Temperature and snow-melt controls on interannual variability in carbon exchange in the high Arctic

Summary Net Ecosystem CO₂ Exchange (NEE) was studied during the summer season (June–August) at a high Arctic heath ecosystem for 5 years in Zackenberg, NE Greenland. Integrated over the 80 day summer season, the heath is presently a sink ranging from −1.4 g C m⁻² in 1997 to −23.3 g C m⁻² in 2003. The results indicate that photosynthesis might be more variable than ecosystem respiration on the seasonal timescale. The years focused on in this paper differ climatically, which is reflected in the measured fluxes. The environmental conditions during the five years strongly indicated that time of snow-melt and air temperature during the growing season are closely related to the interannual variation in the measured fluxes of CO₂ at the heath. Our estimates suggest that net ecosystem CO₂ uptake is enhanced by 0.16 g C m⁻² per increase in growing degree-days during the period of growth. This study emphasises that increased summer time air temperatures are favourable for this particular ecosystem in terms of carbon accumulation.