Abstract:
Methane flux was measured from northern Alaska Arctic Coastal Plain wetlands to assess the spatial and temporal variability of Arctic tundra emissions during the summers of 1987 through 1990. Initially, the role of vegetation in the release of methane from substrate to atmosphere was assessed. Methane emissions were shown to be proportional to the foliage surface area and release of methane from plants controlled by the stomata. Daily values of methane emissions and leaf conductance were correlated (r = 0.95). A satellite-derived regional methane flux estimate had 3 to 5 times greater precision than estimates based on direct expansion. Methane emissions from the tundra exhibit high temporal variability at hourly, daily, seasonal, and annual scales of observation. Daily variability in methane emissions was low near the summer solstice and increased through the growing season. Strong seasonal variation in emissions was related to the position of the local water table, the amount of leaf area above the water, and plant phenological development. An interannual comparison of emissions provided insight into the local and regional scale responses of Arctic tundra to potential climatic warming. Methane emissions in 1989, a warm year, were over three fold greater than in 1987, a "normal" year. Temperaturedependent increases in methane emissions expected as a result of climatic warming are projected to exceed increases due to a longer growing season. The potential for strong positive biological feedback exists whereby the enhanced emissions of methane, a greenhouse gas, to the atmosphere may further accelerate rates of regional and global climatic warming.
