As Permafrost Thaws, Scientists Study the Risks
Katey M. Walter Anthony, a scientist, investigated a plume of
methane, a greenhouse gas, at an Alaskan lake. Dr. Walter Anthony is
a leading researcher in studying the escape of methane. Josh
Haner/The New York Times
By JUSTIN GILLIS
Published: December 16, 2011
FAIRBANKS, Alaska - A bubble rose through a hole in the surface of a
frozen lake. It popped, followed by another, and another, as if a pot
were somehow boiling in the icy depths.
In an Alaskan lake, bubbles of methane, a potent greenhouse
gas, collect beneath the ice. Josh Haner/The New York Times
Every bursting bubble sent up a puff of methane, a powerful
greenhouse gas generated beneath the lake from the decay of plant
debris. These plants last saw the light of day 30,000 years ago and
have been locked in a deep freeze - until now.
"That's a hot spot," declared Katey M. Walter Anthony, a leading
scientist in studying the escape of methane. A few minutes later, she
leaned perilously over the edge of the ice, plunging a bottle into
the water to grab a gas sample.
It was another small clue for scientists struggling to understand one
of the biggest looming mysteries about the future of the earth.
Experts have long known that northern lands were a storehouse of
frozen carbon, locked up in the form of leaves, roots and other
organic matter trapped in icy soil - a mix that, when thawed, can
produce methane and carbon dioxide, gases that trap heat and warm the
planet. But they have been stunned in recent years to realize just
how much organic debris is there.
A recent estimate suggests that the perennially frozen ground known
as permafrost, which underlies nearly a quarter of the Northern
Hemisphere, contains twice as much carbon as the entire atmosphere.
Temperatures are warming across much of that region, primarily,
scientists believe, because of the rapid human release of greenhouse
gases. Permafrost is warming, too. Some has already thawed, and other
signs are emerging that the frozen carbon may be becoming unstable.
"It's like broccoli in your freezer," said Kevin Schaefer, a
scientist at the National Snow and Ice Data Center in Boulder, Colo.
"As long as the broccoli stays in the freezer, it's going to be O.K.
But once you take it out of the freezer and put it in the fridge, it
will thaw out and eventually decay."
If a substantial amount of the carbon should enter the atmosphere, it
would intensify the planetary warming. An especially worrisome
possibility is that a significant proportion will emerge not as
carbon dioxide, the gas that usually forms when organic material
breaks down, but as methane, produced when the breakdown occurs in
lakes or wetlands. Methane is especially potent at trapping the sun's
heat, and the potential for large new methane emissions in the Arctic
is one of the biggest wild cards in climate science.
Scientists have declared that understanding the problem is a major
priority. The United States Department of Energy and the European
Union recently committed to new projects aimed at doing so, and NASA
is considering a similar plan. But researchers say the money and
people devoted to the issue are still minimal compared with the risk.
For now, scientists have many more questions than answers.
Preliminary computer analyses, made only recently, suggest that the
Arctic and sub-Arctic regions could eventually become an annual
source of carbon equal to 15 percent or so of today's yearly
emissions from human activities.
But those calculations were deliberately cautious. A recent survey
drew on the expertise of 41 permafrost scientists to offer more
informal projections. They estimated that if human fossil-fuel
burning remained high and the planet warmed sharply, the gases from
permafrost could eventually equal 35 percent of today's annual human
The experts also said that if humanity began getting its own
emissions under control soon, the greenhouse gases emerging from
permafrost could be kept to a much lower level, perhaps equivalent to
10 percent of today's human emissions.
Even at the low end, these numbers mean that the long-running
international negotiations over greenhouse gases are likely to become
more difficult, with less room for countries to continue burning
large amounts of fossil fuels.
In the minds of most experts, the chief worry is not that the carbon
in the permafrost will break down quickly - typical estimates say
that will take more than a century, perhaps several - but that once
the decomposition starts, it will be impossible to stop.
"Even if it's 5 or 10 percent of today's emissions, it's
exceptionally worrying, and 30 percent is humongous," said Josep G.
Canadell, a scientist in Australia who runs a global program to
monitor greenhouse gases. "It will be a chronic source of emissions
that will last hundreds of years."
A troubling trend has emerged recently: Wildfires are increasing
across much of the north, and early research suggests that extensive
burning could lead to a more rapid thaw of permafrost.
Rise and Fall of Permafrost
Standing on a bluff the other day, overlooking an immense river
valley, A. David McGuire, a scientist from the University of Alaska,
Fairbanks, sketched out two million years of the region's history. It
was the peculiar geology of western North America and eastern
Siberia, he said, that caused so much plant debris to get locked in
an ice box there.
