A model for under-ice-target acoustic scattering.

A model is described that has been developed to calculate the scatter of a high-frequency acoustic pulse that originates from a stationary source and is incident on and is scattered from the under-ice surface characteristic of the Arctic and from a stationary target. The under-ice surface is modeled by an ensemble of ice keels, and ice keels are modeled by an ensemble of ice blocks with rectangular facets. The Helmholtz–Kirchhoff integral in the Kirchhoff approximation is used to calculate the scatter from an ice facet. The scatter from an ice keel is given by a coherent sum of the scatter from all the ice facets. A T-matrix is used to calculate the scatter from the stationary target. The first order terms in the multiple scattering process between the target and the ice surface are also calculated, i.e., the scattering from the target of the free field scatter from ice facets and the scatter from ice facets of the free field scatter of the target. Numerical results show the extent to which the scatter from the target in the under-ice environment differs from its free field scatter.