Sources of methane to an Arctic lake in Alaska: An isotopic investigation

• Published in: Journal of Geophysical Research: Biogeosciences
• Main Authors: Lecher, Alanna L., Chuang, Pei -Chuan, Singleton, Michael, Paytan, Adina
• Language: unknown
• Published: 2021
• Subjects: 58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; Arctic; Arctic Lake; Alaska
• Online Access: http://www.osti.gov/servlets/purl/1542702; https://www.osti.gov/biblio/1542702; https://doi.org/10.1002/2016JG003491

Sources of dissolved methane (CH 4 ) at Toolik Lake, Alaska, include both diffusion from lake sediments and groundwater entering the lake from its perimeter. Here we use hydrogen and oxygen isotopes in water (H 2 O), carbon and hydrogen isotopes in CH 4 , and carbon isotopes in dissolved inorganic carbon (DIC) to calculate the relative importance of lake sediment and groundwater discharge as sources of dissolved CH 4 to Toolik Lake. We also resolve the relative importance of the source contribution spatially within the lake and determine the processes controlling CH 4 concentrations in groundwater surrounding the lake. Our findings, from a mixing model based on isotopes in CH 4 , suggest that groundwater is a more important source of CH 4 at the perimeter of the lake where the water-to-air flux is high. In addition, we find on the local scale that high groundwater methane concentrations may be better linked to areas around the lake where rain is the dominant source of water to the active layer, indicating that changes in precipitation and active layer thaw depth will impact methane concentrations in the active layer and, ultimately, the groundwater associated flux to Toolik Lake.