Scale invariance of the intensity anomaly induced by the ice cover in the sound field of a tone source in an arctic waveguide

Abstract

On the basis of the normal mode method and the theory of sound scattering by a stochastically rough surface of an elastic layer, the specific features of the frequency dependence of the intensity anomaly induced by the ice cover in the sound field generated by a tone source in an arctic waveguide are studied. The anomaly is determined by the difference between the level (in dB) of the coherent component of the sound intensity that occurs in the waveguide with the ice cover and the intensity level in a waveguide with an ice-free surface. Using the WKB approach, it is shown that the intensity anomaly is invariant for all values of the frequency, the mean ice thickness, and the rms amplitude and correlation radius characterizing the rough undersurface of ice on the condition that the ratios of all the aforementioned geometric parameters to the sound wavelength in water remain constant. This property is confirmed by precise calculations of the anomaly by the mode program and explained by the specific features of the frequency dependence of attenuation coefficients and their distribution in the numbers of normal modes. Possible practical applications of the revealed property of the intensity anomaly are suggested.