Modeling high-frequency acoustic backscatter for remote sensing of oil under sea ice and oil encapsulated in sea ice

Abstract

High-frequency acoustic systems provide one of the potentially practical means for remote sensing of oil-in-ice. Sea ice is a complex medium that reflects, refracts, and scatters sound waves in complicated manner. The presence of oil adds additional complexity. A set of high-frequency acoustic data were taken at the Cold Regions Research and Environmental Laboratory (Hannover, NH) where crude oil was injected underneath artificial sea ice. A physics-based model is developed to interpret the data. The model consists of four layers to respectively describe the homogeneous half-space of water, the heterogeneous oil layer under ice, a thin skeletal ice layer, and a thick layer for the body of ice. The skeletal layer is allowed to have very different properties from the body of ice. All the interfaces at the boundaries of the layers are assumed rough. The model predicts scattered sound intensity in the time domain. Model results are discussed when it is applied to the acoustics data taken at both normal and 20-degree oblique incidence angles. The utility and the applicability of the model to actual arctic environments are anticipated.