Millennial-scale variations of the Holocene North Atlantic mid-depth gyre inferred from radiocarbon and neodymium isotopes in cold water corals

• Published in: Quaternary Science Reviews
• Main Authors: Colin, Christophe, Tisnerat-Laborde, Nadine, Mienis, Furu, Collart, Tim, Pons-Branchu, Edwige, Dubois-Dauphin, Quentin, Frank, Norbert, Dapoigny, Arnaud, Ayache, Mohamed, Swingedouw, Didier, Dutay, Jean-Claude, Eynaud, Frédérique, Debret, Maxime, Blamart, Dominique, Douville, Eric
• Other Authors: Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), 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), Géochrononologie Traceurs Archéométrie (GEOTRAC), 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), Royal Netherlands Institute for Sea Research (NIOZ) and Utrecht University, Den Burg, Netherlands, Ghent University, Dept. of Geology, Ghent, Belgium, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Modélisation du climat (CLIM), Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Paléocéanographie (PALEOCEAN)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Panoply; Cold-water corals; Rockall Trough; Holocene; Nd isotopic composition; radiocarbon; North Atlantic gyre dynamics; [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Nordic Sea; North Atlantic
• Online Access: https://hal.archives-ouvertes.fr/hal-02087629; https://hal.archives-ouvertes.fr/hal-02087629/document; https://hal.archives-ouvertes.fr/hal-02087629/file/1-s2.0-S0277379119301180-am.pdf; https://doi.org/10.1016/j.quascirev.2019.03.011

International audience Variations in North Atlantic Ocean mid-depth circulation during the Holocene are poorly understood. It is believed that they had a significant influence on the properties of water entering the Nordic Sea by redistributing heat and freshwater, potentially affecting deep-water formation and climate. To improve our knowledge of the NE Atlantic mid-depth circulation, radiocarbon and neodymium isotope analyses have been then carried out on precisely dated (U-Th) L. pertusa and M. oculata coral fragments from two sediment cores taken at ∼750 m water depth on the SW Rockall Trough margin. Cold-water coral (CWC) εNd values vary between −12.2 ± 0.3 and −16.6 ± 0.4 and result from variable contributions of unradiogenic mid-depth subpolar gyre (mid-SPG) water (∼-15) and more radiogenic Eastern North Atlantic Water (ENAW) (∼-11) which is transported northward to the Rockall Trough by boundary currents along the European margin. Increased coral εNd reflects a westward contraction of the mid-SPG water and a higher proportion of ENAW. The mid-Holocene (from 8.8 to 6.8 ka BP) is marked by unradiogenic coral εNd (from −16.6 ± 0.4 to −14.6 ± 0.5) indicating a greater eastward extension of the mid-SPG. This is followed by a shift from 6.8 to 5 ka BP toward more radiogenic εNd values (from −15.4 ± 0.3 to −13.3 ± 0.2) suggesting a westward contraction of the mid-SPG and a higher proportion of ENAW. The mid-Holocene long-term change in εNd is characterized by millennial variations of up to 2.5 epsilon units well marked during the Late Holocene, indicating that eastward extension of the mid-SPG coeval with warm periods in northern Europe (e.g. the Medieval Climatic Anomaly and the Roman Warm Period). Most of the CWC-derived Δ14C values match the global ocean values indicating that the water masses bathing the corals were generally well ventilated; the exceptions are a few short intervals of eastward extension of the mid-SPG, which are characterized by lower Δ14C during the late Holocene. We propose that these ...