Boron isotope evidence for oceanic carbon dioxide leakage during the last deglaciation

• Published in: Nature
• Main Authors: Martínez-Botí, M A, Marino, G, Foster, G L, Ziveri, P, Henehan, M J, Rae, J W B, Mortyn, P G, Vance, D
• Other Authors: University of St Andrews.School of Earth & Environmental Sciences, University of St Andrews.St Andrews Isotope Geochemistry, University of St Andrews.Earth and Environmental Sciences
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: GB Physical geography; GE Environmental Sciences; NDAS; BDC; R2C; SDG 13 - Climate Action; GB; GE; Antarctic; Southern Ocean; Pacific; Antarc*; ice core
• Online Access: https://hdl.handle.net/10023/7180; https://doi.org/10.1038/nature14155

Financial support was provided by the European Community through a Marie Curie Intra-European Fellowship for Career Development to M.A.M.-B., the Universitat Autònoma de Barcelona through a Postdoctoral Research Grant to G.M., the Spanish Ministry of Science and Innovation (PROCARSO project CGL2009-10806) to G.M., P.Z. and P.G.M., a NERC PhD studentship awarded to M.J.H., a NOAA/UCAR Climate and Global Change Postdoctoral Fellowship to J.W.B.R., and NERC grant NE/D00876/X2 to G.L.F. G.M. was also supported by the Australian Laureate Fellowship project FL120100050 (E. J. Rohling). 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, ...