Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Trends and variability in the ocean carbon sink

Nature Reviews Earth & Environment volume 4, pages 119–134 (2023)Cite this article

Subjects

Abstract

The ocean has absorbed 25 ± 2% of the total anthropogenic CO2 emissions from the early 1960s to the late 2010s, with rates more than tripling over this period and with a mean uptake of –2.7 ± 0.3 Pg C year–1 for the period 1990 through 2019. This growth of the ocean sink matches expectations based on the increase in atmospheric CO2, but research has shown that the sink is more variable than long assumed. In this Review, we discuss trends and variations in the ocean carbon sink. The sink stagnated during the 1990s with rates hovering around –2 Pg C year–1, but strengthened again after approximately 2000, taking up around –3 Pg C year–1 for 2010–2019. The most conspicuous changes in uptake occurred in the high latitudes, especially the Southern Ocean. These variations are caused by changes in weather and climate, but a volcanic eruption-induced reduction in the atmospheric CO2 growth rate and the associated global cooling contributed as well. Understanding the variability of the ocean carbon sink is crucial for policy making and projecting its future evolution, especially in the context of the UN Framework Convention on Climate Change stocktaking activities and the deployment of CO2 removal methods. This goal will require a global-level effort to sustain and expand the current observational networks and to better integrate these observations with models.

Key points

  • The long-term trend in the ocean carbon sink since the early 1960s was primarily driven by the increasing uptake of anthropogenic CO2. Although the ocean is expected to have lost a few petagrams of natural CO2 to the atmosphere in response to ocean warming, this loss cannot be quantified conclusively with observations.

  • The oceanic uptake of anthropogenic CO2 scaled proportionally with the increase in atmospheric CO2 between the early 1960s and late 2010s, as expected given the quasi-exponential growth of atmospheric CO2 during this period.

  • The average ocean uptake rate of –2.7 ± 0.3 Pg C year–1 for the period 1990 through 2019 is commensurate with a sensitivity β of 1.4 ± 0.1 Pg C per ppm atmospheric CO2, suggesting a trend in the uptake of –0.4 ± 0.1 Pg C year–1 per decade.

  • The annual mean ocean carbon sink varies by about ±20% around this trend, primarily caused by changes in the sources and sinks of natural CO2, with a lesser role for variations in atmospheric CO2 growth rates impacting the uptake of anthropogenic CO2.

  • The net oceanic uptake rate of CO2 will likely decrease in the future owing to several converging trends: reduced emissions of CO2 leading to reduced atmospheric CO2 growth rates in response to climate policy; reduced storage capacity owing to continuing ocean acidification; and enhanced outgassing of natural CO2 owing to ocean warming and changes in ocean circulation and biology.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Get just this article for as long as you need it

$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Ocean uptake and storage of anthropogenic CO2.
Fig. 2: Climatological mean sea-to-air CO2 flux.
Fig. 3: Temporal evolution of the global ocean CO2 sink.
Fig. 4: Zonally integrated anomalous CO2 fluxes and their components.
Fig. 5: Interannual to decadal variability in the ocean carbon sink.

References

  1. Friedlingstein, P. et al. Global Carbon Budget 2021. Earth Syst. Sci. Data 14, 1917–2005 (2022). This work is the most recent version of the GCB, an international effort led by the Global Carbon Project to synthesize all components of the global carbon cycle.

    Article  Google Scholar 

  2. Sabine, C. L. et al. The oceanic sink for anthropogenic CO2. Science 305, 367–371 (2004). This work is the first observation-based global inventory of anthropogenic CO2 providing a key constraint for the global anthropogenic CO2 budget.

    Article  Google Scholar 

  3. Khatiwala, S., Primeau, F. & Hall, T. Reconstruction of the history of anthropogenic CO2 concentrations in the ocean. Nature 462, 346–349 (2009). This work reconstructs the entire history of the oceanic uptake of anthropogenic CO2.

    Article  Google Scholar 

  4. Gruber, N. et al. The oceanic sink for anthropogenic CO2 from 1994 to 2007. Science 363, 1193–1199 (2019). This work presents an inventory of anthropogenic CO2 that provided a second time point describing the accumulation of anthropogenic CO2 in the ocean based on ocean interior observations.

    Article  Google Scholar 

  5. Revelle, R. in The Global Carbon Cycle and Atmospheric CO2: Natural Variations Archean to Present (eds Sundquist, E. T. & Broecker, W. S.) 1–4 (AGU, 1985).

  6. Heimann, M. A review of the contemporary global carbon cycle and as seen a century ago by Arrhenius and Hogbom. Ambio 26, 17–24 (1997).

    Google Scholar 

  7. Arrhenius, S. Lehrbuch der kosmischen Physik Vol. 2 (Hirzel, 1903).

  8. Archer, D., Kheshgi, H. & Maier-Reimer, E. Multiple timescales for neutralization of fossil fuel CO2. Geophys. Res. Lett. 24, 405–408 (1997).

    Article  Google Scholar 

  9. Sarmiento, J. L. & Gruber, N. Ocean Biogeochemical Dynamics (Princeton Univ. Press, 2006).

  10. Callendar, G. S. The artificial production of carbon dioxide and its influence on climate. Q. J. R. Meteor. Soc. 64, 223–240 (1938).

    Article  Google Scholar 

  11. Revelle, R. & Suess, H. E. Carbon dioxide exchange between atmosphere and ocean and the question of an increase of atmospheric CO2 during the past decades. Tellus 9, 18–27 (1957).

