Climate Change is Turning Arctic's Carbon Sinks into Carbon Emitters

The Arctic regions have historically acted as carbon sinks, absorbing CO2 from the atmosphere and trapping carbon in permafrost (or frozen soil), thus taking in more greenhouse gasses than they release.

This has been the norm for tens of thousands of years. However, according to a study recently published in the journal Nature, this precedent may be about to change—if it hasn't already. Emission data shows that the thawing of permafrost is turning these areas from carbon sinks into carbon emitters.

Researchers found that if greenhouse gas emissions continue at their current rate (RCP 8.5), carbon dioxide "lost" from permafrost each winter could increase 41 percent by the end of the century. Under a more moderate climate scenario (RCPb 4.5), it is still predicted to increase by a hefty 17 percent.

"We've known that warmer temperatures and thawing permafrost have been accelerating winter CO2 emissions, but we haven't had a clear accounting of the winter carbon balance," lead author Sue Natali, Wood's Hole Research Center (WHRC) Arctic Program Director, said in a statement.

"These results, which provide a new baseline for winter CO2 emissions from the Arctic, indicate that winter CO2 loss may already be offsetting growing season carbon uptake and these losses will increase as the climate continues to warm."

Natali and colleagues came to these conclusions after studying on-the-ground observations of CO2 emissions at more than 100 locations across the Arctic region to analyze current winter carbon losses and predict what might happen in the future.

The researchers calculated a "contemporary loss" of approximately 1,662 teragrams (or 1.7 billion metric tons) of carbon during the winter months, which runs from October through to May. In comparison, they say, the average growing season absorbs an estimated 1 billion metric tons.

Permafrost covers 24 percent of the Northern Hemisphere, including large swathes of Alaska, Canada, Greenland and Siberia. It is of huge importance to climate scientists because combined, the world's permafrost regions store greater quantities of carbon than that released by humans in the entirety of our history, the researchers say.

The problem that we're currently facing is that human-driven climate change is causing it to thaw—and release tons of carbon (as well as acid, prehistoric viruses and potentially deadly pathogens) as it does. In May, Newsweek reported on a study that found thawing permafrost could double warming generated by gases released from the ground.

siberia permafrost
Areas of tundra like Urengoy, Siberia, are starting to release more carbon than they capture, the new research shows. Georgy_Golovin/iStock

This new study adds to the current body of research by looking at what happens in the winter months.

"We've known for a while that thawed soils release CO2 during the summer, but we really didn't realize how much CO2 is being emitted during the snow-covered winter months," WHRC scientist Jennifer Watts said in a statement.

"However, our data remain limited, especially considering the vast amount of land within the permafrost region. Because of this, it is difficult to get a real-time picture of how quickly ecosystems are changing."

The study authors explain that carbon release by thawing permafrost is often excluded from climate models as well as reports that form the basis of political action on climate change.

"This is basically a new baseline for all kinds of future studies and refinements," Torsten Sachs, Head of Earth-Atmosphere Interactions and an assistant professor of atmospheric physics, told Newsweek. "It's just the beginning, there is still a lot to do and learn."

Correction (11/6/19): This article has been updated to correct 1.7 million metric tons of carbon to 1.7 billion metric tons, and change the incorrect use of the term "melting" to "thawing."

Climate Change is Turning Arctic's Carbon Sinks into Carbon Emitters | Tech & Science