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 storage1,2, probably modulated by processes in the Southern Ocean, where much of the deep ocean is ventilated3. 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 records4,5,6. 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 ventilation6, but not in ocean carbon content, whereas proxies that record increased deglacial upwelling4,7 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 Ocean8,9, 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.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Köhler, P., Fischer, H., Munhoven, G. & Zeebe, R. E. Quantitative interpretation of atmospheric carbon records over the last glacial termination. Glob. Biogeochem. Cycles 19, GB4020 (2005)
Yu, J. et al. Loss of carbon from the deep sea since the Last Glacial Maximum. Science 330, 1084–1087 (2010)
Sigman, D. M., Hain, M. P. & Haug, G. H. The polar ocean and glacial cycles in atmospheric CO2 concentration. Nature 466, 47–55 (2010)
Anderson, R. F. et al. Wind-driven upwelling in the Southern Ocean and the deglacial rise in atmospheric CO2 . Science 323, 1443–1448 (2009)
Schmitt, J. et al. Carbon isotope constraints on the deglacial CO2 rise from ice cores. Science 336, 711–714 (2012)
Burke, A. & Robinson, L. F. The Southern Ocean’s role in carbon exchange during the last deglaciation. Science 335, 557–561 (2012)
Spero, H. J. & Lea, D. W. The cause of carbon isotope minimum events on glacial terminations. Science 296, 522–525 (2002)
Marshall, J. & Speer, K. Closure of the meridional overturning circulation through Southern Ocean upwelling. Nature Geosci. 5, 171–180 (2012)
Liu, Z. Y. & Yang, H. J. Extratropical control of tropical climate, the atmospheric bridge and oceanic tunnel. Geophys. Res. Lett. 30, 1230 (2003)
Sarmiento, J. L., Gruber, N., Brzezinski, M. A. & Dunne, J. P. High-latitude controls of thermocline nutrients and low-latitude biological productivity. Nature 427, 56–60 (2004)
Takahashi, T. et al. Climatological mean and decadal change in surface ocean pCO2, and net sea-air CO2 flux over the global oceans. Deep-Sea Res. I 56, 2075–2076 (2009)
Keeling, R. F. & Visbeck, M. Palaeoceanography: Antarctic stratification and glacial CO2 . Nature 412, 605–606 (2001)
Martínez-Garcia, A. et al. Links between iron supply, marine productivity, sea surface temperature, and CO2 over the last 1.1 Ma. Paleoceanography 24, PA1207 (2009)
Bradtmiller, L. I., Anderson, R. F., Fleisher, M. Q. & Burckle, L. H. Diatom productivity in the equatorial Pacific Ocean from the last glacial period to the present: a test of the silicic acid leakage hypothesis. Paleoceanography 21, PA4201 (2006)
Ninnemann, U. S. & Charles, C. D. Regional differences in Quaternary Subantarctic nutrient cycling: Link to intermediate and deep water ventilation. Paleoceanography 12, 560–567 (1997)
Hönisch, B. & Hemming, N. G. Surface ocean pH response to variations in pCO2 through two full glacial cycles. Earth Planet. Sci. Lett. 236, 305–314 (2005)
Foster, G. L. Seawater pH, pCO2 and [CO2−3] variations in the Caribbean Sea over the last 130 kyr: a boron isotope and B/Ca study of planktic foraminifera. Earth Planet. Sci. Lett. 271, 254–266 (2008)
Toggweiler, J. R., Dixon, K. & Broecker, W. S. The Peru upwelling and the ventilation of the South Pacific thermocline. J. Geophys. Res. 96, 20467–20497 (1991)
Goodman, P. J., Hazeleger, W., De Vries, P. & Cane, M. Pathways into the Pacific equatorial undercurrent: a trajectory analysis. J. Phys. Oceanogr. 35, 2134–2151 (2005)
Zeebe, R. E. & Wolf-Gladrow, D. A. CO2 in Seawater: Equilibrium, Kinetics, Isotopes (Elsevier, 2001)
