Computational analysis of under-ice propagation in deep Arctic Ocean environments using elastic parabolic equation solutions

Deep Arctic environments have specific conditions that affect acoustic propagation. The presence of an overlying ice layer, as well as single- and double-ducted water sound speed profiles cause variations in travel-time and transmission loss. Compared to other methods, parabolic equation solutions incorporating these environmental challenges provide an effective approach for analysis of their impact on received acoustics signals. Particularly, range dependent variations in the thermohaline structure and ice layer thickness can be difficult to model with normal mode or spectral methods. Practical use of ray-based models for such complicated environments is usually limited by the requirement for acoustic frequencies be sufficiently high. Another significant complication in arctic geo-acoustic modeling is caused by shear elasticity of the ice cover that normally supports both compressional and shear waves. Here, to quantify contributions of shear effects in range-dependent arctic environments, we compare calculations of under-ice transmission loss made using fluid and elastic parabolic equation techniques. The results are presented for various combinations of ice layer and water duct parameters, as well as various source and receiver depths, ranges, and sound frequencies. Specific examples are presented for configurations and environments similar to those found at recent experiments in the Beaufort Sea. Work supported by ONR.