    Article  Google Scholar 

  12. Revelle, R., Broecker, W. S., Craig, H., Keeling, C. D. & Smagorinsky, J. in Restoring the Quality of Our Environment. Appendix Y4: Atmospheric Carbon Dioxide 111–133 (US Gov. Printing Office, 1965).

  13. Charney, J. G. et al. Carbon Dioxide and Climate: A Scientific Assessment (National Academy of Sciences, 1979).

  14. Keeling, C. D. The concentration and isotopic abundances of carbon dioxide in the atmosphere. Tellus 12, 200–203 (1960).

    Article  Google Scholar 

  15. Wallace, D. W. R. in Ocean Circulation and Climate Ch. 6.3 (eds Siedler, G., Church, J. & Gould, J.) 489–521, XLIX-L (Academic, 2001).

  16. Keppler, L., Landschützer, P., Gruber, N., Lauvset, S. K. & Stemmler, I. Seasonal carbon dynamics in the near‐global ocean. Glob. Biogeochem. Cycles 34, e2020GB006571 (2020).

    Article  Google Scholar 

  17. Canadell, P. G. et al. in Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (eds Masson-Delmotte, V. et al.) 673–816 (IPCC, 2021).

  18. Oeschger, H., Siegenthaler, U., Schotterer, U. & Gugelmann, A. A box diffusion model to study the carbon dioxide exchange in nature. Tellus 27, 168–192 (1975).

    Article  Google Scholar 

  19. Brewer, P. G. Direct observation of the oceanic CO2 increase. Geophys. Res. Lett. 5, 997–1000 (1978).

    Article  Google Scholar 

  20. Chen, C.-T. A. & Millero, F. J. Gradual increase of oceanic CO2. Nature 277, 205–206 (1979).

    Article  Google Scholar 

  21. Sabine, C. L. & Tanhua, T. Estimation of anthropogenic CO2 inventories in the ocean. Ann. Rev. Mar. Sci. 2, 175–198 (2010).

    Article  Google Scholar 

  22. Olsen, A. 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).

    Article  Google Scholar 

  23. DeVries, T. et al. Decadal trends in the ocean carbon sink. Proc. Natl Acad. Sci. USA 116, 201900371 (2019).

    Article  Google Scholar 

  24. Gruber, N., Landschützer, P. & Lovenduski, N. S. The variable Southern Ocean carbon sink. Ann. Rev. Mar. Sci. 11, 159–186 (2019).

    Article  Google Scholar 

  25. Hauck, J. et al. Consistency and challenges in the ocean carbon sink estimate for the global carbon budget. Front. Mar. Sci. 7, 1–33 (2020). This work describes and assesses the ocean biogeochemical models currently used to determine the oceanic uptake of CO2 in the context of the GCB.

    Article  Google Scholar 

  26. Landschützer, P., Gruber, N., Bakker, D. C. E. & Schuster, U. Recent variability of the global ocean carbon sink. Glob. Biogeochem. Cycles 28, 927–949 (2014).

    Article  Google Scholar 

  27. Landschützer, P., Gruber, N. & Bakker, D. C. E. Decadal variations and trends of the global ocean carbon sink. Glob. Biogeochem. Cycles 30, 1396–1417 (2016).

    Article  Google Scholar 

  28. Le Quere, C. et al. Saturation of the Southern Ocean CO2 sink due to recent climate change. Science 316, 1735–1738 (2007).

    Article  Google Scholar 

  29. Lovenduski, N. S., Gruber, N., Doney, S. C. & Lima, I. D. Enhanced CO2 outgassing in the Southern Ocean from a positive phase of the Southern Annular Mode. Global Biogeochem. Cycles https://doi.org/10.1029/2006GB002900 (2007).

    Article  Google Scholar 

  30. Le Quéré, C., Orr, J. C., Monfray, P., Aumont, O. & Madec, G. Interannual variability of the oceanic sink of CO2 from 1979 through 1997. Glob. Biogeochem. Cycles 14, 1247–1265 (2000). This study is the first to point out that the Southern Ocean carbon sink weakened substantially during the 1990s.

    Article  Google Scholar 

  31. Fay, A. R. & McKinley, G. A. Global trends in surface ocean pCO2 from in situ data. Glob. Biogeochem. Cycles 27, 541–557 (2013).

    Article  Google Scholar 

  32. Landschützer, P. et al. The reinvigoration of the Southern Ocean carbon sink. Science 349, 1221–1224 (2015). This work assesses the decadal variability of the ocean carbon sink and reveals it is driven by the extratropical latitudes in both hemispheres.

    Article  Google Scholar 

  33. McKinley, G. A., Fay, A. R., Eddebbar, Y. A., Gloege, L. & Lovenduski, N. S. External forcing explains recent decadal variability of the ocean carbon sink. AGU Adv. 1, 1–10 (2020).

    Article  Google Scholar 

  34. Rogelj, J. et al. in Global Warming of 1.5 °C. An IPCC Special Report 93–174 (IPCC, 2018).

  35. Cheng, L. et al. Another record: ocean warming continues through 2021 despite La Niña conditions. Adv. Atmos. Sci. https://doi.org/10.1007/s00376-022-1461-3 (2022).

    Article  Google Scholar 

  36. Abram, N. et al. in Special Report on the Ocean and Cryosphere (SROCC) Ch. 1 (eds Pörtner, H.-O. et al.) (IPCC, 2019).

