Impact of terrestrial carbon input on methane emissions from an Alaskan Arctic lake

[1] Arctic warming is expected to increase thermokarst erosion in thaw lakes, thus inducing large emissions of CH4 to the atmosphere. To reduce uncertainties about the mechanisms, magnitude and timing of methane emissions, we conducted an in-situ experiment to simulate lake expansion following thermokarst erosion. Three tundra horizons were excavated, incubated at the bottom of a thaw lake and subsequently monitored for CH4 ebullition from mid-season until lake freeze-up. Although the permafrost and seasonally frozen active layer emitted little CH4 throughout the experiment, ebullition from the thawed active layer began the first week, quickly reaching rates (39 mg CH4 m 2 day ) comparable to background ebullition in Siberian thaw lakes. While the long-term fate of permafrost carbon from thermokarst lake expansion remains uncertain, the short-term methane release is dominated by upper active layer carbon. Thus, deepening of the upper active layer in a thaw lake dominated landscape should increase CH4 ebullition rates. Citation: Mazéas, O., J. C. von Fischer, and R. C. Rhew (2009), Impact of terrestrial carbon input on methane emissions from an Alaskan Arctic lake, Geophys. Res. Lett., 36, L18501, doi:10.1029/2009GL039861.