Palmer, M. R. & Pearson, P. N. A 23,000-year record of surface water pH and PCO2 in the western equatorial Pacific Ocean. Science 300, 480–482 (2003)
Kubota, K., Yokoyama, Y., Ishikawa, T., Obrochta, S. & Suzuki, A. Larger CO2 source at the equatorial Pacific during the last deglaciation. Sci. Rep. 4, 5261 (2014)
Douville, E. et al. Abrupt sea surface pH change at the end of the Younger Dryas in the central sub-equatorial Pacific inferred from boron isotope abundance in corals (Porites). Biogeosciences 7, 2445–2459 (2010)
Palter, J. B., Sarmiento, J. L., Gnanadesikan, A., Simeon, J. & Slater, R. D. Fueling export production: nutrient return pathways from the deep ocean and their dependence on the meridional overturning circulation. Biogeosciences 7, 3549–3568 (2010)
Rae, J. W. B. et al. Deep water formation in the North Pacific and deglacial CO2 rise. Paleoceanography 29, 645–667 (2014)
Menviel, L. & Joos, F. Toward explaining the Holocene carbon dioxide and carbon isotope records: results from transient ocean carbon cycle-climate simulations. Paleoceanography 27, PA1207 (2012)
Barker, S. et al. Interhemispheric Atlantic seesaw response during the last deglaciation. Nature 457, 1097–1102 (2009)
Denton, G. H. et al. The last glacial termination. Science 328, 1652–1656 (2010)
McGee, D., Marcantonio, F. & Lynch-Stieglitz, J. Deglacial changes in dust flux in the eastern equatorial Pacific. Earth Planet. Sci. Lett. 257, 215–230 (2007)
Pichevin, L. E. et al. Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean. Nature 459, 1114–1117 (2009)
Reimer, P. J. et al. IntCal13 and Marine13 radiocarbon age calibration curves 0–50,000 years cal BP. Radiocarbon 55, 1869–1887 (2013)
Gersonde, R. et al. Last glacial sea surface temperatures and sea-ice extent in the Southern Ocean (Atlantic-Indian sector): a multiproxy approach. Paleoceanography 18, 1061 (2003)
Mackensen, A., Rudolph, M. & Kuhn, G. Late Pleistocene deep-water circulation in the subantarctic eastern Atlantic. Global Planet. Change 30, 197–229 (2001)
Mix, A. et al. Proceedings ODP, Initial Reports 202 (Ocean Drilling Program, 2003)
Stuiver, M. & Reimer, P. J. Extended 14C database and revised CALIB radiocarbon calibration program. Radiocarbon 35, 215–230 (1993)
Stuiver, M., Reimer, P. J. & Reimer, R. W. CALIB Radiocarbon Calibration http://calib.qub.ac.uk/calib/ (2005)
Key, R. M. et al. A global ocean carbon climatology: results from Global Data Analysis Project (GLODAP). Glob. Biogeochem. Cycles 18, GB4031 (2004)
Siani, G. et al. Carbon isotope records reveal precise timing of enhanced Southern Ocean upwelling during the last deglaciation. Nature Commun. 4, 2758 (2013)
Skinner, L. C., Fallon, S., Waelbroeck, C., Michel, E. & Barker, S. Ventilation of the deep Southern Ocean and deglacial CO2 rise. Science 328, 1147–1151 (2010)
Lea, D. W. et al. Paleoclimate history of Galápagos surface waters over the last 135,000 yr. Quat. Sci. Rev. 25, 1152–1167 (2006)
Pena, L. D., Cacho, I., Ferretti, P. & Hall, M. A. El Niño-Southern Oscillation-like variability during glacial terminations and interlatitudinal teleconnections. Paleoceanography 23, PA3101 (2008)
Marchitto, T. M., Lehman, S. J., Ortiz, J. D., Fluckiger, J. & van Geen, A. Marine radiocarbon evidence for the mechanism of deglacial atmospheric CO2 rise. Science 316, 1456–1459 (2007)
Stott, L., Southon, J., Timmermann, A. & Koutavas, A. Radiocarbon age anomaly at intermediate water depth in the Pacific Ocean during the last deglaciation. Paleoceanography 24, PA2223 (2009)