  37. Bindoff, N. L. et al. in Special Report on the Ocean and Cryosphere (SROCC) Ch. 5 (eds Pörtner, H.-O. et al.) (IPCC, 2019).

  38. Sarmiento, J. L., Orr, J. C. & Siegenthaler, U. A perturbation simulation of CO2 uptake in an ocean general circulation model. J. Geophys. Res. 97, 3621–3645 (1992).

    Article  Google Scholar 

  39. Matsumoto, K. Radiocarbon-based circulation age of the world oceans. J. Geophys. Res. 112, 1–7 (2007).

    Google Scholar 

  40. Holzer, M. & Primeau, F. W. The path-density distribution of oceanic surface-to-surface transport. J. Geophys. Res. Ocean. 113, 1–22 (2008).

    Article  Google Scholar 

  41. Dong, Y. et al. Update on the temperature corrections of global air–sea CO2 flux estimates. Glob. Biogeochem. Cycles 26, 21–35 (2022).

    Google Scholar 

  42. Matsumoto, K. & Gruber, N. How accurate is the estimation of anthropogenic carbon in the ocean? An evaluation of the ΔC* method. Glob. Biogeochem. Cycles https://doi.org/10.1029/2004GB002397 (2005).

    Article  Google Scholar 

  43. Bates, N. et al. A time-series view of changing ocean chemistry due to ocean uptake of anthropogenic CO2 and ocean acidification. Oceanography 27, 126–141 (2014).

    Article  Google Scholar 

  44. Gregor, L. & Gruber, N. OceanSODA-ETHZ: a global gridded data set of the surface ocean carbonate system for seasonal to decadal studies of ocean acidification. Earth Syst. Sci. Data 13, 777–808 (2021).

    Article  Google Scholar 

  45. Broecker, W. S., Takahashi, T., Simpson, H. J. & Peng, T. H. Fate of fossil fuel carbon dioxide and the global carbon budget. Science 206, 409–418 (1979).

    Article  Google Scholar 

  46. Egleston, E. S., Sabine, C. L. & Morel, F. M. M. Revelle revisited: buffer factors that quantify the response of ocean chemistry to changes in DIC and alkalinity. Glob. Biogeochem. Cycles 24, 1–9 (2010).

    Article  Google Scholar 

  47. Jiang, L. Q., Carter, B. R., Feely, R. A., Lauvset, S. K. & Olsen, A. Surface ocean pH and buffer capacity: past, present and future. Sci. Rep. 9, 18624 (2019).

    Article  Google Scholar 

  48. Sarmiento, J. L., LeQuéré, C. & Pacala, S. W. Limiting future atmospheric carbon dioxide. Glob. Biogeochem. Cycles 9, 121–137 (1995).

    Article  Google Scholar 

  49. Joos, F. et al. An efficient and accurate representation of complex oceanic and biospheric models of anthropogenic carbon uptake. Tellus 48B, 397–417 (1996).

    Article  Google Scholar 

  50. Keeling, C. D. The Suess effect: 13-carbon and 14-carbon interactions. Environment Int. 2, 229–300 (1979).

    Article  Google Scholar 

  51. Friedlingstein, P. et al. Global Carbon Budget 2020. Earth Syst. Sci. Data 12, 3269–3340 (2020).

    Article  Google Scholar 

  52. Arora, V. K. et al. Carbon–concentration and carbon–climate feedbacks in CMIP6 models and their comparison to CMIP5 models. Biogeosciences 17, 4173–4222 (2020).

    Article  Google Scholar 

  53. Friedlingstein, P. et al. Climate-carbon cycle feedback analysis: results from the C4MIP model intercomparison. J. Clim. 19, 3337–3353 (2006).

    Article  Google Scholar 

  54. Meinshausen, M. et al. Realization of Paris Agreement pledges may limit warming just below 2 °C. Nature 604, 304–309 (2022).

    Article  Google Scholar 

  55. Joos, F. et al. Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: a multi-model analysis. Atmos. Chem. Phys. 13, 2793–2825 (2013).

    Article  Google Scholar 

  56. Waugh, D. W., Hall, T. M., Mcneil, B. I., Key, R. & Matear, R. J. Anthropogenic CO2 in the oceans estimated using transit time distributions. Tellus B Chem. Phys. Meteorol. 58, 376–389 (2006).

    Article  Google Scholar 

  57. Tanhua, T. et al. Ventilation of the Arctic Ocean: mean ages and inventories of anthropogenic CO2 and CFC-11. J. Geophys. Res. 114, 1–11 (2009).

    Google Scholar 

  58. Raimondi, L., Tanhua, T., Azetsu-Scott, K., Yashayaev, I. & Wallace, D. W. R. A 30-year time series of transient tracer-based estimates of anthropogenic carbon in the Central Labrador Sea. J. Geophys. Res. Ocean. 126, 1–19 (2021).

    Article  Google Scholar 

  59. Ridge, S. M. & McKinley, G. A. Ocean carbon uptake under aggressive emission mitigation. Biogeosciences 18, 2711–2725 (2021).

    Article  Google Scholar 

  60. Archer, D., Kheshgi, H. & Maier-Reimer, E. Dynamics of fossil fuel CO2 neutralization by marine CaCO3. Glob. Biogeochem. Cycles 12, 259–276 (1998).

    Article  Google Scholar 

  61. Bacastow, R. B. & Keeling, C. D. in Workshop on the Global Effects of Carbon Dioxide from Fossil Fuels (eds. Elliott, W. P. & Machta, L.) 72–90 (US Dept. of Energy, 1979).

