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International Conference on Environmental Observations, Modeling and Information Systems ENVIROMIS-2004 17-25 July 2004, Akademgorodok, Tomsk, Russia Modeling of methane emission from natural wetlands and topography-based surface hydrology Krylova A.I. and V.N.Krupchatnikoff Institute of Computational Mathematics and Mathematical Geophysics of Siberian Branch of the Russian Academy of Sciences, pr. Ac.Lavrentieva, 6, Novosibirsk, 630090, Russia, Ph. (8-3832) 356524, e-mail:vkrup@ommfao1.sscc.ru, alla@climate.sscc.ru

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Introduction There are two complementary approaches to determine global and regional wetland source strengths : 1)bottom-up approach: geographical coverage, spatial and temporal flux variations a) using flux measurements and information on emission period and wetland areas to extrapolate to global and annual scales; b) using a climate-sensitive model for methane emissions to extrapolate to the global scale; 2)top-down approach: inverse modeling Information on temporal and spatial variation of methane fluxes from soils is deduced from observational data on CH 4 mixing ratio in air, obtained on a global network of NOAA/CMDL field stations.

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climate soil surface soil depth water table rooting depth soil temperature vegetation CH 4 oxidation NPP CH 4 production CH 4 concentration plant-mediated transport ebullition diffusion CH 4 emission atmosphere oxic soil anoxic soil Schematic of the one-dimensional methane model relative pore space

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The methane emission model Model is based on the one-dimensional continuity equation within the entire soil/water column The diffusive flux F diff is calculated using Fick’s first law: The rate Q ebull at which methane in the form of bubbles is removed from depth z is calculated:

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The methane production rate R prod (t,z) at time t and depth z is described as: The methane emission model The rate Q plant (t,z) at which methane is removed by plants from depth z at time t is calculated from: The total methane flux to the atmosphere

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Boundary conditions at the lower boundary nsoil at the upper boundary u, where u is either the water table w(t) (if w(t) > ns) or the soil surface ns

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Results Figure shows a comparison between simulated and observed methane concentration profiles for the period between 1 June and 30 June 1992. Observational data were taken from Shannon and White [1994]. CH 4 [ M ]

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Coupled model of climate Atmospheric model (INM/RAS) (Alexeev V., E.Volodin, V.Galin, V. Dymnikov, V. Lykosov, 1998 ) Terrain-following vertical coordinate (21 σ-levels) Semi-implicit formulation of integration in time Energy conservation finite-difference schemes (2.5°x 2.5°) Convection (deep, middle, shallow; mass-flux) Radiation (H 2 O, CO 2, O 3, CH 4, N 2 O, O 2 ; 18 spectral bands for SR and 10 spectral bands for LR) PBL (5 σ-levels) Land surface model (ICMMG/SB RAS) (V. Krupchatnikov, 1998) The Land Surface Model considered in this report is an extension of this earlier model development. The model is able to simulate: terrestrial photosynthesis and respiration of CO 2 from land surface, vegetation, methane emissions from natural wetlands, and surface hydrology,surface fluxes of energy and momentum. Model is implemented globally, many surface type needed to be included.

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Atmospheric model Land surface model soil temperature NPP water table CH 4 model global wetland distribution global data sets: plant-mediated transport rooting depth soil depth relative pore space

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Global methane fluxes Results : Observations and Modeling

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Global distribution of peat-rich bogs from 50-60 0 N (from Matthews, E., and I.Fung)

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Regional CH 4 emission

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Tom River basin Data

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Spatial distribution of statistical moments of topographic index

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Upscaling function for obtaining 10’ equivalent of topographic index from its values for 30-arc-second DEM

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This model is a component of the biosphere model in the coupled model of climate. It has allowed us to evaluate global CH 4 fluxes from wetlands, seasonal change of fluxes for the basic areas of concentration peatlands in the northern latitudes. The model has been developed for studying the global natural emission of methane from the surface covered with bogs and lakes. Simulated results confirm the conclusions obtained on the basis of direct measurements, that Big Vasyugan Bog is the largest source of methane emission to the atmosphere. Simulated results allow us to retrieve the character of the distribution and the amount of methane fluxes from the surface earth to the atmosphere. The model can be considered as a basis for further research of interactions of the hydrological cycle, climate and emission of methane from the peat-bog ecosystems. Conclusion

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