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

Abstract:

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.