Doss, W. & Marchitto, T. M. Glacial deep ocean sequestration of CO2 driven by the eastern equatorial Pacific biologic pump. Earth Planet. Sci. Lett. 377–378, 43–54 (2013)
Niebler, H. S. & Gersonde, R. A planktic foraminiferal transfer function for the southern South Atlantic Ocean. Mar. Micropaleontol. 34, 213–234 (1998)
Mortyn, P. G. & Charles, C. D. Planktonic foraminiferal depth habitat and δ18O calibrations: plankton tow results from the Atlantic sector of the Southern Ocean. Paleoceanography 18, 1037 (2003)
Thunell, R. C., Curry, W. B. & Honjo, S. Seasonal variation in the flux of planktonic foraminifera: time series sediment trap results from the Panama Basin. Earth Planet. Sci. Lett. 64, 44–55 (1983)
Thunell, R. C. & Reynolds, L. A. Sedimentation of planktonic foraminifera: seasonal changes in species flux in the Panama Basin. Micropaleontology 30, 243–262 (1984)
Curry, W. B., Thunell, R. C. & Honjo, S. Seasonal-changes in the isotopic composition of planktonic foraminifera collected in Panama Basin sediment traps. Earth Planet. Sci. Lett. 64, 33–43 (1983)
Fairbanks, R. G., Sverdlove, M., Free, R., Wiebe, P. H. & Be, A. W. H. Vertical distribution and isotopic fractionation of living planktonic foraminifera from the Panama Basin. Nature 298, 841–844 (1982)
Faul, K. L., Ravelo, A. C. & Delaney, M. L. Reconstructions of upwelling, productivity, and photic zone depth in the eastern equatorial Pacific Ocean using planktonic foraminiferal stable isotopes and abundances. J. Foraminiferal Res. 30, 110–125 (2000)
Bé, A. W. H. Gametogenic calcification in a spinose planktonic foraminifer, Globigerinoides sacculifer (Brady). Mar. Micropaleontol. 5, 283–310 (1980)
Spero, H. J., Mielke, K. M., Kalve, E. M., Lea, D. W. & Pak, D. K. Multispecies approach to reconstructing eastern equatorial Pacific thermocline hydrography during the past 360 kyr. Paleoceanography 18, 1022 (2003)
Caron, D. A., Anderson, O. R., Lindsey, J. L., Faber, W. W. & Lim, E. L. Effects of gametogenesis on test structure and dissolution of some spinose planktonic-foraminifera and implications for test preservation. Mar. Micropaleontol. 16, 93–116 (1990)
Niebler, H. S. Stable Isotopes Measured on Globigerina Bulloides of Sediment Core PS2498-1 http://doi.pangaea.de/10.1594/PANGAEA.55892 (2004)
Barker, S., Greaves, M. & Elderfield, H. A study of cleaning procedures used for foraminiferal Mg/Ca paleothermometry. Geochem. Geophys. Geosyst. 4, 8407 (2003)
Yu, J. M., Elderfield, H., Greaves, M. & Day, J. Preferential dissolution of benthic foraminiferal calcite during laboratory reductive cleaning. Geochem. Geophys. Geosyst. 8, Q06016 (2007)
Rae, J. W. B., Foster, G. L., Schmidt, D. N. & Elliott, T. Boron isotopes and B/Ca in benthic foraminifera: proxies for the deep ocean carbonate system. Earth Planet. Sci. Lett. 302, 403–413 (2011)
Anand, P., Elderfield, H. & Conte, M. H. Calibration of Mg/Ca thermometry in planktonic foraminifera from a sediment trap time series. Paleoceanography 18, 1050 (2003)
Mashiotta, T. A., Lea, D. W. & Spero, H. J. Glacial-interglacial changes in Subantarctic sea surface temperature and δ18O-water using foraminiferal Mg. Earth Planet. Sci. Lett. 170, 417–432 (1999)
Boyle, E. A. & Keigwin, L. D. Comparison of Atlantic and Pacific paleochemical records for the last 215,000 years: changes in deep ocean circulation and chemical inventories. Earth Planet. Sci. Lett. 76, 135–150 (1985)
Henehan, M. J. et al. Calibration of the boron isotope proxy in the planktonic foraminifera Globigerinoides ruber for use in palaeo-CO2 reconstruction. Earth Planet. Sci. Lett. 364, 111–122 (2013)
Catanzaro, E. J. et al. Boric Acid: Isotopic and Assay Standard Reference Material (National Bureau of Standards Spec. Publ., 260, US Govt Printing Office, 1970)
