A winding river snakes its way across a highland tundra valley floor in Greenland above the Arctic Circle. (Photo: Jason Edwards/Getty Images)
Researchers find that hotter temperatures could be setting off dangerous environmental feedback loops...
Could the impacts of climate change include environmental feedbacks that intensify its effects?
Ecologist Julia Bradley-Cook and her team took samples of western Greenland tundra soil that grows grass and shrubs back to the lab and tested how increases in both temperature and moisture would affect the release of carbon dioxide.
They found that both types of soils released significantly more CO2 as they got warmer and wetter. Grass soils released up to twice as much carbon than the shrub soils as heat and moisture increased.
“I think about it as if you’re pouring Red Bull on the soils,” said Bradley-Cook, who led the study as part of completing her Ph.D. at Dartmouth. “As you ramp up temperatures, you’re giving the microorganisms in the soils all this energy, in an accelerated way. The grass soils are more sensitive to that Red Bull than the shrub soils.”
The grass and shrub soils “are relatively on the lower side, in terms of temperature sensitivity, than some of the permafrost soils in Alaska and in Russia,” which comprise a much larger land area of the Arctic than Greenland, she noted.
“The big picture is that there is twice as much carbon stored in Arctic soils as there is in the atmosphere,” Bradley-Cook said. “What’s going to happen to that carbon that built up in soils over millennia under the conditions of rapid climate change?”
GRID-Arendal, a Norwegian research center affiliated with the United Nations Environment Programme, estimates that Arctic soils hold about 1.8 trillion tons of carbon.
Bradley-Cook acknowledged that her research, which was published in the journal Climate Change Responses, looked solely at how much and the rate at which CO2 was leaving the soil and did not measure how much was being stored at the same time.
So the question of how much carbon Arctic soils are releasing compared to how much they’re sequestering from the atmosphere remains open.
But “there is warming in the Arctic already,” Bradley-Cook said. “We are observing changes in permafrost depths—so, the thawing of permafrost. That would introduce new carbon into the atmosphere from those soils.”
In February, temperatures across the Arctic soared as much as 7.2 degrees Fahrenheit above the 1951 to 1980 average, according to the Colorado-based National Snow and Ice Data Center—blowing away the maximum warming target of 3.6 degrees (2 degrees Celsius) that nations agreed to in last year’s Paris climate accord.
The National Oceanic and Atmospheric Administration confirmed on Thursday that February’s global temperatures set a new heat-increase record by departing 2.18 degrees (1.21 degrees Celsius) from historic norms.