Methane releases from Arctic shelf may be much larger and faster than anticipated

Methane release from the permafrost is the most dangerous amplifying feedback in the entire carbon cycle. Research published in journal Science finds a key “lid” on “the large sub-sea permafrost carbon reservoir” near Eastern Siberia “is clearly perforated, and sedimentary CH4 [methane] is escaping to the atmosphere.”

Fairbanks, (ALA/US) March 4 / 8, 2010 - A section of the Arctic Ocean seafloor that holds vast stores of frozen methane is showing signs of instability and widespread venting of the powerful greenhouse gas, according to the findings of an international research team led by University of Alaska Fairbanks scientists Natalia Shakhova and Igor Semiletov.
The research results, published in the March 5 edition of the journal Science, show that the permafrost under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in methane, is perforated and is starting to leak large amounts of methane into the atmosphere. Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.
"The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the entire world's oceans," said Shakhova, a researcher at UAF's International Arctic Research Center. "Subsea permafrost is losing its ability to be an impermeable cap."
> www.realclimate.org: Arctic Methane on the Move? (Mar 08)
> planetark.org: Methane Bubbles In Arctic Seas Stir Warming Fears (Mar 08)
> www.eurekalert.org: Methane releases from Arctic shelf may be much larger and faster than anticipated
> climateprogress.org: Vast East Siberian Methane stores destabilising and venting
> www.sciencemag.org: Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf

Methane levels may see 'runaway' rise, scientists warn

London, 22 February 2010 - Atmospheric levels of methane, the greenhouse gas which is much more powerful than carbon dioxide, have risen significantly for the last three years running, scientists will disclose today – leading to fears that a major global-warming "feedback" is beginning to kick in.
For some time there has been concern that the vast amounts of methane, or "natural gas", locked up in the frozen tundra of the Arctic could be released as the permafrost is melted by global warming. This would give a huge further impetus to climate change, an effect sometimes referred to as "the methane time bomb".
> www.independent.co.uk: Methane levels may see 'runaway' rise, scientists warn

Methane's Key Role in Global Warming
January 27 2010 - Carbon dioxide is the gas we most associate with global warming, but methane gas also plays an important role. For reasons that are not well understood, methane gas stopped increasing in the atmosphere in the 1990s. But now it appears to be once again on the rise. Scientists are trying to understand why — and what to do about it.
> www.npr.org: Methane's Key Role in Global Warming

Global warming 'speeds' up gas emissions

London, January 14 2010 - Rising temperatures are not just a sign of climate change but are also a cause of it, a new study has suggested.
Higher temperatures on the surface of the earth are fuelling a further increase in emissions of methane, Edinburgh University experts found.
The study indicated warmer temperatures in regions which were at higher latitudes increased methane - exacerbating global warming.
Scientists studying atmospheric levels of methane from the world's largest source of the gas, wetlands such as paddy fields, marshes and bogs, found that emissions were increasing in line with rising temperatures.
> news.bbc.co.uk: Global warming 'speeds' up gas emissions

Methane release 'looks stronger'

Fairbanks (Alaska), 8 January 2010 - Scientists have uncovered what appears to be a further dramatic increase in the leakage of methane gas that is seeping from the Arctic seabed.
Methane is about 20 times more potent than CO2 in trapping solar heat.
The findings come from measurements of carbon fluxes around the north of Russia, led by Igor Semiletov from the University of Alaska at Fairbanks.
> news.bbc.co.uk: Methane release 'looks stronger'

Interactions With Aerosols Boost Warming Potential Of Some Gases incl Methane

ScienceDaily / London, October 31, 2009 — For decades, climate scientists have worked to identify and measure key substances -- notably greenhouse gases and aerosol particles -- that affect Earth's climate. And they've been aided by ever more sophisticated computer models that make estimating the relative impact of each type of pollutant more reliable.
> www.sciencedaily.com: Interactions With Aerosols Boost Warming Potential Of Some Gases
> www.telegraph.co.uk: Methane impact on global warming 'much greater than thought'
> www.timesonline.co.uk: Methane’s impact on global warming far higher than previously thought

