Drivers and mechanisms of ocean deoxygenation

Abstract

Direct observations indicate that the global ocean oxygen inventory is decreasing. Climate models consistently confirm this decline and predict continuing and accelerating ocean deoxygenation. However, current models (1) do not reproduce observed patterns for oxygen changes in the ocean’s thermocline; (2) underestimate the temporal variability of oxygen concentrations and air–sea fluxes inferred from time-series observations; and (3) generally simulate only about half the oceanic oxygen loss inferred from observations. We here review current knowledge about the mechanisms and drivers of oxygen changes and their variation with region and depth over the world’s oceans. Warming is considered a major driver: in part directly, via solubility effects, and in part indirectly, via changes in circulation, mixing and oxygen respiration. While solubility effects have been quantified and found to dominate deoxygenation near the surface, a quantitative understanding of contributions from other mechanisms is still lacking. Current models may underestimate deoxygenation because of unresolved transport processes, unaccounted for variations in respiratory oxygen demand, or missing biogeochemical feedbacks. Dedicated observational programmes are required to better constrain biological and physical processes and their representation in models to improve our understanding and predictions of patterns and intensity of future oxygen change.

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Fig. 1: Thermocline ocean ventilation.
Fig. 2: Warming-induced changes in thermocline ventilation.
Fig. 3: Oxygen change in the ocean.

References

  1. 1.

    Schmidtko, S., Stramma, L. & Visbeck, M. Decline in global oceanic oxygen content during the past five decades. Nature 542, 335–339 (2017).

    Article  Google Scholar 

  2. 2.

    Helm, K. P., Bindoff, N. L. & Church, J. A. Observed decreases in oxygen content of the global ocean. Geophys. Res. Lett. 38, L23602 (2011).

    Article  Google Scholar 

  3. 3.

    Ito, T., Minobe, A., Long, M. C. & Deutsch, C. Upper ocean O2 trends: 1958–2015. Geophys. Res. Lett. 44, 4214–4223 (2017).

    Article  Google Scholar 

  4. 4.

    Bopp, L. et al. Multiple stressors of ocean ecosystems in the 21st century: projections with CMIP5 models. Biogeosciences 10, 6225–6245 (2013).

    Article  Google Scholar 

  5. 5.

    Keeling, R. F., Körtzinger, A. & Gruber, N. Ocean deoxygenation in a warming world. Annu. Rev. Mar. Sci 2, 199–229 (2010).

    Article  Google Scholar 

  6. 6.

    Praetorius, S. K. et al. North Pacific deglacial hypoxic events linked to abrupt ocean warming. Nature 527, 362–366 (2015).

    Article  Google Scholar 

  7. 7.

    Watson, A. J. Oceans on the edge of anoxia. Science 354, 1529–1530 (2016).

    Article  Google Scholar 

  8. 8.

    Watson, A., Lenton, T. & Mills, B. Ocean deoxygenation, the global phosphorus cycle, and the possibility of human-caused large-scale ocean anoxia. Phil. Trans. R. Soc. A 375, 20160318 (2017).

    Article  Google Scholar 

  9. 9.

    Paulmier, A. & Ruiz-Pino, D. Oxygen minimum zones (OMZs) in the modern ocean. Progr. Oceanogr. 80, 113–128 (2009).

    Article  Google Scholar 

  10. 10.

    Wyrtki, K. The oxygen minima in relation to ocean circulation. Deep Sea Res. 9, 11–23 (1962).

    Google Scholar 

  11. 11.

    Karstensen, J., Stramma, L. & Visbeck, M. Oxygen minimum zones in the eastern tropical Atlantic and Pacific oceans. Prog. Oceanogr. 77, 331–350 (2008).

    Article  Google Scholar 

  12. 12.

    Diaz, R. J. & Rosenberg, R. Spreading dead zones and consequences for marine ecosystems. Science 321, 926–929 (2008).

    Article  Google Scholar 

  13. 13.

