Glacier studies on the basis of acoustic measurements

Abstract

The possibility of glacier ice flow studies using the method of acoustic emission (AE) in frequency range from 15 Hz to 20 kHz has been considered. A portable acoustic line system has been developed and a number of methodological issues (mounting of acoustic sensors into glacial ice, their location, reliability of acoustic coupling, etc.) have been solved. Acoustic studies of glacial ice have been performed; rock fall effect, ice cracking and ice movement on bedrock have been simulated. Correspondences of AE parameters to specific sources have been identified. The results of acoustic studies on Aldegondabreen (Spitsbergen), Central Tuyuksu and Molodezhny glaciers (northern Tien Shan) have been summarized. The dependence of the adhesive strength of ice with smooth substrate (serpentenite) on the shear rate has been considered; the effect of tor-shaped obstacle on shear force has been estimated. It is shown that the acoustic effects at cohesive ice failure on obstacles are similar to the observed natural acoustic vibrations generated in glaciers from distant sources. The results might be applied in development of the mobile ice lab and system for remote acoustic monitoring the processes in the bottom layers of glaciers.

Keywords

• acoustic emission
• bedrock conditions
• glacier
• instability
• physical modeling
• rheology of ice