Letter | Published:

Meridional overturning circulation conveys fast acidification to the deep Atlantic Ocean

Nature volume 554, pages 515518 (22 February 2018) | Download Citation


Since the Industrial Revolution, the North Atlantic Ocean has been accumulating anthropogenic carbon dioxide (CO2) and experiencing ocean acidification1, that is, an increase in the concentration of hydrogen ions (a reduction in pH) and a reduction in the concentration of carbonate ions. The latter causes the ‘aragonite saturation horizon’—below which waters are undersaturated with respect to a particular calcium carbonate, aragonite—to move to shallower depths (to shoal), exposing corals to corrosive waters2,3. Here we use a database analysis to show that the present rate of supply of acidified waters to the deep Atlantic could cause the aragonite saturation horizon to shoal by 1,000–1,700 metres in the subpolar North Atlantic within the next three decades. We find that, during 1991–2016, a decrease in the concentration of carbonate ions in the Irminger Sea caused the aragonite saturation horizon to shoal by about 10–15 metres per year, and the volume of aragonite-saturated waters to reduce concomitantly. Our determination of the transport of the excess of carbonate over aragonite saturation (xc[CO32−])—an indicator of the availability of aragonite to organisms—by the Atlantic meridional overturning circulation shows that the present-day transport of carbonate ions towards the deep ocean is about 44 per cent lower than it was in preindustrial times. We infer that a doubling of atmospheric anthropogenic CO2 levels—which could occur within three decades according to a ‘business-as-usual scenario’ for climate change4—could reduce the transport of xc[CO32−] by 64–79 per cent of that in preindustrial times, which could severely endanger cold-water coral habitats. The Atlantic meridional overturning circulation would also export this acidified deep water southwards, spreading corrosive waters to the world ocean.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    et al. Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios. Science 349, aac4722 (2015)

  2. 2.

    et al. in Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel of Climate Change (eds et al.) 411–484 (Cambridge Univ. Press, 2014)

  3. 3.

    Cold-Water Corals: The Biology and Geology of Deep-Sea Coral Habitats (Cambridge Univ. Press, 2009)

  4. 4.

    et al. The shared socioeconomic pathways and their energy, land use, and greenhouse gas emissions implications: an overview. Glob. Environ. Change 42, 153–168 (2017)

  5. 5.

    , , , & Seamounts as refugia from ocean acidification for cold-water stony corals. Mar. Ecol. 31, 212–225 (2010)

  6. 6.

    et al. Will human-induced changes in seawater chemistry alter the distribution of deep-sea scleractinian corals? Front. Ecol. Environ. 4, 141–146 (2006)

  7. 7.

    et al. Climatological distribution of aragonite saturation state in the global oceans. Glob. Biogeochem. Cycles 29, 1656–1673 (2015)

  8. 8.

    et al. Impact of anthropogenic CO2 on the CaCO3 system in the oceans. Science 305, 362–366 (2004)

  9. 9.

    , , & Calcification of the cold-water coral Lophelia pertusa, under ambient and reduced pH. Biogeosciences 6, 1671–1680 (2009)

  10. 10.

    . et al. Hidden impacts of ocean acidification to live and dead coral framework. Proc. R. Soc. Lond. B 282, 20150990 (2015)

  11. 11.

    , , , & Effects of chronic low carbonate saturation levels on the distribution, growth and skeletal chemistry of deep-sea corals and other seamount megabenthos. Mar. Ecol. Prog. Ser. 442, 87–99 (2011)

  12. 12.

    et al. The global ocean data analysis project version 2 (GLODAPv2)—an internally consistent data product for the world ocean. Earth Syst. Sci. Data 8, 297–323 (2016)

  13. 13.

    et al. Global Ocean Data Analysis Project, Version 2 (GLODAPv2) (2015)

  14. 14.

    ., ., ., & Cold-Water Coral Reefs: Out of Sight—No Longer Out of Mind (UNEP-WCMC Biodiversity Series 22, Cambridge, 2004)

  15. 15.

    et al. in Arctic–Subarctic Ocean Fluxes (eds , & ) 629–652 (Springer, 2008)

  16. 16.

