Articles | Volume 12, issue 21
Research article
02 Nov 2015
Research article |  | 02 Nov 2015

Model estimates of climate controls on pan-Arctic wetland methane emissions

X. Chen, T. J. Bohn, and D. P. Lettenmaier

Abstract. Climate factors including soil temperature and moisture, incident solar radiation, and atmospheric carbon dioxide concentration are important environmental controls on methane (CH4) emissions from northern wetlands. We investigated the spatiotemporal distributions of the influence of these factors on northern high-latitude wetland CH4 emissions using an enhanced version of the Variable Infiltration Capacity (VIC) land surface model. We simulated CH4 emissions from wetlands across the pan-Arctic domain over the period 1948–2006, yielding annual average emissions of 36.1 ± 6.7 Tg CH4 yr−1 for the period 1997–2006. We characterized historical sensitivities of CH4 emissions to air temperature, precipitation, incident long- and shortwave radiation, and atmospheric [CO2] as a function of average summer air temperature and precipitation. Emissions from relatively warm and dry wetlands in the southern (permafrost-free) portion of the domain were positively correlated with precipitation and negatively correlated with air temperature, while emissions from wetter and colder wetlands further north (permafrost) were positively correlated with air temperature. Over the entire period 1948–2006, our reconstructed CH4 emissions increased by 20 %, the majority of which can be attributed to an increasing trend in summer air temperature. We estimated future emissions in response to 21st century warming as predicted by CMIP5 (Coupled Model Intercomparison Project Phase 5) model projections to result in end-of-century CH4 emissions 38–53 % higher than our reconstructed 1997–2006 emissions, accompanied by the northward migration of warmer and drier than optimal conditions for CH4 emissions, implying a reduced role for temperature in driving future increases in emissions.

Short summary
We used a process-based model to investigate the sensitivities of pan-Arctic wetland methane emissions to climate factors, as a function of climate. Over the period 1960-2006, temperature was the dominant driver of trends in emissions. Wetlands north of 60N were temperature-limited, and wetlands south of 60N latitude were water-limited. Projected future warming will cause water-limited wetlands to expand northward over the next century, lessening the role of temperature in the future.
Final-revised paper