High-frequency acoustic coherent reflection from sea ice ridges: effect of ice characteristics and geometry

Abstract

Environmental changes in the Arctic have increased the proportion of first-year ice while reducing multiyear ice, altering ice properties. These changes may affect the performance of underwater acoustic systems used for communication, navigation and ocean monitoring systems in Arctic sea. This study investigates the effects of sea ice age and ridge geometry on high-frequency coherent reflection loss. We model acoustic scattering from rough sea ice using the Helmholtz–Kirchhoff integral. The local reflection coefficient is derived from a water–ice–air layered model, and the ridge is assumed to be longitudinally-invariant to reduce computational cost. Results show that the under-ice geometry (keel) significantly influences shadow zone formation and reflection loss, while the upper-ice structure (sail) has a limited effect. The shear wave speed of ice is a key property that determines the grazing angle range for minimal reflection loss, which is critical for long-range propagation. First-year ice, due to its lower shear wave speed, is expected to produce greater reflection loss at low grazing angles than multiyear ice. Time-domain analysis reveals that the keel, ice properties, and thickness lead to multiple signal arrivals. These findings support acoustic propagation modeling and the operation of underwater acoustic systems in the Arctic.