    Kalvelage, T. et al. Nitrogen cycling driven by organic matter export in the South Pacific oxygen minimum zone. Nat. Geosci. 6, 228–234 (2013).

    Article  Google Scholar 

  14. 14.

    Scholz, F., McManus, J., Mix, A. C., Hensen, C. & Schneider, R. R. The impact of ocean deoxygenation on iron release from continental margin sediments. Nat. Geosci. 7, 433–437 (2014).

    Article  Google Scholar 

  15. 15.

    Niemeyer, D., Kemena, T. P., Meissner, K. J. & Oschlies, A. A model study of warming-induced phosphorus–oxygen feedbacks in open-ocean oxygen minimum zones on millennial timescales. Earth Syst. Dynam. 8, 357–367 (2017).

    Article  Google Scholar 

  16. 16.

    Arevalo-Martinez, D. A., Kock, A., Löscher, C. R., Schmitz, R. A. & Bange, H. W. Massive nitrous oxide emissions from the tropical South Pacific Ocean. Nat. Geosci. 8, 530–533 (2015).

    Article  Google Scholar 

  17. 17.

    Martinez-Rey, J., Bopp, L., Gehlen, M., Tagliabue, A. & Gruber, N. Projections of oceanic N2O emissions in the 21st century using the IPSL Earth system model. Biogeosciences 12, 4133–4148 (2015).

    Article  Google Scholar 

  18. 18.

    Landolfi, A., Somes, C. J., Koeve, W., Zamora, L. M. & Oschlies, A. Oceanic nitrogen cycling and N2O flux perturbations in the Anthropocene. Global Biogeochem. Cycles 31, 1236–1255 (2017).

    Article  Google Scholar 

  19. 19.

    Stramma, L., Johnson, G. C., Sprintall, J. & Mohrholz, V. Expanding oxygen-minimum zones in the tropical oceans. Science 320, 655–658 (2008).

    Article  Google Scholar 

  20. 20.

    Breitburg, D. et al. Declining oxygen in the global ocean and coastal waters. Science 359, eaam7240 (2018).

    Article  Google Scholar 

  21. 21.

    Oschlies, A. et al. Patterns of deoxygenation - sensitivity to natural and anthropogenic drivers. Phil. Trans. Roy. Soc. A 375, 20160325 (2017).

    Article  Google Scholar 

  22. 22.

    Long, M. C., Deutsch, C. & Ito, T. Finding forced trends in oceanic oxygen. Global Biogeochem. Cycles 30, 381–397 (2016).

    Article  Google Scholar 

  23. 23.

    Eddebbar, Y. A. et al. Impacts of ENSO on air-sea oxygen exchange: observations and mechanisms. Global Biogeochem. Cycles 31, 901–921 (2017).

    Article  Google Scholar 

  24. 24.

    Stramma, L., Oschlies, A. & Schmidtko, S. Mismatch between observed and modeled trends in dissolved upper-ocean oxygen over the last 50 yr. Biogeosciences 9, 4045–4057 (2012).

    Article  Google Scholar 

  25. 25.

    Frölicher, T. L., Rodgers, K. B., Stock, C. A. & Cheung, W. W. L. Sources of uncertainties in 21st century projections of potential ocean ecosystem stressors. Global Biogeochem. Cycles 30, 1224–1243 (2016).

    Article  Google Scholar 

  26. 26.

    IPCC Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) (Cambridge Univ. Press, 2013).

  27. 27.

    Cabré, A., Marinov, I., Bernardello, R. & Bianchi, D. Oxygen minimum zones in the tropical Pacific across CMIP5 models: mean state differences and climate change trends. Biogeosciences 12, 5429–5454 (2015).

    Article  Google Scholar 

  28. 28.

    Levin, L. A. Manifestation, drivers, and emergence of open ocean deoxygenation. Annu. Rev. Mar. Sci 10, 229–260 (2018).

    Article  Google Scholar 

  29. 29.

