Seasonal and Inter-Annual Variability in Wetland Methane Emissions Simulated by CLM4Me and CAM-Chem and Comparisons to Observations

Tuesday, May 13, 2014 - 07:00
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Understanding the temporal and spatial variation of wetland methane emissions is essential to the estimation of the global methane budget. We examined and evaluated the seasonal and inter-annual variability in wetland methane emissions simulated in CLM4Me, a process-based methane biogeochemical model. We also conducted simulations of the CAM-Chem model using CLM4Me methane emissions along with other methane sources and compared CAM-Chem simulated atmospheric methane concentration with observations. The simulated and observed concentrations were used to improve the magnitude of methane simulated from wetlands in our model. Our analysis suggested that wetland methane emissions peaked in 1994 and decreased since then in the period of 1990-2005. The largest decrease in wetland emissions occurred in the tropics due to the decrease in inundated area, as observed in satellite retrievals. In CLM4Me, the largest seasonal variation was present between 30N and 50N in mid-latitude. The seasonal variation in high latitudes was small in magnitude due to the overall low emissions. CAM-Chem model simulations suggested that both prescribed anthropogenic and predicted wetlands methane emissions contributed substantially to seasonal and inter-annual variability in atmospheric methane concentration. Rice paddies had an important contribution in seasonal variability of atmospheric methane concentration in parts of Asia and North America. This study confirms the significance of tropical wetlands in constraining global wetland methane fluxes.

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