Acoustic emissions from in situ compression and indentation experiments on sea ice

We present results from measurement of acoustic emissions (AE) during compression and indentation of natural sea ice in situ. We show that AE amplitudes are associated with load, so that periods of loading and unloading, and cyclic oscillations in loading during indentation, can be determined from AE records as well as from load measurements. We show that AE measured during these experiments obeys Gutenberg-Richter-type scaling laws, implying that the crack distribution within the sea ice is self-similar. We show that b-values, which indicate the ratio of small cracks to large cracks, decrease during loading, tending towards a value around 1 at failure, and increase again when loading is removed. This suggests that AE can be used to measure, non-invasively, damage and healing of natural sea ice. We conclude by discussion practical applications of these results, and opportunities for further development of AE measurement as a tool for understanding cracking in ice