    Brandt, P. et al. On the role of circulation and mixing in the ventilation of oxygen minimum zones with a focus on the eastern tropical North Atlantic. Biogeosciences 12, 489–512 (2015).

    Article  Google Scholar 

  30. 30.

    Duteil, O., Schwarzkopf, F. U., Böning, C. W. & Oschlies, A. Major role of the equatorial current system in setting oxygen levels in the eastern tropical Atlantic Ocean: a high-resolution model study. Geophys. Res. Lett. 41, 2033–2040 (2014).

    Article  Google Scholar 

  31. 31.

    Ridder, N. N. & England, M. H. Sensitivity of ocean oxygenation to variations in tropical zonal wind stress magnitude. Global Biogeochem. Cycles 28, 909–926 (2014).

    Article  Google Scholar 

  32. 32.

    Liu, C. & Wang, Z. On the response of the global subduction rate to global warming in coupled climate models. Adv. Atmos. Sci. 31, 211 (2014).

    Article  Google Scholar 

  33. 33.

    Durack, P. J. & Wijffels, S. E. Fifty-year trends in global ocean salinities and their relationship to broad-scale warming. J. Clim. 23, 4342–4362 (2010).

    Article  Google Scholar 

  34. 34.

    England, M. H. et al. Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus. Nat. Clim. Change 4, 222–227 (2014).

    Article  Google Scholar 

  35. 35.

    Liu, L. L. & Huang, R. X. The global subduction/obduction rates: their interannual and decadal variability. J. Clim. 25, 1096–1115 (2012).

    Article  Google Scholar 

  36. 36.

    Stouffer, R. J. et al. Investigating the causes of the thermohaline circulation to past and future climate changes. J. Clim. 19, 1365–1387 (2006).

    Article  Google Scholar 

  37. 37.

    Brewer, P. G. & Peltzer, E. T. Depth perception: the need to report ocean biogeochemical rates as functions of temperature, not depth. Phil. Trans. R. Soc. A 375, 20160319 (2017).

    Article  Google Scholar 

  38. 38.

    Oschlies, A., Schulz, K. G., Riebesell, U. & Schmittner, A. Simulated 21st century’s increase in oceanic suboxia by CO2-enhanced biotic carbon export. Global Biogeochem. Cycles 22, GB4008 (2008).

    Article  Google Scholar 

  39. 39.

    Hofmann, M. & Schellnhuber, H.-J. Oceanic acidification affects marine carbon pump and triggers extended marine oxygen holes. Proc. Natl Acad. Sci. USA 106, 3017–3022 (2009).

    Article  Google Scholar 

  40. 40.

    Ito, T., Nenes, A., Johnson, M. S., Meskhidze, N. & Deutsch, C. Acceleration of oxygen decline in the tropical Pacific over the past decades by aerosol pollutants. Nat. Geosci. 9, 443–447 (2016).

    Article  Google Scholar 

  41. 41.

    Segschneider, J. & Bendtsen, J. Temperature-dependent remineralization in a warming ocean increases surface pCO2 through changes in marine ecosystem composition. Global Biogeochem. Cycles 27, 1214–1225 (2013).

    Article  Google Scholar 

  42. 42.

    Wallmann, K. Phosphorus imbalance in the global ocean? Global Biogeochem. Cycles 24, GB4030 (2010).

    Article  Google Scholar 

  43. 43.

    Bendtsen, J., Hilligsøe, K. M., Hansen, J. L. S. & Richardson, K. Analysis of remineralisation, lability, temperature sensitivity and structural composition of organic matter from the upper ocean. Progr. Oceanogr. 130, 125–145 (2015).

    Article  Google Scholar 

  44. 44.

    Bendtsen, J. & Hansen, J. L. S. Effects of global warming on hypoxia in the Baltic Sea–North Sea transition zone. Ecol. Model. 264, 17–26 (2013).

    Article  Google Scholar 

  45. 45.