Methane gas likely spewing into the oceans through vents in sea floor

(Eurekalert), September 2 2009 - Scientists worry that rising global temperatures accompanied by melting permafrost in arctic regions will initiate the release of underground methane into the atmosphere. Once released, that methane gas would speed up global warming by trapping the Earth's heat radiation about 20 times more efficiently than does the better-known greenhouse gas, carbon dioxide.
An MIT paper appearing in the Journal of Geophysical Research online Aug. 29 elucidates how this underground methane in frozen regions would escape and also concludes that methane trapped under the ocean may already be escaping through vents in the sea floor at a much faster rate than previously believed. Some scientists have associated the release, both gradual and fast, of subsurface ocean methane with climate change of the past and future.
> www.eurekalert.org: Methane gas likely spewing into the oceans through vents in sea floor

Our best guess about global warming may be wrong

(CS-Monitor), August 31 2009 - Fifty-five million years ago, the world was a much warmer place. The poles were ice-free year-round. Palm trees grew in Alaska. Forests stretched right into the Arctic Circle.
There, swamps like those in today’s southeastern United States hosted alligators, snakes, and giant tortoises.
Scientists call this time in Earth’s history the Eocene, the dawn of the age of mammals. And climatologists have naturally taken a keen interest in how it began.
They know that a dramatic spike in carbon dioxide associated with rapid climate change kicked off the epoch – called the “Paleocene-Eocene Thermal Maximum” (PETM). But what scientists don’t understand about the PETM may hold the most relevant lessons for where the world’s climate is headed today.
> www.csmonitor.com: Our best guess about global warming may be wrong
> www.rice.edu: Our best guess is likely wrong / Unknown processes account for much of warming in ancient hot spell (Jul 14)
> www.nature.com: Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming (Abstract Jul 13))

Climate trouble may be bubbling up in far north

Mackenzie river delta, Northwest Territories, August 31 2009 - Only a squawk from a sandhill crane broke the Arctic silence — and a low gurgle of bubbles, a watery whisper of trouble repeated in countless spots around the polar world.
"On a calm day, you can see 20 or more `seeps' out across this lake," said Canadian researcher Rob Bowen, sidling his small rubber boat up beside one of them. A tossed match would have set it ablaze.
"It's essentially pure methane."
Pure methane, gas bubbling up from underwater vents, escaping into northern skies, adds to the global-warming gases accumulating in the atmosphere. And pure methane escaping in the massive amounts known to be locked in the Arctic permafrost and seabed would spell a climate catastrophe.
Is such an unlocking under way?
> news.yahoo.com: Climate trouble may be bubbling up in far north

Methane seeps from Arctic sea-bed

London, August 19 /24, 2009 - Scientists say they have evidence that the powerful greenhouse gas methane is escaping from the Arctic sea-bed.
Researchers say this could be evidence of a predicted positive feedback effect of climate change.
A paper in Geophysical Research Letters details the findings, made on an expedition in Autumn 2008 in the British research ship RRS James Clark Ross.
The team of scientists from Birmingham University, the National Oceanography Centre, Southampton and Royal Holloway University think the gas is being released from methane hydrate beneath the seabed, which is melting because of warming waters above.
Similar gas plumes have been found elsewhere in places like the Black Sea and the Gulf of Mexico, but this is the first time scientists have found them in where the conditions for their occurrence can be clearly attributed to climate warming.
'Various people have predicted this for several years, and methane from hydrate beneath the sea bed has been strongly appealed to by scientists looking to explain past climate shifts,' says Professor Graham Westbrook, a geophysicist at Birmingham University. 'But this is first time anyone's discovered a situation where it actually seems to be happening now as a result of rising water temperatures,' he adds.
> news.bbc.co.uk: Methane seeps from Arctic sea-bed (August 19)
> planetearth.nerc.ac.uk: Warming waters release methane plumes into Arctic sea (August 24)
> www.noc.soton.ac.uk: Warming Ocean Contributes to Global Warming (August 06)
> www.agu.org: Escape of methane gas from the seabed along the West Spitsbergen continental margin (August 06)

