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Methane emissions from wet polygonal tundra I: Growing-season flux measurements on the ecosystem scale and plot scale, Samoylov Island, Lena Delta, Siberia

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Sachs, T. , Giebels, M. , Wille, C. , Kutzbach, L. and Boike, J. (2007): Methane emissions from wet polygonal tundra I: Growing-season flux measurements on the ecosystem scale and plot scale, Samoylov Island, Lena Delta, Siberia , International Conference "Cryogenic Resources of Polar Regions", June 17-21, 2007, Salekhard, Russia .
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Abstract:

Arctic tundra ecosystems have been major carbon sinks throughout the Holocene. However, during the past decades the Arctic has been observed to warm faster than lower latitudes in the context of global climate change. Large uncertainties about the actual and consequently also the future contribution of these environments to the global carbon cycle remain especially with regard to methane emissions. In order to address this uncertainty, landscape-scale measurements (1-1000 m) as well as investigations of the small-scale variability of methane emission are necessary in different arctic ecosystems. Eddy covariance measurements of methane flux were carried out in northern Siberian wet polygonal tundra during 41 days in July/August of 2005 and during 122 days covering the entire growing season from end of May until end of September in 2006. Additionally, closed chamber measurements of methane fluxes were conducted daily at 15 plots (50x50 cm) in four different types of depressed polygon centers and a polygon wall during August 2005 and from July through September in 2006. Floating chambers were used to investigate the contribution of water-filled cracks and thermokarst lakes. This study adds significant findings on methane emission at different scales in an area that is seriously underrepresented in current efforts to quantify carbon emissions from high latitude environments. Our study site was located in the zone of continuous permafrost in the southern part of the Lena River Delta (72°N, 126°E). On the ecosystem scale we found relatively low fluxes and identified near-surface turbulence, air pressure and air temperature as the main driving parameters of methane emission. Fluxes varied strongly between different micro-sites. We present the 2006 growing season methane budget as determined by eddy covariance and closed chamber methods, the driving parameters for methane emission on the different scales, as well as robust statistical models for the different scales based on the identified variables.

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