Proceedings of the International Conference “Underwater Acoustic Measurements: Technologies &Results” Heraklion, Crete, Greece, 28 th June – 1 st July 2005 REMOTE ACOUSTIC OBSERVATION OF ICE CRACKING AND CALVING EVENTS ON THE ANTARCTICA ICE SHELF A. N. Gavrilov, A. L. Maggi and G. Vazquez Centre for Marine Science and Technology, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia E-mail: A.Gavrilov@cmst.curtin.edu.au Abstract: 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 0 0 to about 150 0 E 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. Keywords: Antarctic ice shelf, ice rifting, remote acoustic observations 1. INTRODUCTION The ice shelf calving events observed for the past two decades have been extraordinary, and have led to significant changes in the Antarctic ice sheet. The total ice mass discharge due to those events is considerably greater than the average Antarctic snow accumulation [1].