Scientists Resurrect 40,000-Year-Old Microbes From Alaskan Permafrost. What They Found Raised Worries About the Future of a Warming Arctic

The experiments offer new insights into one of the “biggest unknowns” in how the climate will change in the years to come

Sarah Kuta | Daily Correspondent

October 15, 2025

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Roughly 40,000 years ago, microbes went dormant in a rock-like layer of frozen soil near the future site of Fairbanks, Alaska. Now, researchers have successfully “reawakened” the tiny creatures, raising concerns about how those microbes could increase greenhouse gas emissions in a warming Arctic.

They describe the results in a paper published September 23 in the Journal of Geophysical Research: Biogeosciences. “These ecosystems, even though they’re in suspended animation, they’re very much still capable of supporting life from a microbiological or a climate perspective,” Tristan Caro, a geobiologist at the California Institute of Technology and the lead author of the paper, told Alaska Public Media’s Casey Grove.

Permafrost is soil, sand, sediment and rock that remains at or below freezing temperatures for at least two years. It’s found primarily in the Arctic and high-latitude regions around the world. Permafrost exists beneath roughly 85 percent of Alaska’s land area, for instance.

As the Arctic heats up, scientists are worried about permafrost thaw for numerous reasons. But a major concern is the resurrection of ancient microbes, which they expect to start chowing down on organic matter and producing greenhouse gases like carbon dioxide and methane. These gases, in turn, would further contribute to global warming, leading to more permafrost thaw and more greenhouse gas-spewing microbes—a vicious, unstoppable cycle.

The new study offers insights into what this process might look like, including the resuscitation and growth rates of long-dormant microbes.

“It’s one of the biggest unknowns in climate responses,” says study co-author Sebastian Kopf, a geological scientist at the University of Colorado Boulder, in a statement. “How will the thawing of all this frozen ground, where we know there’s tons of carbon stored, affect the ecology of these regions and the rate of climate change?”

Researchers visited the U.S. Army Corps of Engineers’ Permafrost Tunnel Research Facility, a subterranean channel 50 feet below the surface in central Alaska. First excavated in the 1960s, the tunnel is roughly the same width as a mine shaft and more than 350 feet long. It contains massive ice wedges, green grass from thousands of years ago and the preserved remains of animals from the Pleistocene Epoch, including bison, mammoths and horses.

Scientists collected permafrost samples from the tunnel’s walls. Back in the laboratory, they moistened the samples with water that contained heavy hydrogen atoms known as deuterium. They then placed the samples in sealed chambers set to temperatures of 25, 39 or 54 degrees Fahrenheit. The goal? To simulate increasingly warm Alaskan summers under future climate conditions.

At first, the microbes were slow to wake up, shaking roughly one out of every 100,000 cells awake per day. But after roughly six months, the scientists noticed “dramatic” changes in the samples, they write in the paper. The microbes became highly active, even producing slimy biofilms visible to the naked eye.

Speaking with Alaska Public Media, Caro likened himself and other researchers to traffic cops “shooting the radar gun at these microbes and seeing how fast they're acting and putting a number to it.”

“We found that it did indeed take months for these organisms to wake up, to really convince themselves that, yes, it’s time to start processing carbon and exhaling [carbon dioxide] and methane,” Caro, who completed the research while at the University of Colorado Boulder, tells Alaska Public Media. “Somewhere between one and six months. And that’s an important finding.”

Because of the deuterium they added to the samples, the researchers were also able to track how much water the microbes consumed to build the fatty membranes around their cells. Glycolipids seem to have played “a key physiological role” in helping them survive dark, freezing conditions for millennia, per the paper.

The temperature didn’t seem to affect the speed at which the microorganisms woke up in the experiments, which suggests scientists should be less concerned about brief Arctic hot spells and more concerned about longer, hotter summers that could provide plenty of time for the cells to awaken.

“You might have a single hot day in the Alaskan summer, but what matters much more is the lengthening of the summer season to where these warm temperatures extend into the autumn and spring,” says Caro in the statement.

Sarah Kuta | Read More

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.