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Current Atlantic Meridional Overturning Circulation weakest in last millennium


The Atlantic Meridional Overturning Circulation (AMOC)—one of Earth’s major ocean circulation systems—redistributes heat on our planet and has a major impact on climate. Here, we compare a variety of published proxy records to reconstruct the evolution of the AMOC since about ad 400. A fairly consistent picture of the AMOC emerges: after a long and relatively stable period, there was an initial weakening starting in the nineteenth century, followed by a second, more rapid, decline in the mid-twentieth century, leading to the weakest state of the AMOC occurring in recent decades.

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Fig. 1: SST-based AMOC reconstructions compared with various proxy reconstructions.

Data availability

The proxy datasets that are analysed in this study are available in a GitHub repository:

Code availability

The scripts for the change point and the significance testing are available in a GitHub repository:


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L.C., N.C. and G.D.McC. are supported by the A4 project. A4 (Grant-Aid Agreement no. PBA/CC/18/01) is carried out with the support of the Marine Institute under the Marine Research Programme funded by the Irish Government, co-financed by the European Regional Development Fund. D.J.R.T. is supported by UK NERC grant NE/S009736/1.

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S.R. initiated the study. L.C. created the figure and wrote the manuscript. N.C. performed the significance testing. All authors discussed and interpreted the results and provided input to the manuscript.

Corresponding author

Correspondence to L. Caesar.

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The authors declare no competing interests.

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Peer review information Nature Geoscience thanks the anonymous reviewers for their contribution to the peer review of this work. Primary Handling Editor: James Super.

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

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Caesar, L., McCarthy, G.D., Thornalley, D.J.R. et al. Current Atlantic Meridional Overturning Circulation weakest in last millennium. Nat. Geosci. 14, 118–120 (2021).

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