Underwater robots deployed to study Nord Stream gas leaks

The Nord Stream pipelines were commissioned in 2011 to move natural gas from Russian fields into Western Europe.

But on 26 September 2022, both pipelines experienced multiple large pressure drops to almost zero, attributed to three unexplained underwater explosions that caused the gas inside to leak into the sea.

The study from a team at the University of Gothenburg is being conducted to follow how chemistry and life in the sea changes over time due to the large release of methane gas.

Three remote-controlled robots, which will be managed by the Voice of the Ocean Foundation (VOTO), will move around the sea and record water data continuously for the next 15 weeks.

“They are called gliders and are provided by VOTO, who also manages their operation. The robots can give us measurements over a series of time about how the chemistry and quality of the water is affected by the natural gas leak,” said oceanographer Bastien Queste at the University of Gothenburg.

Since March 2021, VOTO has had two gliders in the area which functions as one of the foundation’s ocean observatories and where the water quality is measured non-stop.

The robots go down to the bottom and then turn up to the surface, something that is repeated over a pre-set distance. Every time the glider is at the surface, the latest measurement data is sent to the researchers via satellite.

One of the three additional robots that was dropped into the sea last week has been equipped with a special sensor to measure the change in the methane content over the next 15 weeks.

“With the new robots in place, we receive continuous reports on the state of the water near the Nord Stream pipeline leaks. They are deployed solely for this purpose,” Queste said.

“The point is that we get measurements from the water over a long period of time and over a larger area. We can see how long it takes for the methane to disappear and how the aquatic environment reacts over time. The response in the sea is often delayed. It may take days or weeks before we see a change.”

The underwater robots that were already deployed will continue to contribute important data as they measure salinity, temperature, oxygen content and the amount of chlorophyll to provide a complete picture of how the water in the Baltic Sea has been affected by the gas leak.

In addition, another research vessel – Skagerak – is set to deploy on a new expedition to the Baltic Sea to test run a large, unmanned vessel known as Ran.

Ran will be tested to see how it behaves in seas with varying density levels and how well it can take measurements over sediment-rich bottoms. Ran will also be able to contribute to research into gas emissions because it measures the carbon dioxide and nitrate levels in the water.