Scientists "Reawaken" Microbes from Permafrost—and They Start Eating CO₂

Researchers incubated permafrost samples from Alaska at different temperatures and found that microbes from the last ice age can reactivate and resume breaking down carbon, Sascha Pare reported for Live Science.

Permafrost is a mix of soil, rocks, and ice that has been frozen solid for at least two consecutive years. (Photo: Benjamin Jones, USGS)

Microbes that have been suspended in permafrost for up to 40,000 years could “reawaken” and start churning out greenhouse gases if Arctic summers grow much longer, new research suggests.

Under future climate conditions, microbes dormant since the last ice age (2.6 million to 11,700 years ago) may need only a few months to reactivate, according to a study published Sept. 23 in the Journal of Geophysical Research: Geosciences.

Scientists warn that if they do so even for part of the year, this could trigger a feedback loop that accelerates permafrost thaw and global warming.

Permafrost is a mix of soil, rocks, and ice that has been frozen solid for at least two consecutive years.

A hot spell may thaw the topmost layer of permafrost—known as the active layer—but ancient microbes lurk much deeper, in layers that thaw only if temperatures rise significantly and for extended periods.

For the study, researchers traveled to Alaska, where permafrost underlies about 85% of the land.

“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,” said study lead author Tristan Caro, a postdoctoral research associate in geobiology at Caltech.