[A-CC25] Glaciology

[ACC25-P01] Greenhouse gases in glaciers discharge water in Alaska 2021-2022

*Keiko Konya¹, Go Iwahana^2,3, Tomoaki Morishita⁴, Uetake Jun³, Tetsuo Sueyoshi¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.University of Alaska, Fairbanks, 3.Hokkaido University, 4.Forestry and Foreset Product Research Institute)

Keywords:Greenhouse gas, Methane, Glacier, the Arctic

Methane is the second most influential greenhouse gas. Glacier areas had been discarded for the global methane budget. However, large amounts of methane have been observed at glacier terminus in Greenland and Iceland due to the outflow of meltwater saturated with methane. The mountain glaciers, distributed all over the world, are unknown areas. In this study, we conducted observations to determine whether similar methane emissions are observed in small mountain glaciers in Alaska.
We observed methane emissions from the surface and discharge water at the terminus of glaciers in the Alaska Range and southern Alaska during the summer of 2021 and 2022. Methane emissions were measured using the chamber method, the headspace method, and a portable gas analyzer (Picarro G4301). Gas samples were brought back to FFPRI, and methane and carbon dioxide concentrations were analyzed by gas chromatography. We had higher atmospheric methane concentration than the global average at the glacier terminus and high dissolved methane in discharge waters. Water samples were analyzed for stable isotope ratios and DOC at JAMSTEC. Sediments with water were analyzed by RNA sequencing and compared with previous studies for the methanogen community.