Ancient Arctic carbon could pose problems

Scientists on Tuesday published new evidence that old or even ancient carbon, pulled out of the atmosphere and stored in the bodies of plants hundreds or thousands of years ago, is being set loose again from soils in the Arctic region.

It’s a potentially worrying indicator that these “permafrost” soils may already be worsening the problem of climate change. However, scientists are still debating just how much old carbon Arctic soils should release normally even without climate change, leaving the ultimate significance of the findings unclear.

The new study, which was published in the journal Environmental Research Letters, employed radiocarbon dating to examine the content of river and lake waters in Canada’s Northwest Territories in 2014. It found an increasing prevalence of older dissolved carbon and carbon dioxide in the waters as the summer advanced. The research also discovered one case of carbon in methane gas that was more than 2,000 years old.

The new work isn’t definitive on the question of increasing permafrost carbon emissions — but it’s something to worry about, said Joshua Dean, the study’s lead author and a professor at the University of Stirling in Britain and Vrije University in Amsterdam.

“I would say if you’re looking at anything pushing several hundred years old to a thousand years old, then you have to start wondering whether that should be coming out of this kind of system,” said Dean, who published the work with 11 colleagues from universities and institutions in Britain.

Over thousands of years, the Arctic has stored up massive amounts of carbon as plants have died but have not fully decayed due to the region’s cold temperatures. As a warming climate thaws, more and more of the older carbon will be broken down by microbes and released as carbon dioxide or methane, with the potential to greatly warm the planet. But it’s not clear how much carbon is vulnerable or how fast such a release could happen.