期刊
EARTH AND PLANETARY SCIENCE LETTERS
卷 368, 期 -, 页码 9-19出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.epsl.2013.02.034
关键词
methane; ice core; Greenland; cryobiology; firn; late Holocene climate
资金
- US National Science Foundation (NSF) Office of Polar Programs (OPP) [0944552, 0909541]
- NSF Partnerships in International Research and Education (PIRE) Grant [0968391]
- French ANR RPD COCLICO [ANR-10-RPDOC-002-01]
- ANR NEEM [ANR-07-VULN-09-001]
- European Research Council under the European Community [291062]
- FNRS-CFB in Belgium
- FWO in Belgium
- Canada NRCan/GSC
- China CAS
- Denmark FIST
- France IPEV
- France CNRS/INSU
- France CEA
- France ANR
- Germany AWI
- Iceland RannIs
- Japan NIPR
- Korea KOPRI
- The Netherlands NWO/ALW
- Sweden VR
- Switzerland SNF
- United Kingdom NERC
- USA US NSF, OPP
- European Research Council (ERC) [291062] Funding Source: European Research Council (ERC)
- Office of Polar Programs (OPP)
- Directorate For Geosciences [0806414, 944348] Funding Source: National Science Foundation
- Office of Polar Programs (OPP)
- Directorate For Geosciences [0944552, 0909541] Funding Source: National Science Foundation
Ancient air trapped inside bubbles in ice cores can now be analysed for methane concentration utilising a laser spectrometer coupled to a continuous melter system. We present a new ultra-high resolution record of atmospheric methane variability over the last 1800 yr obtained from continuous analysis of a shallow ice core from the North Greenland Eemian project (NEEM-2011-S1) during a 4-week laboratory-based measurement campaign. Our record faithfully replicates the form and amplitudes of multi-decadal oscillations previously observed in other ice cores and demonstrates the detailed depth resolution (5.3 cm), rapid acquisition time (30 m day(-1)) and good long-term reproducibility (2.6%, 2 sigma) of the continuous measurement technique. In addition, we report the detection of high frequency ice core methane signals of non-atmospheric origin. Firstly, measurements of air from the firn-ice transition region and an interval of ice core dating from 1546-1560 AD (gas age) resolve apparently quasi-annual scale methane oscillations. Traditional gas chromatography measurements on discrete ice samples confirm these signals and indicate peak-to-peak amplitudes of ca. 22 parts per billion (ppb). We hypothesise that these oscillations result from staggered bubble close-off between seasonal layers of contrasting density during time periods of sustained multi-year atmospheric methane change. Secondly, we report the detection of abrupt (20-100 cm depth interval), high amplitude (35-80 ppb excess) methane spikes in the NEEM ice that are reproduced by discrete measurements. We show for the first time that methane spikes present in thin and infrequent layers in polar, glacial ice are accompanied by elevated concentrations of carbon- and nitrogen-based chemical impurities, and suggest that biological in-situ production may be responsible. (C) 2013 Elsevier B.V. All rights reserved.
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