Klochko, K., Kaufman, A. J., Yao, W., Byrne, R. H. & Tossell, J. A. Experimental measurement of boron isotope fractionation in seawater. Earth Planet. Sci. Lett. 248, 276–285 (2006)
Hemming, N. G. & Hanson, G. N. Boron isotopic composition and concentration in modern marine carbonates. Geochim. Cosmochim. Acta 56, 537–543 (1992)
Hemming, N. G., Reeder, R. J. & Hanson, G. N. Mineral-fluid partitioning and isotopic fractionation of boron in synthetic calcium carbonate. Geochim. Cosmochim. Acta 59, 371–379 (1995)
Dickson, A. G. Thermodynamics of the dissociation of boric-acid in synthetic seawater from 273.15 to 318.15 K. Deep-Sea Res. 37, 755–766 (1990)
Foster, G. L., Pogge von Strandmann, P. A. E. & Rae, J. W. B. Boron and magnesium isotopic composition of seawater. Geochem. Geophys. Geosyst. 11, Q08015 (2010)
Henehan, M. J. Ground-Truthing the Boron-Based Proxies PhD thesis, Univ. Southampton (2013)
Prebble, J. G. et al. An expanded modern dinoflagellate cyst dataset for the Southwest Pacific and Southern Hemisphere with environmental associations. Mar. Micropaleontol. 101, 33–48 (2013)
Key, R. M. et al. The CARINA data synthesis project: introduction and overview. Earth Syst. Sci. Data 2, 105–121 (2010)
Lee, K. et al. Global relationships of total alkalinity with salinity and temperature in surface waters of the world’s oceans. Geophys. Res. Lett. 33, L19605 (2006)
Gloor, M. et al. A first estimate of present and preindustrial air-sea CO2 flux patterns based on ocean interior carbon measurements and models. Geophys. Res. Lett. 30, 1010 (2003)
van Heuven, S., Pierrot, D., Rae, J. W. B., Lewis, E. & Wallace, D. W. R. MATLAB Program Developed for CO2 System Calculations http://cdiac.ornl.gov/ftp/co2sys/CO2SYS_calc_MATLAB_v1.1/ (Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, 2011)
Lueker, T. J., Dickson, A. G. & Keeling, C. D. Ocean pCO2 calculated from dissolved inorganic carbon, alkalinity, and equations for K1 and K2: validation based on laboratory measurements of CO2 in gas and seawater at equilibrium. Mar. Chem. 70, 105–119 (2000)
Lee, K. et al. The universal ratio of boron to chlorinity for the North Pacific and North Atlantic oceans. Geochim. Cosmochim. Acta 74, 1801–1811 (2010)
Foster, G. L., Lear, C. H. & Rae, J. W. B. The evolution of pCO2, ice volume and climate during the middle Miocene. Earth Planet. Sci. Lett. 341–344, 243–254 (2012)
Sanyal, A., Bijma, J., Spero, H. & Lea, D. W. Empirical relationship between pH and the boron isotopic composition of Globigerinoides sacculifer: implications for the boron isotope paleo-pH proxy. Paleoceanography 16, 515–519 (2001)
Foster, G. L. et al. Interlaboratory comparison of boron isotope analyses of boric acid, seawater and marine CaCO3 by MC-ICPMS and NTIMS. Chem. Geol. 358, 1–14 (2013)
Sanyal, A., Hemming, N. G., Hanson, G. N. & Broecker, W. S. Evidence for a higher pH in the glacial ocean from boron isotopes in foraminifera. Nature 373, 234–236 (1995)
Schmidt, G. A. Error analysis of paleosalinity calculations. Paleoceanography 14, 422–429 (1999)
Hain, M. P., Sigman, D. M. & Haug, G. H. in Treatise on Geochemistry (eds Holland, H. D. & Turekian, K. K. ) 485–517 (Elsevier, 2014)
Yu, J., Foster, G. L., Elderfield, H., Broecker, W. S. & Clark, E. An evaluation of benthic foraminiferal B/Ca and δ11B for deep ocean carbonate ion and pH reconstructions. Earth Planet. Sci. Lett. 293, 114–120 (2010)
Toggweiler, J. R. Variation of atmospheric CO2 by ventilation of the ocean’s deepest water. Paleoceanography 14, 571–588 (1999)
