Carbon dioxide in the atmosphere: Isotopic exchange with ozone and its use as a tracer in the middle atmosphere

Yung, Yuk L.; Lee, Anthony Y. T.; Irion, F. W.; DeMore, W. B.; Wen, J.

doi:10.1029/97jd00528

Cited by 102 publications

(104 citation statements)

References 25 publications

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“…1 and references therein). In the stratosphere, the oxygen isotopic composition of CO 2 is thought to be modified by oxygen isotope exchange reactions with O( 1 D) generated by ozone photolysis (2), whereas in the troposphere it is controlled by isotope exchange reactions with liquid water in the oceans, soils, and plant leaves (3). The interplay between stratospheric and tropospheric isotope exchange reactions, in principle, could allow the relative abundances of 12 (4,5), but the stratospheric CO 2 photochemical system is still underconstrained, and our understanding of it is incomplete.…”

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confidence: 99%

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Yeung¹,

Affek

Hoag³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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The stratospheric CO 2 oxygen isotope budget is thought to be governed primarily by the O( 1 D)+CO 2 isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO 2 isotopologue 16 O 13 C 18 O, in concert with 18 O and 17 O abundances, provides sensitivities to these additional processes and, thus, is a valuable test of current models. We identify a large and unexpected meridional variation in stratospheric 16 O 13 C 18 O, observed as proportions in the polar vortex that are higher than in any naturally derived CO 2 sample to date. We show, through photochemical experiments, that lower 16 O 13 C 18 O proportions observed in the midlatitudes are determined primarily by the O( 1 D)+CO 2 isotope exchange reaction, which promotes a stochastic isotopologue distribution. In contrast, higher 16 O 13 C 18 O proportions in the polar vortex show correlations with long-lived stratospheric tracer and bulk isotope abundances opposite to those observed at midlatitudes and, thus, opposite to those easily explained by O( 1 D)+CO 2 . We believe the most plausible explanation for this meridional variation is either an unrecognized isotopic fractionation associated with the mesospheric photochemistry of CO 2 or temperature-dependent isotopic exchange on polar stratospheric clouds. Unraveling the ultimate source of stratospheric 16 O 13 C 18 O enrichments may impose additional isotopic constraints on biosphere–atmosphere carbon exchange, biosphere productivity, and their respective responses to climate change.

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confidence: 99%

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Yeung¹,

Affek

Hoag³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…Provided that all of the O atoms in the CO* 3 activated complex are equivalent (12,13), the appropriate chemical rate coefficients are as follows:…”

Section: Mechanismmentioning

confidence: 99%

“…Yung et al (13), for example, have suggested that the upwelling of tropospheric air from the tropics along with downwelling near 30°N could dilute the magnitude of the fractionation induced by photochemistry. It is beyond the scope of this work to provide a detailed explanation of the effect of transport on the isotopic composition of CO 2 .…”

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confidence: 99%

“…Higher in the mesosphere, we discover that the photolysis of 16 biogeochemical cycles ͉ CO2 ͉ mesosphere ͉ stratosphere O f the many trace molecules that can be used to examine atmospheric transport processes and chemistry [e.g., CH 4 , N 2 O, SF 6 , and the chlorofluorocarbons (CFCs)], carbon dioxide is unique in the middle atmosphere, because of its high abundance [Ϸ370 parts per million by volume (ppmv) in the stratosphere, dropping to Ϸ100 ppmv at the homopause]. The massindependent isotopic fractionation of oxygen first discovered in ozone (1)(2)(3)(4)(5)) is thought to be partially transferred to carbon dioxide (3,(6)(7)(8)(9)(10)(11) via the reaction O( 1 D) ϩ CO 2 in the middle atmosphere (12,13). Indeed, whereas the reactions of trace molecules with O( 1 D) usually lead to their destruction (14), the O( 1 D) ϩ CO 2 reaction regenerates carbon dioxide.…”

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confidence: 99%

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Oxygen isotopic composition of carbon dioxide in the middle atmosphere

