Researchers discover previously unknown methane source beneath Greenland’s ice sheet
Methane formed deep in the bedrock hundreds of millions of years ago has been detected in meltwater from Greenland’s glaciers. The findings suggest that geological methane may be a new factor to consider when assessing how methane emissions contribute to climate change.
Methane, a very potent greenhouse gas, is second only to carbon dioxide in contributing to global warming. It is usually produced when microorganisms break down organic matter, such as dead algae on the seabed. However, the gas can also be geological in origin, meaning that it was formed and stored deep within the bedrock over hundreds of millions of years, alongside oil and natural gas.
Now researchers at Linnaeus University, together with colleagues from other institutions, have been able to show that geological methane is carried to the surface by meltwater from Greenland’s glaciers.
Meltwater sampling
The study is based on meltwater sampling carried out during a research expedition to northern Greenland in 2024. The aim of the study was to gain a better understanding of natural methane emissions in the area – but the researchers expected to find only methane of microbial origin.
“It’s well known that there’s oil and gas in the bedrock beneath Greenland. But this is the first time we’ve been able to show that methane from these geological systems reaches the surface via meltwater from the glaciers. The results surprised us; we had to double-check the sample data and look into all possible explanations”, says Marcelo Ketzer, professor of environmental science at Linnaeus University and lead author of the study, which was published in Nature Communications.
Tracing the methane to its source
The researchers were able to determine the origin of the methane by analysing its composition. Although geological and microbial methane are the same gas, they contain different proportions of the isotopes carbon-12 and carbon-13, making it possible to distinguish between them in laboratory tests. The isotopic signatures, together with the knowledge that oil and gas deposits exist beneath Greenland, make the researchers confident about the source of the methane.
“The climate models currently used to calculate how much greenhouse gas is released into the atmosphere assume that natural methane emissions in Greenland come only from microbes. Our results point to an additional source, which may need to be factored in”, says Marcelo Ketzer.
Could be more widespread
The measured concentrations of geological methane in the meltwater was relatively low. The researchers do not yet know how the levels vary over time or how widespread the phenomenon is elsewhere in Greenland. Geological methane could potentially leak out in any area with oil and natural gas deposits; other places where it has been found include the Atlantic, the Mediterranean and Svalbard.
The researchers now see a need to investigate other parts of Greenland thoroughly in order to understand how widespread the phenomenon is.
“Greenland has one of the largest ice sheets in the world. As the ice melts and the land rises, cracks form in the ground, potentially creating new pathways for methane to escape from the ground and into the atmosphere.”
More information
Link to the study: Thermogenic methane beneath the North Greenland Ice Sheet revealed by isotopic and geological evidence
