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<DIV class=timestamp>December 16, 2011</DIV>
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<H1><NYT_HEADLINE version="1.0" type=" ">As Permafrost Thaws, Scientists Study
the Risks</NYT_HEADLINE></H1><NYT_BYLINE>
<H6 class=byline>By <A class=meta-per title="More Articles by Justin Gillis"
href="http://topics.nytimes.com/top/reference/timestopics/people/g/justin_gillis/index.html?inline=nyt-per"
rel=author>JUSTIN GILLIS</A></H6></NYT_BYLINE><NYT_TEXT>
<DIV id=articleBody><NYT_CORRECTION_TOP></NYT_CORRECTION_TOP>
<P>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. </P>
<P>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. </P>
<P>“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. </P>
<P>It was another small clue for scientists struggling to understand one of the
biggest looming mysteries about the future of the earth. </P>
<P>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. </P>
<P>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. </P>
<P>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. </P>
<P>“It’s like broccoli in your freezer,” said Kevin Schaefer, a scientist at the
<A href="http://nsidc.org/">National Snow and Ice Data Center</A> 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.” </P>
<P>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. </P>
<P>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. </P>
<P>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. </P>
<P>But those calculations were deliberately cautious. A <A
title="Paper describing the survey results (PDF)"
href="http://www.lter.uaf.edu/pdf/1562_Schuur_Abbott_2011.pdf">recent survey</A>
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 emissions. </P>
<P>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.
</P>
<P>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. </P>
<P>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. </P>
<P>“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.” </P>
<P>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. </P>
<P><STRONG>Rise and Fall of Permafrost</STRONG> </P>
<P>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. </P>
<P>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.
</P>
<P>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. </P>
<P>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. </P>
<P>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.” </P>
<P>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. </P>
<P>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 areas. </P>
<P>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. </P>
<P>“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. </P>
<P>Scientists need better inventories of the ancient carbon. The <A
title="Link to the paper that includes this estimate (PDF)"
href="http://www.lter.uaf.edu/dev2009/pdf/1350_Tarnocai_Canadell_2009.pdf">best
estimate</A> 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. </P>
<P>Philippe Ciais, a leading French scientist, wrote at the time that he was
“stunned” by the estimate, a large upward revision from previous calculations.
</P>
<P>“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 <A class=meta-classifier
title="Recent and archival news about global warming."
href="http://topics.nytimes.com/top/news/science/topics/globalwarming/index.html?inline=nyt-classifier">global
warming</A>.” </P>
<P><STRONG>Plumes of Methane</STRONG> </P>
<P>Katey Walter Anthony had been told to hunt for methane, and she could not
find it. </P>
<P>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. </P>
<P>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 more visible.
</P>
<P>“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 methane is.” </P>
<P>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. </P>
<P>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. </P>
<P>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. </P>
<P>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. </P>
<P>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. </P>
<P>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 samples. </P>
<P>“This is thinner ice than we like,” she said. “Don’t tell my mother-in-law!
My own mother doesn’t know.” </P>
<P>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. </P>
<P>“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.” </P>
<P>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. </P>
<P>“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. </P>
<P>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. </P>
<P><STRONG>When the Tundra Burns</STRONG> </P>
<P>One day in 2007, on the plain in northern Alaska, a lightning strike set the
tundra on fire. </P>
<P>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 are increasing. </P>
<P>The Anaktuvuk River fire burned about 400 square miles of tundra, and work on
lake sediments showed that <A
title="Paper analyzing the fire history of the region (PDF)"
href="http://www.wildfirepire.org/sites/default/files/hu_2010_tundra_burning_in_alaska_linkages_to_climatic_change_and_sea_ice_retreat.pdf">no
fire of that scale had occurred in the region in at least 5,000 years</A>. </P>
<P>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. </P>
<P>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.
</P>
<P>“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 <A
title="A Nature paper by Dr. Mack and colleagues (PDF)"
href="http://www.indiaenvironmentportal.org.in/files/file/wildfires.pdf">studying
the Anaktuvuk fire</A>. “It’s a rapid and catastrophic way you could completely
change everything.” </P>
<P>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. </P>
<P>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. </P>
<P>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. </P>
<P>“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.” </P><NYT_CORRECTION_BOTTOM>
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<DIV><FONT size=2 face=Verdana>______________________________</FONT></DIV>
<DIV><FONT size=2 face=Verdana>Wayne A. Fox<BR><A
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