Good things come in small packages, like the microbes that live thousands of feet below the icy surface of Antarctica and might be the world’s last line of defense against global warming.

According to a study in Nature Geoscience, microbes may consume almost all the methane trapped down there, preventing the greenhouse gas from escaping into the atmosphere as Antarctica’s ice melts. If it were to be released from the ice and into the air, the methane would block even more heat from leaving the planet, so the microorganisms could serve as a small stopper against climate change.

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The microbes would not be a complete remedy for melting-related climate effects, however: They consume methane for fuel and convert it into carbon dioxide, so that byproduct would still be released into the atmosphere as Antarctica melts. But because methane has a much more powerful greenhouse effect than carbon dioxide, it still represents an improvement in the situation.

Scientists have for some years worried about what they believe is a massive subsurface supply of methane in Antarctica. It would be linked to organic matter left over from warmer times on the southernmost continent throughout Earth’s history.

Just as microbes are converting methane into carbon dioxide, they had originally converted the organic matter — specifically organic carbon — into methane to begin with.

“Aquatic habitats beneath ice masses contain active microbial ecosystems capable of cycling important greenhouse gases,” according to the study.

Glacier_Melting A melting glacier in Antarctica is seen from the air. As this ice melts, microbes that eat methane might reduce the amount of climate-affecting gas being released into the atmosphere. Photo: Jim Yungel/NASA

The researchers drilled about half a mile down into the ice, into the subglacial Whillans Lake in western Antarctica’s Ross Ice Shelf, to collect water and sediment samples. They analyzed those samples for methane concentrations and looked for clues of how microbes play into that cold, deep ecosystem.

They found that the organisms are consuming more than 99 percent of the methane, so they “may mitigate the release of methane to the atmosphere upon subglacial water drainage to ice sheet margins and during periods of deglaciation.”

The microbes are relying on methane for energy in place of sunlight, which does not reach them so far down into the ice.

“There’s been a lot of concern about the amount of methane that’s beneath these ice sheets because we don’t know exactly what’s going to happen to it,” study co-author and microbiologist Brent Christner said in a statement from the University of Florida. “But this is a process that could have climatic implications.”

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According to Christner, methane is 30 times more powerful than carbon dioxide as a greenhouse gas, so even though the microbes would not stop all greenhouse gases from entering the atmosphere as Antarctic ice melts, they will still prevent the scenario from becoming even worse.

“This is an environment that most people look at and don’t think it could ever really directly impact us,” Christner said.

The researchers hope to look at other subglacial lakes across Antarctica to determine whether the microbes are do their same service in those spots as they are in Whillans Lake.