Dear MARMAM subscribers and colleagues, We are pleased to announce the publication of our new study titled: Soundscape and ambient noise levels of the Arctic waters around Greenland Michael Ladegaard, Jamie Macaulay, Malene Simon, Kristin L. Laidre, Aleksandrina Mitseva, Simone Videsen, Michael Bjerre Pedersen, Jakob Tougaard & Peter Teglberg Madsen Scientific Reports 11, article 23360 (2021) https://www.nature.com/articles/s41598-021-02255-6 https://doi.org/10.1038/s41598-021-02255-6
The motivation for doing the study was to establish a base line for the ambient noise levels around Greenland, as the Arctic environment is likely to see considerable changes in the near future. Human encroachment, which is enhanced by the retreating polar ice cap, is likely to result in increased anthropogenic noise emissions, but to monitor changes in noise pollution it is key to establish base lines for future comparison. Here we quantify the ambient noise levels recorded at 26 stations off the Greenland coast. The recording stations provide a large geographical coverage that includes Melville Bay, Baffin Bay and Davis Strait, Southern Greenland, the North Atlantic Ocean off Tasiilaq and the Greenland Sea. The underwater sounds were recorded for durations up to a year at a time so that the soundscapes (i.e. the acoustic environments created by a multitude of different sound sources) could be investigated and compared across seasons and geographic areas. The analysed data consists of ~17 TB of recordings that were sampled at 8, 16 or 32 kHz either continuously or in duty cycles. In addition to our quantifications of ambient noise levels in various frequency bands, we also applied a set of generic detectors in order broadly describe the soundscape and main sound sources. The detectors were set up to find different transients (e.g. seismic airgun pulses, ice-generated transients, and toothed whale echolocation clicks) and tonal sounds (e.g. marine mammal communication sounds and squeaking ice noises). Our study highlights the large noise fluctuations in the Arctic marine environment and we further show that generic detectors serve as a highly useful tool for describing main sound sources in the environment. For example, bearded seals could be vocally highly active for weeks or months at a time without being markedly noticeable from the ambient noise level analysis, however, the tonal detectors readily discovered this key biological feature of the soundscape. The paper is published as 'open access' and can be downloaded using the link above. On behalf of the authors, Michael Ladegaard Abstract A longer Arctic open water season is expected to increase underwater noise levels due to anthropogenic activities such as shipping, seismic surveys, sonar, and construction. Many Arctic marine mammal species depend on sound for communication, navigation, and foraging, therefore quantifying underwater noise levels is critical for documenting change and providing input to management and legislation. Here we present long-term underwater sound recordings from 26 deployments around Greenland from 2011 to 2020. Ambient noise was analysed in third octave and decade bands and further investigated using generic detectors searching for tonal and transient sounds. Ambient noise levels partly overlap with previous Arctic observations, however we report much lower noise levels than previously documented, specifically for Melville Bay and the Greenland Sea. Consistent seasonal noise patterns occur in Melville Bay, Baffin Bay and Greenland Sea, with noise levels peaking in late summer and autumn correlating with open water periods and seismic surveys. These three regions also had similar tonal detection patterns that peaked in May/June, likely due to bearded seal vocalisations. Biological activity was more readily identified using detectors rather than band levels. We encourage additional research to quantify proportional noise contributions from geophysical, biological, and anthropogenic sources in Arctic waters.
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