    Ingall, E. & Jahnke, R. Evidence for enhanced phosphorus regeneration from marine sediments overlain by oxygen depleted waters. Geochim. Cosmochim. Acta 58, 2571–2575 (1994).

    Article  Google Scholar 

  46. 46.

    Conley, D. J., Carstensen, J., Vaquer-Sunyer, R. & Duarte, C. M. Ecosystem thresholds with hypoxia. Hydrobiologia 629, 21–29 (2009).

    Article  Google Scholar 

  47. 47.

    Steinberg, D. K., Goldthwait, S. A. & Hansell, D. A. Zooplankton vertical migration and the active transport of dissolved organic and inorganic nitrogen in the Sargasso Sea. Deep Sea Res. I 49, 1445–1461 (2002).

    Article  Google Scholar 

  48. 48.

    Kiko, R. et al. Biological and physical influences on marine snowfall at the equator. Nat. Geosci. 10, 852–858 (2017).

    Article  Google Scholar 

  49. 49.

    Getzlaff, J. & Oschlies, A. Pilot study on potential impacts of fisheries-induced changes in zooplankton mortality on marine biogeochemistry. Global Biogeochem. Cycles 31, 1656–1673 (2017).

    Article  Google Scholar 

  50. 50.

    Bianchi, D., Galbraith, E. D., Carozza, D. A., Mislan, K. A. S. & Stock, C. A. Intensification of open-ocean oxygen depletion by vertically migrating animals. Nat. Geosci. 6, 545–548 (2013).

    Article  Google Scholar 

  51. 51.

    Deutsch, C., Sarmiento, J. L., Sigman, D. M., Gruber, N. & Dunne, J. P. Spatial coupling of nitrogen inputs and losses in the ocean. Nature 445, 163–167 (2007).

    Article  Google Scholar 

  52. 52.

    Landolfi, A., Dietze, H., Koeve, W. & Oschlies, A. Overlooked runaway feedback in the marine nitrogen cycle: the vicious cycle. Biogeosciences 10, 1351–1363 (2013).

    Article  Google Scholar 

  53. 53.

    Mills, M. M. & Arrigo, K. R. Magnitude of oceanic nitrogen fixation influenced by the nutrient uptake ratio of phytoplankton. Nat. Geosci. 3, 412–416 (2010).

    Article  Google Scholar 

  54. 54.

    Yamamoto, A., Yamanaka, Y., Oka, A. SpringerAmpamp; Abe-Ouchi, A. Ocean oxygen depletion due to decomposition of submarine methane hydrate. Geophys. Res. Lett. 41, 5075–5083 (2014).

    Article  Google Scholar 

  55. 55.

    Luyten, J. R., Pedlosky, J. & Stommel, H. The ventilated thermocline. J. Phys. Oceanogr. 13, 292–309 (1983).

    Article  Google Scholar 

  56. 56.

    Kwon, E. Y., Deutsch, C., Xie, S.-P., Schmidtko, S. & Cho, Y.-K. The North Pacific oxygen uptake rates over the past half century. J. Clim. 29, 61–76 (2016).

    Article  Google Scholar 

  57. 57.

    Brandt, P. et al. Changes in the ventilation of the oxygen minimum zone of the tropical North Atlantic. J. Phys. Oceanogr. 40, 1784–1801 (2010).

    Article  Google Scholar 

  58. 58.

    Hahn, J., Brandt, P., Schmidtko, S. & Krahmann, G. Decadal oxygen change in the eastern tropical North Atlantic. Ocean Sci. 13, 551–576 (2017).

    Article  Google Scholar 

  59. 59.

    Deutsch, C. et al. Centennial changes in North Pacific anoxia linked to tropical trade winds. Science 345, 665–668 (2014).

    Article  Google Scholar 

  60. 60.

    Deutsch, C., Brix, H., Ito, T., Frenzel, H. & Thomson, L. Climate-forced variability of ocean hypoxia. Science 333, 336–339 (2011).

