Methane emissions from western Siberian wetlands: heterogeneity and sensitivity to climate change

Abstract

The prediction of methane emissions from high-latitude wetlands is important given concerns about their sensitivity to a warming climate. As a basis for the prediction of wetland methane emissions at regional scales, we coupled the variable infiltration capacity macroscale hydrological model (VIC) with the biosphere-energy-transfer-hydrology terrestrial ecosystem model (BETHY) and a wetland methane emissions model to make large-scale estimates of methane emissions as a function of soil temperature, water table depth, and net primary productivity (NPP), with a parameterization of the sub-grid heterogeneity of the water table depth based on TOPMODEL. We simulated the methane emissions from a 100 km × 100 km region of western Siberia surrounding the Bakchar Bog, for a retrospective baseline period of 1980-1999 and have evaluated their sensitivity to increases in temperature of 0-5 • C and increases in precipitation of 0-15%. The interactions of temperature and precipitation, through their effects on the water table depth, played an important role in determining methane emissions from these wetlands. The balance between these effects varied spatially, and their net effect depended in part on sub-grid topographic heterogeneity. Higher temperatures alone increased methane production in saturated areas, but caused those saturated areas to shrink in extent, resulting in a net reduction in methane emissions. Higher precipitation alone raised water tables and expanded the saturated area, resulting in a net increase in methane emissions. Combining a temperature increase of 3 • C and an increase of 10% in precipitation to represent climate conditions that may pertain in western Siberia at the end of this century resulted in roughly a doubling in annual emissions.

Present state of global wetland extent and wetland methane modelling: methodology of a model inter-comparison project (WETCHIMP)

“…The University of Washington team used the Variable Infiltration Capacity (VIC) model, version 4.1.2, with some extensions specifically tailored for the modelling of boreal peatlands described in Bohn et al (2007) and Bohn and Lettenmaier (2010). UW-VIC is a large-scale hydrologic model that balances the water and energy budgets of the land surface at an hourly time step and spatial resolutions ranging from 1 • to 5 km.…”

“…Model simulations have also moved on from equilibrium-only simulations to transient simulations (Walter et al, 2001a,b;Shindell et al, 2004;Gedney et al, 2004;Zhuang et al, 2006). Regional-to global-scale models have now been applied for the recent past (Ringeval et al, 2010;Hodson et al, 2011;Spahni et al, 2011;Riley et al, 2011), more distant past climates (Kaplan, 2002;Valdes et al, 2005;Hopcroft et al, 2011;Singarayer et al, 2011;Beerling et al, 2011), and to project responses to future climate change (Shindell et al, 2004;Gedney et al, 2004;Bohn et al, 2007;Bohn and Lettenmaier, 2010;Ringeval, 2011). Wetland and wetland CH 4 models are now becoming included in intermediate complexity (Shindell et al, 2004;Gedney et al, 2004;Avis et al, 2011) and comprehensive (Riley et al, 2011) global climate and earth system models.…”

WETCHIMP-WSL: intercomparison of wetland methane emissions models over West Siberia

“…(b) Dominant land cover at 25 km derived from MODIS-MOD12Q1 500 m land cover classification (Friedl et al, 2010). each grid cell (e.g., Zhuang et al, 2004) to more sophisticated schemes that allow for sub-grid heterogeneity in the water table (e.g., Bohn et al, 2007Bohn et al, , 2013Ringeval et al, 2010;Riley et al, 2011;Kleinen et al, 2012;Stocker et al, 2014;Subin et al, 2014). Finally, peatland soils can be highly acidic and nutrient-poor, and much of the available carbon substrate can be recalcitrant (Clymo et al, 1984;Dorrepaal et al, 2009).…”

Modeling CH4 Emissions from Natural Wetlands on the Tibetan Plateau over the Past 60 Years: Influence of Climate Change and Wetland Loss

“…The value of z is calculated by the soil moisture content in a 0.5˝grid cell. More details about this method are given in previous studies [43][44][45][46][47].…”

“…TOPMODEL has been widely used to simulate the water table distribution of the natural wetlands. It has been validated for both site-specific water table seasonal variation (e.g., [44]) and the spatial variation on the regional and global scales. On the regional scale, areas where the water table is at or above the soil surface level can be interpreted to correspond to the surface water extent.…”