Rapid response of greenhouse gas emission to early spring thaw in a subarctic mire as shown by micrometeorological techniques



Most studies of soil/atmosphere greenhouse gas exchange in Arctic and Sub-Arctic wetlands have been conducted by the use of small scale chamber techniques during the growing season. To improve the knowledge about the processes in the transition period from winter to growth season, an experiment is presented here showing measurements of CH4, CO2 and H2O using both chambers (only CH4) and eddy correlation technique from the thaw period in early spring and during mid summer. The emphasis is on a comparison between eddy correlation and chamber measurements of methane fluxes during spring thawing in a subarctic mire near Abisko, northern Sweden. Methane exchange as measured by the two techniques is compared and evaluated in relation to temperature variations and atmospheric conductance. During the thaw period, integrated daily net fluxes of CH4 flux showed emission rates increasing from 2.6 mg m−2 d−1 to 22.5 mg m−2 d−1 within four days; the later rate corresponding to approximately 25% of the mid-summer flux. A profound diurnal cycle was observed in the release of methane, emphasising the importance of continuous measurements when calculating integrated fluxes.