Sound Field in a Shallow-Water Arctic-Type Waveguide with a Bottom Containing a Gas-Saturated Sediment Layer

We have analyzed the possibility of mode description of a sound field in a shallow-water Arctic-type waveguide with a bottom containing a gas-saturated sediment fluid layer lying on an elastic half-space (permafrost). It has been established that the modes, including quasimodes, calculated using Pekeris cuts, yield the best description of the field in the water layer at small distances from the sound source on the order of 1-10 waveguide depths. Calculations of propagation losses in the waveguide for a thickness of the sediment layer comparable to or larger than the length of a sound wave in the sediments have shown that the sea bottom behaves like a homogeneous fluid half-space. Propagation losses sharply increase as the sound speed in the sediments approaches the sound speed in water. We have proposed a technique for estimating the sound speed in the sediment layer based on analysis of the attenuation curves of the sound field components corresponding to different sums of waveguide modes.