Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 4 5 2007 10.5194/bg-4-869-2007 http://www.biogeosciences.net/4/869/2007/ http://www.biogeosciences.net/4/869/2007/bg-4-869-2007.html http://www.biogeosciences.net/4/869/2007/bg-4-869-2007.pdf 869 890 2007-10-18 The exchange of carbon dioxide between wet arctic tundra and the atmosphere at the Lena River Delta, Northern Siberia L. Kutzbach kutzbach@uni-greifswald.de C. Wille E.-M. Pfeiffer Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam, Telegrafenberg A43, 14473 Potsdam, Germany University of Hamburg, Institute of Soil Science, Allende-Platz 2, 20146 Hamburg, Germany now at Ernst Moritz Arndt University Greifswald, Institute for Botany and Landscape Ecology, Grimmer Stra{ß}e 88, 17487 Greifswald, Germany The exchange fluxes of carbon dioxide between wet arctic polygonal tundra and the atmosphere were investigated by the micrometeorological eddy covariance method. The investigation site was situated in the centre of the Lena River Delta in Northern Siberia (72°22' N, 126°30' E). The study region is characterized by a polar and distinctly continental climate, very cold and ice-rich permafrost and its position at the interface between the Eurasian continent and the Arctic Ocean. The soils at the site are characterized by high organic matter content, low nutrient availability and pronounced water logging. The vegetation is dominated by sedges and mosses. The micrometeorological campaigns were performed during the periods July–October 2003 and May–July 2004 which included the period of snow and soil thaw as well as the beginning of soil refreeze. The main CO₂ exchange processes, the gross photosynthesis and the ecosystem respiration, were found to be of a generally low intensity. The gross photosynthesis accumulated to −432 g m^−2 over the photosynthetically active period (June–September). 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