  62. Siegenthaler, U. & Oeschger, H. Predicting future atmospheric carbon dioxide levels. Science 199, 388–395 (1978).

    Article  Google Scholar 

  63. Wallace, D. W. R. Monitoring Global Ocean Carbon Inventories (Ocean Observing System Development Panel, 1995).

  64. Gruber, N., Sarmiento, J. L. & Stocker, T. F. An improved method for detecting anthropogenic CO2 in the oceans. Glob. Biogeochem. Cycles 10, 809–837 (1996).

    Article  Google Scholar 

  65. Gruber, N. Anthropogenic CO2 in the Atlantic Ocean. Glob. Biogeochem. Cycles 12, 165–191 (1998).

    Article  Google Scholar 

  66. Dickson, A. G. & Goyet, C. Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water; version 2. OSTI https://www.osti.gov/biblio/10107773 (1994).

  67. Dickson, A. G., Afghan, J. D. & Anderson, G. C. Reference materials for oceanic CO2 analysis: a method for the certification of total alkalinity. Mar. Chem. 80, 185–197 (2003).

    Article  Google Scholar 

  68. Dickson, A. G. Standards for ocean measurements. Oceanography 23, 34–47 (2010).

    Article  Google Scholar 

  69. Key, R. M. et al. A global ocean carbon climatology: results from Global Data Analysis Project (GLODAP). Glob. Biogeochem. Cycles https://doi.org/10.1029/2004GB002247 (2004).

    Article  Google Scholar 

  70. DeVries, T. The oceanic anthropogenic CO2 sink: storage, air–sea fluxes, and transports over the industrial era. Glob. Biogeochem. Cycles 28, 631–647 (2014).

    Article  Google Scholar 

  71. Orr, J. C. et al. Estimates of anthropogenic carbon uptake from four three-dimensional global ocean models. Glob. Biogeochem. Cycles 15, 43–60 (2001).

    Article  Google Scholar 

  72. Mikaloff Fletcher, S. E. et al. Inverse estimates of anthropogenic CO2 uptake, transport, and storage by the ocean. Glob. Biogeochem. Cycles 20, 1–16 (2006). This ocean inversion-based study describes the regional distribution of the air–sea fluxes of anthropogenic CO2 and its oceanic transport.

    Article  Google Scholar 

  73. Davila, X. et al. How is the ocean anthropogenic carbon reservoir filled? Glob. Biogeochem. Cycles 36, 1–16 (2022).

    Article  Google Scholar 

  74. Groeskamp, S., Lenton, A., Matear, R., Sloyan, B. M. & Langlais, C. Anthropogenic carbon in the ocean—surface to interior connections. Glob. Biogeochem. Cycles 30, 1682–1698 (2016).

    Article  Google Scholar 

  75. Keeling, R. F. & Shertz, S. R. Seasonal and interannual variations in atmospheric oxygen and implications for the global carbon cycle. Nature 358, 723–727 (1992).

    Article  Google Scholar 

  76. Quay, P. D., Tilbrook, B. & Wong, C. S. Oceanic uptake of fossil fuel CO2: carbon-13 evidence. Science 256, 74–79 (1992).

    Article  Google Scholar 

  77. Heimann, M. & Maier-Reimer, E. On the relations between the oceanic uptake of CO2 and its carbon isotopes. Glob. Biogeochem. Cycles 10, 89–110 (1996).

    Article  Google Scholar 

  78. Gruber, N. & Keeling, C. D. An improved estimate of the isotopic air–sea disequilibrium of CO2: implications for the oceanic uptake of anthropogenic CO2. Geophys. Res. Lett. 28, 555–558 (2001).

    Article  Google Scholar 

  79. Khatiwala, S. et al. Global ocean storage of anthropogenic carbon. Biogeosciences 10, 2169–2191 (2013).

    Article  Google Scholar 

  80. Friedrich, T. et al. Detecting regional anthropogenic trends in ocean acidification against natural variability. Nature 2, 167–171 (2012).

    Google Scholar 

  81. Munro, D. R. et al. Recent evidence for a strengthening CO2 sink in the Southern Ocean from carbonate system measurements in the Drake Passage (2002–2015). Geophys. Res. Lett. 42, 7623–7630 (2015).

    Article  Google Scholar 

  82. Talley, L. D. et al. Changes in ocean heat, carbon content, and ventilation: a review of the first decade of GO-SHIP global repeat hydrography. Ann. Rev. Mar. Sci. 8, 185–215 (2016).

    Article  Google Scholar 

  83. Wanninkhof, R. et al. Detecting anthropogenic CO2 changes in the interior Atlantic Ocean between 1989 and 2005. J. Geophys. Res. 115, C11028 (2010).

    Article  Google Scholar 

  84. Friis, K., Körtzinger, A., Pätsch, J. & Wallace, D. W. R. On the temporal increase of anthropogenic CO2 in the subpolar North Atlantic. Deep. Res. Part I 52, 681–698 (2005).

    Article  Google Scholar 

  85. Goodkin, N. F., Levine, N. M., Doney, S. C. & Wanninkhof, R. Impacts of temporal CO2 and climate trends on the detection of ocean anthropogenic CO2 accumulation. Glob. Biogeochem. Cycles 25, 1–11 (2011).

    Article  Google Scholar 

  86. Levine, N. M., Doney, S. C., Wanninkhof, R., Lindsay, K. & Fung, I. Y. Impact of ocean carbon system variability on the detection of temporal increases in anthropogenic CO2. J. Geophys. Res. 113, C03019 (2008).

