Changes in the global atmospheric methane budget over the last decades inferred from <sup>13</sup>C and D isotopic analysis of Antarctic firn air

Bräunlich, Maya; Aballain, Olivier; Marik, Thomas; Jöckel, Patrick; Brenninkmeijer, Carl A. M.; Chappellaz, J.; Barnola, Jean-Marc; Mulvaney, Robert; Sturges, William T.

doi:10.1029/2001jd900190

Cited by 52 publications

(67 citation statements)

References 41 publications

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“…For comparison with the PSU lab, three archived firn air samples were used. Two samples (IMAU402 and IMAU724) from the 1999 drilling at Dome C, Antarctica (Bräunlich et al, 2001) and one sample from Svalbard (IMAU490). The fourth sample corresponds to highly enriched CH 4 (IMAU403).…”

Section: Methane Intercomparisonmentioning

confidence: 99%

“…Isotope measurements can be used as a tool to distinguish contributions from individual sources (Brenninkmeijer et al, 2003) and changes in the sink strength. Measurements from the recent past have been obtained from atmospheric measurement networks (Quay et al, 1999;Miller et al, 2002), from archived air samples (Röckmann and Levin, 2005) and from firn air (Bräunlich et al, 2001;Ishijima et al, 2007). To obtain information on past atmospheric conditions, ice core air analyses are required.…”

Section: Introductionmentioning

confidence: 99%

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Simultaneous stable isotope analysis of methane and nitrous oxide on ice core samples

et al. 2011

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Abstract. Methane and nitrous oxide are important greenhouse gases which show a strong increase in atmospheric mixing ratios since pre-industrial time as well as large variations during past climate changes. The understanding of their biogeochemical cycles can be improved using stable isotope analysis. However, high-precision isotope measurements on air trapped in ice cores are challenging because of the high susceptibility to contamination and fractionation.Here, we present a dry extraction system for combined CH 4 and N 2 O stable isotope analysis from ice core air, using an ice grating device. The system allows simultaneous analysis of δD(CH 4 ) or δ 13 C(CH 4 ), together with δ 15 N(N 2 O), δ 18 O(N 2 O) and δ 15 N(NO + fragment) on a single ice core sample, using two isotope mass spectrometry systems. The optimum quantity of ice for analysis is about 600 g with typical "Holocene" mixing ratios for CH 4 and N 2 O. In this case, the reproducibility (1σ ) is 2.1 ‰ for δD(CH 4 ), 0.18 ‰ for δ 13 C(CH 4 ), 0.51 ‰ for δ 15 N(N 2 O), 0.69 ‰ for δ 18 O(N 2 O) and 1.12 ‰ for δ 15 N(NO + fragment). For smaller amounts of ice the standard deviation increases, particularly for N 2 O isotopologues. For both gases, small-scale intercalibrations using air and/or ice samples have been carried out in collaboration with other institutes that are currently involved in isotope measurements of ice core air. Significant differences are shown between the calibration scales, but those offsets are consistent and can therefore be corrected for.

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Section: Methane Intercomparisonmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Simultaneous stable isotope analysis of methane and nitrous oxide on ice core samples

et al. 2011

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“…In the case of isotopic ratios, the use of a linear inverse technique (Rommelaere et al, 1997) have been thought impossible due to nonlinearities associated with modeling two isotopes simultaneously (Sowers et al, 2005). Approximate methods based on separating the effects of the two isotopes (Trudinger et al, 1997;Sapart et al, 2012;Wang et al, 2012) or Monte-Carlo like testing of numerous atmospheric scenarios (Bräunlich et al, 2001;Sowers et al, 2005) have been developed. The paper is organized as follows.…”

Section: Introductionmentioning

confidence: 99%

Input Estimation from Sparse Measurements in LPV Systems and Isotopic Ratios in Polar Firns

Witrant

Martinerie

2013

IFAC Proceedings Volumes

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Abstract:We adress the problem of inverse input reconstruction for linear parameter-varying (LPV) systems when only a limited amount of data (i.e. sparse measurements at final time) is available. We include the LPV property by deriving a time-varying Green's function that models the input/output behavior. The estimation is achieved by solving a least-squares optimization problem parameterized in terms of the input rugosity (regularization term) to take into account the under-constrained nature of the problem. Several automatic tuning methods for the rugosity are described, based on stochastic analysis of the data. A new LPV model is derived for the isotopic ratio of chemical species and our results are applied to the atmospheric history reconstruction of trace gases from polar firn measurements, a problem of prime interest in the environmental sciences community.

