First measurement of methane emissions from Canadian glaciers in the Yukon

• Main Authors: Sapper, Sarah Elise, Jørgensen, Christian Juncher, Schroll, Moritz, Keppler, Frank, Christiansen, Jesper Riis
• Format: Conference Object
• Language: English
• Published: 2023
• Subjects: Canada; Dusty Glacier; Greenland; Yukon; glacier; glacier*; Iceland
• Online Access: https://curis.ku.dk/portal/da/publications/first-measurement-of-methane-emissions-from-canadian-glaciers-in-the-yukon(df6c7631-e8bf-4b58-9612-63c9c0fb8f66).html; https://meetingorganizer.copernicus.org/EGU23/EGU23-12327.html

Land-terminating glaciers in Greenland and Iceland are sources of methane (CH4) to the atmosphere1,2,3. CH4 is produced through microbial methanogenesis underneath the ice, transported dissolved in subglacial meltwater to the margin where the gas is emitted to the atmosphere via degassing4. However, sparse empirical data exist about the spatial distribution of subglacial CH4 production and emission in other glaciated regions of the world, limiting our understanding of its regional and global importance in atmospheric carbon budgets and its possible role in the climate system. In August 2022, we conducted fieldwork at three outlet glaciers - Dusty, Kluane and Donjek glaciers - of the St. Elias Icefields in Yukon, Canada, to investigate if these alpine glaciers are also sources of CH4 emissions to the atmosphere. The glaciers were chosen due to the absence of proglacial lakes and the presence of meltwater upwellings at the glacier termini, which were accessed via helicopter. In-situ extracted dissolved CH4 and CO2 concentrations were measured in the field with a portable greenhouse gas analyzer. Additionally, extracted gas was collected in exetainers for concentration measurements via gas chromatography and in Tedlar gas bags for stable carbon and hydrogen isotope analyses of CH4 to decipher its origin. Further, water samples were collected for geochemical analyses. At Dusty glacier, we performed a high-intensity sampling campaign over 10 hours and continuous measurements of dissolved CH4 concentrations with a custom-made low-cost and low-power dissolved CH4 sensor5 to study changes in dissolved gas concentrations, stable isotopic signatures and water chemistry during the rising limb of the diurnal discharge curve. In-situ measured CH4 and CO2 concentrations yielded significantly elevated CH4 and depleted CO2 levels in the meltwater of all three glaciers. Discrete gas samples confirmed dissolved CH4 concentrations 45x, 135x and 250x above the atmospheric equilibrium concentration (3.6 nmol L-1) in the meltwater of ...