Oceanography The Official Magazine of
The Oceanography Society
Volume 22 Issue 04

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Volume 22, No. 4
Pages 86 - 93

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Ocean Acidification and the Increasing Transparency of the Ocean to Low-Frequency Sound

Peter G. Brewer Keith Hester
Article Abstract

As the ocean becomes more acidic, low-frequency (~ 1–3 kHz and below) sound travels much farther due to changes in the amounts of pH-dependent species such as dissolved borate and carbonate ions, which absorb acoustic waves. The effect is quite large; a decline in pH of only 0.3 causes a 40% decrease in the intrinsic sound absorption properties of surface seawater. Because acoustic properties are measured on a logarithmic scale, and neglecting other losses, sound at frequencies important for marine mammals and for naval and industrial interests will travel some 70% farther with the ocean pH change expected from a doubling of CO2. This change will occur in surface ocean waters by mid century. The military and environmental consequences of these changes have yet to be fully evaluated. The physical basis for this effect is well known: if a sound wave encounters a charged molecule such as a borate ion that can be “squeezed” into a lower-volume state, a resonance can occur so that sound energy is lost, after which the molecule returns to its normal state. Ocean acousticians recognized this pH-sound linkage in the early 1970s, but the connection to global change and environmental science is in its infancy. Changes in pH in the deep sound channel will be large, and very-low-frequency sound originating there can travel far. In practice, it is the frequency range of ~ 300 Hz–10 kHz and the distance range of ~ 200–900 km that are of interest here.

Citation

Brewer, P.G., and K. Hester. 2009. Ocean acidification and the increasing transparency of the ocean to low-frequency sound. Oceanography 22(4):86–93, https://doi.org/10.5670/oceanog.2009.99.

References

Ainslie, M.A., and J.G. McColm. 1998. A simplified formula for viscous and chemical absorption in sea water. Journal of the Acoustical Society of America 103:1,671–1,672.

Bradshaw, A.L., P.G. Brewer, D.K. Shafer, and R.T. Williams. 1981. Measurements of total carbon dioxide and alkalinity by potentiometric titration in the GEOSECS program. Earth and Planetary Science Letters 55:99–115.

Brewer, P.G., D.M. Glover, C. Goyet, and D.K. Shafer. 1995. pH of the North Atlantic Ocean: Improvements to the global model for sound absorption in sea water. Journal of Geophysical Research 100:8,761–8,776.

Brewer, P.G., and E.T. Peltzer. 2009. Limits to marine life. Science 324:347–348.

Buck, R.P., S. Rondini, A.K. Covington, F.G.K. Baucke, C.M.A. Brett, M.F. Camoes, M.J.T. Milton, T. Mussini, R. Naumann, K.W. Pratt, and others. 2002. Measurement of pH. Definition, standards, and procedures. Pure and Applied Chemistry 74:2,169–2,200.

Craig, H., and R.F. Weiss. 1970. The Geosecs 1969 intercalibration station: Introduction, hydrographic features, and total CO2-O2 relationships. Journal of Geophysical Research 75:7,641–7,647.

Dore, J.E., R. Lukas, D.W. Sadler, M.J. Church, and D.M. Karl. 2009. Physical and biological modulation of ocean acidification in the central North Pacific. Proceedings of the National Academy of Sciences of the United States of America 106:12,235–12,240.

Duda, T.F. 2009. Review and analysis of the acoustic method of ocean acidity measurement. Journal of the Acoustical Society of America 125:1,971–1,981.

Fisher, F.H. 1979. Sound absorption in sea water by a third chemical relaxation. Journal of the Acoustical Society of America 65:1,327–1,329.

Fisher, F.H., and V.P. Simmons.1977. Sound absorption in sea water. Journal of the Acoustical Society of America 62:58–564.

Francois, R.E., and G.R. Garrison.1982. Sound absorption based on ocean measurements. Part II: Boric acid contribution and equation for total absorption. Journal of the Acoustical Society of America 72:1879-1890.

Garland, F., R.C. Patel, and G. Atkinson. 1973. Simulation of sound absorption spectra of sea water systems. Journal of the Acoustical Society of America 54:996–1,003.

Gorshkov, S.G., ed. 1978. World Ocean Atlas, vol. 2, Atlantic and Indian Oceans. Pergamon, New York.

Hester, K.C., E.T. Peltzer, W.J. Kirkwood, and P.G. Brewer. 2008. Unanticipated consequences of ocean acidification: A noisier ocean at lower pH. Geophysical Research Letters 35, L19601, doi:10.1029/2008GL034913.

Jin, G., and P.F. Worcester. 1989. The feasibility of measuring ocean pH by long range acoustics. Journal of Geophysical Research 94:4,749–4,756.

Lovett, J.R. 1975. Northeastern Pacific sound attenuation using low frequency CW sources. Journal of the Acoustical Society of America 58:620–625.

Lovett, J.R. 1980. Geographic variation of low-frequency sound absorption in the Atlantic, Pacific, and Indian Oceans. Journal of the Acoustical Society of America 67:338–340.

Mellen, R.H., and D.G. Browning. 1976. Low frequency attenuation in the Pacific Ocean. Journal of the Acoustical Society of America 59:700–702.

Mellen, R.H., P.H. Schiefele, and D.G. Browning. 1987. Global model for sound absorption in sea water: Scientific and engineering studies. Technical Report 7923, Naval Underwater Systems Center, Newport, RI.

Mellen, R.H., V.P. Simmons, and D.G. Browning. 1979. Sound absorption in sea water: A third chemical relaxation. Journal of the Acoustical Society of America 65:923–925.

Stramma, L., G.C. Johnson, J. Sprintall, and V. Mohrholz. 2008. Expanding oxygen-minimum zones in the tropical oceans. Science 320:655–657.

Takahashi, T., R.F. Weiss, C.H. Culberson, J.M. Edmond, D.E. Hammond, C.S. Wong, Y.-H. Li, and A.E. Bainbridge. 1970. A carbonate chemistry profile at the 1969 Geosecs intercalibration station in the eastern Pacific Ocean. Journal of Geophysical Research 75:7,648–7,666.

Ternon, J.F., C. Oudot, V. Gourlauen, D. Diverres. 2001. The determination of pHT in the equatorial Atlantic Ocean and its role in the sound absorption modeling in seawater. Journal of Marine Systems 30:67–87.

Thorp, W.H. 1965. Deep-ocean sound attenuation in the sub- and low-kilo-cycle-per-second range. Journal of the Acoustical Society of America 38:648–654.

Thorp, W.H. 1967. Analytical description of the low-frequency attenuation coefficient. Journal of the Acoustical Society of America 42:270–271.

Yeager, E., F.H. Fisher, J. Miceli, and R. Bressel. 1973. Origin of the low frequency sound absorption in sea water. Journal of the Acoustical Society of America 53:1,705–1,707.

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