Opposing Effects of Climate and Permafrost Thaw on CH4 and CO2 Emissions From Northern Lakes

Small, organic-rich lakes are important sources of methane (CH4) and carbon dioxide (CO2) to the atmosphere, yet the sensitivity of emissions to climate warming is poorly constrained and potentially influenced by permafrost thaw. Here, we monitored emissions from 20 peatland lakes across a 1,600 km permafrost transect in boreal western Canada. Contrary to expectations, we observed a shift from source to sink of CO2 for lakes warmer regions, driven by greater primary productivity associated with greater hydrological connectivity to lakes and nutrient availability in the absence of permafrost. Conversely, an 8-fold increase in CH4 emissions in warmer regions was associated with water temperature and shifts in microbial communities and dominant anaerobic processes. Our results suggest that the net radiative forcing from altered greenhouse gas emissions of northern peatland lakes this century will be dominated by increasing CH4 emissions and only partially offset by reduced CO2 emissions.
Funding Agencies|Natural Sciences and Engineering Research CouncilNatural Sciences and Engineering Research Council of Canada (NSERC); Campus Alberta Innovates Program; NWT Cumulative Impact Monitoring Program; Northern Scientific Training Program, University of Alberta; UAlberta North, Vanier Canada Graduate Scholarship; W. Garfield Weston Foundation; FAPESPFundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [2018/19,247-0, 2019/24,097-0]; Bruckmann Fund, Peterhouse College, University of Cambridge; H2020 ERC [804673, 725546]; Swedish Research Council VRSwedish Research Council [2016-04829]; FORMASSwedish Research Council Formas [2018-01794]