Atmospheric methane isotope records covering the Holocene period

Research output: Contribution to journalArticle

48 Citations (Scopus)

Abstract

Records of the 13C/12C (δ13CH4) and the D/H (δ DCH4) ratio of atmospheric methane were recovered from the GISP II ice core covering the last 11,000 years. All totaled, 76 samples were analyzed for δ13CH4 and 65 adjacent samples for δ DCH4 between 86 and 1696 m below surface (mbs) providing a temporal resolution that is better than one pair of isotope samples every 200 years. The δ13CH4 record exhibits a decreasing trend throughout the Holocene beginning at -46.4‰ at 11,000 years BP (BP defined as 1950 AD = 11 ka), and decreasing to -48.4‰ at 1 ka. The 2‰ δ13CH4 drop is likely to be a combination of increased CH4 emissions from Arctic lake ecosystems and an increase in the ratio of C3/C4 plants in wetlands where CH4 is emitted. The C3/C4 ratio increase is the result of increasing CO2 values throughout the Holocene combined with the activation of high NH ecosystems that are predominantly C3 type. The δ DCH4 record over the early-mid Holocene shows a slightly decreasing trend that would be predicted by increased CH4 emissions from Arctic lakes. Between 4 ka and 1 ka, δ DCH4 values increase by ∼20‰ while δ13CH4 values remain effectively constant. There are at least two plausible explanations for this 20‰ δ DCH4 shift. First, a dramatic shift in CH4 emissions from higher latitudes to the tropics could account for the observed shift though the lack of a corresponding δ13CH4 shift is difficult to reconcile. Secondly, a gradual release of marine clathrates with enriched δ DCH4 values explains both the δ DCH4 and δ13CH4 records over this period.

Original languageEnglish (US)
Pages (from-to)213-221
Number of pages9
JournalQuaternary Science Reviews
Volume29
Issue number1-2
DOIs
StatePublished - Jan 1 2010

Fingerprint

methane
isotopes
Holocene
isotope
Arctic
Values
Arctic region
clathrate
C4 plant
lake ecosystem
tropics
trend
wetland
lakes
ice core
ecosystems
activation
C4 plants
C3 plants
sampling

All Science Journal Classification (ASJC) codes

  • Global and Planetary Change
  • Archaeology
  • Ecology, Evolution, Behavior and Systematics
  • Archaeology
  • Geology

Cite this

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abstract = "Records of the 13C/12C (δ13CH4) and the D/H (δ DCH4) ratio of atmospheric methane were recovered from the GISP II ice core covering the last 11,000 years. All totaled, 76 samples were analyzed for δ13CH4 and 65 adjacent samples for δ DCH4 between 86 and 1696 m below surface (mbs) providing a temporal resolution that is better than one pair of isotope samples every 200 years. The δ13CH4 record exhibits a decreasing trend throughout the Holocene beginning at -46.4‰ at 11,000 years BP (BP defined as 1950 AD = 11 ka), and decreasing to -48.4‰ at 1 ka. The 2‰ δ13CH4 drop is likely to be a combination of increased CH4 emissions from Arctic lake ecosystems and an increase in the ratio of C3/C4 plants in wetlands where CH4 is emitted. The C3/C4 ratio increase is the result of increasing CO2 values throughout the Holocene combined with the activation of high NH ecosystems that are predominantly C3 type. The δ DCH4 record over the early-mid Holocene shows a slightly decreasing trend that would be predicted by increased CH4 emissions from Arctic lakes. Between 4 ka and 1 ka, δ DCH4 values increase by ∼20‰ while δ13CH4 values remain effectively constant. There are at least two plausible explanations for this 20‰ δ DCH4 shift. First, a dramatic shift in CH4 emissions from higher latitudes to the tropics could account for the observed shift though the lack of a corresponding δ13CH4 shift is difficult to reconcile. Secondly, a gradual release of marine clathrates with enriched δ DCH4 values explains both the δ DCH4 and δ13CH4 records over this period.",
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Atmospheric methane isotope records covering the Holocene period. / Sowers, Todd Anthony.

In: Quaternary Science Reviews, Vol. 29, No. 1-2, 01.01.2010, p. 213-221.

Research output: Contribution to journalArticle

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