Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

摘要

Methane (CH) is the second most important greenhouse gas but itsemissions from northern regions are still poorly constrained. In this study,we analyze a subset of in situ CH aircraft observations made overAlaska during the growing seasons of 2012–2014 as part of the Carbon inArctic Reservoirs Vulnerability Experiment (CARVE). Net surface CHfluxes are estimated using a Lagrangian particle dispersion model whichquantitatively links surface emissions from Alaska and the western Yukon withobservations of enhanced CH in the mixed layer. We estimate thatbetween May and September, net CH emissions from the region ofinterest were 2.2 ± 0.5 Tg, 1.9 ± 0.4 Tg, and2.3 ± 0.6 Tg of CH for 2012, 2013, and 2014, respectively. If emissionsare only attributed to two biogenic eco-regions within our domain, thentundra regions were the predominant source, accounting for over half of theoverall budget despite only representing 18 % of the total surface area.Boreal regions, which cover a large part of the study region, accounted forthe remainder of the emissions. Simple multiple linear regression analysisrevealed that, overall, CH fluxes were largely driven by soiltemperature and elevation. In regions specifically dominated by wetlands,soil temperature and moisture at 10 cm depth were important explanatoryvariables while in regions that were not wetlands, soil temperature andmoisture at 40 cm depth were more important, suggesting deepermethanogenesis in drier soils. Although similar environmental drivers havebeen found in the past to control CH emissions at local scales, thisstudy shows that they can be used to generate a statistical model to estimatethe regional-scale net CH budget.