Sound radiated into the Arctic Ocean by cracks in the polar ice sheet

Abstract

Ambient noise in the Arctic Ocean is caused partly by cracking of the ice sheet. Starting with a suitable “equivalent source” for fracturing processes, an analytical description of the radiated field has been derived when the ice sheet is modeled by an infinite, thick, elastic plate bounding a homogeneous fluid half-space. This simple model can be used to assess the importance of radiation damping, absorption, scattering, and ocean sound-speed profile in the production of real sound fields. Under mid-Arctic conditions at frequencies below about 20 Hz, the model indicates that radiation damping and absorption are very weak, and that a large contribution to the ambient noise could come from elastic waves in the ice that are scattered by inhomogeneities or edges of floes. Therefore, models relating low-frequency ambient noise to sources in the ice should take some account of scattering. At higher frequencies, absorption becomes more important, and the effect of scattering becomes harder to estimate because it depends upon details of the ice structure. [Work supported by Arctic Program, ONR.]