North Atlantic mid-latitude surface-circulation changes through the Plio-Pleistocene intensification of northern hemisphere glaciation

• Published in: Paleoceanography and Paleoclimatology
• Main Authors: Bolton, Clara, Bailey, Ian, Friedrich, Oliver, Tachikawa, Kazuyo, DE GARIDEL-THORON, Thibault, VIDAL, Laurence, Sonzogni, Corinne, Marino, Gianluca, Rohling, Eelco, Robinson, Marci, Ermini, Magali, Koch, Mirjam, Cooper, Matthew, Wilson, Paul
• Other Authors: Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), National Oceanography Centre Southampton (NOC), University of Southampton, University of Vigo Pontevedra, Australian National University (ANU), United States Geological Survey Reston (USGS), Goethe-Universität Frankfurt am Main, Dalhousie University Halifax
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: ice sheets; climate variability; temperature variability; planktonic-foraminifera; late pliocene; cold-core eddy; sea-level; ocean; water; oxygen isotopc composition; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; north atlantic current; North Atlantic; Planktonic foraminifera; Subarctic
• Online Access: https://hal.archives-ouvertes.fr/hal-01884463; https://hal.archives-ouvertes.fr/hal-01884463/document; https://hal.archives-ouvertes.fr/hal-01884463/file/Bolton_et_al-2018-Paleoceanography_and_Paleoclimatology.pdf; https://doi.org/10.1029/2018PA003412

International audience The North Atlantic Current (NAC) transports warm salty water to high northern latitudes, with important repercussions for ocean circulation and global climate. A southward displacement of the NAC and Subarctic Front, which separate subpolar and subtropical water masses, is widely suggested for the Last Glacial Maximum (LGM) and may have acted as a positive feedback in glacial expansion at this time. However, the role of the NAC during the intensification of Northern Hemisphere glaciation (iNHG) at ~3.5 to 2.5 Ma is less clear. Here we present new records from Integrated Ocean Drilling Program Site U1313 (41°N) spanning ~2.8-2.4 Ma to trace the influence of Subarctic Front waters above this mid-latitude site. We reconstruct surface and permanent pycnocline temperatures and seawater δ 18 O using paired Mg/Ca-δ 18 O measurements on the planktic foraminifers Globigerinoides ruber and Globorotalia crassaformis and determine abundances of the subpolar foraminifer Neogloboquadrina atlantica. We find that the first significant glacial incursions of Subarctic Front surface waters above Site U1313 did not occur until ~2.6 Ma. At no time during our study interval was (sub)surface reorganization in the midlatitude North Atlantic analogous to the LGM. Our findings suggest that LGM-like processes sensu stricto cannot be invoked to explain interglacial-glacial cycle amplification during iNHG. They also imply that increased glacial productivity at Site U1313 during iNHG was not only driven by southward deflections of the Subarctic Front. We suggest that nutrient injection from cold-core eddies and enhanced glacial dust delivery may have played additional roles in increasing export productivity in the midlatitude North Atlantic from 2.7 Ma.