    Google Scholar 

  87. Carter, B. R. et al. Two decades of Pacific anthropogenic carbon storage and ocean acidification along Global Ocean Ship-based Hydrographic Investigations Program sections P16 and P02. Glob. Biogeochem. Cycles 31, 306–327 (2017).

    Google Scholar 

  88. Carter, B. R. et al. Pacific anthropogenic carbon between 1991 and 2017. Glob. Biogeochem. Cycles https://doi.org/10.1029/2018GB006154 (2019).

    Article  Google Scholar 

  89. Woosley, R. J., Millero, F. J. & Wanninkhof, R. Rapid anthropogenic changes in CO2 and pH in the Atlantic Ocean: 2003–2014. Glob. Biogeochem. Cycles 30, 70–90 (2016).

    Article  Google Scholar 

  90. Clement, D. & Gruber, N. The eMLR(C*) method to determine decadal changes in the global ocean storage of anthropogenic CO2. Glob. Biogeochem. Cycles 32, 654–679 (2018).

    Article  Google Scholar 

  91. Tanhua, T., Körtzinger, A., Friis, K., Waugh, D. W. & Wallace, D. W. R. An estimate of anthropogenic CO2 inventory from decadal changes in oceanic carbon content. Proc. Natl. Acad. Sci. USA 104, 3037–3042 (2007).

    Article  Google Scholar 

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

    Article  Google Scholar 

  93. Keeling, C. D. Carbon dioxide in surface ocean waters: 4. Global distribution. J. Geophys. Res. 73, 4543–4553 (1968).

    Article  Google Scholar 

  94. Tans, P. P., Fung, I. Y. & Takahashi, T. Observational contrains on the global atmospheric CO2 budget. Science 247, 1431–1438 (1990).

    Article  Google Scholar 

  95. Takahashi, T. et al. Global air–sea flux of CO2: an estimate based on measurements of sea–air pCO2 difference. Proc. Natl Acad. Sci. USA 94, 8292–8299 (1997).

    Article  Google Scholar 

  96. Takahashi, T. et al. Deep-sea research II climatological mean and decadal change in surface ocean pCO2, and net sea–air CO2 flux over the global oceans. Deep-Sea Res. II Top. Stud. Oceanogr. 56, 554–577 (2009).

    Article  Google Scholar 

  97. Bakker, D. C. E. et al. An update to the Surface Ocean CO2 Atlas (SOCAT version 2). Earth Syst. Sci. Data 6, 69–90 (2014).

    Article  Google Scholar 

  98. Pfeil, B. et al. A uniform, quality controlled Surface Ocean CO2 Atlas (SOCAT). Earth Syst. Sci. Data 5, 125–143 (2013).

    Article  Google Scholar 

  99. Bakker, D. C. E. et al. A multi-decade record of high-quality CO2 data in version 3 of the Surface Ocean CO2 Atlas (SOCAT). Earth Syst. Sci. Data 8, 383–413 (2016).

    Article  Google Scholar 

  100. Rödenbeck, C. et al. Data-based estimates of the ocean carbon sink variability—first results of the Surface Ocean pCO2 Mapping intercomparison (SOCOM). Biogeosciences 12, 7251–7278 (2015).

    Article  Google Scholar 

  101. Landschützer, P. et al. A neural network-based estimate of the seasonal to inter-annual variability of the Atlantic Ocean carbon sink. Biogeosciences 10, 7793–7815 (2013).

    Article  Google Scholar 

  102. Gregor, L., Lebehot, A. D., Kok, S. & Scheel Monteiro, P. M. A comparative assessment of the uncertainties of global surface ocean CO2 estimates using a machine-learning ensemble (CSIR-ML6 version 2019a)—have we hit the wall? Geosci. Model. Dev. 12, 5113–5136 (2019).

    Article  Google Scholar 

  103. Fay, A. R. et al. SeaFlux: harmonization of air–sea CO2 fluxes from surface pCO2 data products using a standardized approach. Earth Syst. Sci. Data 13, 4693–4710 (2021).

    Article  Google Scholar 

  104. Gruber, N. et al. Oceanic sources, sinks, and transport of atmospheric CO2. Glob. Biogeochem. Cycles 23, https://doi.org/10.1029/2008GB003349 (2009).

  105. Regnier, P., Resplandy, L., Najjar, R. G. & Ciais, P. The land-to-ocean loops of the global carbon cycle. Nature 603, 401–410 (2022).

    Article  Google Scholar 

  106. Sarmiento, J. L. & Sundquist, E. T. Revised budget for the oceanic uptake of anthropogenic carbon dioxide. Nature 356, 589–593 (1992).

    Article  Google Scholar 

  107. Regnier, P. et al. Anthropogenic perturbation of the carbon fluxes from land to ocean. Nat. Geosci. 6, 597–607 (2013).

    Article  Google Scholar 

  108. Resplandy, L. et al. Revision of global carbon fluxes based on a reassessment of oceanic and riverine carbon transport. Nat. Geosci. 11, 504–509 (2018).

    Article  Google Scholar 

  109. Landschützer, P., Ilyina, T. & Lovenduski, N. S. Detecting regional modes of variability in observation-based surface ocean pCO2. Geophys. Res. Lett. 46, 2670–2679 (2019).

    Article  Google Scholar 

  110. Ritter, R. et al. Observation-based trends of the Southern Ocean carbon sink. Geophys. Res. Lett. 44, 12,339–12,348 (2017).

