Summary
The calving activity of the Antarctic ice shelves is one of the major indicators of global climate change. Whereas massive calving events are well observed post factum from satellites, ice rifting and ice shelf breaks of smaller volumes are not monitored and statistically analysed. In-situ observations require great effort and expense and at present are not capable of providing long-term, real time monitoring of the Antarctic ice shelf disintegration. Remote acoustic observation using hydroacoustic receive systems, such as the hydroacoustic stations of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), can provide a cost-effective way to monitor ice rifting and calving in Antarctica. All the coastline of Eastern Antarctica from 00 to about 1500E can be observed from three IMS hydroacoustic stations in the Indian Ocean. Processing of the acoustic recordings on the station off Cape Leeuwin, Australia, has shown that a large number of the signals arrived from Antarctica have a pulse-like waveform and spectrograms revealing strong waveguide dispersion typical for long range propagation in a near-surface acoustic channel in the Southern Ocean south of the Antarctic Convergence. A comparison between the spectral characteristics of the received signals and the results of numerical modelling showed that those signals were emitted by short, pulse-like physical processes, which are most likely ice rifting and calving events.