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Greenland melt drives continuous export of methane from the ice-sheet bed

机译：格陵兰熔体推动冰盖床中甲烷的连续出口

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摘要

Ice sheets are currently ignored in global methane budgets(1,2). Although ice sheets have been proposed to contain large reserves of methane that may contribute to a rise in atmospheric methane concentration if released during periods of rapid ice retreat(3,4), no data exist on the current methane footprint of ice sheets. Here we find that subglacially produced methane is rapidly driven to the ice margin by the efficient drainage system of a subglacial catchment of the Greenland ice sheet. We report the continuous export of methane-supersaturated waters (CH4(aq)) from the ice-sheet bed during the melt season. Pulses of high CH4(aq) concentration coincide with supraglacially forced subglacial flushing events, confirming a subglacial source and highlighting the influence of melt on methane export. Sustained methane fluxes over the melt season are indicative of subglacial methane reserves that exceed methane export, with an estimated 6.3 tonnes (discharge-weighted mean; range from 2.4 to 11 tonnes) of CH4(aq) transported laterally from the ice-sheet bed. Stable-isotope analyses reveal a microbial origin for methane, probably from a mixture of inorganic and ancient organic carbon buried beneath the ice. We show that subglacial hydrology is crucial for controlling methane fluxes from the ice sheet, with efficient drainage limiting the extent of methane oxidation(5) to about 17 per cent of methane exported. Atmospheric evasion is the main methane sink once runoff reaches the ice margin, with estimated diffusive fluxes (4.4 to 28 millimoles of CH4 per square metre per day) rivalling that of major world rivers(6). Overall, our results indicate that ice sheets overlie extensive, biologically active methanogenic wetlands and that high rates of methane export to the atmosphere can occur via efficient subglacial drainage pathways. Our findings suggest that such environments have been previously underappreciated and should be considered in Earth's methane budget.
机译：目前，全球甲烷预算中忽略了冰盖（1,2）。尽管已经提出冰盖含有大量甲烷，如果在快速退冰期间释放，可能会导致大气中甲烷浓度的升高（3,4），但目前冰盖的甲烷足迹尚无数据。在这里，我们发现格陵兰冰原的冰川下集水区的高效排水系统将冰川下产生的甲烷迅速驱至冰缘。我们报告了在融化季节，冰盖床中甲烷过饱和水（CH4（aq））的持续出口。 CH4（aq）浓度高的脉冲与冰川上强迫的冰川下冲刷事件相吻合，证实了冰川下的来源并突出了熔体对甲烷输出的影响。融化季节甲烷通量的持续增加表明冰下甲烷的储量超过甲烷的出口量，估计有6.3吨（排放加权平均值；范围从2.4吨至11吨）CH4（aq）从冰盖床横向运输。稳定同位素分析揭示了甲烷的微生物起源，可能来自埋在冰下的无机碳和古老有机碳的混合物。我们表明，冰川下水文学对于控制冰盖中的甲烷通量至关重要，而有效的排水将甲烷氧化的程度限制在甲烷的氧化程度（5）约占出口甲烷的17％。一旦径流到达冰边缘，大气逃逸是主要的甲烷汇，估计的扩散通量（每天每平方米CH4为4.4至28毫摩尔）可与世界主要河流相媲美（6）。总体而言，我们的结果表明，冰盖覆盖着广泛的，具有生物活性的产甲烷湿地，甲烷通过有效的冰川下排水路径可以大量排放到大气中。我们的发现表明，这种环境以前并未得到充分重视，应在地球的甲烷预算中予以考虑。

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  • 来源
    《Nature》 |2019年第7737期|73-77|共5页
  • 作者

    Lamarche-Gagnon Guillaume; Wadham Jemma L.; Lollar Barbara Sherwood; Arndt Sandra; Fietzek Peer; Beaton Alexander D.; Tedstone Andrew J.; Telling Jon; Bagshaw Elizabeth A.; Hawkings Jon R.; Kohler Tyler J.; Zarsky Jakub D.; Mowlem Matthew C.; Anesio Alexandre M.; Stibal Marek;

  • 作者单位

    Univ Bristol, Sch Geog Sci, Bristol, Avon, England;

    Univ Bristol, Sch Geog Sci, Bristol, Avon, England;

    Univ Toronto, Dept Earth Sci, Toronto, ON, Canada;

    Univ Libre Bruxelles, Dept Geosci Environm & Soc, Brussels, Belgium;

    Kongsberg Maritime Contros GmbH, Kiel, Germany;

    Natl Oceanog Ctr, Southampton, Hants, England;

    Univ Bristol, Sch Geog Sci, Bristol, Avon, England;

    Newcastle Univ, Sch Nat & Environm Sci, Newcastle Upon Tyne, Tyne & Wear, England;

    Cardiff Univ, Sch Earth & Ocean Sci, Cardiff, S Glam, Wales;

    Univ Bristol, Sch Geog Sci, Bristol, Avon, England|Florida State Univ, Earth Ocean & Atmospher Sci, Tallahassee, FL 32306 USA|German Res Ctr Geosci GFZ, Potsdam, Germany;

    Florida State Univ, Natl High Magnet Field Lab, Tallahassee, FL 32306 USA|Charles Univ Prague, Dept Ecol, Fac Sci, Prague, Czech Republic;

    Charles Univ Prague, Dept Ecol, Fac Sci, Prague, Czech Republic;

    Natl Oceanog Ctr, Southampton, Hants, England;

    Aarhus Univ, Dept Environm Sci, Roskilde, Denmark;

    Charles Univ Prague, Dept Ecol, Fac Sci, Prague, Czech Republic;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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