Melting ice sheets in Greenland are releasing tonnes of methane (CH4) into the atmosphere, a new study led by the researchers from the University of Bristol has found.
According to the study, microorganism presents in sediments beneath the Greenland Ice Sheet produce methane, which is then released into the atmosphere by meltwater during summers. Based on the new finding, the researchers suggest that the impact of the subglacial biological activity on the atmosphere could actually be much more than previously thought.
Methane is an important greenhouse gas in the atmosphere. While it is found in lower quantities in the atmosphere compared to carbon dioxide (CO2), it is more potent than CO2 and can have disproportionate impact on atmospheric temperatures. On Earth, methane is mostly produced by microorganisms, farm animals, or through fossil fuels.
In the past, some studies have reported detecting methane in Greenland ice cores, but this is the first time that researchers have found methane being emitted from the ice sheet beds during summers.
In the current study, the research team camped close to the Greenland Ice Sheet for about three months and collected samples of the meltwater running off a large catchment (with area more than 600 square kilometres) of the Ice Sheet during the summer months. The team used advanced sensors to measure the amount of methane dissolved in the discharged water in real time, and found that the water was supersaturated with methane.
Based on the calculations, the team estimated that this specific portion of the Ice Sheet alone exported at least 6.3 tonnes of methane to the measuring site.
According to researchers, the study provides evidence of a widespread subglacial microbial system, with active microorganisms living under massive ice sheets and likely impacting other parts of the Earth system.
A stable-isotope analysis indicated a microbial origin for methane, most likely from a mixture of inorganic and ancient organic carbon buried below the ice.
"This subglacial methane is essentially a biomarker for life in these isolated habitats," said Guillaume Lamarche-Gagnon from Bristol's School of Geographical Sciences and the lead author of the study.
According to researchers, the ice sheet beds in Greenland - holding massive reserves of carbon, water, microorganisms, but little oxygen - provide just perfect conditions to microorganisms to produce methane gas.
"The new sensor technologies that we used give us a window into this previously unseen part of the glacial environment," said co-researcher Dr Elizabeth Bagshaw from Cardiff University.
The findings of the study are published in journal Nature.
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