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

View Issue TOC
Volume 22, No. 4
Pages 36 - 47

Ocean Acidification: Present Conditions and Future Changes in a High-CO2 World

Richard A. Feely Scott C. Doney Sarah R. Cooley
Article Abstract

The uptake of anthropogenic CO2 by the global ocean induces fundamental changes in seawater chemistry that could have dramatic impacts on biological ecosystems in the upper ocean. Estimates based on the Intergovernmental Panel on Climate Change (IPCC) business-as-usual emission scenarios suggest that atmospheric CO2 levels could approach 800 ppm near the end of the century. Corresponding biogeochemical models for the ocean indicate that surface water pH will drop from a pre-industrial value of about 8.2 to about 7.8 in the IPCC A2 scenario by the end of this century, increasing the ocean’s acidity by about 150% relative to the beginning of the industrial era. In contemporary ocean water, elevated CO2 will also cause substantial reductions in surface water carbonate ion concentrations, in terms of either absolute changes or fractional changes relative to pre-industrial levels. For most open-ocean surface waters, aragonite undersaturation occurs when carbonate ion concentrations drop below approximately 66 µmol kg-1. The model projections indicate that aragonite undersaturation will start to occur by about 2020 in the Arctic Ocean and 2050 in the Southern Ocean. By 2050, all of the Arctic will be undersaturated with respect to aragonite, and by 2095, all of the Southern Ocean and parts of the North Pacific will be undersaturated. For calcite, undersaturation occurs when carbonate ion concentration drops below 42 µmol kg-1. By 2095, most of the Arctic and some parts of the Bering and Chukchi seas will be undersaturated with respect to calcite. However, in most of the other ocean basins, the surface waters will still be saturated with respect to calcite, but at a level greatly reduced from the present.


Feely, R.A., S.C. Doney, and S.R. Cooley. 2009. Ocean acidification: Present conditions and future changes in a high-CO2 world. Oceanography 22(4):36–47, https://doi.org/10.5670/oceanog.2009.95.


Bates, N.R. 2007. Interannual variability of the oceanic CO2 sink in the subtropical gyre of the North Atlantic Ocean over the last 2 decades. Journal of Geophysical Research 112, C09013, doi:10.1029/2006JC003759.

Bates, N.R., and A.J. Peters. 2007. The contribution of atmospheric acid deposition to ocean acidification in the subtropical North Atlantic Ocean. Marine Chemistry 107(4):547–558.

Broecker, W., and E. Clarke. 2001. A dramatic Atlantic dissolution event at the onset of the last glaciation. Geochemistry Geophysics Geosystems 2(11):1,065, doi:10.1029/2001GC000185. 

Caldeira, K., and M.E. Wickett. 2003. Anthropogenic carbon and ocean pH. Nature 425(6956):365.

Caldeira, K., and M.E. Wickett. 2005. Ocean model predictions of chemistry changes from carbon dioxide emissions to the atmosphere and ocean. Journal of Geophysical Research 110, C09S04, doi:10.1029/2004JC002671.

Canadell, J.G., C. Le Quéré, M.R. Raupach, C.B. Field, E.T. Buitenhuis, P. Ciais, T.J. Conway, N.P. Gillett, R.A. Houghton, and G. Marland. 2007. Contributions to accelerating atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of natural sinks. Proceedings of the National Academy of Sciences of the United States of America 104(47):18,866–18,870, doi:10.1073pnas.0702737104.

Chung, S.N., G.-H. Park, K. Lee, R.M. Key, F.J. Millero, R.A. Feely, C.L. Sabine, and P.G. Falkowski. 2004. Postindustrial enhancement of aragonite undersaturation in the upper tropical and subtropical Atlantic Ocean: The role of fossil fuel CO2. Limnology and Oceanography 49(2):315–321.

Cooley, S.R., H.L. Kite-Powell, and S.C. Doney. 2009. Ocean acidification’s potential to alter global marine ecosystem services. Oceanography 22(4):172–181.

Dickson, A.G., C.L. Sabine, and J.R. Christian, eds. 2007. Guide to Best Practices for Ocean CO2 Measurements. PICES Special Publication 3, 191 pp.

Doney, S.C., V.J. Fabry, R.A. Feely, and J.A. Kleypas. 2009. Ocean acidification: The other CO2 problem. Annual Reviews of Marine Science 1:169–192.

Doney, S.C., K. Lindsay, I. Fung, and J. John. 2006. Natural variability in a stable 1000 year coupled climate-carbon cycle simulation. Journal of Climate 19(13):3,033–3,054.

Dore, J.E., R. Lukas, D.W. Sadler, M.J. Church, and D.M. Karl. 2009. Physical and biogeochemical modulation of ocean acidification in the central North Pacific. Proceedings of the National Academy of Sciences of the United States of America 106(30):12,235–12,240.

Fabry, V.J., B.A. Seibel, R.A. Feely, and J.C. Orr. 2008. Impacts of ocean acidification on marine fauna and ecosystem processes. ICES Journal of Marine Science 65(3):414–432.

