This is an interesting question. Just how stable is the permafrost.
Particularly as it could actually be a remnant of the Ice Age
itself. It may still be in the long process of simply disappearing
by cycling back and forth over centuries.
In the event, it nicely explains the long release of CO2 in the post
Ice Age geological record that has been observed over millions of
years. This release cycle typically last over several centuries.
For the present, warmer Arctic summers appear to be nicely causing
the permafrost to contract modestly.
June 24, 2013: Flying
low and slow above the pristine terrain of Alaska's North Slope
research scientist Charles Miller of NASA's Jet Propulsion Laboratory
surveys the white expanse of tundra and permafrost below. On the
horizon, a long, dark line appears. His plane draws nearer, and the
mysterious object reveals itself to be a massive herd of migrating
caribou, stretching for miles.
It's a sight Miller
won't soon forget.
"Seeing those
caribou marching single-file across the tundra puts what we're doing
here in the Arctic into perspective," says Miller, who is on
five-year mission named “CARVE” to study how climate change is
affecting the Arctic's carbon cycle.
A new ScienceCast
video peeks beneath the topsoil to inspect the carbon stores of
Arctic permafrost.Play it
CARVE is short for the
“Carbon in Arctic Reservoirs Vulnerability Experiment.” Now
in its third year, the airborne campaign is testing the hypothesis
that Arctic carbon reservoirs are vulnerable to warming, while
delivering the first source-maps of greenhouse gases carbon dioxide
and methane. About two dozen scientists from 12 institutions are
participating.
"The Arctic is
critical to understanding global climate," says Miller. "Climate
change is already happening in the Arctic, faster than its ecosystems
can adapt. Looking at the Arctic is like looking at the canary in the
coal mine for the entire Earth system."
Over hundreds of
millennia, Arctic permafrost soils have accumulated vast stores of
organic carbon - an estimated 1,400 to 1,850 billion metric tons of
it. That's about half of all the estimated organic carbon
stored in Earth's soils. In comparison, about 350 billion metric tons
of carbon have been emitted from all fossil-fuel combustion and human
activities since 1850. Most of the Arctic’s sequestered carbon is
located in thaw-vulnerable topsoils within 3 meters of the surface.
But, as scientists are
learning, permafrost - and its stored carbon - may not be as
permanent as its name implies. And that has them concerned.
"Permafrost
soils are warming even faster than Arctic air temperatures - as much
as 1.5 to 2.5 degrees Celsius in just the past 30 years," says
Miller. "As heat from Earth's surface penetrates into
permafrost, it threatens to mobilize these organic carbon reservoirs
and release them into the atmosphere as carbon dioxide and methane,
upsetting the Arctic's carbon balance and greatly exacerbating global
warming."
CARVE campaign flights
are conducted aboard a specially instrumented NASA C-23 Sherpa
aircraft from NASA's Wallops Flight Facility on Wallops Island in
Virginia. The C-23 won't win any beauty contests - its pilots refer
to it as "a UPS truck with a bad nose job." Inside, it's
extremely noisy - the pilots and crew wear noise-cancelling
headphones to communicate. "When you take the headphones off,
it's like being at a NASCAR race," Miller quipped.
But what the C-23
lacks in beauty and quiet, it makes up for in reliability and its
ability to fly "down in the mud." Most of the time,
it flies about 150 meters above ground level, with periodic ascents
to higher altitudes to collect background data. Onboard the plane,
sophisticated instruments sniff the atmosphere for greenhouse gases.
"[We] need to fly very close to the surface in the Arctic to
capture the interesting exchanges of carbon taking place between
Earth's surface and atmosphere," Miller says.
The CARVE team flew
test flights in 2011 and science flights in 2012. So far in 2013 they
have completed three monthly campaigns--in April, May and June--with
four more to go.
From a base in
Fairbanks, Alaska, the C-23 flies up to eight hours a day to sites on
Alaska's North Slope, interior and Yukon River Valley over tundra,
permafrost, boreal forests, peatlands and wetlands.
Soaring over the
Arctic terrain, Miller has seen many things he won’t forget.
The permafrost data may prove unforgettable, too.
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