Two-element acoustic array gives insight into ice-ocean interactions in Hornsund Fjord, Spitsbergen

Abstract

Glacierized fjords are dynamic regions, with variable oceanographic conditions and complex ice−ocean interactions, which are still poorly understood. Recent studies have shown that passive underwater acoustics offers new promising tools in this branch of polar research. Here, we present results from two field campaigns, conducted in summer 2013 and spring 2014. Several recordings with a bespoke two−hydrophone acoustic buoy were made in different parts of Hornsund Fjord, Spitsbergen in the vicinity of tidewater glaciers to study the directionality of underwater ambient noise. Representative segments of the data are used to illustrate the analyses, and determine the directions of sound sources by using the time differences of arrivals between two horizontally aligned, broadband hydrophones. The results reveal that low frequency noise (< 3 kHz) is radiated mostly from the ice cliffs, while high−frequency (> 3 kHz) noise directionality strongly depends on the distribution of floating glacial ice throughout the fjord. Changing rates of iceberg production as seen for example in field photographs and logs are, in turn, most likely linked to signal amplitudes for relevant directions. These findings demonstrate the potential offered by passive acous− tics to study the dynamics of individual tidewater glaciers.

The impact of glacier meltwater on the underwater noise field in a glacial bay

“…Commonly used satellite methods, short-term oceanographic measurements, or application of deep-water multisensor moorings are very useful, but still limited in terms of their spatial and temporal resolution. Ambient noise oceanography [Medwin and Clay, 1998], a technique that uses naturally generated sounds to obtain insight about sources of underwater noise and the ocean environment the noise propagates through, has been recently applied to polar regions and is proving to be a promising new measurement technique [Tegowski et al, 2011;Pettit et al, 2012;Blondel et al, 2013;Deane et al, 2014;Glowacki and Moskalik, 2014;Glowacki et al, 2015a]. Urick [1971] first identified the dominant mechanism by which melting glacial ice generates underwater noise: pressurized bubbles of air escaping from the ice produce a variety of noise signatures.…”

The Intensity, Directionality, and Statistics of Underwater Noise From Melting Icebergs

“…More than three decades later, Schulz et al () proposed the study of GrIS‐ocean interactions by “listening to glaciers.” This idea has led to the burgeoning field of ambient noise cryology. Measurements made in Svalbard (Deane et al, ; Tegowski et al, ), Alaska, and Antarctica (Pettit et al, ) have proven glacial bays to be one of the noisiest natural environments in the ocean with spatially diverse sources radiating sound in distinct spectral bands (Deane et al, ; Glowacki, Deane, Moskalik, Tegowski, & Blondel, ; Pettit, ; Pettit et al, ). Both laboratory and field experiments reveal a peak in noise power spectra between 1 and 3 kHz related to bubble release events (Blondel et al, ; Lee et al, ; Pettit et al, ).…”