(Stockholm) A team of Swedish researchers has detected a significant natural release of methane, a gas that contributes to global warming, from the deep waters of the Baltic Sea, they said on Friday.
The expedition found this gas at a depth of around 400 meters, off the coast of Nynäshamn in southeastern Sweden, over an area of around 20 km2.
Methane is released from microorganisms living in marine sediments, but it is also produced by human activities, such as agriculture and oil and gas installations.
Methane is responsible for around 30% of global warming since pre-industrial times. Over a period of 20 years, its warming effect is 80 times more powerful than that of carbon dioxide.
“We know that methane bubbles can escape from the shallow coastal seabed of the Baltic Sea, but I have never seen such intense bubble emanation before, and certainly not from such a deep area,” he said. estimated Christian Stranne, researcher cited in the press release from Stockholm University who is leading this project with Linnæus University in Växjö.
Researchers are used to seeing methane bubbles rising 150 to 200 meters above the seabed, but in this case they were surprised to observe bubbles 370 meters above the seabed, or close to the surface. .
“The methane contained in the bubbles is dissolved in the sea and their size therefore gradually decreases as they rise towards the surface of the sea,” according to the professor of marine geophysics.
“I am not aware of any studies where such persistent bubbles have been observed at these depths.”
“This could be a new world record, which could force us to reassess the role of deep areas in terms of contributing to methane in surface waters,” added the researcher.
According to him, in the absence of oxygen in the deep waters of the Baltic, the levels of dissolved methane in the sea can be relatively high and the bubbles remain more intact, therefore can rise the methane higher.
The researchers, who did not quantify the release, took a significant number of sediment cores and water samples to understand why so much methane is being released in this specific area.
The researchers now hope to conduct new analyzes to find out why methane emissions are so high in these areas.