Permafrost melt releasing small traces of ancient carbon

Researchers have confirmed the widespread release of ancient carbon from melting Arctic permafrost in what could be the lit fuse on a climate-change bomb.

A paper published this week in Nature Geoscience has released the first measurements of greenhouse gases from permafrost under Arctic lakes. But while the study confirms those gases locked away in ice for thousands of years are seeping free, it concludes the amounts are not yet large.

“It’s a lit fuse, but the length of that fuse is very long,” said lead author Katey Walter Anthony of the University of Alaska. “According to the model projections, we’re getting ready for the part where it starts to explode. But it hasn’t happened yet.”

Scientists have long known permafrost contains vast quantities of carbon in dead plants and other organic material, about twice as much as the entire atmosphere. Now, that permafrost is melting more quickly as the Arctic warms up faster than anywhere else on Earth.

The melt often takes place in Arctic lakes where liquid water thaws long-frozen soil. The material released is digested by tiny bugs and turned into carbon dioxide and methane.

“I’ve been walking on these lakes when they were frozen for a very long time,” said Walter Anthony. “I would go out after the ice formed, look at the lake ice surface and see bubbles. I observed bubbles are most dense and largest along the edge, where margins were expanding, where the permafrost was thawing.”

Her observation led to three questions: Were the bubbles generated by melting permafrost? If so, was the permafrost releasing ancient, long-dormant carbon? And, if so, how much?

Researchers looked at lakes in Alaska and Siberia, as well as data from Canada. They used aerial photographs and other information to measure how the area had changed over the past 60 years.