Increased Ecosystem Productivity Boosts Methane Production in Arctic Lake Sediments

Abstract

Global estimates of methane (CH₄) emissions from lakes to the atmosphere rely on understanding CH₄ processes at the sediment-water interface (SWI). However, in the Arctic, the variability, magnitude, and environmental drivers of CH₄ production and flux across the SWI are poorly understood. Here, we estimate CH₄ diffusive fluxes from the sediment into the water column in 10 lakes in Arctic Scandinavia and Svalbard using porewater modeling and mass transfer estimates, which we then compare with 60 published estimates from the Arctic to the tropics. Diffusion of CH₄ in the sampled lake sediments ranged from −0.46 to 3.1 mmol m⁻² day⁻¹, which is consistent with previous reports for Arctic and boreal lakes, and lower than for temperate and tropical biomes. Methane production occurs primarily within the top ∼10 cm of sediment, indicating a biogenic origin. Random forest predictive modeling of the sampled lakes revealed that conditions promoting production and deposition of autochthonous organic carbon in Arctic lakes drive CH₄ diffusion into the water column by fueling sediment CH₄ production. For small lakes across biomes, determinants of the estimated CH₄ flux were also best captured by climate predictors, with warmer and wetter conditions favoring ecosystem productivity and enhancing flux but also lake morphometry resulting in important regional variability in estimates. Our study emphasizes the importance of quantifying diffusive CH₄ fluxes from sediments in diverse lake types to account for differences in the controls on primary production and the preservation of organic carbon across and within different biomes, to refine CH₄ emission estimates in a warming climate.