Methane emissions from Arctic landscapes during 2000-2015: an analysis withland and lake biogeochemistry models

Wetlands and freshwater bodies (mainly lakes) are the largest natural sources of the greenhouse gas CH4 to the atmosphere. Great efforts have been made to quantify these source emissions and their uncertainties. Previous research suggests that there might be significant uncertainties coming from "double accounting" emissions from freshwater bodies and wetlands. Here we quantify the methane emissions from both land and freshwater bodies in the pan-Arctic with two process-based biogeochemistry models by minimizing the double accounting at the landscape scale. Two non-overlapping dynamic areal change datasets are used to drive the models. We estimate that the total methane emissions from the pan-Arctic are 36.46 +/- 1.02 Tg CH4 yr(-1)during 2000-2015, of which wetlands and freshwater bodies are 21.69 +/- 0.59 Tg CH4 yr(-1) and 14.76 +/- 0.44 Tg CH4 yr(-1), respectively. Our estimation narrows the difference between previous bottom-up (53.9 Tg CH4 yr(-1)) and top-down (29 Tg CH4 yr(-1)) estimates. Our correlation analysis shows that air temperature is the most important driver for methane emissions of inland water systems. Wetland emissions are also significantly affected by vapor pressure, while lake emissions are more influenced by precipitation and landscape areal changes. Sensitivity tests indicate that pan-Arctic lake CH4 emissions were highly influenced by air temperature but less by lake sediment carbon increase.