Tracing the geogenic and biogenic genesis and age of CH4 and CO2 in gas seeps across an Arctic permafrost landscape

The Arctic is warming leading to rapid environmental changes including permafrost thaw, glacier retreat, and altered hydrology. These changes can lead to disintegration of cryospheric caps and mobilize previously stored greenhouse gases (GHGs) of both geogenic and biogenic origin, that represent a little known climatic feedback of permafrost melting. This release mechanism of CH4 and CO2 have been detected along glacier margins of the Greenland Ice Sheet and in Svalbard. Here the partitioning of CH4 and CO2 is strongly dependent on oxidation processes and hydrological connectivity1,2. However, the presence and relative contributions of geogenic and biogenic CH4 and CO2 emissions from ice-free Arctic permafrost landscapes located on top of known geological oil and gas resources remains understudied.To study this, we apply an integrated isotopic approach combining bulk stable isotopes (δ13C(CH4), δ2H(CH4), δ13C(CO2)), clumped isotopes of CH4, and radiocarbon (¹⁴C) analyses of CH4 and CO2, including concentrations of C2/C3 gases, to disentangle gas sources, formation pathways, and cycling processes in an Arctic permafrost. Over a 10-day period gas samples were collected from in situ gas seeps in lakes on top of geological fault zones, natural springs, and permafrost thaw ponds to capture the variation in CH4 and CO2 concentration and isotopic compositions in areas with different geogenic impacts. The field work was carried out on the western tip of the Nuussuaq peninsula in West Greenland (70°29′57.16″ N, 54°10′35.91″ W). Here the landscape is characterized by active permafrost with known geogenic gas and oil seeps.We will present the full isotopic composition of CH4 and CO2 from these gas seeps to show that the combined use of clumped isotopes and radiocarbon enables a clear distinction between microbial, thermogenic and geogenic gas sources, as well as oxidation and mixing processes. Results provide insight on the origin, turnover and fate of CH4 and CO2 in Arctic landscapes to help understand the role of subsurface geology to GHG emissions.References1: Adnew GA, Röckmann T, Blunier T, et al (2025) Clumped isotope measurements reveal aerobic oxidation of methane below the Greenland ice sheet. Geochim Cosmochim Acta 389:249–264. https://doi.org/10.1016/J.GCA.2024.11.0092: Adnew GA, Schroll M, Röckmann T, et al (2025) Radiocarbon and bulk isotope composition of subglacial methane and carbon dioxide emitted at the western margin of the Greenland ice sheet. Geochim Cosmochim Acta