As global warming profoundly transforms Arctic ecosystems, a new study reveals that lakes at high latitudes may be releasing more methane than previously thought. This greenhouse gas, far more potent than CO₂, is produced in the sediments of lakes that have become more biologically productive. A worrying dynamic, revealing new climate feedback loops.
Arctic lakes, long perceived as relatively stable carbon reservoirs, are proving to be a far greater potential source of methane than previously thought. As the region’s temperature rises and local ecosystems change, these lakes, already responsible for a significant amount of methane on a global scale, are likely to release far greater volumes of the greenhouse gas. A study conducted by Marie Bulínová, a PhD candidate at the Arctic University of Norway (UiT), and published on July 23 in the Journal of Geophysical Research: Biogeosciences shows that the biological productivity of Arctic lakes (in other words, the amount of organic matter produced by algae and aquatic plants) directly influences methane production in sediments. A crucial discovery that could help us better understand the role of these lakes in global warming.
Methane is a particularly powerful greenhouse gas, more than 25 times more effective than carbon dioxide at trapping heat in the atmosphere. Although it is already well documented that Arctic lakes emit methane, the exact mechanisms by which this gas is released were until now poorly understood.
Studying 10 lakes spread between Svalbard and subarctic Scandinavia, the research team observed that methane production in sediments was higher in lakes with greater biological productivity. This includes not only a greater amount of algae and aquatic plants, but also the terrestrial vegetation that lines these bodies of water. “We were surprised by how clearly the productivity of the ecosystem was linked to methane production,” explains Marie Bulínová in a press release issued by UiT.
The results of the study reveal that warmer, wetter conditions favor this productivity, leading to an increased release of methane from the sediments into the water column, and eventually into the atmosphere. The researchers calculated methane fluxes from sediments and found that they varied according to the specific characteristics of each lake. “Our results show that warmer and wetter conditions increase biological productivity in Arctic lakes, which in turn drives methane emissions from their sediments,” says Bulínová.
The role of Arctic lakes in global warming
Although methane fluxes observed in Arctic lakes are lower overall than those measured in more temperate or tropical regions, their potential impact on climate remains significant. The team compared Arctic methane fluxes with those from other regions of the world, and found that, although Arctic emissions are lower, they vary significantly from lake to lake. These differences are largely influenced by local factors such as vegetation cover, lake shape, and sediment composition.
The study also shows that some Arctic lakes, particularly those at higher latitudes, are releasing much higher levels of methane than expected, reinforcing the idea that these ecosystems could become increasingly responsible for emissions of this gas in the future. “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,” adds Marie Bulínová.
This regional variability, which stems from factors as diverse as lake morphometry, sediment chemistry and local climatic conditions, makes estimating methane fluxes on an Arctic scale all the more complex. Researchers have developed predictive models using machine learning techniques to better understand these variables. These models identified the main factors influencing methane emissions, namely temperature, precipitation and lake primary productivity. The study underlines the importance of a better understanding of these dynamics to predict the evolution of methane emissions in a context of global warming.
Climate in high gas mode
The results of this study reveal a vicious circle that could accelerate global warming. As temperatures continue to rise and plant growing seasons extend, Arctic ecosystems are expected to become more productive, which could lead to an increased release of methane. A phenomenon that risks reinforcing the effects of global warming rather than mitigating them. “The Arctic is changing rapidly, and we need to understand all the feedbacks involved. Our work suggests that increases in ecosystem productivity—something we could think of being positive—can also increase methane release and further accelerate warming,” she concludes.
Arctic lakes, often overlooked in greenhouse gas balances, could play a more central role than expected in future strategies to combat global warming. At a time when the scientific community is seeking to refine climate models and better understand methane emissions in northern ecosystems, this study highlights the importance of taking all factors (biological, geochemical and climatic) into account to correctly assess the risks associated with these ecosystems.