South Atlantic intermediate water advances into the North-east Atlantic with reduced Atlantic meridional overturning circulation during the last glacial period

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Dubois-Dauphin, Q., Bonneau, Lucile, Colin, Christophe, Montero Serrano, J.C, Montagna, P., Blamart, D., Hebbeln, D., Van Rooij, D., Pons-Branchu, E., Hemsing, F., Wefing, A.M., Frank, Norbert
• Other Authors: Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Géosystèmes (FRE CNRS 3298), Université de Lille, Istituto di Scienze Marine Bologna (ISMAR), Istituto di Science Marine (ISMAR ), Consiglio Nazionale delle Ricerche (CNR)-Consiglio Nazionale delle Ricerche (CNR), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Paléocéanographie (PALEOCEAN), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-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)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Center for Marine Environmental Sciences Bremen (MARUM), Universität Bremen, RCMG Ghent, Universiteit Gent = Ghent University Belgium (UGENT), Géochrononologie Traceurs Archéométrie (GEOTRAC), Institute of Environmental Physics Heidelberg (IUP), Universität Heidelberg Heidelberg
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: Panoply; [SDU]Sciences of the Universe [physics]; Antarctic; Antarc*; Iceberg*; North East Atlantic
• Online Access: https://hal.archives-ouvertes.fr/hal-01417326; https://hal.archives-ouvertes.fr/hal-01417326/document; https://hal.archives-ouvertes.fr/hal-01417326/file/2016GC006281.pdf; https://doi.org/10.1002/2016GC006281

International audience The Nd isotopic composition (εNd) of seawater and cold-water coral (CWC) samples from the Gulf of Cádiz and the Alboran Sea, at a depth of 280–827 m were investigated in order to constrain middepth water mass dynamics within the Gulf of Cádiz over the past 40 ka. εNd of glacial and Holocene CWC from the Alboran Sea and the northern Gulf of Cádiz reveals relatively constant values (−8.6 to −9.0 and −9.5 to −10.4, respectively). Such values are similar to those of the surrounding present-day middepth waters from the Mediterranean Outflow Water (MOW; εNd ∼ −9.4) and Mediterranean Sea Water (MSW; εNd ∼ −9.9). In contrast, glacial εNd values for CWC collected at thermocline depth (550–827 m) in the southern Gulf of Cádiz display a higher average value (−8.9 ± 0.4) compared to the present-day value (−11.7 ± 0.3). This implies a higher relative contribution of water masses of Mediterranean (MSW) or South Atlantic origin (East Antarctic Intermediate Water, EAAIW). Our study has produced the first evidence of significant radiogenic εNd values (∼ −8) at 19, 23–24, and 27 ka, which are coeval with increasing iceberg discharges and a weakening of Atlantic Meridional Overturning Circulation (AMOC). Since MOW εNd values remained stable during the last glacial period, it is suggested that these radiogenic εNd values most likely reflect an enhanced northward propagation of glacial EAAIW into the eastern Atlantic Basin.