Liang

Blake

Lewis

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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The isotopic composition of long-lived trace molecules provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 parts per million by volume (ppmv) in the mesosphere. Here, we successfully reproduce the isotopic composition of CO 2 in the middle atmosphere, which has not been previously reported. The mass-independent fractionation of oxygen in CO 2 can be satisfactorily explained by the exchange reaction with O( 1 D). In the stratosphere, the major source of O( 1 D) is O3 photolysis. Higher in the mesosphere, we discover that the photolysis of 16 biogeochemical cycles ͉ CO2 ͉ mesosphere ͉ stratosphere O f the many trace molecules that can be used to examine atmospheric transport processes and chemistry [e.g., CH 4 , N 2 O, SF 6 , and the chlorofluorocarbons (CFCs)], carbon dioxide is unique in the middle atmosphere, because of its high abundance [Ϸ370 parts per million by volume (ppmv) in the stratosphere, dropping to Ϸ100 ppmv at the homopause]. The massindependent isotopic fractionation of oxygen first discovered in ozone (1-5) is thought to be partially transferred to carbon dioxide (3, 6-11) via the reaction O( 1 D) ϩ CO 2 in the middle atmosphere (12, 13). Indeed, whereas the reactions of trace molecules with O( 1 D) usually lead to their destruction (14) ) than those seen at 30°N over a similar altitude range and a slope of m ϭ 1.72 Ϯ 0.22 (2 ). Over smaller altitude intervals, a similar analysis yields m ϭ 2.06 Ϯ 1.16 (2 ) for samples from the Arctic vortex (6) and 1.64 Ϯ 0.38 (2 ) from the lower stratosphere (7). Slopes near 1.6-1.7 have been successfully reproduced in laboratory photochemical experiments under approximately stratospheric conditions (17).Despite the large uncertainties in m, induced by the challenges associated with the sample collection and mass spectrometry of middle atmospheric O 3 (2, 5) and CO 2 (8, 10, 11), it is worth examining the potential sources of variation in the isotopic composition of carbon dioxide, both to better understand the atmosphere and as a guide for future observations. Yung et al.(13), for example, have suggested that the upwelling of tropospheric air from the tropics along with downwelling near 30°N could dilute the magnitude of the fractionation induced by photochemistry. It is beyond the scope of this work to provide a detailed explanation of the effect of transport on the isotopic composition of CO 2 . Briefly, the key concept is the ''age of air,'' with the clock being set to zero at the tropopause. As the air parcel travels to the middle atmosphere, it ages, and there is more time for photochemical equilibrium to be reached. Morgan et al. (18) discuss these issues at length and give a heuristic relation between the intrinsic enrichment factor ( ) and the resulting isotopic composition (␦) for the one-dimensional (1D) diffusion-limited transport case:where r ϭ chem /4 trans with chem ϭ chemical lifetime (here the isotopic exchange time) and trans ϭ transport time (here...

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“…(iv) HO x that receives the oxygen isotope signature from NO x : (Yung et al, 1991(Yung et al, , 1997Barth and Zahn, 1997). In the case of H 2 O, O( 1 D) is only weakly involved in the oxygen isotope transfer (Table 6).…”

Section: The Formation Of New Oh Bondsmentioning

confidence: 99%

Modelling the budget of middle atmospheric water vapour isotopes

Zahn¹,

Franz

Bechtel

et al. 2006

Atmos. Chem. Phys.

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Abstract.A one-dimensional chemistry model is applied to study the stable hydrogen (D) and stable oxygen isotope ( 17 O, 18 O) composition of water vapour in stratosphere and mesosphere. In the troposphere, this isotope composition is determined by "physical" fractionation effects, that are phase changes (e.g. during cloud formation), diffusion processes (e.g. during evaporation from the ocean), and mixing of air masses. Due to these processes water vapour entering the stratosphere first shows isotope depletions in D/H relative to ocean water, which are ∼5 times of those in 18 In the stratosphere the known mass-independent fractionation (MIF) signal in O 3 is in a first step transferred to the NO x family and only in a second step to HO x and H 2 O. In contrast to CO 2 , O( 1 D) only plays a minor role in this MIF transfer. The major uncertainty in our calculation arises from poorly quantified isotope exchange reaction rate coefficients and kinetic isotope fractionation factors.

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Carbon dioxide in the atmosphere: Isotopic exchange with ozone and its use as a tracer in the middle atmosphere

Abstract: Abstract. Atmospheric heavy ozone is enriched in the isotopes

Cited by 102 publications

References 25 publications

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Oxygen isotopic composition of carbon dioxide in the middle atmosphere

Modelling the budget of middle atmospheric water vapour isotopes

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Carbon dioxide in the atmosphere: Isotopic exchange with ozone and its use as a tracer in the middle atmosphere

Abstract: Abstract. Atmospheric heavy ozone is enriched in the isotopes

Cited by 102 publications

References 25 publications

Large and unexpected enrichment in stratospheric 16 O 13 C 18 O and its meridional variation

Large and unexpected enrichment in stratospheric 16 O 13 C 18 O and its meridional variation

Oxygen isotopic composition of carbon dioxide in the middle atmosphere

Modelling the budget of middle atmospheric water vapour isotopes

Contact Info

Product

Resources

About

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation