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Recent Southern Ocean warming and freshening driven by greenhouse gas emissions and ozone depletion

Nature Geoscience volume 11, pages 836–841 (2018)Cite this article

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Abstract

The Southern Ocean has, on average, warmed and freshened over the past several decades. As a primary global sink for anthropogenic heat and carbon, to understand changes in the Southern Ocean is directly relevant to predicting the future evolution of the global climate system. However, the drivers of these changes are poorly understood, owing to sparse observational sampling, large amplitude internal variability, modelling uncertainties and the competing influence of multiple forcing agents. Here we construct an observational synthesis to quantify the temperature and salinity changes over the Southern Ocean and combine this with an ensemble of co-sampled climate model simulations. Using a detection and attribution analysis, we show that the observed changes are inconsistent with the internal variability or the response to natural forcing alone. Rather, the observed changes are primarily attributable to human-induced greenhouse gas increases, with a secondary role for stratospheric ozone depletion. Physically, the simulated changes are primarily driven by surface fluxes of heat and freshwater. The consistency between the observed changes and our simulations provides increased confidence in the ability of climate models to simulate large-scale thermohaline change in the Southern Ocean.

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Fig. 1: Observed and simulated changes in temperature and salinity.
Fig. 2: Detection and attribution scaling factors.
Fig. 3: Fingerprints of temperature and salinity change.
Fig. 4: Observed and simulated changes in temperature and salinity in density space.
Fig. 5: Southern Ocean heat and salt budget.

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Data availability

All the data used in this article are publicly available. The CanESM2 large ensembles are available at http://open.canada.ca/data/en/dataset/aa7b6823-fd1e-49ff-a6fb-68076a4a477c. The RG Argo climatology is available at http://sio-argo.ucsd.edu/RG_Climatology.html. The historical profiles from the World Ocean Database can be found at https://www.nodc.noaa.gov/OC5/WOD/pr_wod.html.

References

  1. Armour, K., Marshall, J., Scott, J., Donohoe, A. & Newsom, E. Southern Ocean warming delayed by circumpolar upwelling and equatorward transport. Nat. Geosci. 9, 549–554 (2016).

    Article  Google Scholar 

  2. Fan, T., Deser, C. & Schneider, D. P. Recent Antarctic sea ice trends in the context of Southern Ocean surface climate variations since 1950. Geophys. Res. Lett. 41, 2419–2426 (2014).

    Article  Google Scholar 

  3. Parkinson, C. L. & Cavalieri, D. J. Antarctic sea ice variability and trends, 1979–2010. Cryosphere 6, 871–880 (2012).

    Article  Google Scholar 

  4. Gille, S. T. Warming of the Southern Ocean since the 1950s. Science 295, 1275–1277 (2002).

    Article  Google Scholar 

  5. Gille, S. T. Decadal-scale temperature trends in the Southern Hemisphere ocean. J. Clim. 21, 4749–4765 (2008).

    Article  Google Scholar 

  6. 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 

  7. Roemmich, D. et al. Unabated planetary warming and its ocean structure since 2006. Nat. Clim. Change 5, 240–245 (2015).

    Article  Google Scholar 

  8. Khatiwala, S., Primeau, F. & Hall, T. Reconstruction of the history of anthropogenic CO2 concentrations in the ocean. Nature 462, 346–349 (2009).

    Article  Google Scholar 

  9. 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 

  10. Böning, C., Dispert, A., Visbeck, M., Rintoul, S. & Schwarzkopf, F. The response of the Antarctic Circumpolar Current to recent climate change. Nat. Geosci. 1, 864–869 (2008).

    Article  Google Scholar 

  11. Gent, P. R. & Danabasoglu, G. Response to Increasing Southern Hemisphere Winds in CCSM4. J. Climate 24, 4992–4998 (2011).

    Article  Google Scholar 

  12. Swart, N. C. & Fyfe, J. C. The influence of recent Antarctic ice sheet retreat on simulated sea ice area trends. Geophys. Res. Lett. 40, 4328–4332 (2013).

