics of the Barents Sea Polar Front in the region near Bear Isla nd. Oceanographic observations from shipboard hydrography and moored s ensors allowed the construction of the internal wave frequency spectru m for the area. A rapidly sampled tomographic section from a 224-Hz, 1 6-Hz-bandwidth acoustic source to a 16-element vertical receiving arra y enabled the monitoring of travel-time fluctuations over the internal wave frequency band. To describe the measured acoustic fluctuations, theoretical expressions have been developed for the travel-time varian ces which are functions of the internal wave oceanographic field, the local acoustic propagation characteristics, and the acoustical system' s properties, Both ray and mode theory expressions are generated, as t he experiment was performed in shallow water and both ray and mode arr ivals were resolvable. Comparison of the theory with the data shows ge nerally good agreement. However, due to the fact that the internal wav e study is a secondary objective of this experiment, the data are not of the quality eventually hoped for. Directions for future research in this area are outlined and discussed. (C) 1996 Acoustical Society of America.