Evidence for a higher pH in the glacial ocean from boron isotopes in foraminifera

Sanyal, Abhijit; Hemming, N. Gary; Hanson, Gilbert N.; Broecker, Wallace S.

doi:10.1038/373234a0

Cited by 339 publications

(236 citation statements)

References 14 publications

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“…For comparison, the average 2σ standard deviation of replicates within each experimental group is ±0.08 μmol/mol. With a glacial/interglacial pH-difference of 0.15 pH units (Foster, 2008;Hönisch and Hemming, 2005;Sanyal et al, 1995) the glacial/interglacial Ba/Ca change predicted by this observed relationship would not be detectable. Fig.…”

Section: Carbonate Chemistry Light Level and Foraminifer Speciesmentioning

confidence: 99%

Planktic foraminifers as recorders of seawater Ba/Ca

Hönisch

Allen

Russell

et al. 2011

Marine Micropaleontology

105

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Recent studies have used the Ba/Ca ratio of planktic foraminifer shells as a proxy for river run-off at oceanic sites near estuaries. Such studies assume that the Ba/Ca ratio in planktic foraminifer shells is primarily controlled by the Ba/Ca concentration of seawater and that other parameters such as salinity, temperature and pH do not compromise the primary Ba concentration relationship. Here we provide new insights from culture experiments and review published studies to confirm that environmental parameters including pH, temperature, salinity, and symbiont photosynthesis do not affect Ba substitution into planktic foraminiferal calcite. The partition coefficient for Ba in spinose planktic foraminifers is estimated as D Ba = 0.15 ± 0.05 (95% confidence limits). The same factor also seems applicable to the non-spinose genus Neogloboquadrina but not to specimens of the non-spinose genus Globorotalia.

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Section: Carbonate Chemistry Light Level and Foraminifer Speciesmentioning

confidence: 99%

Planktic foraminifers as recorders of seawater Ba/Ca

Hönisch

Allen

Russell

et al. 2011

Marine Micropaleontology

105

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“…Sanyal et al [1995] used this glacial pCO2 value, combined with an estimate of seaxvater pH based on boron isotope analyses of tbramini/Era, to calculate the implied changes in ocean alkalinity. Because pH is proportional to the HCO3'/CO2 ratio, an increase in pH based on the boron isotopic composition of tbraminifera can be interpreted as a decrease in atmospheric pCO2 as seawater HCO3' can be assumed to be approximately constant.…”

Section: 2s Is Due To the T•tct That The Distribution Of The Two mentioning

confidence: 99%

Seasonal variations in the boron isotopic composition of coral: A productivity signal?

Hemming¹,

Guilderson²,

Fairbanks³

1998

Global Biogeochemical Cycles

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Abstract. Micro-analysis of a western equatorial Pacific coral across two annual cycles reveals seasonal variation in the boron isotope cronposition. A heavy boron isotope spike is found coincident with a heavy carbon isotope spike in samples collected frmn the high density bands in the coral head. The heavy isotope values in both carbon and boron are consistent with high productivity of coral symbionts during periods of high insolation. During these high productivity periods, the symbionts fix carbon and thus produce a residual heavy carbon pool and CO2 depletion. Calcification from the resulting high pH pool results in heavier boron isotope compositions in the coral as the isotopic composition of the aqueous boron species that is incorporated in the coral skeleton (BOH4-) increases with pH. This study suggests that coupled carbon and boron isotope studies may lead to a better understanding of coral calcification processes and a lnore lucid understanding of coral b•3C records.

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“…To date, there is no consensus on the processes that are responsible for the generation of the remaining 90%. The search for the processes that could help to explain the rest of the observed 85 ppm focuses on a possible decrease in the effectiveness of the ocean's biological pump (Broecker, 1995), increased deposition of reef carbonates (Berger, 1982;Opdyke and Walker, 1992;Walker and Opdyke, 1995;Kleypas et al, 1999) and changes in deep ocean pH (Sanyal et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Modelled glacial and non-glacial HCO3−, Si and Ge fluxes since the LGM: little potential for impact on atmospheric CO2 concentrations and a potential proxy of continental chemical erosion, the marine Ge/Si ratio

Jones¹,

Munhoven²,

Tranter³

et al. 2002

Global and Planetary Change

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The runoff and riverine fluxes of HCO 3 À , Si and Ge that arise from chemical erosion in non-glaciated terrain, are modelled at six time steps from the Last Glacial Maximum (LGM) to the present day. The fluxes that arise from the Great Ice Sheets are also modelled. Terrestrial HCO 3 À fluxes decrease during deglaciation, largely because of the reduction in the area of the continental shelves as sea level rises. The HCO 3 À fluxes, and the inferred consumption of atmospheric CO 2 are used as inputs to a carbon cycle model that estimates their impact on atmospheric CO 2 concentrations ( atms CO 2 ). A maximum perturbation of atms CO 2 by f 5.5 ppm is calculated. The impact of solutes from glaciated terrain is small in comparison to those from non-glaciated terrain. Little variation in terrestrial Si and Ge fluxes is calculated ( < 10%). However, the global average riverine Ge/Si ratio may be significantly perturbed if the glacial Ge/Si ratio is high. At present, variations in terrestrial chemical erosion appear to have only a reduced impact on atms CO 2 , and only little influence on the global Si and Ge cycle and marine Ge/Si ratios during deglaciation. D

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Evidence for a higher pH in the glacial ocean from boron isotopes in foraminifera

Cited by 339 publications

References 14 publications

Planktic foraminifers as recorders of seawater Ba/Ca

Planktic foraminifers as recorders of seawater Ba/Ca

Seasonal variations in the boron isotopic composition of coral: A productivity signal?

Modelled glacial and non-glacial HCO3−, Si and Ge fluxes since the LGM: little potential for impact on atmospheric CO2 concentrations and a potential proxy of continental chemical erosion, the marine Ge/Si ratio

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