Methane is escaping from cracks in the seabed of the Barents Sea

The illustration shows columns of methane gas several hundred meters high rising from the seabed. The image is based, among other things, on seismic and sonar data.

(Image: Serov et al., 2024 / CC BY 4.0)

But does it have an impact on the climate?

The seabed in parts of the Barents Sea is riddled with cracks. Methane gas seeps out of some of these cracks, forming gas columns that rise from the seafloor.

While methane gas is an important component of the natural gas produced by oil platforms, these emissions are natural, not industrial, in nature.

The gas escapes from large deposits of oil and gas beneath the seafloor and emerges from thousands of cracks and faults.

Seafloor studies have identified over 21,000 locations where methane is rising from the seafloor. This finding is detailed in a new study published in Frontiers in Earth Science.

Natural leakage

“This area is unique because there are so many natural leaks,” Monica Winsborrow tells sciencenorway.no.

She is an associate professor at UiT The Arctic University of Norway and one of the researchers behind the new study.

Researchers estimate that around 9,800 tons of methane leak through these cracks into the seafloor and oceans every year.

“We think there are one or two orders of magnitude more leakage here than in other similar ocean areas,” she says.

A key factor in the high leakage is that multiple ice ages have eroded the seabed over time.

“Over the course of two million years, several ice sheets have grown and disappeared. “The ice sheet is eroding the seafloor, so the hydrocarbons are getting closer and closer to the seafloor,” she says.

The study is based on a large-scale mapping of the seafloor around Norway, called Mareano, carried out by the Geological Survey of Norway (NGU). This research represents an important part of the knowledge base for seabed mining, which you can read more about here.

But where does all the methane go? And does it get into the atmosphere?

Illustration shows how the seabed is mapped with a research vessel.

(Image: Norwegian Mapping Authority)

Very little

Researchers aren't sure how much of this methane ends up in the atmosphere, but it's probably a very small amount.

They estimate that only 0.05 percent of total methane emissions enter the atmosphere, although there is considerable uncertainty.

Most of the methane is consumed by microbes living on the seafloor, and some is also carried away by ocean currents, explains Winsborrow.

The methane is oxidized and breaks down into oxygen and CO₂.

Winsborrow points out that there are still many unknowns, such as how these emissions change throughout the year and whether microbial activity changes with the seasons.

To better understand the processes, more precise air measurements are needed over these ocean areas at different times of the year.

Methane as a greenhouse gas

Despite this leak, the Barents Sea is a relatively small source of atmospheric methane compared to other sources.

Overall, researchers estimate that about 600 million tons of methane are released into the atmosphere each year, although there is considerable uncertainty surrounding this number.

While carbon dioxide is the most widely discussed greenhouse gas, methane also plays a significant role in global emissions.

Methane is far more effective than CO₂ It traps heat, making it a much more effective greenhouse gas. According to the US Environmental Protection Agency, it is 28 times more effective.

About a third of all methane emissions come from natural sources.

“Most natural methane emissions come from wetlands,” says Ragnhild Bieltvedt Skeie. She is an atmospheric researcher at the Cicero Center for International Climate Research.

Some methane also comes from geological processes.

However, the majority of methane emissions are due to human activities.

“Over the last decade, human-caused methane emissions have increased, and we have seen a significant increase in methane concentrations in the atmosphere,” she says.

Skeie explains that most of these emissions come from livestock, waste management and oil and gas production.

———

Translated by Alette Bjordal Gjellesvik

Read the Norwegian version of this article on forskning.no

Reference:

Serov et al. Geological and glaciological controls of 21,700 active methane seeps in the northern Norwegian Barents Sea. Frontiers in Earth Science, Vol. 122024. DOI: 10.3389/feart.2024.1404027