Hain, M. P., Sigman, D. M. & Haug, G. H. Carbon dioxide effects of Antarctic stratification, North Atlantic Intermediate Water formation, and subantarctic nutrient drawdown during the last ice age: diagnosis and synthesis in a geochemical box model. Glob. Biogeochem. Cycles 24, GB4023 (2010)
R Development Core Team. R: A Language and Environment for Statistical Computing (R Foundation for Statistical Computing, 2013)
Monnin, E. et al. Atmospheric CO2 concentrations over the last glacial termination. Science 291, 112–114 (2001)
Lourantou, A. et al. Constraint of the CO2 rise by new atmospheric carbon isotopic measurements during the last deglaciation. Glob. Biogeochem. Cycles 24, GB2015 (2010)
Chandler, R. & Scott, M. Statistical Methods for Trend Detection and Analysis in the Environmental Sciences (Wiley, 2011)
Rohling, E. J. et al. Sea-level and deep-sea-temperature variability over the past 5.3 million years. Nature 508, 477–482 (2014)
Stocker, T. F. The seesaw effect. Science 282, 61–62 (1998)
Barbante, C. et al. One-to-one coupling of glacial climate variability in Greenland and Antarctica. Nature 444, 195–198 (2006)
Orsi, A. H., Whitworth, T. & Nowlin, W. D. On the meridional extent and fronts of the Antarctic Circumpolar Current. Deep Sea Res. I 42, 641–673 (1995)
González-Dávila, M. et al. Carbonate system in the water masses of the Southeast Atlantic sector of the Southern Ocean during February and March 2008. Biogeosciences 8, 1401–1413 (2011)
Arbuszewski, J. A., Demenocal, P. B., Cleroux, C., Bradtmiller, L. & Mix, A. Meridional shifts of the Atlantic intertropical convergence zone since the Last Glacial Maximum. Nature Geosci. 6, 959–962 (2013)
Koutavas, A. & Lynch-Stieglitz, J. in Hadley Circulation: Present, Past and Future Vol. 21 (eds Diaz, H. F. & Bradley, R. S. ) 347–369 (Kluwer, 2004)
Dubois, N., Kienast, M., Normandeau, C. & Herbert, T. D. Eastern equatorial Pacific cold tongue during the Last Glacial Maximum as seen from alkenone paleothermometry. Paleoceanography 24, PA4207 (2009)
Sadekov, A. Y. et al. Palaeoclimate reconstructions reveal a strong link between El Niño-Southern Oscillation and Tropical Pacific mean state. Nature Commun. 4, 2692 (2013)
Lukas, R. The termination of the equatorial undercurrent in the eastern Pacific. Prog. Oceanogr. 16, 63–90 (1986)
Tsuchiya, M., Lukas, R., Fine, R. A., Firing, E. & Lindstrom, E. Source waters of the Pacific equatorial undercurrent. Prog. Oceanogr. 23, 101–147 (1989)
Fine, R. A., Lukas, R., Bingham, F. M., Warner, M. J. & Gammon, R. H. The western equatorial Pacific: a water mass crossroads. J. Geophys. Res. 99, 25063–25080 (1994)
Acknowledgements
We thank the International Ocean Drilling Program for providing samples from ODP Leg 202, R. Gersonde and A. Mackensen for the PS2498-1 core material, J. F. McManus for sharing his unpublished benthic isotope data for ODP1238, and E. J. Rohling, M. P. Hain and C. Beaulieu for discussions. For the calibration of G. bulloides, we thank M. Kucera for providing core-top samples from the archives at the University of Tübingen, H. C. Bostock for samples from the National Institute for Water and Atmospheric Research, Wellington, and B. J. Marshall and R. Thunell for samples from the Cariaco Basin sediment trap time series. J. A. Milton, M. J. Cooper and A. Michalik provided assistance during ICP-MS analyses and sample preparation in the laboratory. C. Alt and M. T. Horigome helped with foraminifera picking. We thank the other members of ‘The B-Team’ at the National Oceanography Centre Southampton for their contributions. 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).
