title: Boron isotope evidence for oceanic carbon dioxide leakage during the last deglaciation.
abstract: Atmospheric CO2 fluctuations over glacial-interglacial cycles remain a major challenge to our understanding of the carbon cycle and the climate system. Leading hypotheses put forward to explain glacial-interglacial atmospheric CO2 variations invoke changes in deep-ocean carbon storage, probably modulated by processes in the Southern Ocean, where much of the deep ocean is ventilated. A central aspect of such models is that, during deglaciations, an isolated glacial deep-ocean carbon reservoir is reconnected with the atmosphere, driving the atmospheric CO2 rise observed in ice-core records. However, direct documentation of changes in surface ocean carbon content and the associated transfer of carbon to the atmosphere during deglaciations has been hindered by the lack of proxy reconstructions that unambiguously reflect the oceanic carbonate system. Radiocarbon activity tracks changes in ocean ventilation, but not in ocean carbon content, whereas proxies that record increased deglacial upwelling do not constrain the proportion of upwelled carbon that is degassed relative to that which is taken up by the biological pump. Here we apply the boron isotope pH proxy in planktic foraminifera to two sediment cores from the sub-Antarctic Atlantic and the eastern equatorial Pacific as a more direct tracer of oceanic CO2 outgassing. We show that surface waters at both locations, which partly derive from deep water upwelled in the Southern Ocean, became a significant source of carbon to the atmosphere during the last deglaciation, when the concentration of atmospheric CO2 was increasing. This oceanic CO2 outgassing supports the view that the ventilation of a deep-ocean carbon reservoir in the Southern Ocean had a key role in the deglacial CO2 rise, although our results allow for the possibility that processes operating in other regions may also have been important for the glacial-interglacial ocean-atmosphere exchange of carbon.
authors: Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton Waterfront Campus, Southampton SO14 3ZH, UK.
authors: M A
authors: MA
authors: Martínez-Botí
authors: 1] Institute of Environmental Science and Technology (ICTA), Universitat Autònoma de Barcelona, Bellaterra, Catalonia, 08193, Spain [2] Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory 2601, Australia.
authors: G
authors: G
authors: Marino
authors: Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton Waterfront Campus, Southampton SO14 3ZH, UK.
authors: G L
authors: GL
authors: Foster
authors: 1] Institute of Environmental Science and Technology (ICTA), Universitat Autònoma de Barcelona, Bellaterra, Catalonia, 08193, Spain [2] Institució Catalana de Recerca i Estudis Avançats, ICREA, Barcelona, Catalonia, 08010, Spain [3] Earth and Climate Cluster, Department of Earth Sciences, Faculty of Earth and Life Sciences, VU Universiteit Amsterdam, 1081HV Amsterdam, The Netherlands.
authors: P
authors: P
authors: Ziveri
authors: 1] Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton Waterfront Campus, Southampton SO14 3ZH, UK [2] Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06511, USA.
authors: M J
authors: MJ
authors: Henehan
authors: 1] Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA [2] Department of Earth and Environmental Sciences, University of St Andrews, St Andrews KY16 9AL, UK.
authors: J W B
authors: JW
authors: Rae
authors: 1] Institute of Environmental Science and Technology (ICTA), Universitat Autònoma de Barcelona, Bellaterra, Catalonia, 08193, Spain [2] Department of Geography, Universitat Autònoma de Barcelona, Bellaterra, Catalonia, 08193, Spain.
authors: P G
authors: PG
authors: Mortyn
authors: Institute of Geochemistry and Petrology, Department of Earth Sciences, ETH Zürich, NW D81.4, Zürich 8092, Switzerland.
authors: D
authors: D
authors: Vance
mesh_terms: D001272:Atmosphere / Q000737:chemistry; D001895:Boron / Q000032:analysis* / Q000737:chemistry*; D002245:Carbon Dioxide / Q000032:analysis*; D002980:Climate; D056908:Foraminifera; D005615:Freezing; D049690:History, Ancient; D006863:Hydrogen-Ion Concentration; D046448:Ice Cover / Q000737:chemistry*; D007554:Isotopes; D009792:Oceans and Seas; D012623:Seawater / Q000737:chemistry*
chemical_list: D007554:Isotopes; D002245:Carbon Dioxide; D001895:Boron