The soundscape in the Marginal Ice Zone
The soundscape in the Marginal Ice Zone (MIZ) is comprised of seismic airgun noise, ship cavitation noise, and natural background noise due to different geophysical processes in the MIZ. Cavitation noise from the research ice-breaker dominated the sound scape at times. Noise from distant seismic airgun operations was surprisingly prevanlent. Natural noise is primarily due to interactions between ice floes.Frequent marine mammal vocalizations were observed. Listen to the under ice soundscape in the MIZ here.
These are some of the results of two four days field campaigns carried out during fall 2012 and 2013 in the MIZ in the Fram Strait, between Svalbard and Greenland. Four Nansen Center scientists, led by Dr. Florian Geyer, and in cooperation with Scripps Institution of Oceanography have published the paper Identification and quantification of soundscape components in the Marginal Ice Zone paper in Journal of the Acoustical Society of America.
In the paper they have identified and quantified the major sound contributors in the MIZ. Their acoustic experiments using an integrated ice station were carried out in the MIZ in Fram Strait during August 2012 and September 2013. The two experiments lasted four days each and collected under-ice acoustic recordings together with wave-in-ice and meteorological data. Synthetic aperture radar (SAR) 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, e.g. along the Norwegian coast, was present during 117 out of 188 observation hours, causing an 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.
The results are part of the Waves-in-ice forecasting for Arctic Operators (WIFAR) and Arctic Ocean under Melting Ice (UNDER ICE) projects.
Paper citation: Florian Geyer, Hanne Sagen, Gaute Hope, Mohamed Babiker and Peter F. Worcester (2016): Identification and quantification of soundscape components in the Marginal Ice Zone. J. Acoust. Soc. Am. 139 (4), April 2016, p. 1873–1885. Doi: 10.1121/1.4945989. Copyright (2016) Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.
Full figure caption: Overview of passive acoustic recording during the 2012 experiment with spectrogram of 15-min mean acoustic noise levels (NLs). The main different sound types visible are ice breaking noise (12–50 Hz), seismic exploration noise (20–120 Hz, maximum at 40 Hz), marine mammal vocalizations (80–500 Hz, maximum at 120 Hz) and ship engine noise (horizontal lines at 330 Hz and various higher frequencies). The increased NLs at hours 50 and 64 are due to hydrophone hits; increased noise at hours 87–89 is due to extraordinary ship maneuvering activties.