Soil moisture control over autumn season methane flux, Arctic Coastal Plain of Alaska

Abstract

Accurate estimates of annual budgets of methane (CH 4) efflux in arctic regions are severely constrained by the paucity of non-summer measurements. Moreover, the incomplete understanding of the ecosystem-level sensitivity of CH 4 emissions to changes in tundra moisture makes prediction of future CH 4 release from the Arctic extremely difficult. This study addresses some of these research gaps by presenting an analysis of eddy covariance and chamber measurements of CH 4 efflux and supporting environmental variables during the autumn season and associated beginning of soil freeze-up at our large-scale water manipulation site near Barrow, Alaska (the Biocomplexity Experiment). We found that the autumn season CH 4 emission is significant (accounting for 21-25% of the average growing season emission), and that this emission is mostly controlled by the fraction of inundated landscape, atmospheric turbulence, and the decline in unfrozen water during the period of soil freezing. Drainage decreased autumn CH 4 emission by a factor of 2.4 compared to our flooded treatment. Flooding slowed the soil freezing process which has implications for extending elevated CH 4 emissions longer into the winter season. © Author(s) 2012. CC Attribution 3.0 License.