Author information
Authors and Affiliations
Contributions
M.A.M.-B., G.M., G.L.F. and P.Z. designed the study; G.M. and M.A.M.-B. produced the δ11B and trace element records for PS2498-1; M.A.M.-B. produced the δ11B and trace element records for ODP1238; G.M. produced the δ18O and δ13C data; M.J.H. developed the G. bulloides δ11B–pH calibration; J.W.B.R. sampled sediment core PS2498-1. M.A.M.-B. and G.M. wrote the first draft jointly, and all authors contributed to the interpretation and the preparation of the final manuscript.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Extended data figures and tables
Extended Data Figure 1 Comparison of PS2498-1 (blue) and ODP1238 (red) records.
a, δ11B. b, pH. c, .
Extended Data Figure 2 δ11B-derived compilation for the equatorial Pacific during the last deglaciation and Holocene.
Foraminifera-based record from the western equatorial Pacific21 (grey), Porites coral-based record from the central equatorial Pacific22,23 (as published in ref. 22, green), and foraminifera-based record from the EEP (this study, red). The records of refs 21, 22 have been smoothed by fitting a LOESS function with degrees of smoothing (span) of 0.2 and 0.4, respectively (Methods), to allow a better comparison with the ODP1238 record (see main text). ODP1238 is located in the EEP, and therefore represents a direct record of upwelling of CO2-rich waters, while the signal at central and western equatorial sites may have been modified during the westward transit of waters by, for example, equilibration with the atmosphere and/or nutrient utilization by the biological pump.
Extended Data Figure 3 Planktic δ18O and δ13C records from ODP1238.
a, Planktic δ18O records from OPD1238. Red, G. ruber sensu stricto (ss) 250–355 μm; green, G. sacculifer (mixed morphotypes) 355–425 μm; black, N. dutertrei 355–500 μm. b, Planktic δ13C records from OPD1238. To facilitate comparison between species, δ13C data has been normalized53. Red, G. ruber ss 250–355 μm; green, G. sacculifer (mixed morphotypes) 355–425 μm; black, N. dutertrei 355–500 μm.
Extended Data Figure 4 records from the SAA and the EEP during the last deglaciation, compared with indicators of dust input.
a–c, SAA; d–f, EEP. a, δ11B-derived in core PS2498-1. b, Logarithm of the mass accumulation rates (MAR) of iron (Fe) in the sub-Antarctic site ODP109013. c, f, measured on a suite of Antarctic ice cores5. d, δ11B-derived in core ODP1238. e, Dust fluxes in the EEP29. Dust fluxes from ref. 29 were de-meaned and divided by their own standard deviation, and are displayed in standard deviation units.
Extended Data Figure 5 Age model for PS2498-1.
a, Chronology of SAA core PS2498-1. Carbon-14 calendar age/depth relationships in core PS2498-1. Grey shading indicates 95% confidence limits of calendar ages. b, PS2498-1 G. bulloides δ11B record plotted using the different chronologies described in Methods and compared with atmospheric CO2 (green; refs 5, 87, 88) and with Antarctic opal flux4 (orange) records. Red, constant ΔR = 300 yr; green, ΔR = 900 yr for intervals older than 16 kyr and ΔR = 300 yr for younger intervals6; magenta, variable ΔR correction38 (ranging between 500 and 900 yr between 13 and 16 kyr ago).
Extended Data Figure 6 Age model for ODP1238.
a, Radiocarbon ages for ODP1238 determined from N. dutertrei tests at LLNL-CAMS. b, Chronology of EEP core ODP1238. Orange circles, calendar ages; black line, linear fit; red line, third-order polynomial fit (Methods).
Extended Data Figure 7 Benthic and planktic δ18O stratigraphy for ODP1238.
a, Benthic δ18O stratigraphy for ODP1238 compared with other benthic δ18O stratigraphies from EEP cores. Black circles, unpublished benthic δ18O data for ODP1238 generated by J. F. McManus (LDEO, Columbia University); red line, site TR163-2240; blue line, sites RC13-140, RC23-22 and RC23-1544. b, Globigerinoides ruber δ18O stratigraphy for ODP1238 compared with other G. ruber stratigraphies from EEP cores. Black circles, ODP1238 (Methods); green squares, site TR163-197; red line, site TR163-2240; blue line, site ODP124041.
