High‐frequency anderice acoustic backscattering: A simulation model study

Abstract

A simulation model that evaluates the backscatter of a high‐frequency acoustic pulse from the underice surface of pack ice regions, characteristic of the interior Arctic, has been used to investigate the extent to which various morphologic, geometric, and acoustic parameters, used to describe the underice surface, influence the backscatter. The simulation model utilizes a three‐dimensional underice canopy synthesized from two‐dimensional acoustic profile data. The large scale scattering features of the underice surface are modeled as first‐year ice keels and sloping flat ice regions. The small scale surface structure is modeled as an ensemble of randomly oriented ice blocks. The Kirchhoff approximation is used to evaluate the scattering strength of an individual ice block which, in turn, is used to calculate the scattering strength of the underice surface. The sonar equation is used to calculate reverberation. The parameters used in the model may be divided into four groups: canopy, ice keel, ice block, and acoustic parameters. Parameters used to identify and classify the constituent ice features of the canopy are varied, and it is shown that, for physically reasonable parameters, reverberation is essentially independent of the feature identification and classification criteria. Reverberation is also shown to be largely independent of the parameters that describe only the large scale structure of the ice keel, but is strongly dependent upon parameters that effect the area and spatial orientation of individual ice blocks.