Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation

A Corrigendum to this article was published on 24 September 2015

This article has been updated

Abstract

Possible changes in Atlantic meridional overturning circulation (AMOC) provide a key source of uncertainty regarding future climate change. Maps of temperature trends over the twentieth century show a conspicuous region of cooling in the northern Atlantic. Here we present multiple lines of evidence suggesting that this cooling may be due to a reduction in the AMOC over the twentieth century and particularly after 1970. Since 1990 the AMOC seems to have partly recovered. This time evolution is consistently suggested by an AMOC index based on sea surface temperatures, by the hemispheric temperature difference, by coral-based proxies and by oceanic measurements. We discuss a possible contribution of the melting of the Greenland Ice Sheet to the slowdown. Using a multi-proxy temperature reconstruction for the AMOC index suggests that the AMOC weakness after 1975 is an unprecedented event in the past millennium (p > 0.99). Further melting of Greenland in the coming decades could contribute to further weakening of the AMOC.

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Figure 1: Linear trends of annual surface temperature since AD 1901.
Figure 2: Connection between the AMOC stream function and the temperature-based AMOC index in a global warming scenario (RCP8.5).
Figure 3: Surface temperature time series for different regions.
Figure 4: Spectral analysisof the proxy-based AMOC index shown in Fig. 3b.
Figure 5: A compilation of different indicators for Atlantic ocean circulation.
Figure 6: Mass balance terms of the Greenland Ice Sheet.

Change history

  • 03 September 2015

    In the version of this Article originally published, in Fig. 1 the data plotted were for the calendar month of December and not the annual mean data. This has been replaced with a new global temperature trend map for annual mean data, in which (due to the reduced variability of annual as compared with monthly data) the cooling patch in the subpolar North Atlantic stands out even more. The first sentence of the caption for Fig. 1 has been amended to: 'Linear trends of annual surface temperature since AD 1901'. None of the conclusions in the Article are affected by this error.

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Acknowledgements

We thank O. Sherwood for providing coral data. M.E.M. acknowledges support for this work from the ATM program of the National Science Foundation (grant ATM-0902133).

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S.Rahmstorf conceived and designed the research and wrote the paper, E.J.S., S.Rutherford, A.R. and G.F. performed the research, M.E.M. and J.E.B. contributed materials/analysis tools and co-wrote the paper.

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Correspondence to Stefan Rahmstorf.

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Rahmstorf, S., Box, J., Feulner, G. et al. Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation. Nature Clim Change 5, 475–480 (2015). https://doi.org/10.1038/nclimate2554

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