Arctic lakes produce less methane than previously thought

In the realm of greenhouse gasses, methane stands out as a significant contributor due to its abundance and potent heat-trapping properties, about 25 times more potent than carbon dioxide. 

With the Arctic being the fastest warming part of the globe, understanding methane emissions becomes crucial. 

Focus of the study

Experts at Brown University used satellite and airborne imagery from NASA to provide new insights into methane emissions from Arctic lakes and wetlands, previously largely unmapped.

Contrary to earlier research estimating that these unmapped lakes contribute around 40 percent of the region’s methane emissions, the current study found that small unmapped lakes contribute only about three percent to the overall emissions. 

New insights 

The high-resolution imagery allowed researchers to more accurately estimate the area covered by these smaller lakes, revealing that they are more significant emitters per unit area than previously thought.

“What the research has shown is that these smaller lakes are the greater emitters of methane on a per-area basis, which means even though they take up a small amount of the landscape, they have a disproportionate level of emissions,” said lead author Ethan D. Kyzivat, a postdoctoral fellow at Brown. 

The study challenges close to 15 years of research based on older datasets with lower resolution quality, which had overestimated the number of small lakes and their cumulative methane emissions.

Unexpected findings 

The focus of the study was on small lakes, roughly a tenth of a square kilometer or smaller. The research team, including Brown professor Laurence C. Smith, analyzed high-resolution airborne data and a global map of lakes in the Arctic region to produce more accurate estimates. 

The study revealed fewer small, unmapped lakes than previously thought, leading to a significant reduction in the cumulative methane emissions attributed to them.

The unexpected findings also include the discovery of double-counting of lakes as wetlands, affecting methane emission estimates. 

Study implications 

Furthermore, the study may help reconcile the longstanding discrepancy between “bottom-up” estimates, which model emissions based on Earth maps, and “top-down” estimates, which use atmospheric measurements. 

The improved satellite resolution now allows for a closer examination of methane emissions, potentially unifying these two approaches.

The experts see this NASA-funded study as a proof of concept and plan to expand their methane modeling technique to other regions globally. “The next step is to go global,” Kyvizat concluded.

More about methane

Methane is a potent greenhouse gas, with a global warming potential significantly higher than carbon dioxide on a per-molecule basis, especially over a 20-year period. It is released into the atmosphere through a variety of sources, including natural processes like wetland decomposition and geological seepage, as well as human activities such as agriculture (particularly livestock digestion and rice paddies), waste management (landfills), and the production and transport of fossil fuels like natural gas and oil.

Methane’s significant impact on climate change is due to its ability to trap heat in the atmosphere very effectively. However, it has a shorter atmospheric lifetime than carbon dioxide, lasting about 9-12 years before breaking down. This means that reducing methane emissions can have a rapid and significant impact on mitigating global warming.

Efforts to reduce methane emissions include improving agricultural practices, capturing gas from landfills and livestock, fixing leaks in natural gas pipelines, and transitioning to renewable energy sources. The importance of addressing methane emissions is increasingly recognized in global climate change discussions and policy-making.

The study is published in the journal Geophysical Research Letters.

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