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

• Published in: Climate of the Past
• Main Authors: Waelbroeck, Claire, Pichat, Sylvain, Böhm, Evelyn, Lougheed, Bryan C., Faranda, Davide, Vrac, Mathieu, Missiaen, Lise, Vázquez Riveiros, Natalia, Burckel, Pierre, Lippold, Jörg, Arz, Helge W., Dokken, Trond, Thil, François, Dapoigny, Arnaud
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Paléocéanographie (PALEOCEAN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Extrèmes : Statistiques, Impacts et Régionalisation (ESTIMR), Oeschger Centre for Climate Change Research (OCCR), Universität Bern / University of Bern (UNIBE), Bjreknes Centre for Climate Research, Géochrononologie Traceurs Archéométrie (GEOTRAC), ANR-09-BLAN-0347,RETRO(2009), European Project: 339108,EC:FP7:ERC,ERC-2013-ADG,ACCLIMATE(2014)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: Panoply; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Greenland; North Atlantic
• Online Access: https://hal.science/hal-02407248; https://hal.science/hal-02407248/document; https://hal.science/hal-02407248/file/cp-14-1315-2018.pdf; https://doi.org/10.5194/cp-14-1315-2018

International audience 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 stadi-als). These rainfall events are recorded in MD09-3257 as peaks in ln(Ti / Ca). New sedimentary Pa / Th data indicate that mid-depth western equatorial water mass transport decreased during all of the Greenland stadials of the last 40 kyr. Using cross-wavelet transforms and spectrogram analysis, we assess the relative phase between the MD09-3257 sed-imentary Pa / Th and ln(Ti / Ca) signals. We show that decreased water mass transport between a depth of ∼ 1300 and 2300 m in the western equatorial Atlantic preceded increased rainfall over the adjacent continent by 120 to 400 yr at Dansgaard-Oeschger (D-O) frequencies, and by 280 to 980 yr 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 DO stadials supports the hypothesis that a feedback such as this was not triggered in the case of DO stadials, with circulation slowdowns and subsequent changes remaining more limited during DO stadials than Heinrich stadials.