Geospatial analysis of Alaskan lakes indicates wetland fraction and
surface water area are useful predictors of methane ebullition
Abstract
Arctic-Boreal lakes emit methane (CH₄), a powerful greenhouse gas.
Recent studies suggest ebullition may be a dominant methane emission
pathway in lakes but its drivers are poorly understood. Various
predictors of lake methane ebullition have been proposed, but are
challenging to evaluate owing to different geographical characteristics,
field locations, and sample densities. Here we compare large geospatial
datasets of lake area, lake perimeter, permafrost, landcover,
temperature, soil organic carbon content, depth, and greenness with
remotely sensed methane ebullition estimates for 5,143 Alaskan lakes. We
find that lake wetland fraction (LWF), a measure of lake wetland and
littoral zone area, is a leading predictor of methane ebullition (adj.
R² = 0.211), followed by lake surface area (adj. R² = 0.201). LWF is
inversely correlated with lake area, thus higher wetland fraction in
smaller lakes may explain a commonly cited inverse relationship between
lake area and methane ebullition. Lake perimeter (adj. R² = 0.176) and
temperature (adj. R² = 0.157) are moderate predictors of lake
ebullition, and soil organic carbon content, permafrost, lake depth, and
greenness are weak predictors. The low adjusted R² values are typical
and informative for methane attribution studies. A multiple regression
model combining LWF, area, and temperature performs best (adj. R² =
0.325). Our results suggest landscape-scale geospatial analyses can
complement smaller field studies, for attributing Arctic-Boreal lake
methane emissions to readily available environmental variables.