Enhanced surface melting of the Fennoscandian Ice Sheetduring periods of North Atlantic cooling

• Published in: Geology
• Main Authors: Boswell, Steven M., Toucanne, Samuel, Pitel-Roudaut, Mathilde, Creyts, Timothy T., Eynaud, Frédérique, Bayon, Germain
• Other Authors: Laboratoire Géodynamique et enregistrement Sédimentaire (LGS), Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-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)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDU]Sciences of the Universe [physics]; Fennoscandian; Ice Sheet; North Atlantic; Northeast Atlantic
• Online Access: https://hal.science/hal-04202305; https://doi.org/10.1130/G46370.1

International audience Heinrich events (HEs) are dramatic episodes of marine-terminating ice discharge and sediment rafting during periods of cold North Atlantic climate. However, the causal chain of events leading to their occurrence is unresolved. Here, we demonstrate that enhanced surface melting of land-terminating margins of the southern Fennoscandian Ice Sheet (FIS) is a recurring feature of Heinrich stadials (HSs), the cold periods during which HEs occur. We use neodymium isotopes to show that the Channel River transported detrital sediments from the interior of eastern Europe to the Bay of Biscay in the northeast Atlantic Ocean at ca. 158–154 ka. Based on similar evidence from the last glacial period, we infer that this interval corresponds to the melting and retreat of the southern FIS margin despite contemporaneous cooling in the North Atlantic and central Europe. The FIS melting episode occurred just prior to a HE, consistent with findings from the more recent HSs 1, 2, and 3. Based on this evidence, we clarify a sequence of events that precedes HEs. Precursor melting of North Atlantic–adjacent ice sheets induces an initial Atlantic meridional overturning circulation (AMOC) slowdown. Atmospheric changes during the resulting HS cause summertime warming in northern Europe that drives enhanced FIS melting. Subsequent meltwater discharge to the North Atlantic further weakens the AMOC and warms the intermediate water masses that contribute to HEs.