has found Arctic soil has warmed to the point where it releases more
carbon in winter than northern plants can absorb during the summer.
finding means the extensive belt of tundra around the globe — a
vast reserve of carbon that dwarfs what's held in the atmosphere —
is becoming a source of greenhouse gas emissions responsible for
a net loss," said Dalhousie University's Jocelyn Egan, one of 75
co-authors of a paper published in Nature Climate Change.
a given year, more carbon is being lost than what is being taken in.
It is happening already."
research by scientists in 12 countries and from dozens of
institutions is the latest warning that northern natural systems that
once reliably kept carbon out of the atmosphere are starting to
now, little was known about winter emissions from permafrost and the
soil above it. Even scientists assumed the microbial processes that
release the gases came to a halt in the cold.
people think in the winter, there's no respiration, that the microbes
eating the carbon that produce these emissions aren't active, which
isn't actually the case," Egan said.
scientists placed carbon dioxide monitors along the ground at more
than 100 sites around the circumpolar Arctic to see what was actually
happening and took more than 1,000 measurements.
found much more carbon was being released than previously thought.
The results found carbon dioxide emissions of 1.7 billion tonnes a
year are about twice as high as previous estimates.
plants are thought to take in just over one billion tonnes of the gas
from the atmosphere every year during growing season. The net result
is that Arctic soil around the globe is probably already releasing
more than 600 million tonnes of CO2 annually.
previously thought carbon absorbed by tundra plants during the summer
more or less made up for what was emitted in the winter as well as
for what was released from melting permafrost during warm months.
not what's happening, said Egan.
seeing that the value emitted in the winter is larger than the net
uptake for the growing season."
more, the pace of the emissions is likely to increase.
a business-as-usual scenario, emissions from northern soil would be
likely to release 41 per cent more carbon by the end of the century.
the Arctic is already warming at three times the pace of the rest of
the globe. Even if significant mitigation efforts are made, those
emissions will increase by 17 per cent, said the report.
notes the research didn't measure methane, a greenhouse gas about 30
times more potent than carbon dioxide that is also released from
findings echo previous studies.
summer, research suggested that larger, hotter wildfires are turning
boreal forests into carbon sources. Another paper found that instead
of melting slowly and steadily, permafrost is subject to sudden
collapses that speed up the rate of carbon release.
won't stop the problem any more, said Egan, but it will help.
report by The Canadian Press was first published Oct. 22, 2019.