Unexpected Changes to the Global Methane Budget over the Past 2000 Years

Ferretti, D. F.; Miller, J. B.; White, James W. C.; Etheridge, D. M.; Lassey, Keith R.; Lowe, David C.; Meure, Cecilia MacFarling; Dreier, Mark F.; Trudinger, C. M.; Ommen, T. D. van; Langenfelds, R. L.

doi:10.1126/science.1115193

Cited by 337 publications

(410 citation statements)

References 26 publications

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“…This period of low CO 2 coincides with high ı 13 C interpreted by the KFDD as terrestrial uptake, which could be caused by a decrease of the Northern Hemispheric or global surface temperature [Mann et al, 2008;Oppo et al, 2009] Trudinger et al [1999] suggested that the lower temperature reduced both the release of CO 2 (soil respiration) and the uptake (photosynthesis) of CO 2 by the terrestrial biosphere, with the respiration reduction dominating, causing the terrestrial biosphere to accumulate carbon. Lower atmospheric CH 4 was found to be a likely result of land surface cooling during that period [Etheridge et al, 1998;Ferretti et al, 2006;Mitchell et al, 2011].…”

Section: Preindustrialmentioning

confidence: 99%

A revised 1000 year atmospheric δ¹³C‐CO₂ record from Law Dome and South Pole, Antarctica

et al. 2013

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[1] We present new measurements of ı 13 C of CO 2 extracted from a high-resolution ice core from Law Dome (East Antarctica), together with firn measurements performed at Law Dome and South Pole, covering the last 150 years. Our analysis is motivated by the need to better understand the role and feedback of the carbon (C) cycle in climate change, by advances in measurement methods, and by apparent anomalies when comparing ice core and firn air ı 13 C records from Law Dome and South Pole. We demonstrate improved consistency between Law Dome ice, South Pole firn, and the Cape Grim (Tasmania) atmospheric ı 13 C data, providing evidence that our new record reliably extends direct atmospheric measurements back in time. We also show a revised version of early ı 13 C measurements covering the last 1000 years, with a mean preindustrial level of -6.50 . Finally, we use a Kalman Filter Double Deconvolution to infer net natural CO 2 fluxes between atmosphere, ocean, and land, which cause small ı 13 C deviations from the predominant anthropogenically induced ı 13 C decrease. The main features found from the previous ı 13 C record are confirmed, including the ocean as the dominant cause for the 1940 A.D. CO 2 leveling. Our new record provides a solid basis for future investigation of the causes of decadal to centennial variations of the preindustrial atmospheric CO 2 concentration. Those causes are of potential significance for predicting future CO 2 levels and when attempting atmospheric verification of recent and future global carbon emission mitigation measures through Coupled Climate Carbon Cycle Models.

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Section: Preindustrialmentioning

confidence: 99%

A revised 1000 year atmospheric δ¹³C‐CO₂ record from Law Dome and South Pole, Antarctica

et al. 2013

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“…For all measured parameters, we chose to state the uncertainty with the highest value, independent of the method from which it was derived. We therefore conclude a measurement uncertainty of 0.09 ‰ for δ 13 C-CH 4 (BFI), 0.6 ‰ for δ 15 N-N 2 O (QCS) and 0.7 ‰ for δ 18 O-N 2 O (BFI), which is comparable to or better than those of Sowers et al (2003), Ferretti et al (2005), Schaefer and Whiticar (2007), Behrens et al (2008), Sowers (2009), Sapart et al (2011) and Melton et al (2011b).…”

Section: Precision Of the Setupmentioning

confidence: 86%

“…Brenninkmeijer et al (2003) describe how the isotope fractionation of specific source and sink processes affect the integrated isotopic composition of the respective trace gases in the atmosphere. In an inverse approach, ice core isotope records of CH 4 and N 2 O provide distinct constraints on biogeochemical processes that can be linked to the variability observed in the CH 4 and N 2 O mixing ratios on decadal to millennial timescales (Sowers et al, 2003(Sowers et al, , 2005Sowers, 2006Sowers, , 2009Ferretti et al, 2005;Schaefer et al, 2006;Bock et al, 2010b;Melton et al, 2011a;Sapart et al, 2012). Because ice core records of CH 4 and N 2 O isotopic composition indicate the natural response of specific greenhouse gas sinks and sources to palaeoclimate changes, this information is of great interest to global warming predictions.…”

Section: P Sperlich Et Al: Ch 4 and N 2 O Isotopes In Ice Core Samplesmentioning

confidence: 99%

An automated GC-C-GC-IRMS setup to measure palaeoatmospheric δ13C-CH4, δ15N-N2O and δ18O-N2O in one ice core sample

