Dataset Information

Unexpected variations in the triple oxygen isotope composition of stratospheric carbon dioxide.

ABSTRACT: We report observations of stratospheric CO2 that reveal surprisingly large anomalous enrichments in (17)O that vary systematically with latitude, altitude, and season. The triple isotope slopes reached 1.95 ± 0.05(1?) in the middle stratosphere and 2.22 ± 0.07 in the Arctic vortex versus 1.71 ± 0.03 from previous observations and a remarkable factor of 4 larger than the mass-dependent value of 0.52. Kinetics modeling of laboratory measurements of photochemical ozone-CO2 isotope exchange demonstrates that non-mass-dependent isotope effects in ozone formation alone quantitatively account for the (17)O anomaly in CO2 in the laboratory, resolving long-standing discrepancies between models and laboratory measurements. Model sensitivities to hypothetical mass-dependent isotope effects in reactions involving O3, O((1)D), or CO2 and to an empirically derived temperature dependence of the anomalous kinetic isotope effects in ozone formation then provide a conceptual framework for understanding the differences in the isotopic composition and the triple isotope slopes between the laboratory and the stratosphere and between different regions of the stratosphere. This understanding in turn provides a firmer foundation for the diverse biogeochemical and paleoclimate applications of (17)O anomalies in tropospheric CO2, O2, mineral sulfates, and fossil bones and teeth, which all derive from stratospheric CO2.

SUBMITTER: Wiegel AA

PROVIDER: S-EPMC3816447 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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Unexpected variations in the triple oxygen isotope composition of stratospheric carbon dioxide.

Wiegel Aaron A AA Cole Amanda S AS Hoag Katherine J KJ Atlas Elliot L EL Schauffler Sue M SM Boering Kristie A KA

Proceedings of the National Academy of Sciences of the United States of America 20130812 44

We report observations of stratospheric CO2 that reveal surprisingly large anomalous enrichments in (17)O that vary systematically with latitude, altitude, and season. The triple isotope slopes reached 1.95 ± 0.05(1σ) in the middle stratosphere and 2.22 ± 0.07 in the Arctic vortex versus 1.71 ± 0.03 from previous observations and a remarkable factor of 4 larger than the mass-dependent value of 0.52. Kinetics modeling of laboratory measurements of photochemical ozone-CO2 isotope exchange demonstr ...[more]

PMID: 23940331

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Project description:BackgroundThe oxygen (?(18)O) and carbon (?(13)C) isotope compositions of bioapatite from skeletal remains of fossil mammals are well-established proxies for the reconstruction of palaeoenvironmental and palaeoclimatic conditions. Stable isotope studies of modern analogues are an important prerequisite for such reconstructions from fossil mammal remains. While numerous studies have investigated modern large- and medium-sized mammals, comparable studies are rare for small mammals. Due to their high abundance in terrestrial ecosystems, short life spans and small habitat size, small mammals are good recorders of local environments.Methodology/findingsThe ?(18)O and ?(13)C values of teeth and bones of seven sympatric modern rodent species collected from owl pellets at a single locality were measured, and the inter-specific, intra-specific and intra-individual variations were evaluated. Minimum sample sizes to obtain reproducible population ?(18)O means within one standard deviation were determined. These parameters are comparable to existing data from large mammals. Additionally, the fractionation between coexisting carbonate (?(18)O(CO3)) and phosphate (?(18)O(PO4)) in rodent bioapatite was determined, and ?(18)O values were compared to existing calibration equations between the ?(18)O of rodent bioapatite and local surface water (?(18)O(LW)). Specific calibration equations between ?(18)O(PO4) and ?(18)O(LW) may be applicable on a taxonomic level higher than the species. However, a significant bias can occur when bone-based equations are applied to tooth-data and vice versa, which is due to differences in skeletal tissue formation times. ?(13)C values reflect the rodents' diet and agree well with field observations of their nutritional behaviour.Conclusions/significanceRodents have a high potential for the reconstruction of palaeoenvironmental conditions by means of bioapatite ?(18)O and ?(13)C analysis. No significant disadvantages compared to larger mammals were observed. However, for refined palaeoenvironmental reconstructions a better understanding of stable isotope signatures in modern analogous communities and potential biases due to seasonality effects, population dynamics and tissue formation rates is necessary.

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Unexpected variations in the triple oxygen isotope composition of stratospheric carbon dioxide.

Publications

Unexpected variations in the triple oxygen isotope composition of stratospheric carbon dioxide.

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