    Article  Google Scholar 

  61. 61.

    Andrews, O. D., Bindoff, N. L., Halloran, P. R., Ilyina, T. & Le Quéré, C. Detecting an external influence on recent changes in oceanic oxygen using an optimal fingerprinting method. Biogeosciences 10, 1799–1813 (2013).

    Article  Google Scholar 

  62. 62.

    Montes, E. et al. Decadal variability in the oxygen inventory of North Atlantic subtropical underwater captured by sustained, long-term oceanographic time series observations. Global Biogeochem. Cycles 30, 460–478 (2016).

    Article  Google Scholar 

  63. 63.

    Di Lorenzo, E. et al. Synthesis of Pacific Ocean climate and ecosystem dynamics. Oceanography 26, 68–81 (2013).

    Article  Google Scholar 

  64. 64.

    Dietze, H. & Loeptien, U. Revisiting “nutrient trapping” in global coupled biogeochemical ocean circulation models. Global Biogeochem. Cycles 27, 265–284 (2013).

    Article  Google Scholar 

  65. 65.

    Pozo Buil, M. & Di Lorenzo, E. Decadal dynamics and predictability of oxygen and subsurface tracers in the California Current System. Geophys. Res. Lett. 44, 4204–4213 (2017).

    Article  Google Scholar 

  66. 66.

    Peña-Izquierdo, J. et al. Water mass pathways to the North Atlantic oxygen minimum zone. J. Geophys. Res. Oceans 120, 3350–3372 (2015).

    Article  Google Scholar 

  67. 67.

    Chang, P. et al. Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon. Nat. Geosci. 1, 444–448 (2008).

    Article  Google Scholar 

  68. 68.

    Rabe, B., Schott, F. A. & Köhl, A. Mean circulation and variability of the tropical Atlantic during 1952–2001 in the GECCO assimilation fields. J. Phys. Oceanogr. 38, 177–192 (2008).

    Article  Google Scholar 

  69. 69.

    Sloyan, B. M. et al. Deep ocean changes near the western boundary of the South Pacific Ocean. J. Phys. Oceanogr. 43, 2132–2141 (2015).

    Article  Google Scholar 

  70. 70.

    Cheng, L. et al. Improved estimates of ocean heat content from 1960 to 2015. Sci. Adv. 3, e1601545 (2017).

    Article  Google Scholar 

  71. 71.

    Stendardo, I. & Gruber, N. Oxygen trends over five decades in the North Atlantic. J. Geophys. Res. 117, C11004 (2012).

    Article  Google Scholar 

  72. 72.

    Hummels, R. et al. Interannual circulation in the Atlantic at 11°S. Geophys. Res. Lett. 42, 7615–7622 (2015).

    Article  Google Scholar 

  73. 73.

    Whitney, F. A., Freeland, H. J. & Robert, M. Persistently declining oxygen levels in the interior waters of the eastern subarctic Pacific. Prog. Oceanogr. 75, 179–199 (2007).

    Article  Google Scholar 

  74. 74.

    Watanabe, Y. W., Wakita, M., Maeda, N., Ono, T. & Gamo, T. Synchronous bidecadal periodic changes of oxygen, phosphate and temperature between the Japan Sea deep water and the North Pacific intermediate water. Geophys. Res. Lett. 30, 2273 (2003).

    Article  Google Scholar 

  75. 75.

    Yasuda, I., Osafune, S. & Tatebe, H. Possible explanation linking 18.6-year period nodal tidal cycle with bi-decadal variations of ocean and climate in the North Pacific. Geophys. Res. Lett. 33, L08606 (2006).

    Google Scholar 

  76. 76.

    Kim, K. et al. Warming and structural changes in the East (Japan) Sea: a clue to future changes in global oceans? Geophys. Res. Lett. 28, 3293–3296 (2001).

    Article  Google Scholar 

  77. 77.

