Holocene shifts in sub-surface water circulation of the North-East Atlantic inferred from Nd isotopic composition in cold-water corals

• Published in: Marine Geology
• Main Authors: Dubois-Dauphin, Quentin, Colin, Christophe, Elliot, Mary, Dapoigny, Arnaud, Douville, Eric
• Other Authors: Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique UMR 6112 (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-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)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Panoply; [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; North East Atlantic
• Online Access: https://hal.archives-ouvertes.fr/hal-02149410; https://hal.archives-ouvertes.fr/hal-02149410/document; https://hal.archives-ouvertes.fr/hal-02149410/file/1-s2.0-S0025322718302810-am.pdf; https://doi.org/10.1016/j.margeo.2019.01.004

International audience Variations of the Sub-Polar Gyre (SPG) and the Sub-Tropical Gyre (STG) circulation during the Holocene are believed to be related to regional and global climate over this time period. To improve our understanding of these phenomena we provide new constraints on variations in surface circulation patterns using neodymium isotopes (εNd) on precisely U-Th dated coral fragments of L. pertusa. The fragments were retrieved from two sediment cores taken from cold-water coral (CWC) mounds at ~ 127–134 m water depth in the Mingulay Reef Complex located on the Western British continental shelf. The results have been combined with εNd analyzed on seawater samples from two stations located on the continental shelf and margin in order to establish whether εNd is a reliable proxy of the ocean circulation variations and notably of the relative contribution of water originating from the SPG and STG. εNd values in CWCs from the Mingulay Reef Complex range from −14.5 ± 0.4 to −11.8 ± 0.3, highlighting two major variations. Unradiogenic εNd values (−14.5 ± 0.4) indicate a higher contribution of water from the SPG around 2.8 ka. Conversely, more radiogenic values at 3.4 ka (−11.8 ± 0.3) point to a declining SPG strength, accompanied by stronger northward penetration of STG water along the western European margin transported by the Shelf Edge Current (SEC) and/or cooler and fresher waters from the interior Seas. The eastward extension of the SPG at 2.8 ka is associated with lower 14C reservoir age (200 yrs) compared to periods associated with a higher contribution of STG waters. This indicates that 14C reservoir ages are mainly a function of vertical mixing of the sub-surface of the ocean. As stronger vertical ventilation is not associated with a higher proportion of local radiogenic surface water, we hypothesize it could represent vertical ventilation in the North-Eastern Atlantic. Active SPG is associated with a better ventilation of the water masses within the SPG and warmer climatic conditions in Northern ...