Inhomogeneous sound speed field in the seabed of the Kara Sea and its effect on acoustic wave propagation

A statistical analysis of spatial variations in the sound speed in the upper sedimentary layer for one of the regions of the Kara Sea was carried out. For analysis, we used the distribution of sound speed obtained from 3D seismic data. A spatial anisotropy of this quasi-random physical quantity was found. Its spatial correlation radius can vary from hundreds of meters to a few kilometers, depending on the chosen direction in the horizontal plane. The problem of normal mode coupling in a shallow water area of a constant depth at a frequency of 250 Hz above the bottom with varying impedance is considered. It was assumed that the change in impedance is due to the variations in the sound velocity profile in the bottom sedimentary layer noted above. It is shown that for typical horizontal gradients of the sound speed in the bottom of the Kara Sea and when using a point sound source, the mode coupling is weak, therefore, the adiabatic approximation can be used to calculate the sound field. However, this coupling can be noticeable upon excitation of individual waveguide modes.