A recent study conducted by researchers from the University of Gothenburg and the Voice of the Ocean research foundation has revealed that methane from the Nord Stream pipelines, which were destroyed in September 2022, spread over a large part of the southern Baltic Sea and remained for several months.

The study found that while a significant amount of the methane gas from the Nord Stream leak rose directly to the sea surface and into the atmosphere, some of it remained below the surface and was dispersed by ocean currents.

Martin Mohrmann, a researcher at Voice of the Ocean, stated, “The results of our measurements show that methane spread to large parts of the southern Baltic Sea, from the coast of Danish Zealand in the west, to the Polish Gulf of Gdansk in the east.”

The Voice of the Ocean Foundation deployed gliders outside the exclusion zone around the leaks to measure methane concentrations over a large area, from the surface to the depths, continuing their measurements for three months after the spill. They combined these observations with surface data collected by the German research institute IOW from a ferry to ensure robust estimations.

During the initial period following the pipeline explosion, methane levels in the waters were significantly elevated, sometimes reaching levels 1,000 times above normal. Abnormal concentrations of methane were still present in some areas several months after the release, before being diluted, consumed by bacteria, or escaping to the atmosphere.

Mohrmann added, “We estimate that over 14% of the entire Baltic Sea was exposed to methane levels that were at least five times above normal.” The ocean currents transported the methane to 23 marine protected areas.

The study results, published in Nature Communications, along with two other studies mapping the impact of the Nord Stream emission on the atmosphere, have provided valuable insights. Researchers have utilized their measurements to create a model detailing how the methane was dispersed in the water.