Carbon and hydrogen isotopic compositions of stratospheric methane: 2. Two‐dimensional model results and implications for kinetic isotope effects

McCarthy, Michael C.; Boering, K. A.; Rice, A. L.; Tyler, S. C.; Connell, Peter S.; Atlas, E.

doi:10.1029/2002jd003183

Cited by 35 publications

(57 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Griffith et al, 2000;Röckmann et al, 2001;McCarthy et al, 2003;Rice et al, 2003;Park et al, 2004;Toyoda et al, 2001), Kaiser et al (2006) presented a detailed interpretation of N 2 O isotope measurements from the majority of balloon samples presented in this study. Similar to N 2 O, the chemical lifetime of CH 4 throughout most of the stratosphere is longer than typical transport times and most of the CH 4 is actually removed in the middle to upper stratosphere.…”

Section: Global Scale Interpretation From the Chemical And Dynamical mentioning

confidence: 71%

“…Ideally, these deviations are constant, but they can also increase or decrease with mixing ratio, as observed. Because of this non-constant deviation, the ER-2 data discussed by Rice et al (2003) and McCarthy et al (2003) show a more pronounced relative vertical increase of δD in the stratosphere, i.e. a generally higher slope of δD(c) relation, and consequently slightly higher KIE D -values are reported by Rice et al (2003) and McCarthy et al (2003).…”

Section: δD Comparisonmentioning

confidence: 85%

“…The classical formal sink partitioning, which is based on the assumption that all sinks act simultaneously, underestimates the contribution from OH, because the KIE values derived in the stratosphere are less influenced by the removal in the lower stratosphere compared to the upper stratosphere. Therefore, global models that include the isotopic composition are needed to derive a reliable sink partitioning from the measurements, similar to the study by McCarthy et al (2003).…”

Section: Discussionmentioning

confidence: 99%

“…In the absence of in situ sources CH 4 mixing ratios decrease strongly in the stratosphere due to the removal by the three chemical (1st order) reactions with OH, O( 1 D) and Cl (Wahlen et al, 1989;Wahlen, 1993;Brenninkmeijer et al, 1995;Irion et al, 1996;Sugawara et al, 1997;Ridal and Siskind, 2002;McCarthy et al, 2003;Rice et al, 2003). Removal of CH 4 by photolysis becomes important only in the mesosphere.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The isotopic composition of methane in the stratosphere: high-altitude balloon sample measurements

et al. 2011

View full text Add to dashboard Cite

Abstract.The isotopic composition of stratospheric methane has been determined on a large suite of air samples from stratospheric balloon flights covering subtropical to polar latitudes and a time period of 16 yr. 154 samples were analyzed for δ 13 C and 119 samples for δD, increasing the previously published dataset for balloon borne samples by an order of magnitude, and more than doubling the total available stratospheric data (including aircraft samples) published to date. The samples also cover a large range in mixing ratio from tropospheric values near 1800 ppb down to only 250 ppb, and the strong isotope fractionation processes accordingly increase the isotopic composition up to δ 13 C = −14 ‰ and δD = +190 ‰, the largest enrichments observed for atmospheric CH 4 so far. When analyzing and comparing kinetic isotope effects (KIEs) derived from single balloon profiles, it is necessary to take into account the residence time in the stratosphere in combination with the observed mixing ratio and isotope trends in the troposphere, and the range of isotope values covered by the individual profile. The isotopic composition of CH 4 in the stratosphere is affected by both chemical and dynamical processes. This severely hampers interpretation of the data in terms of the relative fractions of the three important sink mechanisms (reaction with OH, O( 1 D) and Cl). It is shown that a formal sink partitioning using the measured data severely underestimates the fraction removed by OH, which is likely due to the insensitivity of the measurements to the kinetic fractionation in the lower stratosphere. Full quantitative interpretation of the CH 4 isotope data in terms of the three sink reactions requires a global model.

show abstract

Section: Global Scale Interpretation From the Chemical And Dynamical mentioning

confidence: 71%

Section: δD Comparisonmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The isotopic composition of methane in the stratosphere: high-altitude balloon sample measurements

