Acoustic critical opalescence of the transitional under-ice layer in the Arctic

Arguments are presented for the existence of an under-ice transitional layer, which significantly affects the under-ice acoustic wave propagation. We have developed a novel model based on the first principles of statistical physics that considers the transitional under-ice layer and the unconsolidated sea-bottom layer. This model predicts the existence of transitional Layers, in which the transition from nonrigid, liquid phase to rigid phase occurs. It further predicts these transitions to be second order phase transitions, which leads to Large scale spatial variations of rigidity. The statistical description of these variations is obtained and the parameters of the statistical description are related to the Local environmental characteristics, such as the sea-bottom geology and the average turbulent energy in the under-ice environment. The predicted relations are in good agreement with the experimental data. We have calculated acoustic wave attenuation and phase variations due to scattering by rigidity variations and due to propagation in random transitional Layers. Predictions of the developed theory are compared to the published experimental data. This comparison shows good agreement with the data on Arctic transmission loss and on random phase variations in the acoustic field.