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NSF-supported scientists from the University of California, Los Angeles and their colleagues from the Russian Academy of Sciences drill into frozen Siberian peat bogs to determine the bogs' impact on climate. Credit: Laurence C. Smith / National Science Foundation Select image for larger version (Size: 233KB) |
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ARLINGTON, Va.—Massive Siberian peat bogs, widely known as
the permanently frozen home of untold kilometers of moss and
uncountable hordes of mosquitoes, also are huge repositories
for gases that are thought to play an important role in the
Earth's climate balance, according to newly published
research by a team of U.S. and Russian scientists in the
Jan. 16 edition of the journal Science.
Those gases, carbon dioxide and methane, are known to trap
heat in the Earth's atmosphere, but the enormous amounts of
the gases contained in the bogs haven't previously been
accounted for in climate-change models.
The new research, said Laurence Smith, an associate
professor at the University of California, Los Angeles and a
primary author on the paper, could help to refine those
materials. Smith's work was funded by the National Science
Foundation (NSF), an independent federal agency that
supports fundamental research and education across all
fields of science and engineering.
A key finding of the research, unrelated to modern climate
change, is that the bogs themselves came into being suddenly
about 11,500 to 9,000 years ago—much earlier than previously
thought—and expanded very rapidly to fill the niche they now
occupy. Their appearance coincides with an abrupt and well-
documented spike in the amount of atmospheric methane
recorded in ancient climate records. The finding counters
previously held views that the bogs were largely
unchanged—and unchanging—over millennia. The rapid
appearance of the bogs provides strong evidence that this is
not the case.
Scientists have hotly debated the origin of the methane
spike, variously attributing it to sources in tropical
wetlands and offshore sediments. The new research
conclusively points for the first time to Siberia as a
likely methane source.
But the researchers also point out that the bogs—which
collectively cover an area of roughly 603,000 square
kilometers (233,000 square miles)—have long absorbed and
held vast amounts of carbon dioxide, while releasing large
amounts of methane in the atmosphere.
If, as many scientists predict, a regional Arctic warming
trend thaws the bogs and causes the trapped gases to be
released into the atmosphere, that could result in a major
and unexpected shift in climate trends, according to the
researchers.
The teams spent three seasons in the Siberian Arctic,
drilling several meters down into the sphagnum moss to
produce the peat samples for analysis.
Smith said thawing of the permafrost would essentially turn
the carbon and methane balance in the peat bogs from a
scientific constant in climate-change equations to a
variable.
"Traditionally, we had thought these areas were simply a
gradually varying source of methane and an important sink
for atmospheric carbon," he said. "They've been viewed as a
stable thing that we always count on. The bottom line is
Siberian peat lands may be a bigger player in climate change
than we knew before."
"There are natural sources of greenhouse gases out there
that are potentially enormous that we need to know about,"
Smith said. "One of the concerns is that up until now, the
bogs have been more or less a sink for CO2, absorbing carbon
dioxide from the atmosphere. In an extreme scenario, not
only would they stop taking up CO2, they would release a lot
of the carbon they have taken up for centuries."
Smith conceded that the team searched their Siberian peat
samples for evidence that such a drastic release of gas
occurred in the past, with inconclusive results.
But, he added, as other research into Earth's ancient
climate begins to yield evidence that changes have occurred
before, accounting for unknowns such as the carbon and
methane balance in the bogs becomes more important.
"It emphasizes a point that has been emerging over the past
few years; the idea that the climate system is highly
unpredictable and full of thresholds that can trigger
greenhouse gas sources and sinks to abruptly switch on and
off," he said. "The more of them we can identify, the more
accurately we can model and anticipate changes in the
future."
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