Stressed Crops Emit More Methane Than Thought
Calgary, (Canada) August 19, 2009 Scientists at the University of Calgary have found that methane emission by plants could be a bigger problem in global warming than previously thought.
> www.seeddaily.com: Stressed Crops Emit More Methane Than Thought

Warming ocean contributes to global warming
August 14th, 2009 The warming of an Arctic current over the last 30 years has triggered the release of methane, a potent greenhouse gas, from methane hydrate stored in the sediment beneath the seabed.
Scientists at the National Oceanography Centre Southampton working in collaboration with researchers from the University of Birmingham, Royal Holloway London and IFM-Geomar in Germany have found that more than 250 plumes of bubbles of methane gas are rising from the seabed of the West Spitsbergen continental margin in the Arctic, in a depth range of 150 to 400 metres.
> www.physorg.com: Warming ocean contributes to global warming"

“Methane levels rose in 2008 for the second consecutive year"

Washington, April 25 2009 - Two of the most important climate change gases increased last year, according to a preliminary analysis for NOAA’s annual greenhouse gas index, which tracks data from 60 sites around the world.
Researchers measured an additional 16.2 billion tons of carbon dioxide (CO2) — a byproduct of fossil fuel burning — and 12.2 million tons of methane in the atmosphere at the end of December 2008. This increase is despite the global economic downturn, with its decrease in a wide range of activities that depend on fossil fuel use.
> climateprogress.org: Methane levels rose in 2008 for the second consecutive year"
> www.noaanews.noaa.gov: Greenhouse Gases Continue to Climb Despite Economic Slump
See also:
> Permafrost Thaw

Climate-Warming Methane Levels Rose Fast In 2007
Washington (US) October 31, 2008 - Levels of climate-warming methane -- a greenhouse gas 25 times as potent as carbon dioxide -- rose abruptly in Earth's atmosphere last year, and scientists who reported the change don't know why it occurred.
www.planetark.com: Climate-Warming Methane Levels Rose Fast In 2007
www.enn.com / MIT: Levels of the greenhouse gas methane begin to increase again
www.newscientist.com: Global-warming methane spiked in 2007

The methane time bomb

London, 23 / 25 September 2008 - British scientists have discovered hundreds more methane "plumes" bubbling up from the Arctic seabed, in an area to the west of the Norwegian island of Svalbard. It is the second time in a week that scientists have reported methane emissions from the Arctic.
Methane is 20 times more potent than carbon dioxide as a greenhouse gas and the latest findings from two separate teams of scientists suggest it is being released in significant amounts from within the Arctic Circle.
On Tuesday, The Independent revealed that scientists on board a Russian research ship had detected vast quantities of methane breaking through the melting permafrost under the seabed of the shallow continental shelf off the Siberian coast.
Preliminary findings suggest that massive deposits of subsea methane are bubbling to the surface as the Arctic region becomes warmer and its ice retreats.
www.independent.co.uk: Hundreds of methane 'plumes' discovered
www.independent.co.uk: The methane time bomb
www.independent.co.uk: The ultimate gas leak that scientists dreaded
www.hydratech.bham.ac.uk: Techniques for the quantification of methane hydrate in European continental margins
www.youtube.com: The methane time bomb
www.iarc.uaf.edu: International Siberian Shelf Study
www.damocles-eu.org: Understanding Climate Change in the Arctic
See also:
Permafrost Thaw

Methane gas oozing up from Siberian seabed: Swedish researcher
Stockholm, (Sweden), August 30, 2008 - Methane, a potent greenhouse gas, is leaking from the permafrost under the Siberian seabed, a researcher on an international expedition in the region told Swedish daily Dagens Nyheter on Saturday.
www.physorg.com: Methane gas oozing up from Siberian seabed: Swedish researcher

Not-So-Permafrost: Big Thaw of Arctic Soil May Unleash Runaway Warming
Anchorage, (Alaska), August 28, 2008 - New estimates show that frozen Arctic soil contains far more potential greenhouse gas than previously recognized--and could speed climate change as it melts.
www.sciam.com: Big Thaw of Arctic Soil May Unleash Runaway Warming
www.eurekalert.org: Thawing permafrost likely to boost global warming

