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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 11 | Copyright
Clim. Past, 12, 2061-2075, 2016
https://doi.org/10.5194/cp-12-2061-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 08 Nov 2016

Research article | 08 Nov 2016

Changes in the geometry and strength of the Atlantic meridional overturning circulation during the last glacial (20–50 ka)

Pierre Burckel1,2, Claire Waelbroeck1, Yiming Luo3, Didier M. Roche1,4, Sylvain Pichat5, Samuel L. Jaccard6, Jeanne Gherardi1, Aline Govin1, Jörg Lippold6, and François Thil1 Pierre Burckel et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
  • 2Institut de Physique du Globe de Paris, Université Sorbonne Paris Cité, 75238 Paris, France
  • 3Dalhousie University, Department of Oceanography, 1355 Oxford Street, P.O. BOX 15000, Halifax, NS B3H 4J1, Canada
  • 4Department of Earth Sciences, Earth and Climate Cluster, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
  • 5Laboratoire de Géologie de Lyon (LGL-TPE), Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69007 Lyon, France
  • 6Institute of Geological Sciences and Oeschger Centre for Climate Change Research, University of Bern, Baltzerstr. 1 & 3, 3012, Bern, Switzerland

Abstract. We reconstruct the geometry and strength of the Atlantic meridional overturning circulation during the Heinrich stadial 2 and three Greenland interstadials of the 20–50ka period based on the comparison of new and published sedimentary 231Pa/230Th data with simulated sedimentary 231Pa/230Th. We show that the deep Atlantic circulation during these interstadials was very different from that of the Holocene. Northern-sourced waters likely circulated above 2500m depth, with a flow rate lower than that of the present-day North Atlantic deep water (NADW). Southern-sourced deep waters most probably flowed northwards below 4000m depth into the North Atlantic basin and then southwards as a return flow between 2500 and 4000m depth. The flow rate of this southern-sourced deep water was likely larger than that of the modern Antarctic bottom water (AABW). Our results further show that during Heinrich stadial 2, the deep Atlantic was probably directly affected by a southern-sourced water mass below 2500m depth, while a slow, southward-flowing water mass originating from the North Atlantic likely influenced depths between 1500 and 2500m down to the equator.

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In this paper, we compare new and published Atlantic sedimentary Pa/Th data with Pa/Th simulated using stream functions generated under various climatic conditions. We show that during Greenland interstadials of the 20–50 ka period, the Atlantic meridional overturning circulation was very different from that of the Holocene. Moreover, southern-sourced waters dominated the Atlantic during Heinrich stadial 2, a slow northern-sourced water mass flowing above 2500 m in the North Atlantic.
In this paper, we compare new and published Atlantic sedimentary Pa/Th data with Pa/Th simulated...
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