title: Iron fertilization of the Subantarctic ocean during the last ice age.
abstract: John H. Martin, who discovered widespread iron limitation of ocean productivity, proposed that dust-borne iron fertilization of Southern Ocean phytoplankton caused the ice age reduction in atmospheric carbon dioxide (CO2). In a sediment core from the Subantarctic Atlantic, we measured foraminifera-bound nitrogen isotopes to reconstruct ice age nitrate consumption, burial fluxes of iron, and proxies for productivity. Peak glacial times and millennial cold events are characterized by increases in dust flux, productivity, and the degree of nitrate consumption; this combination is uniquely consistent with Subantarctic iron fertilization. The associated strengthening of the Southern Ocean's biological pump can explain the lowering of CO2 at the transition from mid-climate states to full ice age conditions as well as the millennial-scale CO2 oscillations.
authors.affiliation: Geological Institute, ETH Zürich, 8092 Zürich, Switzerland.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Martínez-García
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Sigman
authors.forename: Haojia
authors.initials: H
authors.lastname: Ren
authors.forename: Robert F
authors.initials: RF
authors.lastname: Anderson
authors.forename: Marietta
authors.initials: M
authors.lastname: Straub
authors.forename: David A
authors.initials: DA
authors.lastname: Hodell
authors.forename: Samuel L
authors.initials: SL
authors.lastname: Jaccard
authors.forename: Timothy I
authors.initials: TI
authors.lastname: Eglinton
authors.forename: Gerald H
authors.initials: GH
authors.lastname: Haug
mesh_terms: D000864:Antarctic Regions; D001267:Atlantic Ocean; D001272:Atmosphere; D018533:Biomass; D002245:Carbon Dioxide / Q000032:analysis; D002980:Climate; D003080:Cold Temperature; D056908:Foraminifera / Q000737:chemistry / Q000378:metabolism; D019015:Geologic Sediments / Q000737:chemistry; D046448:Ice Cover; D007501:Iron / Q000032:analysis; D009566:Nitrates / Q000032:analysis / Q000378:metabolism; D009587:Nitrogen Isotopes / Q000032:analysis; D010839:Phytoplankton / Q000254:growth & development / Q000378:metabolism; D012623:Seawater / Q000737:chemistry; D013995:Time
chemical_list: D009566:Nitrates; D009587:Nitrogen Isotopes; D002245:Carbon Dioxide; D007501:Iron