Approximately 465 thousand metric tonnes of methane were emitted by the Nord Stream submarine gas pipeline leaks in 2022, according to three studies published in the journals Nature and Nature Communications. This is the largest amount of methane released by a single transient event reported to date, although it represents only 0.1% of anthropogenic methane emissions for 2022.
Submarine natural gas leaks resulting from pipeline ruptures can emit large quantities of methane — an important greenhouse gas — into the ocean and the atmosphere. In September 2022, damage to the twin Nord Stream pipeline systems (a network of offshore pipelines lying beneath the Baltic Sea) led to the release of natural gases, predominantly methane, at four different locations.
However, the total amount of methane released to the atmosphere and dissolved in the ocean remains uncertain, and the potential environmental and climatic impacts are not clear.
In an article published in the journal Nature, Stephen Harris and their colleagues simulated the emission rates from pipeline ruptures and integrated them with other methane estimates to model the amount of atmospheric emissions from the leaks.
The authors also compared these results with emission estimates derived from aerial data, satellite data and weather towers. Harris and their colleagues found that approximately 465 thousand metric tonnes of methane were emitted to the atmosphere. The atmospheric emissions from the leaks account for about 1.2% of natural gas sector emissions and 0.3% of methane emissions from agriculture in 2022.
In a companion article to Nature Communications, Martin Mohrmann and colleagues investigated the spread of dissolved methane across different regions of the Baltic Sea and in marine protected areas. They suggest that 14% of the Baltic Sea registered concentrations five times higher than natural baseline levels. This may have affected 23 marine protected areas, though the consequences for the ecosystem are not clear.
In a second article in Nature Communications, Friedemann Reum and colleagues quantified the secondary release of methane to the atmosphere, which was initially dissolved in seawater. They were able to estimate the magnitude and distribution of these emissions, helping to determine the fate of the methane that escaped from the pipelines.
