Shear speed in Arctic ice and underwater acoustic reflection

The underwater reflected sound wave under a sheet of Arctic ice contains information about the ice including thickness and mechanical properties. The ideal case of a perfectly flat ice floe floating above the water may be modeled using the OASES wavenumber integration code. A spectrogram of the acoustic response contains features related to the compressional and shear waves. The resonance associated with the shear wave speed in the ice is particularly distinctive. In the real world, the ice-water interface is not perfectly smooth. The finite element code SPECFEM2D is used to simulate the response of ice with a rough ice–water interface. It is particularly well suited to this problem since it accounts for all orders of multiple reflections. It shows the effects of fine-scale roughness on the acoustic response. Depending on the severity of the roughness, it may enhance or diminish the acoustic features related to the properties of the ice. [Work supported by the U. S. Office of Naval Research, Code 32 Grant N00014-20-1-2041 (N. Chotiros). G. Bayrakci and A. Best were funded by the UK Defence and Security Accelerator, Grant ACC2016927. The Texas Advanced Computing Center provided the high-performance computing resources.]