Scientists Found 40,000-Year-Old Frozen Microbes in an Alaska Tunnel…Six Months Later, They Became Active Again

Ancient microbes locked in Arctic ice for tens of thousands of years are starting to wake up as permafrost thaws. Scientists say this slow return to life could add to the release of greenhouse gases already shaping the climate. Across northern regions, frozen ground that once seemed inactive is beginning to change. Material buried since the Ice Age is now exposed to warmer temperatures, and that shift is triggering biological activity that had been paused for millennia.

Permafrost covers nearly a quarter of the Northern Hemisphere and stores massive amounts of organic material. As this frozen layer softens, it reveals plant remains, animal bones, and vast populations of microorganisms preserved in place for tens of thousands of years. Researchers are trying to understand what happens when these microbes become active again. Even though the process starts slowly, it could still influence how carbon moves between the ground and the atmosphere.

A Controlled Experiment In Alaska’s Frozen Tunnel

To explore this, a team led by Tristan Caro collected permafrost samples from a tunnel in central Alaska maintained by the U.S. Army Corps of Engineers. The tunnel stretches about 350 feet and offers a direct look into ancient frozen layers, with remains of bison and mammoths visible in the walls.

According to the study published in the Journal of Geophysical Research: Biogeosciences, researchers thawed the samples at temperatures between 39 and 54 degrees Fahrenheit, similar to conditions during an Alaskan summer.

The goal was to see whether anything inside the frozen ground was still alive and capable of activity. He also noted that even the smell of the tunnel hinted at microbial life.

“The first thing you notice when you walk in there is that it smells really bad. It smells like a musty basement that’s been left to sit for way too long,” he remarked. “To a microbiologist, that’s very exciting because interesting smells are often microbial.”

Slow Growth, But Clear Signs of Life

At first, the microbes showed very little activity. As the researchers explained in the study, during the first few months only about one in every 100,000 cells reproduced each day. This is extremely slow compared to typical bacteria in laboratory settings, which can multiply in just a few hours.

After about six months, the situation began to change. Some microbial communities started forming biofilms, which are slimy, structured layers that signal active growth and cooperation between cells.

“These are not dead samples by any means,” said Caro in a statement available on the website of the University of Colorado Boulder. “They’re still very much capable of hosting robust life that can break down organic matter and release it as carbon dioxide.”

This change from being almost totally dormant to showing visible activity shows that even after tens of thousands of years, these organisms can start doing basic life stuff again when conditions are right.

The Small Process with Outsized Power

The reactivation of these microbes has broader implications. As they break down ancient organic material, they release carbon dioxide and methane, both of which contribute to warming in the atmosphere.

As Sebastian Kopf, a professor of geological sciences involved in the research, pointed out, thawing permafrost remains one of the biggest uncertainties in climate science.

“It’s one of the biggest unknowns in climate responses,”he stated. “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?”

There are still open questions. Scientists have only studied a small portion of global permafrost, and it is unclear whether microbes in other regions behave the same way or at the same pace.

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