    Article  Google Scholar 

  13. Polvani, L. M. & Smith, K. L. Can natural variability explain observed Antarctic sea ice trends? New modeling evidence from CMIP5. Geophys. Res. Lett. 40, 3195–3199 (2013).

    Article  Google Scholar 

  14. Gagné, M.-È., Gillett, N. P. & Fyfe, J. C. Observed and simulated changes in Antarctic sea ice extent over the past 50 years. Geophys. Res. Lett. 42, 90–95 (2015).

    Article  Google Scholar 

  15. Zunz, V., Goosse, H. & Massonnet, F. How does internal variability influence the ability of CMIP5 models to reproduce the recent trend in Southern Ocean sea ice extent? Cryosphere 7, 451–468 (2013).

    Article  Google Scholar 

  16. Lovenduski, N. S., Fay, A. R. & McKinley, G. A. Observing multidecadal trends in Southern Ocean CO2 uptake: what can we learn from an ocean model? Global. Biogeochem. Cycles 29, 416–426 (2015).

    Article  Google Scholar 

  17. Fyfe, J. Southern Ocean warming due to human influence. Geophys. Res. Lett. 33, L19701 (2015).

    Article  Google Scholar 

  18. Sigmond, M., Reader, M. C., Fyfe, J. C. & Gillett, N. P. Drivers of past and future Southern Ocean change: stratospheric ozone versus greenhouse gas impacts. Geophys. Res. Lett. 38, L12601 (2011).

    Article  Google Scholar 

  19. Solomon, A., Polvani, L. M., Smith, K. L. & Abernathey, R. P. The impact of ozone depleting substances on the circulation, temperature, and salinity of the Southern Ocean: an attribution study with CESM1(WACCM). Geophys. Res. Lett. 42, 5547–5555 (2015).

    Article  Google Scholar 

  20. Barnett, T. P., Pierce, D. W. & Schnur, R. Detection of anthropogenic climate change in the world’s oceans. Science 292, 270–274 (2001).

    Article  Google Scholar 

  21. Barnett, T. P. et al. Penetration of human-induced warming into the world’s oceans. Science 309, 284–287 (2005).

    Article  Google Scholar 

  22. Pierce, D. et al. Anthropogenic warming of the oceans: observations and model results. J. Clim. 19, 1873–1900 (2006).

    Article  Google Scholar 

  23. Pierce, D. W., Gleckler, P. J., Barnett, T. P., Santer, B. D. & Durack, P. J. The fingerprint of human-induced changes in the ocean’s salinity and temperature fields. Geophys. Res. Lett. 39, L21704 (2012).

    Article  Google Scholar 

  24. Roemmich, D. & Gilson, J. The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Prog. Oceanogr. 82, 81–100 (2009).

    Article  Google Scholar 

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

  26. Gillett, N. P., Arora, V. K., Matthews, D. & Allen, M. R. Constraining the ratio of global warming to cumulative CO2 emissions using CMIP5 simulations. J. Clim. 26, 6844–6858 (2013).

    Article  Google Scholar 

  27. Levitus, S. et al. Anthropogenic warming of Earth’s climate system. Science 292, 267–270 (2001).

    Article  Google Scholar 

  28. Bitz, C. & Polvani, L. Antarctic climate response to stratospheric ozone depletion in a fine resolution ocean climate model. Geophys. Res. Lett. 39, L20705 (2012).

    Article  Google Scholar 

  29. Sigmond, M. & Fyfe, J. C. Has the ozone hole contributed to increased Antarctic sea ice extent? Geophys. Res. Lett. 37, L18502 (2010).

    Google Scholar 

  30. Bindoff, N. L. & McDougall, T. J. Decadal changes along an Indian Ocean section at 32° S and their interpretation. J. Phys. Oceanogr. 30, 1207–1222 (2000).

    Article  Google Scholar 

  31. Banks, H. T. & Bindoff, N. L. Comparison of observed temperature and salinity changes in the Indo-Pacific with results from the coupled climate model HadCM3: processes and mechanisms. J. Clim. 16, 156–166 (2003).

    Article  Google Scholar 

  32. Aoki, S., Bindoff, N. & Church, J. Interdecadal water mass changes in the Southern Ocean between 30° E and 160° E. Geophys. Res. Lett. 32, L07607 (2005).

