title: Deep ocean carbonate ion increase during mid Miocene CO2 decline.
abstract: Characterised by long term cooling and abrupt ice sheet expansion on Antarctica ~14 Ma ago, the mid Miocene marked the beginning of the modern ice-house world, yet there is still little consensus on its causes, in part because carbon cycle dynamics are not well constrained. In particular, changes in carbonate ion concentration ([CO3(2-)]) in the ocean, the largest carbon reservoir of the ocean-land-atmosphere system, are poorly resolved. We use benthic foraminiferal B/Ca ratios to reconstruct relative changes in [CO3(2-)] from the South Atlantic, East Pacific, and Southern Oceans. Our results suggest an increase of perhaps ~40 μmol/kg may have occurred between ~15 and 14 Ma in intermediate to deep waters in each basin. This long-term increase suggests elevated alkalinity input, perhaps from the Himalaya, rather than other shorter-term mechanisms such as ocean circulation or ecological changes, and may account for some of the proposed atmospheric CO2 decline before ~14 Ma.
authors.affiliation: 1] British Geological Survey, Keyworth, Nottingham NG12 5GG, UK [2] Department of Geology, University of Leicester, Leicester LE1 7RH, UK.
authors.forename: Sev
authors.initials: S
authors.lastname: Kender
authors.affiliation: Research School of Earth Sciences, The Australian National University, Canberra, Australia.
authors.forename: Jimin
authors.initials: J
authors.lastname: Yu
authors.affiliation: British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Peck
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D002245:Carbon Dioxide / Q000032:analysis*; D057231:Climate Change; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D009792:Oceans and Seas; D014867:Water / Q000737:chemistry*
chemical_list: D007477:Ions; D014867:Water; D002245:Carbon Dioxide