Analysis of atmospheric CH4 in Canadian Arctic and estimation of the regional CH4 fluxes

The Canadian Arctic (> 60 degrees N, 60-141 degrees W) may undergo drastic changes if the Arctic warming trend continues. For methane (CH4), Arctic reservoirs are large and widespread, and the climate feedbacks from such changes may be potentially substantial. Current bottom-up and top-down estimates of the regional CH4 flux range widely. This study analyzes the recent observations of atmospheric CH4 from five arctic monitoring sites and presents estimates of the regional CH4 fluxes for 2012-2015. The observational data reveal sizeable synoptic summertime enhancements in the atmospheric CH4 that are distinguishable from background variations, which indicate strong regional fluxes (primarily wetland and biomass burning CH4 emissions) around Behchoko and Inuvik in the western Canadian Arctic. Three regional Bayesian inversion modelling systems with two Lagrangian particle dispersion models and three meteorological datasets are applied to estimate fluxes for the Canadian Arctic and show relatively robust results in amplitude and temporal variations across different transport models, prior fluxes, and subregion masking. The estimated mean total CH4 flux for the entire Canadian Arctic is 1.8 +/- 0.6 Tg CH4 yr(-1). The flux estimate is partitioned into biomass burning of 0.3 +/- 0.1 Tg CH4 yr(-1) and the remaining natural (wetland) flux of 1.5 +/- 0.5 Tg CH4 yr(-1). The summer natural CH4 flux estimates clearly show inter-annual variability that is positively correlated with surface temperature anomalies. The results indicate that years with warmer summer conditions result in more wetland CH4 emissions. More data and analysis are required to statistically characterize the dependence of regional CH4 fluxes on the climate in the Arctic. These Arctic measurement sites will aid in quantifying the inter-annual variations and long-term trends in CH4 emissions in the Canadian Arctic.