Decrease in 230Th in the Amundsen Basin since 2007: far-field effect of increased scavenging on the shelf?

• Published in: Ocean Science
• Main Authors: Valk, Ole, Rutgers van Der Loeff, Michiel, Geibert, Walter, Gdaniec, Sandra, Moran, S. Bradley, Lepore, Kate, Edwards, Robert Lawrence, Lu, Yanbin, Puigcorbe, Viena, Casacuberta, Nuria, Paffrath, Ronja, Smethie, William, Roy-Barman, Matthieu
• Other Authors: Alfred Wegener Institute for Polar and Marine Research (AWI), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine (AWI), Helmholtz-Gemeinschaft = Helmholtz Association, Stockholm University, University of Alaska Fairbanks (UAF), Mount Holyoke College, University of Minnesota System (UMN), Nanyang Technological University Singapour, Edith Cowan University (ECU), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich), University of Oldenburg, Lamont-Doherty Earth Observatory (LDEO), Columbia University New York, Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), 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)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Géochimie Des Impacts (GEDI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-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)-Direction de Recherche Fondamentale (CEA) (DRF (CEA))
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Panoply; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; amundsen basin; Arctic Ocean; Barents Sea; Fram Strait
• Online Access: https://cea.hal.science/cea-02614695; https://cea.hal.science/cea-02614695/document; https://cea.hal.science/cea-02614695/file/os-16-221-2020.pdf; https://doi.org/10.5194/os-16-221-2020

International audience This study provides dissolved and particulate 230Th and 232Th results as well as particulate 234Th data collected during expeditions to the central Arctic Ocean (GEOTRACES, an international project to identify processes and quantify fluxes that control the distributions of trace elements; sections GN04 and GIPY11). Constructing a time series of dissolved 230Th from 1991 to 2015 enables the identification of processes that control the temporal development of 230Th distributions in the Amundsen Basin. After 2007, 230Th concentrations decreased significantly over the entire water column, particularly between 300 and 1500 m. This decrease is accompanied by a circulation change, evidenced by a concomitant increase in salinity. A potentially increased inflow of water of Atlantic origin with low dissolved 230Th concentrations leads to the observed depletion in dissolved 230Th in the central Arctic. Because atmospherically derived tracers (chlorofluorocarbon (CFC), sulfur hexafluoride (SF6)) do not reveal an increase in ventilation rate, it is suggested that these interior waters have undergone enhanced scavenging of Th during transit from Fram Strait and the Barents Sea to the central Amundsen Basin. The 230Th depletion propagates downward in the water column by settling particles and reversible scavenging.