et al. 2011

View full text Add to dashboard Cite

show abstract

“…Many researchers have reported that measurements of stable isotopic compositions of atmospheric CH 4 are useful for constraining the global CH 4 budget (Quay et al 1991(Quay et al , 1999Lowe et al 1994Lowe et al , 1997Lowe et al , 1999Lassey et al 2000Lassey et al , 2007Snover et al 2000;Miller et al 2002;Morimoto et al 2006), identifying local CH 4 sources (Sugawara et al 1996;Bergamaschi et al 1998;Yamada et al 2005;Tarasova et al 2006), and estimating chemical loss processes of CH 4 in the troposphere (Allan et al 2001a(Allan et al , 2001b(Allan et al , 2005(Allan et al , 2007 and in the stratosphere (Sugawara et al 1997;Wang et al 2002;Rice et al 2003;McCarthy et al 2003). However, isotopic measurements of atmospheric CH 4 for use with an o¿ine technique have never been expanded to the extent of concentration measurements because of their laborious procedures and their necessity for large volume of air samples (Quay et al 1991(Quay et al , 1999Lowe et al 1994Lowe et al , 1997Lowe et al , 1999Sugawara et al 1996Sugawara et al , 1997.…”

Section: Introductionmentioning

confidence: 99%

A High-precision Measurement System for Carbon and Hydrogen Isotopic Ratios of Atmospheric Methane and Its Application to Air Samples Collected in the Western Pacific Region

Umezawa

Aoki

Nakazawa

et al. 2009

Journal of the Meteorological Society of Japan

View full text Add to dashboard Cite

In order to study temporal and spatial variations of atmospheric CH 4 quantitatively, we originally improved a measurement system for carbon and hydrogen isotopic ratios (d 13 C and dD) of CH 4 to attain high-precision measurements. By analyzing 100 mL aliquots of an ambient air sample, the precision of our system is 0.080 for d 13 C and 2.20 for dD (1s), which are one of the highest precisions reported so far. The system consists mainly of a CH 4 preconcentration device and a continuous-flow gas chromatograph isotope ratio mass spectrometer equipped with a combustion furnace and a pyrolysis furnace for measurements of d 13 C and dD. The preconcentration trap temperature was maintained at À130 G 1 C during collection of CH 4 from the air sample by passing it through the trap, then at À83 G 1 C while remaining air components such as N 2 and O 2 except for CH 4 escaped, and finally at 100 G 1 C for CH 4 elusion. The isotopic values are measured on a mass spectrometer, relative to respective reference gases. For this study, the d 13 C and dD values of the reference gases were calibrated against our primary standards provided by the IAEA: our d 13 C primary standard is NBS18, whereas our dD primary standards are V-SMOW and SLAP. To ensure the long-term stability and reproducibility of our measurement system, a calibrated whole air stored in a high-pressure cylinder, which was called ''test gas,'' was measured at least twice on each day when sample measurements were made. To measure small air samples, such as those extracted from ice cores, we also examined the relation between the sample size and the measured value of d 13 C and dD: gradual enrichment of the d 13 C occurred with decreasing CH 4 content less than 8 nmol whereas no such e¤ect could be seen for the dD. Furthermore, preliminary results of latitudinal distributions of d 13 C and dD were discussed along with CH 4 concentrations obtained by our shipboard air-sampling program.

show abstract

Spatially Resolved Isotopic Source Signatures of Wetland Methane Emissions

Ganesan

Stell

Gedney

et al. 2018

Geophysical Research Letters

108

View full text Add to dashboard Cite

We present the first spatially resolved wetland δ13C(CH4) source signature map based on data characterizing wetland ecosystems and demonstrate good agreement with wetland signatures derived from atmospheric observations. The source signature map resolves a latitudinal difference of ~10‰ between northern high‐latitude (mean −67.8‰) and tropical (mean −56.7‰) wetlands and shows significant regional variations on top of the latitudinal gradient. We assess the errors in inverse modeling studies aiming to separate CH4 sources and sinks by comparing atmospheric δ13C(CH4) derived using our spatially resolved map against the common assumption of globally uniform wetland δ13C(CH4) signature. We find a larger interhemispheric gradient, a larger high‐latitude seasonal cycle, and smaller trend over the period 2000–2012. The implication is that erroneous CH4 fluxes would be derived to compensate for the biases imposed by not utilizing spatially resolved signatures for the largest source of CH4 emissions. These biases are significant when compared to the size of observed signals.

show abstract

Carbon and hydrogen isotopic compositions of stratospheric methane: 2. Two‐dimensional model results and implications for kinetic isotope effects

Cited by 35 publications

References 57 publications

The isotopic composition of methane in the stratosphere: high-altitude balloon sample measurements

The isotopic composition of methane in the stratosphere: high-altitude balloon sample measurements

A High-precision Measurement System for Carbon and Hydrogen Isotopic Ratios of Atmospheric Methane and Its Application to Air Samples Collected in the Western Pacific Region

Spatially Resolved Isotopic Source Signatures of Wetland Methane Emissions

Contact Info

Product

Resources

About