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Estimated strength of the Atlantic overturning circulation during the last deglaciation


The Atlantic meridional overturning circulation affects the latitudinal distribution of heat, and is a key component of the climate system. Proxy reconstructions, based on sedimentary 231Pa/230Th ratios and the difference between surface- and deep-water radiocarbon ages, indicate that during the last glacial period, the overturning circulation was reduced during millennial-scale periods of cooling1,2,3,4,5. However, much debate exists over the robustness of these proxies6,7,8. Here we combine proxy reconstructions of sea surface and air temperatures and a global climate model to quantitatively estimate changes in the strength of the Atlantic meridional overturning circulation during the last glacial period. We find that, relative to the Last Glacial Maximum, the overturning circulation was reduced by approximately 14 Sv during the cold Heinrich event 1. During the Younger Dryas cold event, the overturning circulation was reduced by approximately 12 Sv, relative to the preceding warm interval. These changes are consistent with qualitative estimates of the overturning circulation from sedimentary 231Pa/230Th ratios. In addition, we find that the strength of the overturning circulation during the Last Glacial Maximum and the Holocene epoch are indistinguishable within the uncertainty of the reconstruction.

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Figure 1: Overview of the performed AMOC hindcasts and reconstructions.
Figure 2: AMOC hindcasts of two model simulations.
Figure 3: Reconstruction of the AMOC of the last deglaciation.
Figure 4: Suitable locations of SST records for the AMOC reconstruction.


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This study was financially supported by GRACCIE (CONSOLIDER-INGENIO 2010) and by the Swiss National Science Foundation. We thank F. Joos and C. Waelbroeck for fruitful discussions, M. Steinacher for providing the CSM data, and J. Jouzel for his help with the uncertainties of the ice core data.

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Authors and Affiliations



S.P.R. and T.F.S. developed the method, A.T. contributed with ideas on method verification and AMOC fingerprinting, S.P.R. performed the B3D simulations, L.M. provided the LVC simulation, J.O.G. provided support of the sediment core data, and S.P.R. and T.F.S. wrote the manuscript. All authors discussed the results and provided input on the manuscript.

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Correspondence to Stefan P. Ritz.

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The authors declare no competing financial interests.

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Ritz, S., Stocker, T., Grimalt, J. et al. Estimated strength of the Atlantic overturning circulation during the last deglaciation. Nature Geosci 6, 208–212 (2013).

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