Feely, R.A., J. Orr, V.J. Fabry, J.A. Kleypas, C.L. Sabine, and C. Langdon. 2009. Present and future changes in seawater chemistry due to ocean acidification. Section 3 in Carbon Sequestration and Its Role in the Global Carbon Cycle. B.J. McPherson and E.T. Sundquist, eds, Geophysical Monograph Series, Vol. 83, American Geophysical Union, Washington, DC.

Feely, R.A., C.L. Sabine, K. Lee, W. Berelson, J. Kleypas, V.J. Fabry, and F.J. Millero. 2004. Impact of anthropogenic CO2 on the CaCO3 system in the oceans. Science 305(5682):362–366, doi:10.1126/science.1097329.

Friedlingstein, P., P. Cox, R. Betts, C. Jones, W. von Bloh, V. Brovkin, P. Cadule, S. Doney, M. Eby, D. Matthews, and others. 2006. Climate-carbon cycle feedback analysis: Results from the C*MIP model intercomparison. Journal of Climate 19(14):3,337–3,353.

Key, R.M., A. Kozyr, C.L. Sabine, K. Lee, R. Wanninkhof, J.L. Bullister, R.A. Feely, F.J. Millero, C. Mordy, and T.-H. Peng. 2004. A global ocean carbon climatology: Results from Global Data Analysis Project (GLODAP). Global Biogeochemical Cycles 18, GB4031, doi:10.1029/2004GB002247.

Langdon, C. 2002. Review of experimental evidence for effects of CO2 on calcification of reef builders. Proceedings of the 9th International Coral Reef Symposium 2:1,091–1,098 (Symposium met October 23–27, 2000, in Bali, Indonesia).

Lueker, T.J., A.G. Dickson, and C.D. Keeling. 2000. Ocean pCO2 calculated from dissolved inorganic carbon, alkalinity, and equations for K-1 and K-2: Validation based on laboratory measurements of CO2 in gas and seawater at equilibrium. Marine Chemistry 70(1–3):105–119.

Lüthi, D., M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T.F. Stocker. 2008. High-resolution carbon dioxide concentration record 650,000–800,000 years before present. Nature 453:379–382.

Mehrbach, C., C.H. Culberson, J.E. Hawley, and R.M. Pytkowicz, 1973. Measurement of the apparent dissociation constants of carbonic acid at atmospheric pressure. Limnology and Oceanography 18:897–907.

Mucci, A. 1983. The solubility of calcite and aragonite in seawater at various salinities, temperatures, and one atmosphere total pressure. American Journal of Science 283(7):780–799.

Orr, J.C., V.J. Fabry, O. Aumont, L. Bopp, S.C. Doney, R.A. Feely, A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, and others. 2005. Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature 437(7059):681–686.

Sabine, C.L., and R.A. Feely. 2007. The oceanic sink for carbon dioxide. Pp. 31–49 in Greenhouse Gas Sinks. D. Reay, N. Hewitt, J. Grace, and K. Smith, eds, CABI Publishing, Oxfordshire, UK. 

Sabine, C.L., R.M. Key, A. Kozyr, R.A. Feely, R. Wanninkhof, F.J. Millero, T.-H. Peny, J.L. Bullister, and K. Lee. 2005. Global Ocean Data Analysis Project (GLODAP): Results and Data. ORNL/CDIAC-15, NDP-083, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, Oak Ridge, TN. Available online at: http://cdiac.ornl.gov/oceans/glodap/pubs.htm (accessed November 13, 2009).

Santana-Casiano, J.M., M. Gonzalez-Davila, M.J. Rueda, O. Llinas, and E.F. Gonzalez-Davila. 2007. The interannual variability of oceanic CO2 parameters in the Northeast Atlantic subtropical gyre at the ESTOC site. Global Biogeochemical Cycles 21, GB1015, doi:10.1029/2006GB002706.

Steinacher, M., F. Joos, T.L. Frolicher, G.-K. Plattner, and S.C. Doney. 2009. Imminent ocean acidification in the Arctic projected with the NCAR global coupled carbon cycle-climate model. Biogeosciences 6:515–533.

Takahashi, T., S.C. Sutherland, R. Wanninkhof, C. Sweeney, R.A. Feely, D.W. Chipman, B. Hales, G. Friederich, F. Chavez, C. Sabine, and others. 2009. Climatological mean and decadal change in surface ocean pCO2, and net sea-air CO2 flux over the global oceans. Deep Sea Research Part II 56(8–10):554–577.

Thornton, P.E., S.C. Doney, K. Lindsay, J.K. Moore, N. Mahowald, J.T. Randerson, I. Fung, J.-F. Lamarque, J.J. Feddema, and Y.-H. Lee. 2009. Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks: Results from an atmosphere-ocean general circulation model. Biogeosciences 6:2,099–2,120. 

Zeebe, R.E., and D. Wolf-Gladrow. 2001. CO2 in Seawater: Equilibrium, Kinetics, Isotopes. Elsevier Oceanography Series, 65. Elsevier Science, B.V., Amsterdam, 346 pp.