Abstract
Measurements of underwater sound are still scarce in the rapidly changing Arctic. Tele-seismically detectable glacial earthquakes caused by iceberg calving have been known for nearly two decades but their underwater sound levels remain undocumented. Here, we present near-source underwater sound records from a kilometer-scale iceberg calving associated with a glacial earthquake. Records were obtained using an ocean-bottom lander deployed near the calving front of a Greenlandic tidewater Bowdoin Glacier in July 2019. An underwater-detonation-like signal with an overall duration of 30 min and two major phases owing to iceberg detachment and disintegration corresponded to extreme source sound levels (225 ± 10 dBp 2 p re 1 μPa) and acoustic energy on the order of 108-10 J or 0.1-7.6 tonnes TNT-equivalent. Our estimates and comparison with other anthropogenic and natural sources suggest that this type of geophysical event is among the loudest sounds in the Arctic. Such high sound levels are important for estimating the noise budget of the ocean and possible impacts on endemic Arctic species exposed to such sounds. The sound of calving may cause direct mechanical damage to the hearing of marine mammals such as narwhals and seals present in the glacial fjord.
Highlights
Narwhals (Monodon monoceros) are attracted to glacial fjords during the Arctic summer, the reasons for which are unclear (Heide-Jørgensen et al, 2020; Laidre et al, 2016)
To learn more about the underwater sounds of both glacial fjords and narwhals, we analyzed records made by an autonomous bottom-mounted hydrophone in a narwhal summering ground in a glacial fjord in northwest Greenland, representing the closest underwater observations made to date to a marine-terminating glacier in Greenland, and documented a major calving event
We report extreme near-source records of underwater sound produced by a kilometer-scale iceberg calving event obtained with the first-of-its-kind ocean-bottom seismometer (OBS) experiment in Greenland
Summary
Narwhals (Monodon monoceros) are attracted to glacial fjords during the Arctic summer, the reasons for which are unclear (Heide-Jørgensen et al, 2020; Laidre et al, 2016) These relatively small whales are endemic to the Arctic and famous for their spiral tusk. To learn more about the underwater sounds of both glacial fjords and narwhals, we analyzed records made by an autonomous bottom-mounted hydrophone in a narwhal summering ground in a glacial fjord in northwest Greenland, representing the closest underwater observations made to date to a marine-terminating glacier in Greenland, and documented a major calving event These near-source records provide direct and indirect insights into underwater noise and marine life in the Arctic, which nowadays is exposed more frequently to such major acoustic phenomena, since 2010 in west Greenland (Sergeant et al, 2019)
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