Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone

• Published in: Nature Geoscience
• Main Authors: Salter, Ian, Schiebel, Ralf, Ziveri, Patrizia, Movellan, Aurore, Lampitt, Richard, Wolff, George
• Other Authors: Laboratoire d'Ecogéochimie des environnements benthiques (LECOB), Observatoire océanologique de Banyuls (OOB), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique - Angers (LPG-ANGERS), 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)-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), Institute of Environmental Science and Technology Barcelona (ICTA), Universitat Autònoma de Barcelona (UAB), National Oceanography Center-Southampton, University of Southampton
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: [SDU]Sciences of the Universe [physics]; Antarctic; Southern Ocean; Antarc*
• Online Access: https://univ-angers.hal.science/hal-03278278; https://univ-angers.hal.science/hal-03278278/document; https://univ-angers.hal.science/hal-03278278/file/salter_et_al_2014_nature_geoscience.pdf; https://doi.org/10.1038/ngeo2285

International audience The production of organic carbon in the ocean’s surface and its subsequent downward export transfers carbon dioxide to the deep ocean. This CO2 drawdown is countered by the biological precipitation of carbonate, followed by sinking of particulate inorganic carbon, which is a source of carbon dioxide to the surface ocean, and hence the atmosphere over 100–1,000 year timescales1. The net transfer of CO2 to the deep ocean is therefore dependent on the relative amount of organic and inorganic carbon in sinking particles2. In the Southern Ocean, iron fertilization has been shown to increase the export of organic carbon3, 4, 5, but it is unclear to what degree this effect is compensated by the export of inorganic carbon. Here we assess the composition of sinking particles collected from sediment traps located in the Polar Frontal Zone of the Southern Ocean. We find that in high-nutrient, low-chlorophyll regions that are characterized by naturally high iron concentrations, fluxes of both organic and inorganic carbon are higher than in regions with no iron fertilization. However, the excess flux of inorganic carbon is greater than that of organic carbon. We estimate that the production and flux of carbonate in naturally iron-fertilized waters reduces the overall amount of CO2 transferred to the deep ocean by 6–32%, compared to 1–4% at the non-fertilized site. We suggest that an increased export of organic carbon, stimulated by iron availability in the glacial sub-Antarctic oceans, may have been accompanied by a strengthened carbonate counter pump.