Methane release could cause abrupt, far-reaching climate change
Washington (US), May 29 2008 - An abrupt release of methane, a powerful greenhouse gas, from ice sheets that extended to Earth's low latitudes some 635 million years ago caused a dramatic shift in climate, scientists funded by the National Science Foundation (NSF) report in this week's issue of the journal Nature. The shift triggered events that resulted in global warming and an ending of the last "snowball" ice age.
www.enn.com: Methane release could cause abrupt, far-reaching climate change
www.nature.com: Snowball Earth: Exit strategy
www.nature.com: Snowball Earth termination by destabilization of equatorial permafrost methane clathrate

A Storehouse of Greenhouse Gases Is Opening in Siberia
Vienna, April 17 2008 - Researchers have found alarming evidence that the frozen Arctic floor has started to thaw and release long-stored methane gas. The results could be a catastrophic warming of the earth, since methane is a far more potent greenhouse gas than carbon dioxide. But can the methane also be used as fuel?
www.spiegel.de: A Storehouse of Greenhouse Gases Is Opening in Siberia
www.reuters.com: Burning Ice Baby.....
en.wikipedia.org: Methane clathrate

Methane sources over the last 30,000 years
Vienna, April 17 2008 - Ice cores are essential for climate research, because they represent the only archive which allows direct measurements of atmospheric composition and greenhouse gas concentrations in the past. Using novel isotopic studies, scientists from the European Project for Ice Coring In Antarctica (EPICA) were now able to identify the most important processes responsible for changes in natural methane concentrations over the transition from the last ice age into our warm period.
www.awi.de: Methane sources over the last 30,000 years

Ancient Warming Caused Huge Spike in Temps, Study Says

A chart of temperature data for the past 65 milion years shows the sudden and brief spike known as the Paleocene-Eocene thermal maximum (PETM).
The spike may have been caused when vast icelike reserves of greenhouse gases melted in response to a small warming event, according to a new study that raises dire possibilities for Earth's current warming. Image by Robert A. Rohde/Global Warming Art under GNU Free Documentation License Version 1.2

Utrecht (NL), December 19, 2007 - What started out as a moderate global warm-up about 55 million years ago triggered a massive injection of greenhouse gases into the atmosphere that sent temperatures skyrocketing, a new study says.
The finding suggests that today's temperature rise may just be priming the planet for a carbon belch of epic proportions.
news.nationalgeographic.com: Ancient Warming Caused Huge Spike in Temps, Study Says

Siberian thaw could speed up global warming
September 26, 2007 - Parts of the permafrost in Russia's northern wilderness are melting. Dmitry Solovyov and Alister Doyle from Reuters reveal how that could affect us all - severely.
www.smh.com.au: Siberian thaw could speed up global warming
www.sciam.com: The North Pole Is Melting
September 14: Satellites witness lowest Arctic ice coverage in history