    Article  Google Scholar 

  111. Gloege, L. et al. Quantifying errors in observationally‐based estimates of ocean carbon sink variability. Glob. Biogeochem. Cycles https://doi.org/10.1029/2020gb006788 (2021).

    Article  Google Scholar 

  112. Watson, A. J. et al. Revised estimates of ocean–atmosphere CO2 flux are consistent with ocean carbon inventory. Nat. Commun. 11, 1–6 (2020).

    Article  Google Scholar 

  113. Wanninkhof, R., Asher, W. E., Ho, D. T., Sweeney, C. & Mcgillis, W. R. Advances in quantifying air-sea gas exchange and environmental forcing. Ann. Rev. Mar. Sci. 1, 213–244 (2009).

    Article  Google Scholar 

  114. DeVries, T., Holzer, M. & Primeau, F. Recent increase in oceanic carbon uptake driven by weaker upper-ocean overturning. Nature 542, 215–218 (2017).

    Article  Google Scholar 

  115. Wolter, K. & Timlin, M. S. El Niño/Southern Oscillation behaviour since 1871 as diagnosed in an extended multivariate ENSO index (MEI.ext). Int. J. Climatol. 31, 1074–1087 (2011).

    Article  Google Scholar 

  116. Frölicher, T. L. et al. Dominance of the Southern Ocean in anthropogenic carbon and heat uptake in CMIP5 models. J. Clim. 28, 862–886 (2015).

    Article  Google Scholar 

  117. McKinley, G. A., Rödenbeck, C., Gloor, M., Houweling, S. & Heimann, M. Pacific dominance to global air–sea CO2 flux variability: a novel atmospheric inversion agrees with ocean models. Geophys. Res. Lett. 31, 10.1029/2004GL021069 (2004).

    Article  Google Scholar 

  118. Lenton, A. & Matear, R. J. Role of the Southern Annular Mode (SAM) in Southern Ocean CO2 uptake. Glob. Biogeochem. Cycles 21, 1–17 (2007).

    Article  Google Scholar 

  119. Keppler, L. & Landschützer, P. Regional wind variability modulates the Southern Ocean carbon sink. Sci. Rep. 9, 7384 (2019).

    Article  Google Scholar 

  120. Le Quéré, C., Takahashi, T., Buitenhuis, E. T., Rödenbeck, C. & Sutherland, S. C. Impact of climate change and variability on the global oceanic sink of CO2. Glob. Biogeochem. Cycles 24, https://doi.org/10.1029/2009GB003599 (2010).

    Article  Google Scholar 

  121. Feely, R. A., Wanninkhof, R., Takahashi, T. & Tans, P. Influence of El Niño on the equatorial Pacific contribution to atmospheric CO2 accumulation. Nature 398, 597–601 (1999).

    Article  Google Scholar 

  122. Ishii, M. et al. Air–sea CO2 flux in the Pacific Ocean for the period 1990–2009. Biogeosciences 11, 709–734 (2014).

    Article  Google Scholar 

  123. McKinley, G. A., Follows, M. J. & Marshall, J. Mechanisms of air–sea CO2 flux variability in the equatorial Pacific and the North Atlantic. Glob. Biogeochem. Cycles https://doi.org/10.1029/2003GB002179 (2004).

    Article  Google Scholar 

  124. Chatterjee, A. et al. Influence of El Niño on atmospheric CO2 over the tropical Pacific Ocean: findings from NASA’s OCO-2 mission. Science. 358, eaam5776 (2017).

    Article  Google Scholar 

  125. Keeling, C. D., Whorf, T. P., Wahlen, M. & Plicht, J. V. D. Interannual extremes in the rate of atmospheric carbon dioxide since 1980. Nature 375, 666–670 (1995).

    Article  Google Scholar 

  126. Crisp, D. et al. How well do we understand the land–ocean–atmosphere carbon cycle. Rev. Geophys. https://doi.org/10.1029/2021rg000736 (2022).

    Article  Google Scholar 

  127. Angert, A., Biraud, S., Bonfils, C., Buermann, W. & Fung, I. CO2 seasonality indicates origins of post-Pinatubo sink. Geophys. Res. Lett. 31, 1999–2002 (2004).

    Article  Google Scholar 

  128. Eddebbar, Y. A. et al. El Niño-like physical and biogeochemical ocean response to tropical eruptions. J. Clim. 32, 2627–2649 (2019).

    Article  Google Scholar 

  129. Marshall, L. R. et al. Volcanic effects on climate: recent advances and future avenues. Bull. Volcanol. 84, 54 (2022).

    Article  Google Scholar 

  130. Thompson, D. W. J. & Solomon, S. Interpretation of recent southern hemisphere climate change. Science 296, 895–899 (2002).

    Article  Google Scholar 

  131. Hauck, J. et al. Seasonally different carbon flux changes in the Southern Ocean in response to the Southern Annular Mode. Glob. Biogeochem. Cycles 27, 1236–1245 (2013).

    Article  Google Scholar 

  132. Lovenduski, N. S., Gruber, N. & Doney, S. C. Toward a mechanistic understanding of the decadal trends in the Southern Ocean carbon sink. Glob. Biogeochem. Cycles 22, 1–9 (2008).

    Article  Google Scholar 

  133. Gillett, N. P. & Thompson, D. W. J. Simulation of recent southern hemisphere climate change. Science 302, 273–275 (2003).

