Permafrost-affected soils in the Arctic have been accumulating organic matter for thousands of years and form a carbon storage of global relevance. Large fractions of this carbon pool may, however, be remobilized in the form of greenhouse gases through the effects of Arctic warming and permafrost degradation. Within several Russian-German cooperation projects, we have been investigating the inter-annual variability of CO2 exchange fluxes of lowland polygonal tundra on Samoylov Island in the Lena River Delta in the Siberian Arctic (72°N, 126°E) with the eddy covariance technique. Our results from field campaigns during 16 consecutive years indicate that the polygonal tundra on Samoylov Island is on average a small annual net CO2-C sink (median: -0.2 g m-2 a-1), while inter-annual variability is high (max: 25.9 g m-2 a-1; min: -23.6 g m-2 a-1). We found that annual CO2-C balance variability is best explained by the variability in NEE sums of the cold and late growing season (see Fig. 1). Additionally, cold season NEE sums increase with the Arctic Oscillation Index (AOI) and therefore vary with large scale weather patterns, where a positive AOI denotes rising influence of warm western winds from the Atlantic on Siberia.