A study by researchers from the University of Gothenburg and the Voice of the Ocean research foundation reveals that methane released from the damaged Nord Stream pipelines affected a vast area of the southern Baltic Sea and lingered for several months.
A significant portion of the methane gas from the Nord Stream leakage quickly ascended to the ocean’s surface and entered the atmosphere. However, some of the methane remained submerged and was subsequently carried away by ocean currents.
“Our measurement findings indicate that methane spread widely across the southern Baltic Sea, reaching from the coastline of Danish Zealand in the west to the Polish Gulf of Gdansk in the east,” states Martin Mohrmann, a researcher at Voice of the Ocean, VOTO.
Precise Measurements
The Voice of the Ocean Foundation utilized an underwater robot, known as a glider, positioned just outside the exclusion zone surrounding the leaks. This device provided the researchers with the ability to assess methane levels over a broad area, from the water’s surface to deeper levels. Additionally, they continued their measurements with the glider for three months after the incident, ultimately gathering the most precise data from the vicinity of the leaks, which greatly enhances the reliability of their findings.
“To achieve the most reliable estimates, we combined data gathered by the gliders with surface readings acquired by our colleagues at the German research institute IOW, collected from a ferry. It was rewarding to see the consistency between these results and those from the expedition conducted by the University of Gothenburg’s research vessel in the Nord Stream leak area. This comprehensive approach has given us confidence that we have captured an accurate representation of the methane dispersion in the Baltic Sea, over both time and distance,” remarks Bastien Queste, an oceanographer at the University of Gothenburg.
Substantially Elevated Levels
Shortly after the pipeline explosion in late September 2022, methane concentrations in the waters were often found to be 1,000 times higher than normal. In certain locations, elevated methane levels persisted for several months following the release, before being diluted, consumed by bacteria, or released into the atmosphere.
“Our gliders, coupled with ocean modeling of the southern Baltic Sea, have provided us with a clear understanding of the regions impacted by the spill. Overall, we estimate that over 14 percent of the entire Baltic Sea experienced methane levels at least five times higher than normal,” states Martin Mohrmann.
Impact on Marine Protected Areas
The findings of this study have been published in Nature Communications, together with two additional studies that have assessed the ramifications of the Nord Stream emission on the atmosphere. Researchers from VOTO and the University of Gothenburg utilized their measurements to build a strong model illustrating how methane was dispersed through the water. The ocean currents carried methane to 23 designated marine protected areas.
“We now have a clearer understanding of the regions potentially affected by the methane release. This will simplify the process of determining whether any future issues within the Baltic Sea ecosystems can be traced back to the Nord Stream leak,” explains Bastien Queste.