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“…A few studies investigated the decadal evolution of methane budget (Francey et al, 1999;Lassey et al, 2000;Braünlich et al, 2001;Bousquet et al, 2006), focusing mainly on the period before 2000.…”

Section: Introductionmentioning

confidence: 99%

Interpreting methane variations in the past two decades using measurements of CH<sub>4</sub> mixing ratio and isotopic composition

et al. 2011

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Abstract. The availability δ 13 C-CH 4 measurements from atmospheric samples has significantly improved in recent years, which allows the construction of time series spanning up to about 2 decades. We have used these measurements to investigate the cause of the methane growth rate decline since 1980, with a special focus on the period 1998-2006 when the methane growth came to a halt. The constraints provided by the CH 4 and δ 13 C-CH 4 measurements are used to construct hypothetical source and sink scenarios, which are translated into corresponding atmospheric concentrations using the atmospheric transport model TM3 for evaluation against the measurements. The base scenario, composed of anthropogenic emissions according to EDGAR 4.0, constant emissions from natural sources, and a constant atmospheric lifetime, overestimates the observed global growth rates of CH 4 and δ 13 C-CH 4 by, respectively, 10 ppb yr −1 and 0.02 ‰ yr −1 after the year 2000. It proves difficult to repair this inconsistency by modifying trends in emissions only, notably because a temporary reduction of isotopically light sources, such as natural wetlands, leads to a further increase of δ 13 C-CH 4 . Furthermore, our results are difficult to reconcile with the estimated increase of 5 Tg CH 4 yr −1 in emissions from fossil fuel use in the period 2000-2005. On the other hand, we find that a moderate (less than 5% per decade) increase in the global OH concentration can bring the model in agreement with the measurements for plausible emission scenarios. This study demonstrates the value of global monitoring of methane isotopes, and calls for further investigaCorrespondence to: G. Monteil (g.monteil@uu.nl) tion into the role OH and anthropogenic emissions to further improve our understanding of methane variations in recent years.

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Changes in the global atmospheric methane budget over the last decades inferred from ¹³C and D isotopic analysis of Antarctic firn air

Abstract: Abstract.The atmospheric trend of methane isotopic ratios since the mid20th century has been reconstructed from Antarctic firn air. High volume air samples were extracted at several depth levels at two sites in East Antarctica. Methane concentration and its

Cited by 52 publications

References 41 publications

Simultaneous stable isotope analysis of methane and nitrous oxide on ice core samples

Simultaneous stable isotope analysis of methane and nitrous oxide on ice core samples

Input Estimation from Sparse Measurements in LPV Systems and Isotopic Ratios in Polar Firns

Interpreting methane variations in the past two decades using measurements of CH<sub>4</sub> mixing ratio and isotopic composition

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Changes in the global atmospheric methane budget over the last decades inferred from 13C and D isotopic analysis of Antarctic firn air

Abstract: Abstract.The atmospheric trend of methane isotopic ratios since the mid20th century has been reconstructed from Antarctic firn air. High volume air samples were extracted at several depth levels at two sites in East Antarctica. Methane concentration and its

Cited by 52 publications

References 41 publications

Simultaneous stable isotope analysis of methane and nitrous oxide on ice core samples

Simultaneous stable isotope analysis of methane and nitrous oxide on ice core samples

Input Estimation from Sparse Measurements in LPV Systems and Isotopic Ratios in Polar Firns

Interpreting methane variations in the past two decades using measurements of CH&lt;sub&gt;4&lt;/sub&gt; mixing ratio and isotopic composition

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Changes in the global atmospheric methane budget over the last decades inferred from ¹³C and D isotopic analysis of Antarctic firn air

Interpreting methane variations in the past two decades using measurements of CH<sub>4</sub> mixing ratio and isotopic composition