Net Exchange of CH4 fluxes between terrestrial ecosystem and atmosphere in the Arctic-Boreal Region under future climate change scenarios
Methane (CH4) is an attractive target, due to its relative (approx. 28 times) higher global warming potential (GWP) and shorter lifetime (approx. 9 years), to reduce the total radiative forcing caused by GHGs. Due to large portion of wetland and permafrost distribution as well as great soil carbon storage, boreal and arctic terrestrial ecosystem has long been recognized as a potentially huge CH4 source in the future. In the 21st century, temperature is expected to increase globally, with largest increase in this region, while the change in precipitation may vary substantially across the globe, with high confidence of increasing in the boreal and arctic region. However, the question of how future climate change might influence the CH4 emissions still remains unclear. Increasing disturbances, like permafrost-thaw and climate extreme, would greatly change the patterns and variations of CH4 emission and further affect the feedback between terrestrial ecosystem and climate change. In this study, we used a process-based model (Dynamic Land Ecosystem Model), together with temperature, precipitation, atmospheric CO2, and nitrogen deposition projections under the RCP 26, RCP 45 and RCP 85 scenarios, to quantify the magnitude, spatial and temporal variation of CH4 fluxes across the boreal and arctic regions. By implementing a set of factorial simulations, we further quantify the relative contribution of climate, atmospheric CO2 and nitrogen deposition to the CH4 fluxes.
Our results indicated that the estimated CH4 emission from wetland showed an increasing trend from 2006-2099. Under the RCP26, RCP45 and RCP85 scenarios, the magnitude of CH4 emission from wetland in the study area is expected to increase 5%, 16% and 56% compared with the contemporary level, respectively. The analysis on the attribution of multiple environmental factors on the CH4 emission showed that climate was the dominant factor for the increase in the CH4 emission, followed by atmospheric CO2 and nitrogen deposition. Given the importance of the potential positive feedback between CH4 emission and climate change, it is vital to have reasonable estimation of CH4 emission before developing the adaptation strategies.