A case study synthesis of observed and simulated Arctic tundra and boreal biogenic methane fluxes in Alaska and northwest Canada

Abstract: Thawing permafrost has the potential to release large amounts of heat-trapping methane gas into the atmosphere, thereby accelerating global warming. Much work has been done to both observe and simulate current and potential future biogenic methane fluxes throughout the Arctic tundra and boreal regions of North America. Using a case study approach, we identify key regions of methane emissions and uptake by combining available flux observations and a set of regional and global models. We compare the simulated methane fluxes to observations from eddy flux tower sites and evaluate them using atmospheric methane concentration observations coupled to an atmospheric transport model. This analysis allows us to investigate where, when, and why models do and do not match the observations, which can guide the focus for future model improvements and the potential usefulness of additional observational constraints. We find that global wetland models perform well for boreal wetlands in northwestern Canada but tend to underestimate methane emissions observed by both eddy flux and aircraft over the Alaska North Slope. The lack of simulated wetland methane in this region suggests wetland classification may not be the best indicator of methane emissions in tundra areas. The regional model with more particular representation of Arctic ecosystems performs better for the Alaska North Slope, however, producing significant methane to match the aircraft observations. We also investigate the use of wetness as a metric for methane emissions in areas not classified as wetlands. Overall, this work can provide recommendations for future studies in this region, including insights into our level of understanding for various drivers of methane flux.