Carbon and hydrogen isotopic compositions of stratospheric methane

1. High-precision observations from the NASA ER-2 aircraft

A. L. Rice, S. C. Tyler, M. C. McCarthy, K. A. Boering, Elliot L Atlas

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Measurements of δ13C and δD of atmospheric CH4 from whole air samples collected in the upper troposphere and lower stratosphere aboard the NASA ER-2 aircraft during the SOLVE (2000), POLARIS (1997), and STRAT (1996) campaigns are reported. Samples cover latitudes from 1°S to 89°N and altitudes from 11 to 21 km, providing CH4 mixing ratios that range from 1744 to 716 ppbv. Measurements of isotope ratios were made by continuous-flow gas chromatography isotope ratio mass spectrometry which provides high-precision analyses on 60 ml aliquots of air. These measurements comprise the first upper atmosphere isotopic CH4 data set to date using this technique and the most extensive with respect to latitude and season in any case. Values of δ13C-CH4 on the V-PDB scale range from -47.28‰ near the tropical tropopause to -34.05‰ in the high northern latitude stratosphere. Values of δD on the V-SMOW scale range from -90.9‰ to +26.4‰. Correlations of isotope ratios with CH4 mixing ratios show enrichment in the heavy isotopes as CH4 mixing ratios decrease due to kinetic isotope effects associated with oxidation by reaction with OH, Cl, and O(1D). Empirical fractionation factors are found to be highly dependent on the range of CH4 mixing ratio considered, increasing with decreasing mixing ratio. Systematic nonlinearity in a Rayleigh fractionation model suggests a range of stratospheric fractionation factors, αstrat C = 1.0108 ± 0.0004 to 1.0204 ± 0.0004 (2σ) and αstrat H = 1.115 ± 0.008 to 1.198 ± 0.008 (2σ), from high to low CH4 mixing ratio, respectively. The variation in α over the range in mixing ratios reflect changes in partitioning between CH4 sink reactions in different regions of the stratosphere. In Part 1, these new high-precision observations are discussed and compared with other stratospheric and tropospheric isotope measurements. In Part 2 [McCarthy et al., 2003] the observations are compared with 2-D model results, and implications for the kinetic isotope effects for reactions with OH, Cl, and O(1D) are discussed.

Original languageEnglish (US)
JournalJournal of Geophysical Research C: Oceans
Volume108
Issue number15
StatePublished - Aug 16 2003
Externally publishedYes

Fingerprint

U-2 aircraft
Upper atmosphere
Methane
mixing ratios
Isotopes
mixing ratio
NASA
Hydrogen
aircraft
isotopic composition
Carbon
methane
Aircraft
hydrogen
isotope
carbon
Chemical analysis
isotope ratios
Fractionation
stratosphere

Keywords

  • Carbon isotopes
  • Hydrogen isotopes
  • Methane
  • Methane isotopes
  • Stratospheric methane

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Atmospheric Science
  • Geochemistry and Petrology
  • Geophysics
  • Oceanography
  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Carbon and hydrogen isotopic compositions of stratospheric methane : 1. High-precision observations from the NASA ER-2 aircraft. / Rice, A. L.; Tyler, S. C.; McCarthy, M. C.; Boering, K. A.; Atlas, Elliot L.

In: Journal of Geophysical Research C: Oceans, Vol. 108, No. 15, 16.08.2003.

Research output: Contribution to journalArticle

@article{b0801e7a6974453187e08cab43dc9910,
title = "Carbon and hydrogen isotopic compositions of stratospheric methane: 1. High-precision observations from the NASA ER-2 aircraft",
abstract = "Measurements of δ13C and δD of atmospheric CH4 from whole air samples collected in the upper troposphere and lower stratosphere aboard the NASA ER-2 aircraft during the SOLVE (2000), POLARIS (1997), and STRAT (1996) campaigns are reported. Samples cover latitudes from 1°S to 89°N and altitudes from 11 to 21 km, providing CH4 mixing ratios that range from 1744 to 716 ppbv. Measurements of isotope ratios were made by continuous-flow gas chromatography isotope ratio mass spectrometry which provides high-precision analyses on 60 ml aliquots of air. These measurements comprise the first upper atmosphere isotopic CH4 data set to date using this technique and the most extensive with respect to latitude and season in any case. Values of δ13C-CH4 on the V-PDB scale range from -47.28‰ near the tropical tropopause to -34.05‰ in the high northern latitude stratosphere. Values of δD on the V-SMOW scale range from -90.9‰ to +26.4‰. Correlations of isotope ratios with CH4 mixing ratios show enrichment in the heavy isotopes as CH4 mixing ratios decrease due to kinetic isotope effects associated with oxidation by reaction with OH, Cl, and O(1D). Empirical fractionation factors are found to be highly dependent on the range of CH4 mixing ratio considered, increasing with decreasing mixing ratio. Systematic nonlinearity in a Rayleigh fractionation model suggests a range of stratospheric fractionation factors, αstrat C = 1.0108 ± 0.0004 to 1.0204 ± 0.0004 (2σ) and αstrat H = 1.115 ± 0.008 to 1.198 ± 0.008 (2σ), from high to low CH4 mixing ratio, respectively. The variation in α over the range in mixing ratios reflect changes in partitioning between CH4 sink reactions in different regions of the stratosphere. In Part 1, these new high-precision observations are discussed and compared with other stratospheric and tropospheric isotope measurements. In Part 2 [McCarthy et al., 2003] the observations are compared with 2-D model results, and implications for the kinetic isotope effects for reactions with OH, Cl, and O(1D) are discussed.",
keywords = "Carbon isotopes, Hydrogen isotopes, Methane, Methane isotopes, Stratospheric methane",
author = "Rice, {A. L.} and Tyler, {S. C.} and McCarthy, {M. C.} and Boering, {K. A.} and Atlas, {Elliot L}",
year = "2003",
month = "8",
day = "16",
language = "English (US)",
volume = "108",
journal = "Journal of Geophysical Research: Oceans",
issn = "2169-9275",
publisher = "Wiley-Blackwell",
number = "15",

}

TY - JOUR

T1 - Carbon and hydrogen isotopic compositions of stratospheric methane

T2 - 1. High-precision observations from the NASA ER-2 aircraft

AU - Rice, A. L.