Extended Data Figure 8 δ11B–pH calibrations for G. bulloides and G. sacculifer.
a, Data tabulated; b, Data plotted. The green symbols and text show a new calibration for G. bulloides (with associated 2σ uncertainties). Horizontal error bars for core-top samples are 2σ of intra-annual variability in calculated monthly δ11Bborate, and for sediment trap samples reflect the range of δ11Bborate between December 2006 and February 2007. Vertical error bars represent the analytical reproducibility (2σ) as calculated using equation (1). The most recent PS2498-1 sample (2.2 kyr old) (black-filled circle) was not used in the calibration process, and is included to show its agreement with the calibration line. The red symbols and text show a calibration for G. sacculifer (with associated 2σ uncertainties). The calibration line incorporates both culture78 (empty symbols) and core-top (red-filled symbols) data17. Culture data analysed by N-TIMS (grey symbols and text)78 has been corrected by applying a laboratory offset of −3.32‰ (Methods) (the vertical grey arrow indicates an original N-TIMS calibration data point that falls outside the plot area). The ODP1238 late-Holocene average (black-filled square) was not used to produce the calibration equation, and is included to show its agreement with the calibration line. Horizontal error bars for core-top samples are 2σ of intra-annual variability in calculated monthly δ11Bborate, and for culture samples represent quoted uncertainties78 in pH. Vertical error bars represent quoted uncertainties in δ11B measurements17,78 (2σ). To calculate monthly pH variations at ODP1238, the method described in the G. bulloides calibration section has been used62 (with total alkalinity derived using the total alkalinity/salinity/temperature relationship for the ‘Equatorial upwelling Pacific Zone’ in ref. 72). The black line denotes a 1:1 relationship, that is, a pH sensitivity equal to that of borate ion. Heavily and lightly shaded regions around calibration lines represent 1σ and 2σ uncertainties, respectively.
Extended Data Figure 9 Effect of δ11B–pH calibration, total alkalinity and chronological uncertainties in and records.
a, PS2498-1 δ11B-based record calculated with the G. bulloides calibration equation (thick blue line), and its associated 2σ uncertainty (blue shaded envelope). b, PS2498-1 δ11B-based record assuming a constant total alkalinity of (i) modern values at PS2498-1 (blue), (ii) modern values minus 25 μmol kg−1 (green) and (iii) modern values plus 125 μmol kg−1 (red). c, PS2498-1 record calculated using (i) age derived from our age model (blue), (ii) age plus 0.5 kyr (green) and (iii) age minus 0.5 kyr (red). d, ODP1238 δ11B-based record calculated with the G. sacculifer calibration equation (thick red line), and its associated 2σ uncertainty (shaded red envelope). e, ODP1238 δ11B-based record assuming a constant total alkalinity of (i) modern values at ODP1238 (blue), (ii) modern values minus 25 μmol kg−1 (green) and (iii) modern values plus 125 μmol kg−1 (red). f, ODP1238 record calculated using (i) age derived from our age model (blue), (ii) age plus 0.5 kyr (green) and (iii) age minus 0.5 kyr (red). Note the different horizontal and vertical axes in each panel.
Source data
Rights and permissions
About this article
Cite this article
Martínez-Botí, M., Marino, G., Foster, G. et al. Boron isotope evidence for oceanic carbon dioxide leakage during the last deglaciation. Nature 518, 219–222 (2015). https://doi.org/10.1038/nature14155
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/nature14155
This article is cited by
-
Southern Ocean glacial conditions and their influence on deglacial events
Nature Reviews Earth & Environment (2023)
-
Arctic and Antarctic forcing of ocean interior warming during the last deglaciation
Scientific Reports (2023)
-
Radiocarbon evidence for the stability of polar ocean overturning during the Holocene
Nature Geoscience (2023)
-
Deglacial Subantarctic CO2 outgassing driven by a weakened solubility pump
Nature Communications (2022)
-
Increased interglacial atmospheric CO2 levels followed the mid-Pleistocene Transition
Nature Geoscience (2022)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.