These areas were not covered in glaciers during the last ice age, but
the climate was frigid, with powerful winds. The winds and rivers
carried immense volumes of silt and dust that settled in the lowlands
of Alaska and Siberia.
A thin layer of this soil thawed on top during the summers and
grasses grew, capturing carbon dioxide. In the bitter winters, grass
roots, leaves and even animal parts froze before they could
decompose. Layer after layer of permafrost built up.
At the peak of the ice age, 20,000 years ago, the frozen ground was
more extensive than today, stretching deep into parts of the lower 48
states that were not covered by ice sheets. Climate-change
contrarians like to point to that history, contending that any
melting of permafrost and ice sheets today is simply the tail end of
the ice age.
Citing permafrost temperatures for northern Alaska - which, though
rising rapidly, remain well below freezing - an organization called
the Center for the Study of Carbon Dioxide and Global Change claimed
that permafrost is in "no more danger of being wiped out any time
soon than it was in the days of our great-grandparents."
But mainstream scientists, while hoping the breakdown of permafrost
will indeed be slow, reject that argument. They say the climate was
reasonably stable for the past 10,000 years or so, during the period
when human civilization arose. Now, as people burn immense amounts of
carbon in the form of fossil fuels, the planet's temperature is
rising, and the Arctic is warming twice as fast. That, scientists
say, puts the remaining permafrost deposits at risk.
For several decades, researchers have been monitoring permafrost
temperatures in hundreds of boreholes across the north. The
temperatures have occasionally decreased in some regions for periods
as long as a decade, but the overall trend has been a relentless
rise, with temperatures now increasing fastest in the most northerly
Thawing has been most notable at the southern margins. Across huge
areas, including much of central Alaska, permafrost is hovering just
below the freezing point, and is expected to start thawing in earnest
as soon as the 2020s. In northern Alaska and northern Siberia, where
permafrost is at least 12 degrees Fahrenheit below freezing, experts
say it should take longer.
"Even in a greenhouse-warmed world, it will still get cold and dark
in the Arctic in the winter," said Mark Serreze, director of the snow
and ice data center in Boulder.
Scientists need better inventories of the ancient carbon. The best
estimate so far was published in 2009 by a Canadian scientist,
Charles Tarnocai, and some colleagues. They calculated that there was
about 1.7 trillion tons of carbon in soils of the northern regions,
about 88 percent of it locked in permafrost. That is about two and a
half times the amount of carbon in the atmosphere.
Philippe Ciais, a leading French scientist, wrote at the time that he
was "stunned" by the estimate, a large upward revision from previous
"If, in a warmer world, bacteria decompose organic soil matter
faster, releasing carbon dioxide," Dr. Ciais wrote, "this will set up
a positive feedback loop, speeding up global warming."
Plumes of Methane
Katey Walter Anthony had been told to hunt for methane, and she could
not find it.
As a young researcher at the University of Alaska, Fairbanks, she
wanted to figure out how much of that gas was escaping from lakes in
areas of permafrost thaw. She was doing field work in Siberia in
2000, scattering bubble traps around various lakes in the summer, but
she got almost nothing.
Then, that October, the lakes froze over. Plumes of methane that had
been hard to spot on a choppy lake surface in summer suddenly became
"I went out on the ice, this black ice, and it looked like the starry
night sky," Dr. Walter Anthony said. "You could see these bubble
clusters everywhere. I realized - 'aha!' - this is where all the
When organic material comes out of the deep freeze, it is consumed by
bacteria. If the material is well-aerated, bacteria that breathe
oxygen will perform the breakdown, and the carbon will enter the air
as carbon dioxide, the primary greenhouse gas. But in areas where
oxygen is limited, like the bottom of a lake or wetland, a group of
bacteria called methanogens will break down the organic material, and
the carbon will emerge as methane.
Scientists are worried about both gases. They believe that most of
the carbon will emerge as carbon dioxide, with only a few percent of
it being converted to methane. But because methane is such a potent
greenhouse gas, the 41 experts in the recent survey predicted that it
would trap about as much heat as the carbon dioxide would.
Dr. Walter Anthony's seminal discovery was that methane rose from
lake bottoms not as diffuse leaks, as many scientists had long
assumed, but in a handful of scattered, vigorous plumes, some of them
capable of putting out many quarts of gas per day. In certain lakes
they accounted for most of the emerging methane, but previous
research had not taken them into consideration. That meant big upward
revisions were probably needed in estimates of the amount of methane
lakes might emit as permafrost thawed.
