Abstract
Acoustic experiments using an integrated ice station were carried out during August 2012 and September 2013 in the Marginal Ice Zone (MIZ) of Fram Strait. The two experiments lasted four days each and collected under-ice acoustic recordings together with wave-in-ice and meteorological data. Synthetic aperture radar satellite data provided information on regional ice conditions. Four major components of the under-ice soundscape were identified: ship cavitation noise, seismic airgun noise, marine mammal vocalizations, and natural background noise. Ship cavitation noise was connected to heavy icebreaking. It dominated the soundscape at times, with noise levels (NLs) 100 km from the icebreaker increased by 10-28 dB. Seismic airgun noise that originated from seismic surveys more than 800 km away was present during 117 out of 188 observation hours. It increased NLs at 20-120 Hz by 2-6 dB. Marine mammal vocalizations were a minor influence on measured NLs, but their prevalence shows the biological importance of the MIZ. The 10th percentile of the noise distributions was used to identify the ambient background noise. Background NLs above 100 Hz differed by 12 dB between the two experiments, presumably due to variations in natural noise sources.
Highlights
The focus of this paper is to study the soundscape of the Marginal Ice Zone (MIZ) of Fram Strait, located between Greenland and Svalbard
Ship cavitation, and the variations of the natural background noise due to differing geophysical conditions were all substantial contributors to shaping the soundscape variability during the two four-day experiments
The frequent marine mammal vocalizations played a part in shaping the observed noise spectra in the MIZ
Summary
The focus of this paper is to study the soundscape of the Marginal Ice Zone (MIZ) of Fram Strait, located between Greenland and Svalbard. The wind, wave and mesoscale processes along the ice edge determine the location, configuration, and composition of the MIZ (e.g., Johannessen et al, 2003) These processes are natural sound generation mechanisms in the MIZ, which has a different soundscape compared to the interior Arctic. Recordings in Fram Strait and the Greenland Sea have shown that most of the year signals from seismic airguns dominate the low frequency portion of the soundscape (Moore et al, 2012; Klinck et al, 2012). As the sound reaches the ice edge, it is attenuated with distance into the ice pack (Tollefsen and Sagen, 2014) Human activities, such as icebreaker operations, commercial shipping, and air guns used for seismic exploration, are increasing in Arctic and sub-Arctic areas.
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