Shallow, Meltwater Lakes in Alaska May Release Potent Methane as the Climate Changes

As temperatures warm, more and more methane may be dumped into our planet's atmosphere. Scientists have found that methane-generating microbes found in thawing lake sediments may ramp up production of the potent greenhouse gas, which may lead to further warming.

Thermokarst lakes occur as permafrost thaws. The thawing land creates surface depression where meltwater accumulates, converting what was previously frozen land into small freshwater lakes with active decomposing sediment layers.

Although scientists have long known that methane and carbon dioxide releases from thawing permafrost are important sources of global greenhouse gas emissions, very little is known about the sources and rates of methane production from microbial communities found in these changing environments.

"The large amount of organic matter stored in the thaw layer between the water column and the permafrost table serves as a significant source of carbon for methanogensis," said Paula Matheus Carnevali, the lead author of the new study, in a news release. "Identifying and understanding the production sources of methane will improve our ability to generate accurate predictions about the changing climate in the Arctic."

The researchers examined the methane dynamics within 16 sediment cores collected over a period of four years from two Alaskan thermokarst lakes in Alaska. Then, the researchers performed simulated climate scenarios, and analyzed the potential for increased biological production of methane from methanogens found in the lake sediments, the role of the sediment geochemistry in this process, and the temperature dependency of this process.

"This study marks an important step in recognizing that there are different methane sources in close proximity that may respond different in the changing Alaskan Arctic ecosystems," said Alison Murray, one of the researchers. "In scenarios of warming climate, our measurements indicate that biological methane production may play a larger role in total methane emissions in the future, which could have a significant impact on our climate."

The findings are published in the journal GeoBiology.

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