INTERANNUAL VARIATIONS IN TUNDRA METHANE EMISSION: A 4-YEAR TIME SERIES AT FIXED SITES

This paper summarizes 4 years (19871990) of weekly net CH4 flux measurements at permanent sites representing important plant components of Arctic tundra. The data coincide with variations in precipitation and temperature of interest in regional and global modeling efforts and are useful in placing bounds on the role of tundra in the global CH4 budget. Precipitation in the study area during the summer emission period ranged from twice to half the long-term mean, and air temperature anomalies were about +2 degrees C. This data set also permits consideration of temporal (seasonal to interannual) and spatial variability in CH4 flux. We studied the relationship between the net CH4 flux and subsurface properties (water table depth, thaw depth, soil temperature, rho CH4 distributions) at these permanent sites during the 1988 and 1989 emission periods. Net CH4 emission and subsurface properties are largely unrelated. Relationships between soil temperature (or any single variable) and emission are site specific and are of little value as flux predictors. Parameters that integrate conditions influencing flux appear to be the best flux predictors over the emission period. We estimate that Arctic wet meadow and tussock:shrub tundra presently emit about 42 +/- 26 Tg CH4 yr(-1) to the atmosphere. This estimate has a North American bias, but it is supported by measurements in a range of locations, transect studies, and model calculations.