AU - Tyler, S. C.

AU - McCarthy, M. C.

AU - Boering, K. A.

AU - Atlas, Elliot L

PY - 2003/8/16

Y1 - 2003/8/16

N2 - Measurements of δ13C and δD of atmospheric CH4 from whole air samples collected in the upper troposphere and lower stratosphere aboard the NASA ER-2 aircraft during the SOLVE (2000), POLARIS (1997), and STRAT (1996) campaigns are reported. Samples cover latitudes from 1°S to 89°N and altitudes from 11 to 21 km, providing CH4 mixing ratios that range from 1744 to 716 ppbv. Measurements of isotope ratios were made by continuous-flow gas chromatography isotope ratio mass spectrometry which provides high-precision analyses on 60 ml aliquots of air. These measurements comprise the first upper atmosphere isotopic CH4 data set to date using this technique and the most extensive with respect to latitude and season in any case. Values of δ13C-CH4 on the V-PDB scale range from -47.28‰ near the tropical tropopause to -34.05‰ in the high northern latitude stratosphere. Values of δD on the V-SMOW scale range from -90.9‰ to +26.4‰. Correlations of isotope ratios with CH4 mixing ratios show enrichment in the heavy isotopes as CH4 mixing ratios decrease due to kinetic isotope effects associated with oxidation by reaction with OH, Cl, and O(1D). Empirical fractionation factors are found to be highly dependent on the range of CH4 mixing ratio considered, increasing with decreasing mixing ratio. Systematic nonlinearity in a Rayleigh fractionation model suggests a range of stratospheric fractionation factors, αstrat C = 1.0108 ± 0.0004 to 1.0204 ± 0.0004 (2σ) and αstrat H = 1.115 ± 0.008 to 1.198 ± 0.008 (2σ), from high to low CH4 mixing ratio, respectively. The variation in α over the range in mixing ratios reflect changes in partitioning between CH4 sink reactions in different regions of the stratosphere. In Part 1, these new high-precision observations are discussed and compared with other stratospheric and tropospheric isotope measurements. In Part 2 [McCarthy et al., 2003] the observations are compared with 2-D model results, and implications for the kinetic isotope effects for reactions with OH, Cl, and O(1D) are discussed.

AB - Measurements of δ13C and δD of atmospheric CH4 from whole air samples collected in the upper troposphere and lower stratosphere aboard the NASA ER-2 aircraft during the SOLVE (2000), POLARIS (1997), and STRAT (1996) campaigns are reported. Samples cover latitudes from 1°S to 89°N and altitudes from 11 to 21 km, providing CH4 mixing ratios that range from 1744 to 716 ppbv. Measurements of isotope ratios were made by continuous-flow gas chromatography isotope ratio mass spectrometry which provides high-precision analyses on 60 ml aliquots of air. These measurements comprise the first upper atmosphere isotopic CH4 data set to date using this technique and the most extensive with respect to latitude and season in any case. Values of δ13C-CH4 on the V-PDB scale range from -47.28‰ near the tropical tropopause to -34.05‰ in the high northern latitude stratosphere. Values of δD on the V-SMOW scale range from -90.9‰ to +26.4‰. Correlations of isotope ratios with CH4 mixing ratios show enrichment in the heavy isotopes as CH4 mixing ratios decrease due to kinetic isotope effects associated with oxidation by reaction with OH, Cl, and O(1D). Empirical fractionation factors are found to be highly dependent on the range of CH4 mixing ratio considered, increasing with decreasing mixing ratio. Systematic nonlinearity in a Rayleigh fractionation model suggests a range of stratospheric fractionation factors, αstrat C = 1.0108 ± 0.0004 to 1.0204 ± 0.0004 (2σ) and αstrat H = 1.115 ± 0.008 to 1.198 ± 0.008 (2σ), from high to low CH4 mixing ratio, respectively. The variation in α over the range in mixing ratios reflect changes in partitioning between CH4 sink reactions in different regions of the stratosphere. In Part 1, these new high-precision observations are discussed and compared with other stratospheric and tropospheric isotope measurements. In Part 2 [McCarthy et al., 2003] the observations are compared with 2-D model results, and implications for the kinetic isotope effects for reactions with OH, Cl, and O(1D) are discussed.

KW - Carbon isotopes

KW - Hydrogen isotopes

KW - Methane

KW - Methane isotopes

KW - Stratospheric methane

UR - http://www.scopus.com/inward/record.url?scp=1342269842&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=1342269842&partnerID=8YFLogxK

M3 - Article

VL - 108

JO - Journal of Geophysical Research: Oceans

JF - Journal of Geophysical Research: Oceans

SN - 2169-9275

IS - 15

ER -