Groundwater discharge as a driver of methane emissions from Arctic lakes

Lateral CH₄ inputs to Arctic lakes through groundwater discharge could be substantial and constitute an important pathway that links CH₄ production in thawing permafrost to atmospheric emissions via lakes. Yet, groundwater CH₄ inputs and associated drivers are hitherto poorly constrained because their dynamics and spatial variability are largely unknown. Here, we unravel the important role and drivers of groundwater discharge for CH₄ emissions from Arctic lakes. Spatial patterns across lakes suggest groundwater inflows are primarily related to lake depth and wetland cover. Groundwater CH₄ inputs to lakes are higher in summer than in autumn and are influenced by hydrological (groundwater recharge) and biological drivers (CH₄ production). This information on the spatial and temporal patterns on groundwater discharge at high northern latitudes is critical for predicting lake CH₄ emissions in the warming Arctic, as rising temperatures, increasing precipitation, and permafrost thawing may further exacerbate groundwater CH₄ inputs to lakes.