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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 9 | Copyright
Clim. Past, 14, 1315-1330, 2018
https://doi.org/10.5194/cp-14-1315-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 18 Sep 2018

Research article | 18 Sep 2018

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

Claire Waelbroeck1, Sylvain Pichat2,3, Evelyn Böhm1, Bryan C. Lougheed1, Davide Faranda1, Mathieu Vrac1, Lise Missiaen1, Natalia Vazquez Riveiros1,4, Pierre Burckel5, Jörg Lippold6, Helge W. Arz7, Trond Dokken8, 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
  • 4Ifremer, Unité de Geosciences Marines, 29280 Plouzané, France
  • 5IPGP, Université Sorbonne, 75238 Paris, France
  • 6Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany
  • 7Leibniz-Institute for Baltic Sea Research Warnemünde, Seestrasse 15, 18119 Rostock, Germany
  • 8Uni Research and Bjreknes Centre for Climate Research, Nygårdsgaten 112, 5008 Bergen, Norway

Abstract. Thanks to its optimal location on the northern 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 as peaks in ln(TiCa). New sedimentary PaTh data indicate that mid-depth western equatorial water mass transport decreased during all of the Greenland stadials of the last 40kyr. Using cross-wavelet transforms and spectrogram analysis, we assess the relative phase between the MD09-3257 sedimentary PaTh and ln(TiCa) signals. We show that decreased water mass transport between a depth of  ∼ 1300 and 2300m in the western equatorial Atlantic preceded increased rainfall over the adjacent continent by 120 to 400yr at Dansgaard–Oeschger (D–O) frequencies, and by 280 to 980yr 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 a feedback such as this 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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Recording the precise timing and sequence of events is essential for understanding rapid climate changes and improving 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 kyr. We show that decreased mid-depth water mass transport in the western equatorial Atlantic preceded increased rainfall over the adjacent continent by 120 to 980 yr, depending on the type of climate event.
Recording the precise timing and sequence of events is essential for understanding rapid climate...
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