Methane fluxes between terrestrial ecosystems and the atmosphere at northern high latitudes during the past century: A retrospective analysis with a process‐based biogeochemistry model

Abstract

[1] We develop and use a new version of the Terrestrial Ecosystem Model (TEM) to study how rates of methane (CH 4 ) emissions and consumption in high-latitude soils of the Northern Hemisphere have changed over the past century in response to observed changes in the region's climate. We estimate that the net emissions of CH 4 (emissions minus consumption) from these soils have increased by an average 0.08 Tg CH 4 yr À1 during the twentieth century. Our estimate of the annual net emission rate at the end of the century for the region is 51 Tg CH 4 yr À1 . Russia, Canada, and Alaska are the major CH 4 regional sources to the atmosphere, responsible for 64%, 11%, and 7% of these net emissions, respectively. Our simulations indicate that large interannual variability in net CH 4 emissions occurred over the last century. Our analyses of the responses of net CH 4 emissions to the past climate change suggest that future global warming will increase net CH 4 emissions from the Pan-Arctic region. The higher net CH 4 emissions may increase atmospheric CH 4 concentrations to provide a major positive feedback to the climate system.

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

“…Our estimate of CH 4 emissions, 47~51 Tg CH 4 yr À1 , is within the range of these estimates and is comparable to the estimates from Bartlett and Harriss [1993] and Zhuang et al [2004] focusing on the same region.…”

“…The grid cell mean WTD was first simulated by a sophisticated hydrological model, which is able to simulate the soil moisture profile and WTD for wetland ecosystems [Zhuang et al, 2002[Zhuang et al, , 2004. Then we used the TOPMODEL-based formulation to represent the spatially distributed WTD for each 1 km pixel within a 0.5 grid cell:…”

“…[4] Estimates of wetland CH 4 emissions are often obtained using "bottom-up" approaches, ranging from simple empirical or statistical models [e.g., Andronova and Karol, 1993;Granberg et al, 1997;Levy et al, 2011] to detailed process-based models [e.g., Cao et al, 1996;Walter et al, 2001;Zhuang et al, 2004]. Previous process-based model simulations presented a large uncertainty in the estimates of [5] The uncertainty in these estimates could result from many sources including model structures, assumptions, parameterization, and choice of forcing data.…”

Reduced methane growth rate explained by decreased Northern Hemisphere microbial sources

“…Improved management of landfills also may have contributed to Northern Hemisphere source reductions 23 . For ruminant animals and wetlands, however, key processes regulating these sources have not changed in a way that is consistent with the long-term decreases in emissions needed to explain the atmospheric observations [21][22][23][24][25] .…”

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).…”