Letter abstract

Nature Geoscience 3, 18 - 22 (2010)
Published online: 20 December 2009 | doi:10.1038/ngeo719

Subject Category: Oceanography

Future ocean increasingly transparent to low-frequency sound owing to carbon dioxide emissions

Tatiana Ilyina1, Richard E. Zeebe1 & Peter G. Brewer2


Low-frequency sound in the ocean is produced by natural phenomena such as rain, waves and marine life, as well as by human activities, such as the use of sonar systems, shipping and construction. Sea water absorbs sound mainly owing to the viscosity of the water and the presence of chemical constituents, such as magnesium sulphate, boric acid and carbonate ions. The concentration of dissolved chemicals absorbing sound near 1kHz depends on the pH of the ocean1, which has declined as a result of increases in acidity due to anthropogenic emissions of carbon dioxide2, 3, 4. Here we use a global ocean model5, 6 forced with projected carbon dioxide emissions7 to predict regional changes in pH, and thus sound absorption, in the years 1800–2300. According to our projections, ocean pH could fall by up to 0.6 units by 2100. Sound absorption—in the range between ~100Hz and ~10kHz—could fall by up to 60% in the high latitudes and in areas of deep-water formation over the same time period. We predict that over the twenty-first century, chemical absorption of sound in this frequency range will nearly halve in some of the regions that experience significant radiated noise from industrial activity, such as the North Atlantic Ocean. We suggest that our forecast of reduced sound absorption in acoustic hotspots will help in identifying target regions for future monitoring.

  1. School of Ocean and Earth Science and Technology, Department of Oceanography, University of Hawaii, 1000 Pope Road, Honolulu, Hawaii 96822, USA
  2. Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, California 95039, USA

Correspondence to: Tatiana Ilyina1 e-mail: ilyina@soest.hawaii.edu

Correspondence to: Richard E. Zeebe1 e-mail: zeebe@soest.hawaii.edu


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