    Article  Google Scholar 

  134. Gruber, N., Bates, N. R. & Keeling, C. D. Interannual variability in the North Atlantic carbon sink. Science 298, 2374–2378 (2002).

    Article  Google Scholar 

  135. Frölicher, T. L., Joos, F., Raible, C. C. & Sarmiento, J. L. Atmospheric CO2 response to volcanic eruptions: the role of ENSO, season, and variability. Glob. Biogeochem. Cycles 27, 239–251 (2013).

    Article  Google Scholar 

  136. DeVries, T. Atmospheric CO2 and sea surface temperature variability cannot explain recent decadal variability of the ocean CO2 sink. Geophys. Res. Lett. 49, 1–12 (2022).

    Article  Google Scholar 

  137. Terhaar, J., Frölicher, T. L. & Joos, F. Observation-constrained estimates of the global ocean carbon sink from Earth system models. Biogeosciences 19, 4431–4457 (2022).

    Article  Google Scholar 

  138. Rogelj, J., McCollum, D. L., O’Neill, B. C. & Riahi, K. 2020 emissions levels required to limit warming to below 2 °C. Nat. Clim. Chang. 3, 405–412 (2012).

    Article  Google Scholar 

  139. Keller, D. P. et al. The effects of carbon dioxide removal on the carbon cycle. Curr. Clim. Chang. Rep. 4, 250–265 (2018).

    Article  Google Scholar 

  140. Smith, P. et al. Biophysical and economic limits to negative CO2 emissions. Nat. Clim. Chang. 6, 42–50 (2016).

    Article  Google Scholar 

  141. National Academies of Sciences. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration (National Academies Press, 2022).

  142. Aricò, S. et al. Integrated Ocean Carbon Research: A Summary of Ocean Carbon Research, and Vision of Coordinated Ocean Carbon Research and Observations for the Next Decade Report No. 158 (IOC, 2021).

  143. Gruber, N., Boyd, P. W., Frölicher, T. L. & Vogt, M. Biogeochemical extremes and compound events in the ocean. Nature 600, 395–407 (2021).

    Article  Google Scholar 

  144. Djeutchouang, L. M., Chang, N., Gregor, L., Vichi, M. & Monteiro, P. M. S. The sensitivity of pCO2 reconstructions to sampling scales across a Southern Ocean sub-domain: a semi-idealized ocean sampling simulation approach. Biogeosciences 19, 4171–4195 (2022).

    Article  Google Scholar 

  145. Majkut, J. D. et al. An observing system simulation for Southern Ocean carbon dioxide uptake. Philos. Trans. R. Soc. A Math. Phys. Eng. Sci. 372, 20130046–20130046 (2014).

    Article  Google Scholar 

  146. Claustre, H., Johnson, K. S. & Takeshita, Y. Observing the global ocean with Biogeochemical-Argo. Ann. Rev. Mar. Sci. 12, 23–48 (2020).

    Article  Google Scholar 

  147. Gray, A. R. et al. Autonomous biogeochemical floats detect significant carbon dioxide outgassing in the high-latitude Southern Ocean. Geophys. Res. Lett. 45, 9049–9057 (2018).

    Article  Google Scholar 

  148. Bushinsky, S. M. et al. Reassessing Southern Ocean air–sea CO2 flux estimates with the addition of biogeochemical float observations. Glob. Biogeochem. Cycles 33, 1–19 (2019).

    Article  Google Scholar 

  149. Verdy, A. & Mazloff, M. R. A data assimilating model for estimating Southern Ocean biogeochemistry. J. Geophys. Res. Ocean. 122, 6968–6988 (2017).

    Article  Google Scholar 

  150. Carroll, D. et al. Attribution of space–time variability in global‐ocean dissolved inorganic carbon. Glob. Biogeochem. Cycles 36, 1–24 (2022).

    Article  Google Scholar 

  151. Bennington, V., Gloege, L. & McKinley, G. A. Variability in the global ocean carbon sink from 1959 to 2020 by correcting models with observations. Geophys. Res. Lett. 49, e2022GL098632 (2022).

    Article  Google Scholar 

  152. Lacroix, F., Ilyina, T. & Hartmann, J. Oceanic CO2 outgassing and biological production hotspots induced by pre-industrial river loads of nutrients and carbon in a global modeling approach. Biogeosciences 17, 55–88 (2020).

    Article  Google Scholar 

  153. Kwon, E. Y. et al. Stable carbon isotopes suggest large terrestrial carbon inputs to the global ocean. Glob. Biogeochem. Cycles https://doi.org/10.1029/2020gb006684 (2021).

    Article  Google Scholar 

  154. Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection. High level review of a wide range of proposed marine geoengineering techniques. Report No. 98. GESAMP.org http://www.gesamp.org/publications/high-level-review-of-a-wide-range-of-proposed-marine-geoengineering-techniques (2019).

  155. Dlugokencky, E. & Tans, P. Trends in atmospheric carbon dioxide. National Oceanic & Atmospheric Administration; Global Monitoring Laboratory (NOAA/GML) http://gml.noaa.gov/ccgg/trends/ (2022).

  156. Gruber, N. & Sarmiento, J. L. in THE SEA: Biological–Physical Interactions in the Oceans Vol. 12 (eds Robinson, A. R., McCarthy, J. J. & Rothschild, B. J.) 337–399 (Wiley, 2002).

  157. Kroeker, K. J. et al. Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming. Glob. Chang. Biol. 19, 1884–1896 (2013).

