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Warming Arctic lakes may release more methane than expected

The findings are important because methane is over 25 times more powerful than carbon dioxide as a greenhouse gas. Arctic lakes are already major natural methane sources globally, but the processes that control how methane is produced and released from lake sediments have remained poorly understood—until now.

In this study, Ph.D. candidate Marie Bulínová from the Geosciences Department at UiT The Arctic University of Norway worked with an international team that investigated 10 Arctic lakes across Svalbard and subarctic Scandinavia. They found that methane production in lake sediments was highest where lakes had greater productivity—more algae, aquatic plants, and land vegetation, and shallower depths. The findings are in the Journal of Geophysical Research: Biogeosciences.

"We were surprised by how clearly the productivity of the ecosystem was linked to methane production," said Marie. "Our results show that warmer and wetter conditions increase biological productivity in Arctic lakes, which in turn drives methane emissions from their sediments."

Most methane was produced within the top 10 cm of lake sediment. In these shallow layers, the combination of fresh, organic-rich material and enhanced microbial activity creates ideal conditions for methane generation. The researchers calculated how much methane is likely to diffuse from the sediment into the overlying water and eventually into the atmosphere.

Striking differences between Arctic lakes and beyond

The team compared their findings with data from over 60 lakes worldwide. This revealed that methane fluxes from individual Arctic lakes are generally lower than those in tropical or temperate regions, but still significant and highly variable considering the large number of lakes in northern landscapes. And surprisingly, they are similar to some boreal lakes.

Marie explained, "One of the striking aspects of this work is how different Arctic lakes are from each other. Some release much more methane than others, depending on local factors like vegetation cover, lake shape, or sediment composition. That's why it's essential to study a wide range of lake types if we want to understand the Arctic's role in future climate feedbacks."

The researchers also built predictive models using machine learning to identify the most important factors driving methane emissions across different biomes. This helped to highlight the importance of primary productivity and climate variables—especially temperature and precipitation.

Tracking climate feedbacks in a changing Arctic

This research adds an important piece to the puzzle of how Arctic ecosystems respond to climate change. As temperatures rise and growing seasons lengthen, Arctic landscapes are greening and lakes are expected to become more productive, which could lead to higher methane emissions.

The study underscores the importance of including lake sediments in Arctic greenhouse gas budgets. It also shows that seemingly small environmental changes can have large effects on methane emissions.

"The Arctic is changing rapidly, and we need to understand all the feedback involved," said Marie. "Our work suggests that increases in ecosystem productivity—something we could think of being positive—can also increase methane release and further accelerate warming."