Effects of sea-ice ridges on sound propagation in the Arctic Ocean

Abstract

An environmental/acoustic model of sound propagation in the Arctic Ocean, which accounts for reflection losses from ridged sea ice, has been developed. In this model sea-ice ridges are represented as infinitely long, randomly distributed, elliptical half-cylinders. Under-ice reflection losses for acoustic wavelengths either large or small compared to ridge dimensions are computed from theoretical equations as a function of average keel depth and width, number of ridges per km, and grazing angle. Numerical values of under-ice reflection loss as a function of grazing angle are then incorporated into ray theoretical computations of transmission loss assuming a single sound speed'profile which is characteristic of the central Arctic Ocean. The validity of the concepts, approximations, and the limitations of the model, and the accuracy of coincident measurements of environmental and acoustic parameters required to validate the model are discussed. To illustrate the predictions and accuracy of the model under diverse ice conditions, several comparisons of theoretical and experimental determinations of under-ice transmission loss in the central Arctic Ocean are presented.