Predictions of future methane ebullition in subarctic lakes using long-term climate data and energy proxies

Tuesday, 16 December 2014: 5:45 PM
Brett F Thornton, Martin Wik and Patrick M Crill, Stockholm University, Dept. of Geological Sciences, Stockholm, Sweden
Correlations between seasonal energy input and methane (CH4) bubbling (ebullition) in northern lakes suggest that energy proxies might provide a constraint on the magnitude of future CH4 emissions. Ebullition is a major pathway for transporting anaerobically produced CH4 from lake sediments to the atmosphere, and represents a difficult to quantify CH4 source. In post-glacial arctic lakes during the ice-free season, solar shortwave energy input can constrain CH4 productivity via control of sediment temperature. Utilizing long-term temperature trends we calculate CH4 ebullition from three subarctic lakes in northern Sweden over the period of 1916-2079. Using observed energy trends, the average lake emission is estimated at 1128 mg m-2 yr-1 for 1916-1926; we predict an approximately 2000 mg m-2 yr-1 in the 2040-2079 period. Our study lakes and our measured CH4 ebullition rates are typical for the pan-Arctic, suggesting that such increases in CH4 ebullition might be widespread.