    Google Scholar 

  33. Gille, S. T. Meridional displacement of the Antarctic Circumpolar Current. Phil. Trans. R. Soc. 372, 20130273 (2014).

    Article  Google Scholar 

  34. Freeman, N. M., Lovenduski, N. S. & Gent, P. R. Temporal variability in the Antarctic Polar Front (2002–2014). J. Geophys. Res. Oceans 121, 7263–7276 (2016).

    Article  Google Scholar 

  35. Pauling, A. G., Bitz, C. M., Smith, I. J. & Langhorne, P. J. The response of the Southern Ocean and Antarctic sea ice to freshwater from ice shelves in an Earth system model. J. Clim. 29, 1655–1672 (2016).

    Article  Google Scholar 

  36. Fyfe, J. C., Gillett, N. P. & Marshall, G. J. Human influence on extratropical Southern Hemisphere summer precipitation. Geophys. Res. Lett. 39, L23711 (2012).

    Article  Google Scholar 

  37. Abernathey, R. et al. Water-mass transformation by sea ice in the upper branch of the Southern Ocean overturning. Nat. Geosci. 9, 596–601 (2016).

    Article  Google Scholar 

  38. Haumann, A., Gruber, N., Münnich, M., Frenger, I. & Kern, S. Sea-ice transport driving Southern Ocean salinity and its recent trends. Nature 537, 89–92 (2016).

    Article  Google Scholar 

  39. Polvani, L. M., Previdi, M. & Deser, C. Large cancellation, due to ozone recovery, of future Southern Hemisphere atmospheric circulation trends. Geophys. Res. Lett. 38, L04707 (2011).

    Article  Google Scholar 

  40. Previdi, M. & Polvani, L. M. Climate system response to stratospheric ozone depletion and recovery. Q. J. R. Meteorol. Soc. 140, 2401–2419 (2014).

    Article  Google Scholar 

  41. Pritchard, H. D. et al. Antarctic ice-sheet loss driven by basal melting of ice shelves. Nature 484, 502–505 (2012).

    Article  Google Scholar 

  42. Arora, V. K. et al. Carbon emission limits required to satisfy future representative concentration pathways of greenhouse gases. Geophys. Res. Lett. 38, L05805 (2011).

    Article  Google Scholar 

  43. Yang, D. & Saenko, O. A. Ocean heat transport and its projected change in CanESM2. J. Clim. 25, 8148–8163 (2012).

    Article  Google Scholar 

  44. Stone, D., Allen, M. R., Selten, F., Kliphuis, M. & Stott, P. A. The detection and attribution of climate change using an ensemble of opportunity. J. Clim. 20, 504–516 (2007).

    Article  Google Scholar 

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Acknowledgements

We acknowledge the Environment and Climate Change Canada’s Canadian Centre for Climate Modelling and Analysis for executing and making available the CanESM2 Large Ensemble simulations used in this study, and the Canadian Sea Ice and Snow Evolution Network for proposing the simulations. S.T.G. acknowledges NSF awards PLR-1425989 and OCE 1658001.

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Authors and Affiliations

  1. Canadian Centre for Climate Modelling and Analysis, Environment and Climate Change Canada, Victoria, BC, Canada

    Neil C. Swart, John C. Fyfe & Nathan P. Gillett

  2. Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA

    Sarah T. Gille

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  1. Neil C. Swart
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Contributions

N.C.S. conducted the analysis the wrote the paper. S.T.G. obtained and preprocessed the observational data. J.C.F. proposed the paper. N.P.G. advised on the detection and attribution. All the authors contributed to the scientific interpretation of the results, and helped to edit the paper.

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Correspondence to Neil C. Swart.

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Supplementary Text and Supplementary Figures 1–8.

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Swart, N.C., Gille, S.T., Fyfe, J.C. et al. Recent Southern Ocean warming and freshening driven by greenhouse gas emissions and ozone depletion. Nature Geosci 11, 836–841 (2018). https://doi.org/10.1038/s41561-018-0226-1

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