Coupled ocean-acoustic model studies of sound propagation through a front

Abstract

A three-dimensional (3-D) numerical ocean model has been used to study sound propagation through an ocean front. The model has been used to provide environmental data for input to a range-dependent acoustic model to study the effect of eddies that form at the front on sound propagation characteristics. The model was set up in an idealized ocean domain but with the model physics and the temperature contrast across the front configured so as to represent the polar front east of Iceland. Acoustic ray tracing was carried out to illustrate the effect of frontal eddy features on sound propagation paths, and propagation loss calculations were performed to quantify their effect acoustically. It was found that dependent upon sound source/receiver depth combinations, the effect of the front and the eddies was to increase propagation loss by as much as 10–20 dB. This is comparable with the magnitude of the frontal effect that is seen in studies using analytical models of ocean fronts and with acoustic calculations that are based on measured environmental data. However, the results of this study have also shown that the acoustic predictions may be sensitive to the choice of ocean model parameter, in particular the horizontal eddy viscosity coefficient.