Stick and slip mechanisms in the acoustic emissions of ice fracture

Abstract

Arctic ice noise has been qualitatively described in terms of crashing and cracking noises. Ships navigating through icy waters and colliding with icebergs have reported distinctive cracking sounds characteristic to the specific environmental conditions and the location. Many previous field studies of ice acoustics have been done with measurements from isolated, single hydrophones. These have provided useful physical insights into the ambient noise characteristics of ice, but the underlying mechanisms of the sounds are still not well understood. The mechanical properties of ice have been extensively studied in laboratory settings, but few studies have examined the acoustics emissions during fracture with respect these properties. The salinity content of sea ice can significantly influence fracture. The acoustics of ice fracture in water and air is investigated in laboratory using simultaneous acoustic and high speed optical measurements. Also, the mechanical properties of ice samples as a function of salinity were studied with three point bending. A stick and slip mechanism found in fracture of low salinity ice is supported by an Empirical Mode Decomposition of the acoustic signals.