The Nord Stream gas remains in the sea

Published 26 June 2024 at 09.18

Domestic. A large part of the methane released into the southern Baltic Sea from the Nord Stream gas pipeline has remained in the water, measurements show.

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It was at the end of September 2022 as the Nord Stream gas pipeline on the bottom of the Baltic Sea exploded east of Bornholm and one of the largest unnatural methane gas emissions ever was a fact.

The methane gas from the pipeline created large bubbles at the water surface and measurements showed elevated levels of methane in the atmosphere.

But large parts of the methane never reached the surface and dissolved in the water instead. This is shown by a scientific study that has now been published in Scientific Reports.

– Thanks to fortunate circumstances, we were able to convene an expedition to the area of ​​the leak in less than a week. Based on what we measured, we estimate that between 10,000 and 50,000 tonnes of methane remained in the sea in dissolved form, says Katarina Abrahamsson, professor of marine chemistry at Gothenburg University.

The methane was spread over large areas and has been dissolved in the water where some is taken care of by bacteria. Even in normal cases, methane is present in the water, it has been formed during the breakdown of organic material in the bottom sediments.

– In our study, we have been able to distinguish the methane that comes from the Nord Stream leak from that which is found naturally in the water , thanks to the fact that the methane from the gas line has a different isotopic composition than that which seeps up from the bottom sediments. It is a strength of our study, says Katarina Abrahamsson in a dispatch.

The water in the sea is normally in different layers due to differences in temperature and salinity. Despite the fact that the methane leaked out of the gas pipeline in large quantities and speed, the researchers could not note any major mixing in the water masses. The layering that normally occurs at the end of September was fixed. The levels of the leaked methane therefore varied greatly in the water. The researchers assume that the methane was diluted in a larger water mass later in the autumn when the water was mixed due to falling water temperature.

What impact the elevated methane levels have on the biological life in the southern Baltic Sea, it is too early to say. about.

– On the expedition there were also researchers who took plankton samples in the affected area, the analyzes of these are not ready yet, says Katarina Abrahamsson.

Three months after the first expedition, a return visits to the area and new measurements were made. Preliminary results show that the activity of the bacteria has been great during these three months. Scientists do not yet know how plant and animal plankton have been affected by it.