et al. 2013

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Abstract. Air bubbles in ice core samples represent the only opportunity to study the mixing ratio and isotopic variability of palaeoatmospheric CH4 and N2O. The highest possible precision in isotope measurements is required to maximize the resolving power for CH4 and N2O sink and source reconstructions. We present a new setup to measure δ13C-CH4, δ15N-N2O and δ18O-N2O isotope ratios in one ice core sample and with one single IRMS instrument, with a precision of 0.09, 0.6 and 0.7‰, respectively, as determined on 0.6–1.6 nmol CH4 and 0.25–0.6 nmol N2O. The isotope ratios are referenced to the VPDB scale (δ13C-CH4), the N2-air scale (δ15N-N2O) and the VSMOW scale (δ18O-N2O). Ice core samples of 200–500 g are melted while the air is constantly extracted to minimize gas dissolution. A helium carrier gas flow transports the sample through the analytical system. We introduce a new gold catalyst to oxidize CO to CO2 in the air sample. CH4 and N2O are then separated from N2, O2, Ar and CO2 before they get pre-concentrated and separated by gas chromatography. A combustion unit is required for δ13C-CH4 analysis, which is equipped with a constant oxygen supply as well as a post-combustion trap and a post-combustion GC column (GC-C-GC-IRMS). The post-combustion trap and the second GC column in the GC-C-GC-IRMS combination prevent Kr and N2O interferences during the isotopic analysis of CH4-derived CO2. These steps increase the time for δ13C-CH4 measurements, which is used to measure δ15N-N2O and δ18O-N2O first and then δ13C-CH4. The analytical time is adjusted to ensure stable conditions in the ion source before each sample gas enters the IRMS, thereby improving the precision achieved for measurements of CH4 and N2O on the same IRMS. The precision of our measurements is comparable to or better than that of recently published systems. Our setup is calibrated by analysing multiple reference gases that were injected over bubble-free ice samples. We show that our measurements of δ13C-CH4 in ice core samples are generally in good agreement with previously published data after the latter have been corrected for krypton interferences.

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“…Etheridge et al 1998) as well as firn air and ice cores (Ferretti et al 2005;Sowers et al 2005) show methane became isotopically heavier during the twentieth century (values increasing from K49‰ to just above K47‰). This implies a shift in the balance of sources towards those that are isotopically heavy (fossil and pyrogenic) in comparison with the isotopically light biogenic sources.…”

Section: The Last 2000 Yearsmentioning

confidence: 99%

Methane and nitrous oxide in the ice core record

Wolff

Spahni

2007

Phil. Trans. R. Soc. A.

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Polar ice cores contain, in trapped air bubbles, an archive of the concentrations of stable atmospheric gases. Of the major non-CO 2 greenhouse gases, methane is measured quite routinely, while nitrous oxide is more challenging, with some artefacts occurring in the ice and so far limited interpretation. In the recent past, the ice cores provide the only direct measure of the changes that have occurred during the industrial period; they show that the current concentration of methane in the atmosphere is far outside the range experienced in the last 650 000 years; nitrous oxide is also elevated above its natural levels. There is controversy about whether changes in the pre-industrial Holocene are natural or anthropogenic in origin. Changes in wetland emissions are generally cited as the main cause of the large glacial-interglacial change in methane. However, changing sinks must also be considered, and the impact of possible newly described sources evaluated. Recent isotopic data appear to finally rule out any major impact of clathrate releases on methane at these time-scales. Any explanation must take into account that, at the rapid Dansgaard-Oeschger warmings of the last glacial period, methane rose by around half its glacial-interglacial range in only a few decades. The recent EPICA Dome C (Antarctica) record shows that methane tracked climate over the last 650 000 years, with lower methane concentrations in glacials than interglacials, and lower concentrations in cooler interglacials than in warmer ones. Nitrous oxide also shows DansgaardOeschger and glacial-interglacial periodicity, but the pattern is less clear.

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Unexpected Changes to the Global Methane Budget over the Past 2000 Years

Cited by 337 publications

References 26 publications

A revised 1000 year atmospheric δ¹³C‐CO₂ record from Law Dome and South Pole, Antarctica

A revised 1000 year atmospheric δ¹³C‐CO₂ record from Law Dome and South Pole, Antarctica

An automated GC-C-GC-IRMS setup to measure palaeoatmospheric δ<sup>13</sup>C-CH<sub>4</sub>, δ<sup>15</sup>N-N<sub>2</sub>O and δ<sup>18</sup>O-N<sub>2</sub>O in one ice core sample

Methane and nitrous oxide in the ice core record

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Unexpected Changes to the Global Methane Budget over the Past 2000 Years

Cited by 337 publications

References 26 publications

A revised 1000 year atmospheric δ13C‐CO2 record from Law Dome and South Pole, Antarctica

A revised 1000 year atmospheric δ13C‐CO2 record from Law Dome and South Pole, Antarctica

An automated GC-C-GC-IRMS setup to measure palaeoatmospheric δ&lt;sup&gt;13&lt;/sup&gt;C-CH&lt;sub&gt;4&lt;/sub&gt;, δ&lt;sup&gt;15&lt;/sup&gt;N-N&lt;sub&gt;2&lt;/sub&gt;O and δ&lt;sup&gt;18&lt;/sup&gt;O-N&lt;sub&gt;2&lt;/sub&gt;O in one ice core sample

Methane and nitrous oxide in the ice core record

Contact Info

Product

Resources

About

A revised 1000 year atmospheric δ¹³C‐CO₂ record from Law Dome and South Pole, Antarctica

A revised 1000 year atmospheric δ¹³C‐CO₂ record from Law Dome and South Pole, Antarctica

An automated GC-C-GC-IRMS setup to measure palaeoatmospheric δ<sup>13</sup>C-CH<sub>4</sub>, δ<sup>15</sup>N-N<sub>2</sub>O and δ<sup>18</sup>O-N<sub>2</sub>O in one ice core sample