Greenland melt drives continuous export of methane from the ice-sheet bed
Détails
ID Serval
serval:BIB_2FCEEBE2EEA6
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Institution
Titre
Greenland melt drives continuous export of methane from the ice-sheet bed
Périodique
Nature
ISSN
0028-0836
1476-4687
1476-4687
Statut éditorial
Publié
Date de publication
01/2019
Peer-reviewed
Oui
Volume
565
Numéro
7737
Pages
73-77
Langue
anglais
Résumé
Ice sheets are currently ignored in global methane budgets. 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, 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 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. 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.
Mots-clé
Attribution, Carbon cycle, Cryospheric science, Hydrology
Pubmed
Web of science
Création de la notice
29/08/2024 10:03
Dernière modification de la notice
22/11/2024 10:24