Estimating wetland methane emissions from the northern high latitudes from 1990 to 2009 using artificial neural networks

摘要

Methane (CH_4) emissions from wetland ecosystems in nothern high latitudes provide a potentially positive feedback to global climate warming. Large uncertainties still remain in estimating wetland CH_4 emisions at regional scales. Here we develop a statistical model of CH_4 emissions using an artificial neural network (ANN) approach and field observations of CH_4 fluxes. Six explanatory variables (air temperature, precipitation, water table depth, soil organic carbon, soil total porosity, and soil pH) are included in the development of ANN models, which are then extrapolated to the northern high latitudes to estimate monthly CH 4 emissions from 1990 to 2009. We estimate that the annual wetland CH_4 source from the northern high latitudes (north of 45°N) is 48.7 Tg CH_4 yr~(-1) (1 Tg = 10~(12) g) with an uncertainty range of 44.0~53.7 Tg CH_4 yr~(-1). The estimated wetland CH_4 emissions show a large spatial variability over the northern high latitudes, due to variations in hydrology, climate, and soil conditions. Significant interannual and seasonal variations of wetland CH 4 emissions exist in the past 2 decades, and the emissions in this period are most sensitive to variations in water table position. To improve future assessment of wetland CH_4 dynamics in this region, research priorities should be directed to better characterizing hydrological processes of wetlands, including temporal dynamics of water table position and spatial dynamics of wetland areas. Key Points Develop wetland CH_4 emissions model using artificial neural networks Estimate wetland CH_4 emissions from the northern high latitudes The wetland CH_4 emissions are most sensitive to variations in water table depth