[A-CG42] Science in the Arctic Region

[ACG42-01] Methane concentration and flux observed over discharge water from glaciers in Alaska range

*Keiko Konya¹, Go Iwahana², Tomoaki Morishita³, Jun Uetake⁴, Masahide Wakita¹, Yota Sato¹, Tetsuo Sueyoshi¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.University of Alaska, Fairbanks, 3.Forest and Forest Product Research Institute, 4.Hokkaido Unversity)

Keywords:Methane, Glaciers, Greenhouse gas, Alaska

Glaciers have not been considered a source of methane emissions. However, a large amount of methane has been observed at the terminus of large glaciers and ice sheet, associated with methane-saturated meltwater runoff. We observed methane concentration at several glaciers in Alaska.

The observation periods were June 12-14, 2022, and June 3-9, 2023, which was the early ablation season for the glacier. We measured methane and CO2 concentrations in ambient air over the water with a portable gas analyzer G4301 (Picarro, Inc.). Dissolved methane concentrations in runoff water were measured using the head-space method of Morishita et al. (2015).

High methane concentration was found above the runoff water of three out of the four glaciers. The highest concentration was observed at Castner Glacier in the Alaska range. The maximum methane concentration in the ambient air near the runoff water was three times higher than the background level, and the concentration decreased as the gas analyzer moved away from the discharging exit. The dissolved methane concentration was saturated. These results suggest that dissolved methane was released from the water flow.

This study was supported by ArCSII project (JPMXD1420318865).