Acoustic Propagation Underneath the Arctic Sea-ice

Abstract

The main objective of this project is to study the effect of sea-ice on underwater acoustic wave propagation. Three main parameters define how acoustic waves react to the presence of seaice: (i) the roughness of the underside of the sea-ice, (ii) the thickness of the sea-ice, and (iii) the elastic parameters of the sea-ice determined by the material composition of the ice. To address the overall objective, field observations from the Marginal Ice Zone (MIZ) in the Fram Strait and from the Van Mijen-fjord were analysed and compared with simulations performed with the seismo-acoustic model OASES50. In the Fram Strait, long-range under-ice acoustic propagation was studied by sending communication signals (centered at 900 Hz) between two ice-tethered buoys. In this study the focus was to understand the effect of sea-ice roughness and thickness on the signal propagation. A seismic survey was conducted in the Van Mijen-fjord, providing observations for a detailed study of how low frequency acoustic and elastic waves (up to 100 Hz) interact with an ice plate. In both studies the OASES model was used for simulating the elastic wave propagation in the complex physical environments. The OASES model can be very computationally intensive for complex problems and a significant effort went into developing and implementing a parallel version of the model in order to vastly reduce the computation time.