National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2014

Antarctic's siren call: The sound of icebergs

Matsumoto, H., R.P. Dziak, D. Bohnenstiehl, J. Tournadre, T.-K. Lau, M. Fowler, J. Haxel, M. Park, and W. Lee

In Proceedings of the 2nd International Conference and Exhibition on Underwater Acoustics (UA2014), Island of Rhodes, Greece, 22–27 June 2014, 403–410 (2014)

While the steady increase in global shipping traffic has been identified as a primary cause of rising ocean noise level, in the Southern Hemisphere, the disintegration of large icebergs was found to be a significant noise source that influences the soundscape of ocean basins. Two large icebergs, B15a and C19a, calved off the Ross Ice Shelf in the early 2000s and drifted eastward to the warmer South Pacific Ocean in late 2007. For the next 1.5 years, while these icebergs were rapidly melting, they not only affected water circulation and the marine ecosystems in their vicinity but also influenced the low-frequency ambient noise level of the South Pacific basin. From 2008 to early 2009, the disintegration of B15a and C19a continuously projected loud, low-frequency sounds into the water column. The sounds propagated efficiently to lower latitudes, influencing the soundscape of the entire South Pacific basin. The icebergs’ sounds were recorded at Juan Fernández Islands (34°S, 79°W) by deep-water hydrophones maintained by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). The sounds also propagated across the equator (~10,000 km from the icebergs) and were recorded by a deep-water hydrophone at 8°N, 110°W, maintained by the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory and Oregon State University. In the 30–36 Hz range, the noise level was ~6 dB and ~2.5 dB higher than in baseline years at the respective location. Spectrogram plotting shows that at CTBTO hydrophones, icebergs’ sounds dominate the frequency range below 100 Hz at which baleen whales vocalize. Some large icebergs in the Southern Ocean have lifespans over a decade. We suggest that icebergs calved off Antarctica can collectively generate a considerable amount of sound energy, which then propagates across ocean basins, influencing the ocean soundscape and marine environment for the duration of the icebergs’ disintegration.

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