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

Martínez‐Botí, Miguel A.; Marino, Gianluca; Foster, Gavin L.; Ziveri, Patrizia; Henehan, Michael J.; Rae, James; Mortyn, P. Graham; Vance, Derek

doi:10.1038/nature14155

Cited by 163 publications

(259 citation statements)

References 96 publications

(73 reference statements)

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“…Recent work shows a pronounced increase in CO 2 outgassing in the East Equatorial Atlantic during the LGM (Foster and Sexton 2014), indicative of enhanced upwelling, while surface water CO 2 in the West Equatorial Atlantic stays close to equilibrium with the atmosphere, suggesting that the upwelled CO 2 and nutrients from the East are progressively drawn-down by biological productivity. In the East (Martínez-Botí et al 2015b) and West (Palmer and Pearson 2003) Equatorial Pacific, ΔpCO 2 is similar to or slightly lower than modern during the LGM, then shows a dramatic increase during the deglaciation, interpreted as an increase in the CO 2 content of upwelled waters. In the Indian Ocean, d…”

Section: Glacial-interglacial Comentioning

confidence: 99%

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Boron Isotopes in Foraminifera: Systematics, Biomineralisation, and CO2 Reconstruction

Rae

2017

Boron Isotopes

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The boron isotope composition of foraminifera provides a powerful tracer for CO 2 change over geological time. This proxy is based on the equilibrium of boron and its isotopes in seawater, which is a function of pH. However while the chemical principles underlying this proxy are well understood, its reliability has previously been questioned, due to the difficulty of boron isotope (d 11 B) analysis on foraminferal samples and questions regarding calibrations between d 11 B and pH. This chapter reviews the current state of the d 11 B-pH proxy in foraminfera, including the pioneering studies that established this proxy's potential, and the recent work that has improved understanding of boron isotope systematics in foraminifera and applied this tracer to the geological record. The theoretical background of the d 11 B-pH proxy is introduced, including an accurate formulation of the boron isotope mass balance equations. Sample preparation and analysis procedures are then reviewed, with discussion of sample cleaning, the potential influence of diagenesis, and the strengths and weaknesses of boron purification by column chromatography versus microsublimation, and analysis by NTIMS versus MC-ICPMS. The systematics of boron isotopes in foraminifera are discussed in detail, including results from benthic and planktic taxa, and models of boron incorporation, fractionation, and biomineralisation. Benthic taxa from the deep ocean have d 11 B within error of borate ion at seawater pH. This is most easily explained by simple incorporation of borate ion at the pH of seawater. Planktic foraminifera have d 11 B close to borate ion, but with minor offsets. These may be driven by physiological influences on the Electronic supplementary material The online version of this chapter

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Section: Glacial-interglacial Comentioning

confidence: 99%

“…Several studies have used d 11 B in planktic foraminifera to reconstruct the extent of disequilibrium (ΔpCO 2 ) between CO 2 in surface waters and the atmosphere (Sanyal et al 1997;Sanyal and Bijma 1999;Palmer and Pearson 2003;Foster and Sexton 2014;Naik et al 2015;Martínez-Botí et al 2015b;see Fig. 5.10).…”

Section: Glacial-interglacial Comentioning

confidence: 99%

Boron Isotopes in Foraminifera: Systematics, Biomineralisation, and CO2 Reconstruction

Rae

2017

Boron Isotopes

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“…During the last two million years the glaciations have been characterized by lower CO 2 concentration in the atmosphere that has been explained by a combination of both biology (strengthening of the biological pump) and physics of the Southern Ocean (Sigman and Boyle, 2000;Kohfeld et al, 2005;Robinson et al, 2005;Martínez-Botí et al, 2015). The higher efficiency of the biological pump was likely linked to higher deposition of eolian iron and more complete utilization of nutrients at high latitudes (Mahowald et al, 2006;Martínez-García et al, 2014).…”

Section: Southern Ocean Carbonate Counter Pump Affected By Different mentioning

confidence: 99%

Planktic foraminifer and coccolith contribution to carbonate export fluxes over the central Kerguelen Plateau

Rembauville

Meilland

Ziveri

et al. 2016

Deep Sea Research Part I: Oceanographic Research Papers

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a b s t r a c tWe report the contribution of planktic foraminifers and coccoliths to the particulate inorganic carbon (PIC) export fluxes collected over an annual cycle (October 2011/September 2012) on the central Kerguelen Plateau in the Antarctic Zone (AAZ) south of the Polar Front (PF). The seasonality of PIC flux was decoupled from surface chlorophyll a concentration and particulate organic carbon (POC) fluxes and was characterized by a late summer (February) maximum. This peak was concomitant with the highest satellite-derived sea surface PIC and corresponded to a Emiliania huxleyi coccoliths export event that accounted for 85% of the annual PIC export. The foraminifer contribution to the annual PIC flux was much lower (15%) and dominated by Turborotalita quinqueloba and Neogloboquadrina pachyderma. Foraminifer export fluxes were closely related to the surface chlorophyll a concentration, suggesting food availability as an important factor regulating the foraminifer's biomass. We compared size-normalized test weight (SNW) of the foraminifers with previously published SNW from the Crozet Islands using the same methodology and found no significant difference in SNW between sites for a given species. However, the SNW was significantly species-specific with a threefold increase from T. quinqueloba to Globigerina bulloides. The annual PIC:POC molar ratio of 0.07 was close to the mean ratio for the global ocean and lead to a low carbonate counter pump effect ( $ 5%) compared to a previous study north of the PF (6-32%). We suggest that lowers counter pump effect south of the PF despite similar productivity levels is due to a dominance of coccoliths in the PIC fluxes and a difference in the foraminifers species assemblage with a predominance of polar species with lower SNW.

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“…Reduced AMOC strength decreased heat transport from the South to the North during the YD and HS1 (5). At the same time, increased Southern Ocean upwelling likely enhanced the release of CO 2 (6,7). Recently, a new, high-resolution Antarctic ice-core record (8) has revealed three abrupt centennial-scale atmospheric CO 2 increases superimposed on the millennial-scale deglacial CO 2 rise, each of 10 to 15 ppmV, contributing a significant portion of the total 90 ppmV deglacial CO 2 increase.…”

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confidence: 99%

Synchronous centennial abrupt events in the ocean and atmosphere during the last deglaciation

Chen

Robinson

Burke

et al. 2015

Science

112

171

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Antarctic ice-core data reveal that the atmosphere experienced abrupt centennial increases in CO 2 concentration during the last deglaciation (~18-11 thousand years, ka).Establishing the role of ocean circulation in these changes requires high-resolution, accurately-dated marine records. Here we report radiocarbon data from uranium-thorium dated deep-sea corals in the Equatorial Atlantic and Drake Passage over the last 25 ka. Two major deglacial radiocarbon increases occurred in phase with centennial atmospheric CO 2 rises at 14.8 ka and 11.7 ka. We interpret these radiocarbon-enriched signals to represent two short-lived (<500 years) 'overshoot' events with Atlantic meridional overturning stronger than modern. These results provide compelling evidence for a close coupling of ocean circulation and centennial climate events during the last deglaciation.

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

Cited by 163 publications

References 96 publications

Boron Isotopes in Foraminifera: Systematics, Biomineralisation, and CO2 Reconstruction

Boron Isotopes in Foraminifera: Systematics, Biomineralisation, and CO2 Reconstruction

Planktic foraminifer and coccolith contribution to carbonate export fluxes over the central Kerguelen Plateau

Synchronous centennial abrupt events in the ocean and atmosphere during the last deglaciation

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