Hydroacoustic signals of Antarctic origin detected at ocean-bottom seismic stations off New Zealand

Glacial calving from polar ice sheets is an important indicator of global climate change, and knowledge of ice discharge rates is useful for predicting global sea level variability and deep ocean circulation patterns. Since calving events are difficult to observe in-situ due to the remoteness of polar regions, the remote detection of hydroacoustic signals originating from these events is a useful monitoring tool for climatologists. We have observed hydroacoustic T-phases on an Ocean Bottom Seismic (OBS) network of 30 seismometers and differential pressure gauges that was deployed off the South Island of New Zealand in 2009–2010. These signals are emergent and strongly dispersive, containing most of their energy in the band between 5 and 15 Hz. We estimated backazimuths for events recorded on differential pressure gauges using array beamforming and F-K analysis. Our results suggest that some observed events originate in the vicinity of Ninnis and Mertz glaciers on George V Coast, East Antarctica, in general agreement with epicenters located by prior surface-wave based calving detection studies.