The base of glaciers and ice sheets provide environments suitable for the production of methane. High pressure conditions beneath the impermeable ‘cap’ of overlying ice promote entrapment of methane reserves that can be released to the atmosphere during ice thinning and meltwater evacuation. However, contemporary glaciers and ice sheets are rarely accounted for as methane contributors through field measurements. Here, we present direct field-based evidence of methane production and release from beneath the Icelandic glacier Sólheimajökull, where geothermal activity creates sub-oxic conditions suited to methane production and preservation along the meltwater flow path. Methane production at the glacier bed (48 tonnes per day, or 39 mM CH4 m−2 day−1), and evasion to the atmosphere from the proglacial stream (41 tonnes per day, or 32 M CH4 m−2 day−1) indicates considerable production and release to the atmosphere during the summer melt season. Isotopic signatures (−60.2‰ to −7.6‰ for δ13Cch4 and −324.3‰ to +161.1‰ for Dch4), support a biogenic signature within waters emerging from the subglacial environment. Temperate glacial methane production and release may thus be a significant and hitherto unresolved contributor of a potent greenhouse gas to the atmosphere.
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机译:冰川和冰盖的底部提供了适合于甲烷生产的环境。覆冰不可渗透的“盖子”下方的高压条件促进了甲烷储量的捕集,甲烷储量可在稀冰和融水疏散过程中释放到大气中。然而,通过实地测量,当代冰川和冰盖很少被认为是甲烷的贡献者。在这里,我们提供了直接的基于现场的甲烷产生和从冰岛冰川Sólheimajökull释放的证据,在该冰川中,地热活动产生了适合于甲烷生产和沿融水流动路径保存的次氧化条件。冰川床的甲烷产量(每天48吨,或39 mM CH4 m -2 sup>天 -1 sup>),并从冰川流向大气中逃逸(41吨)每天,或32 M CH4 m −2 sup>天 −1 sup>)表明在夏季融化季节有大量的生产并释放到大气中。同位素特征(δ 13 sup> Cch4为−60.2‰至−7.6‰,Dch4为−324.3‰至+ 161.1‰),支持从冰下环境中涌出的水域的生物特征。因此,温和的冰川甲烷的产生和释放可能是迄今为止尚未解决的有效温室气体向大气中的重要贡献者。
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