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...

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Veröffentlicht in:AGU Advances 2021-12, Vol.2 (4), p.n/a
Hauptverfasser: Kuhn, McKenzie A., Thompson, Lauren M., Winder, Johanna C., Braga, Lucas P. P., Tanentzap, Andrew J., Bastviken, David, Olefeldt, David
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Sprache:eng
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Zusammenfassung: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. Plain Language SummaryMethane (CH4) and carbon dioxide (CO2) emissions from small lakes are globally significant, yet highly uncertain and our understanding of how CH4 and CO2 emissions from small lakes in the north will change with warming and permafrost (i.e., frozen ground) is not well known. Here, we measured emissions from 20 lakes across a 1,600 km climate and permafrost gradient. Our results show that CH4 and CO2 emissions followed opposing trends along a north‐to‐south gradient. We show that increasing CH4 emissions are strongly associated with warmer temperatures while decreasing CO2 exchange is linked to shifts in hydrology and within‐lake primary productivity brought on by the absence of permafrost. Our results indicate small northern lakes have the potential to be greater sources of CH4 but also greater CO2 sinks. Key PointsLake methane emissions increased moving south along a climate and permafrost gradient and were linked with increasing water temperaturesLake carbon dioxide exchange decreased moving south and was driven by greater hydrological connectivity and nutrient availabilityNet radiative forcing from the lakes will increase due to increased methane emissions, despite decreasing carbon dioxide emissions
ISSN:2576-604X
2576-604X
DOI:10.1029/2021AV000515