Dangerous greenhouse gas methane is leaking from the seafloor in Antarctica, find scientists
The finding is providing researchers a new understanding of the role methane may play
Antarctica is estimated to contain as much as a quarter of the Earth’s marine methane and now scientists have, for the first time, discovered an active leak of methane gas from the seafloor in Antarctica. Methane is a greenhouse gas that is 25 times more powerful than carbon dioxide at warming the planet. The Antarctic marine “methane seep” was found at a site known as Cinder Cones in McMurdo Sound within the Ross Sea. Methane seep is a location where methane gas escapes from an underground reservoir and into the ocean. If the methane reaches the atmosphere, it could intensify global warming.
While the ultimate source of this methane remains unknown, the discovery of active methane seep in Antarctica is providing scientists a new understanding of the methane cycle and the role methane found in this region may play in warming the planet. Most methane in the ocean water and sediment is kept out of the atmosphere by microbes that consume it. However, the researchers found that the most common type of microbe that consumes methane took five years to show up at the seep site, and even then those microbes were not consuming all of the methane. This implies that some methane is being released and is likely working its way into the atmosphere, says the team.
The Ross Sea seep was discovered in an area that scientists have studied for more than 60 years, but the seep was not active until 2011, says Andrew Thurber, author of the study and a marine ecologist at Oregon State University (OSU), US. Methane seeps have been found throughout the world's oceans, but the one discovered in the Ross Sea was the first active seep found in Antarctica, adds Thurber.
“Methane is the second-most effective gas at warming our atmosphere and the Antarctic has vast reservoirs that are likely to open up as ice sheets retreat due to climate change. This is a significant discovery that can help fill a large hole in our understanding of the methane cycle,” writes Thurber in the analysis published in the Proceedings of the Royal Society B.
Thurber happened to be in Antarctica in 2012 when another researcher told him about a “microbial waterfall” and thought it was something he should look at. Thurber was able to confirm the seep's presence, collect samples, and analyze the seep and its environment. When he returned to the site in 2016 to conduct further study, he also discovered a second seep.
Having an active seep to study gives researchers a new understanding of the methane cycle and how that process might differ in Antarctica compared to other places on the planet, nearby. It is important to understand how methane seeps behave in this environment so researchers can begin factoring those differences into climate change models, say experts. “We’ve never had the opportunity to study a seep as it's forming or one in Antarctica. Because of this discovery, we can now uncover whether seeps just function differently in Antarctica or whether it may take years for the microbial communities to become adapted,” explains Thurber.
The analysis shows that an expansive “microbial mat”, about 70 meters long by a meter across, formed on the seafloor about 10 meters below the frozen ocean surface. These mats, which are produced by bacteria that exist in a symbiotic relationship with methane consumers, are a telltale indication of the presence of a seep. “The microbial mat is the road sign that there's a methane seep here. We don't know what caused these seeps to turn on,” says Thurber.
Studying the site over five years allowed researchers to see how microbes respond to the formation of a seep. “What was interesting and exciting was that the microbial community did not develop as we would have predicted based on other methane seeps we have studied around the globe,” says co-author Sarah Seabrook, who earned her doctorate at OSU and is now a post-doctoral scholar at the National Institute of Water and Atmospheric Research in Wellington, New Zealand.
The research team had assumed that microbes should respond quickly to changes in the environment, but that was not reflected in what OSU's team saw in Antarctica. “To add to the mystery of the Antarctic seeps, the microbes we found were the ones we least expected to see at this location,” says Thurber. He adds, “Animals in Antarctica are very different than elsewhere in the world as the continent has been separated from the rest of the globe for more than 30 million years — a long time for evolution to act. That has resulted in a remarkable diversity of fauna that we only find there. That may also contribute to the differences in microbes there.”
The finding that the microbes around the Antarctic seep are fundamentally different than those found elsewhere in the world's oceans is helping the scientists better understand methane cycles and the factors that determine whether methane will reach the atmosphere and contribute to further warming. According to the team, the analysis shows how microorganisms change and develop “may have an unrealized impact on greenhouse gas emission from marine methane reservoirs.”
There may be a succession pattern for microbes, with certain groups arriving first and those that are most effective at eating methane arriving later, the authors explain. The results suggest that the accuracy of future global climate models may be improved by considering the time it will take for microbial communities to respond to novel methane input, says the team.