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Discussion papers | Copyright
https://doi.org/10.5194/cp-2018-22
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 19 Mar 2018

Research article | 19 Mar 2018

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Climate of the Past (CP).

Relative timing of precipitation and ocean circulation changes in the western equatorial Atlantic over the last 45 ky

Claire Waelbroeck1, Sylvain Pichat2,3, Evelyn Böhm1, Bryan C. Lougheed1, Davide Faranda1, Mathieu Vrac1, Lise Missiaen1, Natalia Vazquez Riveiros1, Pierre Burckel4, Jörg Lippold5, Helge W. Arz6, Trond Dokken7, François Thil1, and Arnaud Dapoigny1 Claire Waelbroeck et al.
  • 1LSCE/IPSL, Laboratoire CNRS-CEA-UVSQ, 91198 Gif-sur-Yvette, France
  • 2Laboratoire de Géologie de Lyon (LGL-TPE), Ecole Normale Supérieure de Lyon, Université de Lyon, CNRS UMR5276, 69007 Lyon, France
  • 3Climate Geochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 4IPGP, Université Sorbonne, 75238 Paris, France
  • 5Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany
  • 6Leibniz-Institute for Baltic Sea Research Warnemünde, Seestrasse 15, 18119 Rostock, Germany
  • 7Uni Research and Bjreknes Centre for Climate Research, Nygårdsgaten 112, 5008 Bergen, Norway

Abstract. Thanks to its optimal location on the North Brazilian margin, core MD09-3257 records both ocean circulation and atmospheric changes. The latter occur locally in the form of increased rainfall on the adjacent continent during the cold intervals recorded in Greenland ice and northern North Atlantic sediment cores (i.e. Greenland stadials). These rainfall events are recorded in MD09-3257 by peaks in ln(Ti/Ca). New sedimentary Pa/Th data indicate that mid-depth western equatorial water mass transport decreased during all the Greenland stadials of the last 45ky. Using cross-wavelet transforms and spectrogram analysis, we assess the relative phase between the MD09-3257 sedimentary Pa/Th and ln(Ti/Ca) signals. We show that decreased water mass transport between ~1300 and 2300m depth in the western equatorial Atlantic preceded increased rainfall over the adjacent continent by 110 to 400y at Dansgaard–Oeschger (D–O) frequencies, and by 280 to 980y at Heinrich-like frequencies. We suggest that the large lead of ocean circulation changes with respect to changes in tropical South American precipitation at Heinrich-like frequencies is related to the effect of a positive feedback involving iceberg discharges in the North Atlantic. In contrast, the absence of widespread ice rafted detrital layers in North Atlantic cores during D–O stadials supports the hypothesis that such a feedback was not triggered in the case of D–O stadials, with circulation slowdowns and subsequent changes remaining more limited during D–O stadials than Heinrich stadials.

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Claire Waelbroeck et al.
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Short summary
Documenting the precise timing and sequence of events is a prerequisite to understand rapid climate changes and improve climate model predictive skills. Here, we precisely assess the relative timing between ocean and atmospheric changes, both recorded in the same deep-sea core over the last 45 ky. We show that decreased mid-depth water mass transport in the western equatorial Atlantic preceded increased rainfall over the adjacent continent by 110 to 980 y, depending on the type of climate event.
Documenting the precise timing and sequence of events is a prerequisite to understand rapid...
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