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The Silent World disturbed by icebergs' noise

Image of the Month - September 2016

Localisation of hydrophones in the Pacific ocean (green and yellow circles), in the Atlantic ocean (red circle). Iceberg sound sources is shown with white triangles. The path of the icebergs B15a and C19a are overlaid in red and maroon. White and blue areas correspond to maximum (winter) and minimum (summer) sea-ice extent in 2008. (Credits Ifremer).
Acoustic noise (two different frequencies), winter speed and iceberg volume in the South Pacific. (Credits Ifremer).

The ocean's nickname of the "Silent world" is largely overdone. From whales' songs to fishes nibbling the corals, sound is very much part of the ocean, even without the humans' sonars and engines. However, a natural sound may not be thought of - the sounds of icebergs.
To be sure, human beings have a role in its increase, but there were icebergs before climate change, and they broke and collided noisily, as they are doing now, only more often.

Altimetry do not able to measure sound in the ocean - no more than any other space technique, since the sound does not propagate out of the atmosphere. However, it ables to estimate iceberg concentration.  Comparing in situ acoustic measurements and altimetry-based iceberg concentration show some correlations at given frequencies with specific events like the calving of B15A and C19 icebergs from the Ross ice shelf in Antarctica. The noise of such events could reach (with a time lag) up to the Equatorial area, and is dominating the Southern hemisphere oceans. And any increase in iceberg calving will thus have an impact on the Southern oceans soundscape.

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References:

  • Matsumoto, H., D.W. R. Bohnenstiehl, J. Tournadre, R. P. Dziak, J. H. Haxel, T.-K. A. Lau, M. Fowler, and S. A. Salo (2014), Antarctic icebergs: A significant natural ocean sound source in the Southern Hemisphere, Geochem. Geophys. Geosyst., 15, 3448–3458, doi:10.1002/2014GC005454.
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