Most of the lakes Dr. Walter Anthony studies were formed by a
peculiar mechanism. Permafrost that is frozen hard supports the
ground surface, almost the way a concrete pillar supports a building.
But when thaw begins, the ground sometimes turns to mush and the
entire land surface collapses into a low-lying area, known as a
thermokarst. A lake or wetland can form there, with the dark surface
of the water capturing the sun's heat and causing still more
permafrost to thaw nearby.
Near thermokarst locations, trees often lean crazily because their
roots are disturbed by the rapid changes in the underlying landscape,
creating "drunken forests." And the thawing, as it feeds on itself,
frees up more and more ancient plant debris.
One recent day, in 11-degree weather, Dr. Walter Anthony and an
assistant, Amy Strohm, dragged equipment onto two frozen thermokarst
lakes near Fairbanks. The fall had been unusually warm and the ice
was thin, emitting thunderous cracks - but it held. In spots, methane
bubbled so vigorously it had prevented the water from freezing. Dr.
Walter Anthony, six months pregnant, bent over one plume to retrieve
"This is thinner ice than we like," she said. "Don't tell my
mother-in-law! My own mother doesn't know."
Dr. Walter Anthony had already run chemical tests on the methane from
one of the lakes, dating the carbon molecules within the gas to
30,000 years ago. She has found carbon that old emerging at numerous
spots around Fairbanks, and carbon as old as 43,000 years emerging
from lakes in Siberia.
"These grasses were food for mammoths during the end of the last ice
age," Dr. Walter Anthony said. "It was in the freezer for 30,000 to
40,000 years, and now the freezer door is open."
Scientists are not sure yet whether thermokarst lakes will become
more common throughout the Arctic in a warming climate, a development
that could greatly accelerate permafrost thaw and methane production.
But they have already started to see increases in some regions,
including northernmost Alaska.
"We expect increased thermokarst activity could be a very strong
effect, but we don't really know," said Guido Grosse, another
scientist at the University of Alaska, Fairbanks. He is working with
Dr. Walter Anthony on precision mapping of thermokarst lakes and
methane seeps, in the hope that the team can ultimately use
satellites and aerial photography to detect trends.
With this kind of work still in the early stages, researchers are
worried that the changes in the region may already be outrunning
their ability to understand them, or to predict what will happen.
When the Tundra Burns
One day in 2007, on the plain in northern Alaska, a lightning strike
set the tundra on fire.
Historically, tundra, a landscape of lichens, mosses and delicate
plants, was too damp to burn. But the climate in the area is warming
and drying, and fires in both the tundra and forest regions of Alaska
The Anaktuvuk River fire burned about 400 square miles of tundra, and
work on lake sediments showed that no fire of that scale had occurred
in the region in at least 5,000 years.
Scientists have calculated that the fire and its aftermath sent a
huge pulse of carbon into the air - as much as would be emitted in
two years by a city the size of Miami. Scientists say the fire thawed
the upper layer of permafrost and set off what they fear will be
permanent shifts in the landscape.
Up to now, the Arctic has been absorbing carbon, on balance, and was
once expected to keep doing so throughout this century. But recent
analyses suggest that the permafrost thaw could turn the Arctic into
a net source of carbon, possibly within a decade or two, and those
studies did not account for fire.
"I maintain that the fastest way you're going to lose permafrost and
release permafrost carbon to the atmosphere is increasing fire
frequency," said Michelle C. Mack, a University of Florida scientist
who is studying the Anaktuvuk fire. "It's a rapid and catastrophic
way you could completely change everything."
The essential question scientists need to answer is whether the many
factors they do not yet understand could speed the release of carbon
from permafrost - or, possibly, slow it more than they expect.
For instance, nutrients released from thawing permafrost could spur
denser plant growth in the Arctic, and the plants would take up some
carbon dioxide. Conversely, should fires like the one at Anaktuvuk
River race across warming northern landscapes, immense amounts of
organic material in vegetation, soils, peat deposits and thawed
permafrost could burn.
Edward A. G. Schuur, a University of Florida researcher who has done
extensive field work in Alaska, is worried by the changes he already
sees, including the discovery that carbon buried since before the
dawn of civilization is now escaping.
"To me, it's a spine-tingling feeling, if it's really old carbon that
hasn't been in the air for a long time, and now it's entering the
air," Dr. Schuur said. "That's the fingerprint of a major disruption,
and we aren't going to be able to turn it off someday."
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