    Article  Google Scholar 

  158. Landschützer, P., Gruber, N., Bakker, D. C. E., Stemmler, I. & Six, K. D. Strengthening seasonal marine CO2 variations due to increasing atmospheric CO2. Nat. Clim. Chang. 8, 146–150 (2018).

    Article  Google Scholar 

  159. Hauck, J. & Völker, C. Rising atmospheric CO2 leads to large impact of biology on Southern Ocean CO2 uptake via changes of the Revelle factor. Geophys. Res. Lett. 42, 1459–1464 (2015).

    Article  Google Scholar 

Download references

Acknowledgements

N.G., J.D.M., L.G. and P.L. acknowledge support from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 821003 (project 4C). N.G. also acknowledges support from the EU Horizon project no. 821001 (SO-CHIC). The work of D.C.E.B. was supported by the EU Horizon project no. 820989 (COMFORT). The work reflects only the authors’ views; the European Commission and their executive agency are not responsible for any use that may be made of the information the work contains. G.A.M. acknowledges funding from the National Science Foundation (NSF) through LEAP STC (2019625) and OCE (1948624), the National Aeronautics and Space Administration (NASA) (80NSSC22K0150) and the National Oceanic and Atmospheric Administration (NOAA) (NA20OAR4310340). J.H. received funding from the Helmholtz Young Investigator Group Marine Carbon and Ecosystem Feedbacks in the Earth System (MarESys) (grant number VH-NG-1301). T.D. acknowledges support from NSF award OCE-1948955.

Author information

Authors and Affiliations

  1. Environmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zürich, Switzerland

    Nicolas Gruber, Luke Gregor & Jens Daniel Müller

  2. Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, UK

    Dorothee C. E. Bakker

  3. Department of Geography, University of California, Santa Barbara, CA, USA

    Tim DeVries

  4. Earth Research Institute, University of California, Santa Barbara, CA, USA

    Tim DeVries

  5. Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar und Meeresforschung, Bremerhaven, Germany

    Judith Hauck

  6. The Ocean in the Earth System, Max Planck Institute for Meteorology, Hamburg, Germany

    Peter Landschützer

  7. Department Research, Flanders Marine Institute (VLIZ), Ostend, Belgium

    Peter Landschützer

  8. Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA

    Galen A. McKinley

  9. Lamont Doherty Earth Observatory, Palisades, NY, USA

    Galen A. McKinley

Authors
  1. Nicolas Gruber
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Dorothee C. E. Bakker
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Tim DeVries
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Luke Gregor
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Judith Hauck
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Peter Landschützer
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Galen A. McKinley
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Jens Daniel Müller
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

N.G. led the conceptual design and the implementation and also wrote the first draft. J.D.M. was responsible for the generation of Fig. 1 and Table 1. P.L. generated Fig. 2, L.G. generated Figs. 3 and 4, and N.G. drew Fig. 5. All authors contributed to the outline, discussed the content and conclusions and provided input to the manuscript during all drafting stages.

Corresponding author

Correspondence to Nicolas Gruber.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Reviews Earth & Environment thanks K. Matsumoto and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

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

Supplementary information

Glossary

Air–sea gas exchange

A diffusion-driven process governing the transfer of gases across the air–sea interface, driven by the concentration gradient of the gas across the interface and controlled by the level of turbulence at the interface.

Buffer factor

How well seawater is able to buffer an increase in surface ocean CO2 (ocean partial pressure of CO2), which is crucial for determining the amount of anthropogenic CO2 the surface ocean can hold; also called the Revelle factor.

Dissolved inorganic carbon

(DIC). The sum of all dissolved inorganic carbon species in the seawater, including dissolved CO2 (CO2aq), carbonic acid (H2CO3), bicarbonate (HCO3–) and carbonate (CO32−).

El Niño Southern Oscillation

(ENSO). A quasi-periodic oscillation of the coupled ocean–atmosphere system with the majority of the action being focused on the eastern tropical Pacific; it is globally the dominant mode of climate variability.

External forcing

Processes leading to changes in the ocean carbon sink driven by processes external to the climate system, such as volcanic eruptions.

Forward models

A class of models that start from initial conditions and solve the governing balance equations by time-integrating them forward using a set of provided boundary conditions.

Inverse models

A class of models that fuse observations and models in order to improve our quantitative understanding of a set of processes.

Internal forcing

Processes leading to changes in the ocean carbon sink, primarily associated with (internally generated) weather and climate variations.

Ocean partial pressure of CO2

(Ocean pCO2). The partial pressure of CO2 measured in the air in equilibrium with the water parcel under consideration at 1 atm total pressure and at the in situ temperature of the water parcel; often also referred to as pCO2oc.

Ocean acidification

Change in the ocean’s seawater chemistry (pH, [CO32−], CaCO3 saturation state and so on) as a consequence of the oceanic uptake of anthropogenic CO2.

Ocean biogeochemical models

A class of ocean models where the most important biogeochemical processes are explicitly represented, namely air–sea gas exchange, chemical speciation and biological processes.

Southern Annular Mode

(SAM). A mode of variations in the polar atmosphere of the southern hemisphere, characterized by fluctuations in the strength of the circumpolar vortex.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Gruber, N., Bakker, D.C.E., DeVries, T. et al. Trends and variability in the ocean carbon sink. Nat Rev Earth Environ 4, 119–134 (2023). https://doi.org/10.1038/s43017-022-00381-x

Download citation

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s43017-022-00381-x

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing