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Cessation of deep convection in the open Southern Ocean under anthropogenic climate change


In 1974, newly available satellite observations unveiled the presence of a giant ice-free area, or polynya, within the Antarctic ice pack of the Weddell Sea, which persisted during the two following winters1. Subsequent research showed that deep convective overturning had opened a conduit between the surface and the abyssal ocean, and had maintained the polynya through the massive release of heat from the deep sea2,3. Although the polynya has aroused continued interest1,2,3,4,5,6,7,8,9, the presence of a fresh surface layer has prevented the recurrence of deep convection there since 19768, and it is now largely viewed as a naturally rare event10. Here, we present a new analysis of historical observations and model simulations that suggest deep convection in the Weddell Sea was more active in the past, and has been weakened by anthropogenic forcing. The observations show that surface freshening of the southern polar ocean since the 1950s has considerably enhanced the salinity stratification. Meanwhile, among the present generation of global climate models, deep convection is common in the Southern Ocean under pre-industrial conditions, but weakens and ceases under a climate change scenario owing to surface freshening. A decline of open-ocean convection would reduce the production rate of Antarctic Bottom Waters, with important implications for ocean heat and carbon storage, and may have played a role in recent Antarctic climate change.

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Figure 1: Spatial pattern of Southern Ocean deep convection in observations and models.
Figure 2: Southern polar ocean freshening and stratification.
Figure 3: Southern Ocean (55° S–90° S) convection area.
Figure 4: Southern polar ocean freshening and stratification in CMIP5 models.

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  1. Carsey, F. D. Microwave observation of the Weddell Polynya. Mon. Weath. Rev. 108, 2032–2044 (1980).

    Article  Google Scholar 

  2. Martinson, D. G., Killworth, P. D. & Gordon, A. L. A convective model for the Weddell Polynya. J. Phys. Oceanogr. 11, 466–488 (1981).

    Article  Google Scholar 

  3. Gordon, A. L. Weddell deep water variability. J. Mar. Res. 40, 199–217 (1982).

    Article  Google Scholar 

  4. Parkinson, C. L. On the development and cause of the Weddell Polynya in a sea ice simulation. J. Phys. Oceanogr. 13, 501–511 (1983).

    Article  Google Scholar 

  5. Killworth, P. D. Deep convection in the world ocean. Rev. Geophys. 21, 1–26 (1983).

    Article  Google Scholar 

  6. Martinson, D. G. in Deep Convection and Deep Water Formation in the Oceans (eds Chu, P. C. & Gascard, J. C.) 37–52 (Elsevier Oceanography Series, 1991).

    Google Scholar 

  7. Holland, D. M. Explaining the Weddell Polynya—a large ocean eddy shed at Maud Rise. Science 292, 1697–1700 (2001).

    Article  CAS  Google Scholar 

  8. Gordon, A. L., Visbeck, M. & Comiso, J. C. A possible link between the Weddell Polynya and the Southern Annular Mode. J. Clim. 20, 2558–2571 (2007).

    Article  Google Scholar 

  9. Hirabara, M., Tsujino, H., Nakano, H. & Yamanaka, G. Formation mechanism of the Weddell Sea Polynya and the impact on the global abyssal ocean. J. Oceanogr. 68, 771–796 (2012).

    Article  Google Scholar 

  10. Heuzé, C., Heywood, K. J., Stevens, D. P. & Ridley, J. K. Southern Ocean bottom water characteristics in CMIP5 models. Geophys. Res. Lett. 40, 1409–1414 (2013).

    Article  Google Scholar 

  11. Johnson, G. C. Quantifying Antarctic Bottom Water and North Atlantic Deep Water volumes. J. Geophys. Res. 113, C05027 (2008).

    Google Scholar 

  12. Purkey, S. G. & Johnson, G. C. Global contraction of Antarctic Bottom Water between the 1980s and 2000s. J. Clim. 25, 5830–5844 (2012).

    Article  Google Scholar 

  13. Azaneu, M., Kerr, R., Mata, M. M. & Garcia, C. A. E. Trends in the deep Southern Ocean (1958–2010): implications for Antarctic Bottom Water properties and volume export. J. Geophys. Res. 118, 4213–4227 (2013).

    Article  Google Scholar 

  14. Meehl, G. A., Hu, A., Arblaster, J. M., Fasullo, J. T. & Trenberth, K. E. Externally forced and internally generated decadal climate variability associated with the Interdecadal Pacific Oscillation. J. Clim. 26, 7298–7310 (2013).

    Article  Google Scholar 

  15. Orsi, A. H., Smethie, W. M. Jr & Bullister, J. L. On the total input of Antarctic waters to the deep ocean: a preliminary estimate from chlorofluorocarbon measurements. J. Geophys. Res. 107, 3122–3135 (2002).

    Article  Google Scholar 

  16. Wüst, G. Der Ursprung der Atlantischen Tiefenwasser. Gesellsch. f. Erdk. Zeits. 409–509 (1928).

  17. Durack, P. J., Wijffels, S. E. & Matear, R. J. Ocean salinities reveal strong global water cycle intensification during 1950 to 2000. Science 336, 455–458 (2012).

    Article  CAS  Google Scholar 

  18. 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 

  19. Rignot, E., Jacobs, S., Mouginot, J. & Scheuchl, B. Ice-shelf melting around Antarctica. Science 341, 266–270 (2013).

    Article  CAS  Google Scholar 

  20. Gordon, A. L. & Huber, B. A. Southern Ocean winter mixed layer. J. Geophys. Res. 95, 11655–11672 (1990).

    Article  Google Scholar 

  21. Galbraith, E. D. et al. Climate variability and radiocarbon in the CM2Mc Earth System Model. J. Clim. 24, 4230–4254 (2011).

    Article  Google Scholar 

  22. Akitomo, K. Open-ocean deep convection due to thermobaricity: 1. Scaling argument. J. Geophys. Res. 104, 5225–5234 (1999).

    Article  Google Scholar 

  23. Martin, T., Park, W. & Latif, M. Multi-centennial variability controlled by Southern Ocean convection in the Kiel Climate Model. Clim. Dynam. 40, 2005–2022 (2013).

    Article  Google Scholar 

  24. Taylor, K. E., Stouffer, R. J. & Meehl, G. A. An overview of CMIP5 and the experiment design. Bull. Am. Meteorol. Soc. 93, 485–498 (2012).

    Article  Google Scholar 

  25. Latif, M., Martin, T. & Park, W. Southern Ocean sector centennial climate variability and recent decadal trends. J. Clim. 26, 7767–7782 (2013).

    Article  Google Scholar 

  26. Church, J. A. et al. Revisiting the Earth’s sea-level and energy budgets from 1961 to 2008. Geophys. Res. Lett. 38, L18601 (2011).

    Article  Google Scholar 

  27. Burke, A. & Robinson, L. F. The Southern Ocean’s role in carbon exchange during the last deglaciation. Science 335, 557–561 (2012).

    Article  CAS  Google Scholar 

  28. Ridgway, K. R., Dunn, J. R. & Wilkin, J. L. Ocean interpolation by four-dimensional weighted least squares—application to the waters around Australasia. J. Atmos. Oceanic Technol. 19, 1357–1375 (2002).

    Article  Google Scholar 

  29. de Boyer Montégut, C., Madec, G., Fischer, A. S., Lazar, A. & Iudicone, D. Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology. J. Geophys. Res. 109, C12003 (2004).

    Article  Google Scholar 

  30. Parkinson, C. L., Comiso, J. C. & Zwally, H. J. Nimbus-5 ESMR polar gridded sea ice concentrations. September 1974–1976 Boulder, Colorado USA: National Snow and Ice Data Center. (1999, updated 2004).

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We thank D. Bianchi for his help with the analysis. This work was supported by the Stephen and Anastasia Mysak Graduate Fellowship in Atmospheric and Oceanic Sciences, by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery programme, by the Canadian Institute for Advanced Research (CIFAR) and by computing infrastructure provided to E.D.G. by the Canadian Foundation for Innovation and Compute Canada. R.B. and I.M. were financially supported by grant NOAA-NA10OAR4310092.

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All authors shared responsibility for writing the manuscript. C.d.L. assembled and analysed observational data and model output. J.B.P. and E.D.G. conceived and supervised the study. I.M., R.B., E.D.G. and J.B.P. designed the CM2Mc experiments. R.B. performed the CM2Mc experiments.

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Correspondence to Casimir de Lavergne.

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de Lavergne, C., Palter, J., Galbraith, E. et al. Cessation of deep convection in the open Southern Ocean under anthropogenic climate change. Nature Clim Change 4, 278–282 (2014).

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