    & Further intensification of deep convection in the Labrador Sea in 2016. Geophys. Res. Lett. 44, 1429–1438 (2017)

  17. 17.

    et al. Variability of the meridional overturning circulation at the Greenland–Portugal OVIDE section from 1993 to 2010. Prog. Oceanogr. 132, 250–261 (2015)

  18. 18.

    et al. The Nordic Seas carbon budget: sources, sinks, and uncertainties. Glob. Biogeochem. Cycles 25, GB4010 (2011)

  19. 19.

    et al. Atlantic Ocean CO2 uptake reduced by weakening of the meridional overturning circulation. Nat. Geosci. 6, 146–152 (2013)

  20. 20.

    IPCC Working Group. Climate Change 2013: The Physical Science Basis. Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, 2014)

  21. 21.

    The implications of COP21 for our future climate. Public Health Rev. 37, 29 (2016)

  22. 22.

    et al. Changes of anthropogenic CO2 and CFCs in the North Atlantic between 1981 and 2004. Glob. Biogeochem. Cycles 20, GB4017 (2006)

  23. 23.

    ., ., & Inventory changes in anthropogenic carbon from 1997–2003 in the Atlantic Ocean between 20° S and 65° N. Glob. Biogeochem. Cycles 23, GB3010 (2009)

  24. 24.

    et al. in Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel of Climate Change (eds et al.) 1655–1731 (Cambridge Univ. Press, 2014)

  25. 25.

    et al. Projected pH reductions by 2100 might put deep North Atlantic biodiversity at risk. Biogeosciences 11, 6955–6967 (2014)

  26. 26.

    , , , & Future-proofing marine protected area networks for cold water coral reefs. ICES J. Mar. Sci. 71, 2621–2629 (2014)

  27. 27.

    , & Physically driven patchy O2 changes in the North Atlantic Ocean simulated by the CMIP5 Earth system models: CMIP5: modeled O2 trends in the NA. Glob. Biogeochem. Cycles. 731, 10.1002/2016GB005617 (2017)

  28. 28.

    , , & Role of mode and intermediate waters in future ocean acidification: analysis of CMIP5 models. Geophys. Res. Lett. 40, 3091–3095 (2013)

  29. 29.

    , , , & Dissolved organic carbon in the North Atlantic meridional overturning circulation. Sci. Rep. 6, 26931 (2016)

  30. 30.

    , , & Impacts of ocean acidification on marine fauna and ecosystem processes. ICES J. Mar. Sci. 65, 414–432 (2008)

  31. 31.

    , , & Ocean acidification at high latitudes: the bellwether. Oceanography 22, 160–171 (2009)

  32. 32.

    , , & The composition of standard seawater and the definition of the reference-composition salinity scale. Deep Sea Res. I 55, 50–72 (2008)

  33. 33.

    et al. A novel determination of calcite dissolution kinetics in seawater. Geochim. Cosmochim. Acta 170, 51–68 (2015)

  34. 34.

    & A comparison of the equilibrium constants for the dissociation of carbonic acid in seawater media. Deep Sea Res. A 34, 1733–1743 (1987)

  35. 35.

    The solubility of calcite and aragonite in seawater at various salinities, temperatures, and one atmosphere total pressure. Am. J. Sci. 283, 780–799 (1983)

  36. 36.

    ., & Program Developed For CO2 System Calculations (Carbon Dioxide Information Analysis Center, U.S. Department of Energy, 1998)

  37. 37.

    ., ., & MATLAB Program Developed for CO2 System Calculations (Carbon Dioxide Information Analysis Center, U.S. Department of Energy, 2009)

  38. 38.

    et al. Temporal variability of the anthropogenic CO2 storage in the Irminger Sea. Biogeosciences 5, 1669–1679 (2008)

  39. 39.

    et al. Anthropogenic carbon distributions in the Atlantic Ocean: data-based estimates from the Arctic to the Antarctic. Biogeosciences 6, 439–451 (2009)

  40. 40.

    , , , & An estimate of anthropogenic CO2 inventory from decadal changes in oceanic carbon content. Proc. Natl Acad. Sci. USA 104, 3037 (2007)

  41. 41.

    & How accurate is the estimation of anthropogenic carbon in the ocean? An evaluation of the ΔC* method. Glob. Biogeochem. Cycles 19, GB3014 (2005)

  42. 42.

    , , , & in Seamounts: Ecology, Fisheries and Conservation (eds et al.) 141–169 (Blackwell, 2007)

  43. 43.

    , , & Deep-sea coral distribution on seamounts, oceanic islands, and continental slopes in the Northeast Atlantic. Bull. Mar. Sci. 81, 135–146 (2007)

  44. 44.

    et al. Global distribution of cold-water corals (version 3.0). UNEP World Conservation Monitoring Centre . (2017)

  45. 45.

    et al. A multiparametric method of interpolation using WOA05 applied to anthropogenic CO2 in the Atlantic. Sci. Mar. 74, 21–32 (2010)

  46. 46.

