A late-autumn shoulder is consistently observed in the seasonal cycles of atmospheric methane at high latitude sites, but the sources responsible remain uncertain. This study reports methane flux measurements from a high Arctic setting during the onset of soil freezing. The integral of the emissions during this freeze-in period amount to approximately the same amount of methane emitted during the entire summer season. It is found that the observed early winter emission burst improves the agreement between the simulated seasonal cycle and atmospheric data from latitudes north of 60°N. The results suggest that permafrost associated freeze-in bursts of methane emissions from tundra regions could be an important component of the seasonal distribution of methane emissions from high latitudes.
- Mikhail Mastepanov
- Charlotte Sigsgaard
- Torben R. Christensen
