Marine-ending glaciers and the ocean surface have been observed to show complex and dynamic climate-driven ice-water interactions in their contact zone. Different types of icebergs have been discovered to have their own acoustic signature in the process of calving away from the ice. In order to truly and reliably estimate and predict mass erosion from glaciers, it may be essential to describe the mechanisms controlling the path of calving in detail.
In 2002, Scambos et al., 2003, 2004; Rignot et al., 2004 shed light on ice sheet stability impact and its correlation with climate shifts based on the remarkable separation of 3200 km2 of glacial ice from the Larsen B Ice Shelf, followed by the total fragmentation of 15 km Jakobshavn Glacier – a Greenlandic marine- ending outlet glacier, which revealed the occurrence of such events in diverse environments in both hemispheres. This disintegration is said to contribute to global sea level changes. Moreover, Glowacki et al. 2015 investigate varying styles of the naturally derived sculpting, offering the prospect of hydroacoustic techniques. The study blends high-frequency underwater ambient noise recordings with the time-lapsed photographs of the Hans Glacier cliff in Hornsung Fjord, Spitsbergen; identifying three categories of events: subaerial, sliding subaerial and submarine.
While recent studies have utilised seismic measurements to track glacial calving, contemporary technological advancements demonstrate that underwater acoustics may provide possible solutions. The hydroacoustic network consists of 11 stations that monitor compliance with the Comprehensive Nuclear Test Ban Treaty in oceans around the world. It is therefore a part of the International Monitoring System. The natural acoustic ocean, the Sound Fixing and Ranging channel (SOFAR), permits underwater sound to resound over large distances without much crowding from background noise.
Glowacki et al. 2015 revealed that the study reached high frequency ambient noise linked to sliding events from the friction between calved iceberg and the coarse surface of the ice cliff. Combining underwater (acoustic) and above water (photographic) glacier monitoring, the results extended the idea of acoustic detection to embrace the identification of specific and distinguishable modes of calving based on the progression of their spectral qualities with time. “We know now that when a submarine event starts, there is a disintegration below the sea surface, there are many cracks, and cracks are propagating and we can listen to this underwater.” reflected Dr Glowacki.
The results of the study were said to confirm the successful detection of individual ice detachments using passive acoustic at higher frequencies of up to several tens of kilohertz; a phenomenon already demonstrated by other researchers including Tegowski et al., 2011, 2012; Pettit, 2012; and Pettit et al., 2012. The data gave a new perspective on a narrowly understood wonder, implying the submarine iceberg noise generation to be controlled by a series of physical stages.
Looking ahead, as the data only represents 12 well-constrained calving events originating from a single tidewater outlet glacier, similar experiments might be conducted on a longer time scale under different conditions.
How might underwater acoustics enhance climate change research?