    . et al. World Ocean Atlas 2013. Volume 1: Temperature (NOAA Atlas NESDIS, 2013)

  47. 47.

    . et al. World Ocean Atlas 2013. Volume 2: Salinity (NOAA Atlas NESDIS, 2013)

  48. 48.

    . et al. World Ocean Atlas 2013. Volume 3: Dissolved Oxygen, Apparent Oxygen Utilization, and Oxygen Saturation. (NOAA Atlas NESDIS, 2014)

  49. 49.

    . et al. World Ocean Atlas 2013, Volume 4: Dissolved Inorganic Nutrients (Phosphate, Nitrate, Silicate). (NOAA Atlas NESDIS, 2014)

  50. 50.

    , & Reconstruction of the history of anthropogenic CO2 concentrations in the ocean. Nature 462, 346–349 (2009)

  51. 51.

    et al. The Atlantic meridional overturning circulation and the subpolar gyre observed at the A25-OVIDE section in June 2002 and 2004. Deep Sea Res. I 57, 1374–1391 (2010)

  52. 52.

    , , & Altimetry combined with hydrography for ocean transport estimation. J. Atmos. Ocean. Technol. 28, 1324–1337 (2011)

  53. 53.

    , & Circulation and transport at the southeast tip of Greenland. J. Phys. Oceanogr. 41, 437–457 (2011)

  54. 54.

    et al. Fossil-fueled development (SSP5): an energy and resource intensive scenario for the 21st century. Glob. Environ. Change 42, 297–315 (2017)

Download references


The OVIDE research project was co-funded by the Institut Français de Recherche pour l’Exploitation de la Mer (IFREMER) and CNRS/Institut National des Sciences de l’Univers (INSU)/Les Enveloppes Fluides et l’Environnement (LEFE). H.M. was supported by CNRS. This is a contribution to the AtlantOS project funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement 633211. This study is also a contribution to the BOCATS project (CTM2013-41048-P) supported by the Spanish Ministry of Economy and Competitiveness and co-funded by the Fondo Europeo de Desarrollo Regional 2014–2020 (FEDER). We thank the captain of the research vessel Sarmiento Gamboa—A. Campos—and her crew for help that made possible the success of the BOCATS cruise. We thank D. Barton for revision of the manuscript.

Author information

Author notes

    • Fiz F. Perez
    • , Marcos Fontela
    • , Maribel I. García-Ibáñez
    •  & Herlé Mercier

    These authors contributed equally to this work.


  1. Instituto Investigaciones Marinas (IIM, CSIC), calle Eduardo Cabello, 6, 36208, Vigo, Spain

    • Fiz F. Perez
    • , Marcos Fontela
    • , Maribel I. García-Ibáñez
    • , Anton Velo
    • , Mercedes de la Paz
    • , Fernando Alonso-Pérez
    • , Elisa F. Guallart
    •  & Xose A. Padin
  2. Centre National de la Recherche Scientifique (CNRS), Ifremer, Université de Brest, Institut de Recherche pour le Développement, Laboratoire d’Océanographie Physique et Spatiale (LOPS), Centre Ifremer de Bretagne, 29280, Plouzané, France

    • Herlé Mercier
    • , Pascale Lherminier
    •  & Patricia Zunino


  1. Search for Fiz F. Perez in:

  2. Search for Marcos Fontela in:

  3. Search for Maribel I. García-Ibáñez in:

  4. Search for Herlé Mercier in:

  5. Search for Anton Velo in:

  6. Search for Pascale Lherminier in:

  7. Search for Patricia Zunino in:

  8. Search for Mercedes de la Paz in:

  9. Search for Fernando Alonso-Pérez in:

  10. Search for Elisa F. Guallart in:

  11. Search for Xose A. Padin in:


F.F.P., H.M. and P.L. designed the program and executed the fieldwork. F.F.P, M.F., M.I.G-I., A.V., M.P., F.A-P., E.F.G. and X.A.P. contributed to the chemical determination of nutrients and carbon system. H.M., P.L. and P.Z. contributed to the measurement of currents and the inverse-model results. All authors contributed to discussion and writing.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Fiz F. Perez.

Reviewer Information Nature thanks J. Dunne, M. Roberts and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

About this article

Publication history







By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.