    Shaffer, G. et al. Warming and circulation change in the eastern South Pacific Ocean. Geophys. Res. Lett. 27, 1247–1250 (2000).

    Article  Google Scholar 

  78. 78.

    Lachkar, Z., Levy, M. & Smith, S. Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity. Biogeosciences 15, 159–186 (2018).

    Article  Google Scholar 

  79. 79.

    Purkey, S. G. & Johnson, G. C. Warming of global abyssal and deep Southern Ocean waters between the 1990s and 2000s: contributions to global heat and sea level rise budgets. J. Clim. 23, 6336–6351 (2010).

    Article  Google Scholar 

  80. 80.

    Johnson, G. C., Purkey, S. G. & Toole, J. M. Reduced Antarctic meridional overturning circulation reaches the North Atlantic Ocean. Geophys. Res. Lett. 35, L22601 (2008).

    Article  Google Scholar 

  81. 81.

    Andrie, C. et al. Variability of AABW properties in the equatorial channel at 35°W. Geophys. Res. Lett. 30, 8007 (2003).

    Article  Google Scholar 

  82. 82.

    van Wijk, E. M. & Rintoul, S. R. Freshening drives contraction of Antarctic Bottom Water in the Australian Antarctic Basin. Geophys. Res. Lett. 41, 1657–1664 (2014).

    Article  Google Scholar 

  83. 83.

    Church, M. J., Lomas, M. W. & Muller-Karger, F. Sea change: charting the course for biogeochemical ocean time-series research in a new millennium. Deep Sea Res. II 93, 2–15 (2013).

    Article  Google Scholar 

  84. 84.

    Keeling, R. F. & Garcia, H. E. The change in oceanic O2 inventory associated with recent global warming. Proc. Natl Acad. Sci. USA 99, 7848–7853 (2002).

    Article  Google Scholar 

  85. 85.

    Henson, S. A. Slow science: the value of long biological records. Phil. Trans. R. Soc. A 372, 20130334 (2014).

    Article  Google Scholar 

  86. 86.

    Duteil, O., Böning, C. W. & Oschlies, A. Variability in subtropical-tropical cells drives oxygen levels in the tropical Pacific Ocean. Geophys. Res. Lett. 41, 8926–8934 (2014).

    Article  Google Scholar 

  87. 87.

    Orr, J. C. et al. Biogeochemical protocols and diagnostics for the CMIP6 Ocean Model Intercomparison Project (OMIP). Geosci. Mod. Dev 10, 2169–2199 (2017).

    Article  Google Scholar 

  88. 88.

    Karstensen, J. et al. Upwelling and isolation in oxygen-depleted anticyclonic modewater eddies and implications for nitrate cycling. Biogeosciences 14, 2167–2181 (2017).

    Article  Google Scholar 

  89. 89.

    Thomsen, S. et al. Do submesoscale processes ventilate the oxygen minimum zone off Peru? Geophys. Res. Lett. 43, 8133–8142 (2016).

    Article  Google Scholar 

  90. 90.

    Gruber, N. Warming up, turning sour, losing breath: ocean biogeochemistry under global change. Phil. Trans. R. Soc. A 369, 1980–1996 (2011).

    Article  Google Scholar 

Download references

Acknowledgements

This work was supported by the German Research Foundation (DFG) as part of the research project SFB 754 ‘Climate-Biogeochemistry Interactions in the Tropical Ocean’ and is a contribution to the Global Ocean Oxygen Network (GO2NE). We thank R. Erven for help with the graphics.

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All authors discussed the results and wrote the manuscript. A.O. led the writing of the manuscript, P.B. and L.S. led the sections on thermocline and deep-ocean oxygen changes and S.S. led the data analysis.

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Correspondence to Andreas Oschlies.

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Oschlies, A., Brandt, P., Stramma, L. et al. Drivers and mechanisms of ocean deoxygenation. Nature Geosci 11, 467–473 (2018). https://doi.org/10.1038/s41561-018-0152-2

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