https://doi.pangaea.de/10.1594/PANGAEA.993007Hatton, Jade ElizabethJade ElizabethHatton0000-0002-9408-7981UK Centre for Ecology & HydrologyStehrer-Polášková, AnnaAnnaStehrer-PoláškováCharles UniversityPika, PhilipPhilipPikaUniversité Libre de BruxellesGarnett, Mark HMark HGarnett0000-0001-6486-2126National Environmental Isotope Facility, Radiocarbon LaboratoryKlimova, PetraPetraKlimovaCharles UniversityWentzel, LiaLiaWentzelCharles UniversityJakub, ZarskyZarskyJakubCharles UniversityArndt, SandraSandraArndt0000-0002-0235-8124Université Libre de BruxellesAlun, HubbardHubbardAlunThe Arctic University of NorwayJakub, TrubacTrubacJakubCharles UniversityYde, JacobJacobYdeWestern Norway University of Applied SciencesJon, HawkingsHawkingsJonDepartment of Earth and Environmental Science, University of PennsylvaniaEva, DotingDotingEvaNorwegian Institute for Nature ResearchJack, MurphyMurphyJackDepartment of Earth and Environmental Science, University of PennsylvaniaGuillaume, Lamarche-GagnonLamarche-GagnonGuillaumeThe Arctic University of NorwayWadham, JemmaJemmaWadhamThe Arctic University of NorwaySarah, SapperSapperSarahDepartment of Geosciences and Natural Resource Management, University of CopenhagenChristiansen, Jesper RiisJesper RiisChristiansen0000-0002-3277-0734Department of Geosciences and Natural Resource Management, University of CopenhagenChristian, JorgensenJorgensenChristianDepartment of Geosciences and Natural Resource Management, University of CopenhagenStibal, MarekMarekStibal0000-0002-9998-5086Charles UniversityPANGAEA2026dissolved methaneglacial meltGlacial releaseGreenland ice sheetHolocene climateMethaneRadiocarbon AMS datingstable carbon isotopesEvent labelDATE/TIMEDate/Time localLATITUDELONGITUDEpHConductivityOxygenMethane, dissolvedActivity of radiocarbon in percent of modern carbonActivity of radiocarbon in percent of modern carbon, standard deviationAge, dated, range, minimumAge, dated, range, maximumδ13C, methane, dissolvedδ Deuterium, methanePortable 2-channel multimeter, Hach, HQ40DMicroportable Greenhouse Gas AnalyzerSilonite canisterPortable multimeter, Hach, HQ4300Off-axis integrated cavity output spectroscopy (OA-ICOS) gas analyzerAge, 14C AMSAge, 14C calibrated, OxCal 4.4 and IntCal20Age, 14C calibrated, IntCal20 (Reimer et al. 2020)GasBench+PreCon trace gas concentration system (ThermoFinnigan) coupled to a DELTA V plus IRMSMARCH4G_2021MARCH4G_2022MARCH4G_20232021-08-05T15:30:00/2023-07-15T18:00:00Dataset10.1002/eco.161710.1002/rcm.6549370 data pointstext/tab-separated-valuesCreative Commons Attribution 4.0 InternationalData access is restricted (moratorium, sensitive data, license constraints)A field sampling campaign spanning the entire western margin of the Greenland Ice Sheet was conducted in the summer melt seasons of 2021, 2022, and 2023, to measure release of dissolved methane from meltwater streams draining the subglacial environment of the Greenland Ice Sheet. The campaign was designed to assess whether subglacial methane export is ubitiqous from the GrIS, and the source and age of this methane released.
Twenty-six rivers draining from the GrIS were sampled in the summers of 2021, 2022 and 2023 along the west coast of Greenland, forming a north to south transect from Qaanaaq to Narsarsuaq. We split these rivers into regional areas of northwest (NW), central west (CW), and southwest (SW). Most of these rivers drained directly from the subglacial environment, whether via an upwelling (proglacial spring) or subglacial portal. Samples were taken as close to the upwelling or portal as possible, to get the most representative view of the subglacial system, with limited off-gassing or dilution effects from supraglacial meltwaters.
Basic stream geochemistry (pH, EC, O2) was measured in the field using a WTW 3430 multimeter. Dissolved CH4 was extracted (Garnett et al., 2016) into a nitrogen headspace, via 5L water samples were collected into a 10L accordion water carrier, 1-2L of pure N2 headspace was added and the water carrier was shaken for 3 minutes to equilibrate the CH4. The headspace CH4 concentrations were measured directly in the field using a using a micro portable greenhouse gas analyser (MGGA, ABB GLA1313 Series, using Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) technology). The headspace with extracted sample was stored in a pre-evacuated 15L Silonite™ cannisters with TrueSeal Valve™ (Entech Instruments) or pre-evacuated 150ml glass serum vials (Wheaton™) using a 150 ml glass syringe and sealed with 15 mm crimped (13mm) chlorobutyl rubber stoppers (Bellco Glass) ahead of radio- and stable- carbon isotope analysis, respectively.
We provide measured and 'corrected' radiocarbon ages of dissolved methane. We recognise that the CH4 extracted and measured in each water sample is a homogenised sample, likely containing subglacially produced CH4 combined with some modern CH4, when supraglacial water is routed through moulins to the bed and through the subglacial system. Therefore, it is likely that our water samples encompass some portion of modern-day CH4, and accounting for this provides a more accurate assessment of the 14C-age of the subglacial carbon source for methanogenesis. We used a simple mass balance approach to consider what proportion of our sampled CH4 is potentially modern-day atmospheric, based on the measured atmospheric CH4 concentration measured during a survey of the supraglacial area inland.-69.019667-45.1165861.1454177.719667Ilulissat, GreenlandQaanaaq, GreenlandKangerlussuaq, GreenlandUpernavik, GreenlandNarsarsuaq, GreenlandMinistry of Education, Youth and Sportshttps://doi.org/10.13039/501100001823LL2004MARCH4G