Modeling annual variations in high-frequency scattering from sea ice

Abstract

As sea ice evolves naturally through its different growth and decay structures, so too does it manifest important changes in physical properties affecting its acoustic response. Variations in the porosity, permeability, and roughness of the ice lead to changes in scattered and reflected acoustic energy as well as the degree of attenuation. Knowledge of the long-term variations of high-frequency under-ice scattering over annual formation and melting cycles is essentially non-existent as only a limited number of measurements have been performed. Owing to this lack of data, fundamental questions remain as to the dominant mechanisms influencing the under-ice scattering process at any given time. In this work, we will show modeling results for high-frequency acoustic scattering from different types of sea ice as it forms and melts, highlighting the relative influence of various ice parameters on mean scattered levels and the dependence of these levels on frequency and grazing angle. Results yield insight into controlling factors and lead to recommendations for planned long-term measurements from moored instruments.