From: Woods Hole Oceanographic Institution
Published August 6, 2015 07:15 AM

Study shows some permafrost carbon transported by river to the ocean

As temperatures rise, some of the organic carbon stored in Arctic permafrost meets an unexpected fate—burial at sea. As many as 2.2 million metric tons of organic carbon per year are swept along by a single river system into Arctic Ocean sediment, according to a new study an international team of researchers published today in Nature. This process locks away carbon dioxide (CO2) - a greenhouse gas - and helps stabilize the earth’s CO2 levels over time, and it may help scientists better predict how the natural carbon cycle will interplay with the surge of CO2 emissions due to human activities.

“The erosion of permafrost carbon is very significant,” says Woods Hole Oceanographic Institution (WHOI) Associate Scientist Valier Galy, a co-author of the study. “Over thousands of years, this process is locking CO2away from the atmosphere in a way that amounts to fairly large carbon stocks. If we can understand how this process works, we can predict how it will respond as the climate changes.”

Permafrost—frozen ground found in the Arctic and in some alpine regions—is known to hold billions of tons of organic material. Amid concerns about rising Arctic temperatures and their impact on permafrost, many researchers have directed their efforts to studying the permafrost carbon cycle—the processes through which carbon circulates between the atmosphere, the soil and plants (the biosphere), and the sea. Yet how this cycle works and how it responds to the warming, changing climate remains poorly understood.

Galy and his colleagues from Durham University, the Institut de Physique du Globe de Paris, the NERC Radiocarbon Facility, Stockholm University, and the Universite Paris-Sud set out to characterize the carbon cycle in one particular piece of the Arctic landscape—northern Canada’s Mackenzie River, the largest river flowing into the Arctic Ocean from North America and that ocean’s greatest source of sediment. The researchers hypothesized that the Mackenzie’s muddy water might erode soils along its path, some from places where permafrost is melting, and wash that biosphere-derived material and the organic carbon within it into the ocean, preventing the degradation of organic carbon and associated release of CO2 into the atmosphere.

Image shows WHOI Associate Scientist Valier Galy lowering a sampling device into the Mackenzie River. Chemical analysis of the collected samples revealed that the river’s transport of organic carbon creates a carbon sink, burying CO2 in Arctic Ocean sediments without releasing it into the atmosphere. (Photo by Robert Hilton, Durham University)

Read more at Woods Hole Oceanographic Institution.

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