Receding permafrost is a bone-hunters' bounty but threatens the world
Chersky, (Russia) September 17/18, 2007 - One day, climate change could cost the earth. For now, it is a nice little earner for Russian hunter Alexander Vatagin.
In Siberia's northernmost reaches, high up in the Arctic Circle, the changing temperature is thawing out the permafrost to reveal the bones of prehistoric animals like mammoths, woolly rhinos and lions that have been buried for thousands of years.
Rising temperatures cause Russian permafrost to thaw, leading to an even faster rate of global warming.
Some large sections of permafrost in Siberia have been thawing out in the last few years due to climate change. If the thaw continues apace (or speeds up) researchers worry that much more organic matter -- leftover plant and animal leavings from thousands of years ago, like mammoth dung, that never fully decayed due to sustained below-freezing temperatures -- will thaw out and start decomposing, which could significantly speed up climate change with massive doses of methane and carbon dioxide.
"The deposits of organic matter in these soils are so gigantic that they dwarf global oil reserves," says climate scientist Sergei Zimov. "This will lead to a type of global warming which will be impossible to stop."
The United Nations agreed in a recent report that large-scale permafrost thaw could be quite nasty, climate-wise, but since the bulk of permafrost is still frosty, it's regarded as mostly a potential threat for now.
In the Arctic, average temperatures have increased at almost twice the global rate in the past 100 years.
Temperatures at the top of the permafrost layer have generally increased since the 1980s by up to 3°C (5.4°F) the UN climate secretariat says.
In the Russian Arctic, buildings are collapsing because permafrost under their foundations has melted, the UNFCCC says.
Thee permafrost-decay, together with other aspects of climate change, are issues in the UN General Assembly of the end of September (2007).
www.unep.org 06042007: Melting Ice-A Hot Topic? New UNEP Report Shows Just How Hot It's Getting
www.reuters.com: Receding permafrost is a bone-hunters' bounty
www.reuters.com: Russian permafrost begins to thaw
www.planetark.com: Mammoth Dung, Prehistoric Goo May Speed Warming
www.msnbc.msn.com: Dung from mammoths sends warming signal
See also the Dutch page on permafrost
Arctic ice retreating more quickly than computer models project

Tipping points in the Earth system

London, August 30, 2007 - (by Timothy M. Lenton) - The Intergovernmental Panel on Climate Change (IPCC) in its many excellent reports tends to portray climate change as a smooth transition. Although the projections are rarely straight lines the underlying system and its responses appear ‘linear’ (in mathematical terms). There are, of course, exceptions to this, notable ones being the possible collapse of the Atlantic thermohaline circulation or irreversible melt of the Greenland ice sheet, which both get significant attention in the latest IPCC report (IPCC, 2007). These represent large scale ‘non-linear’ components of the Earth system.
researchpages.net: Tipping points in the Earth system

The highest concentrations of dissolved methane ever measured in the Arctic Ocean found beneath the sea-ice on the Laptev Sea shelf

Fairbanks, (AL/US), May 4, 2007 - The Arctic Ocean is a vulnerable environment with unique ecosystems that are adapted to harsh conditions. Enormous stores of methane gas, referred to commonly as the “Arctic Carbon Hyper Pool”, are present in the Arctic Ocean sediments.
These stores include three basic reservoirs of methane: methane trapped within seabed permafrost, methane stored in a form of gas hydrate deposit beneath the permafrost, and thermogenic methane (free gas) that comes upward from deep within the earth.
The amount of methane within seabed permafrost is unknown but it is presumed to be significant. Gas hydrate deposits beneath the Siberian Arctic shelf are predicted to contain about 60 Giga-tons of C-CH4 (carbon within the methane deposits); the amount of free gas underlying the gas hydrates is likely to be one half to two thirds the amount of gas stored in gas hydrate.
www.iarc.uaf.edu: The highest concentrations of dissolved methane ever measured in the Arctic Ocean found beneath the sea-ice on the Laptev Sea shelf

IPCC Report - The Arctic: Thawing Permafrost, Melting Sea Ice And More Significant Changes
London, April 11, 2007 - (Unep/Science Daily) - Dramatic changes to the lives and livelihoods of Arctic-living communities are being forecast unless urgent action is taken to reduce greenhouse gases, according to the Intergovernmental Panel on Climate Change (IPCC).
www.sciencedaily.com: The Arctic: Thawing Permafrost, Melting Sea Ice And More Significant Changes

Tundra disappearing at rapid rate
Alberta, 05 March 2007 - Forests of spruce trees and shrubs in parts of northern Canada are taking over what were once tundra landscapes -- forcing out the species that lived there. This shift can happen at a much faster speed than scientists originally thought, according to a new University of Alberta study that adds to the growing body of evidence on the effects of climate change.
www.eurekalert.org: Tundra disappearing at rapid rate
www.sciencedaily.com: Tundra disappearing at rapid rate

Alaska natives left out in the cold
Anchorage, January 4 2007 - While the rest of the world argues about the best way to curb future climate change, says Patricia Cochran in this week's Green Room, native communities within the Arctic Circle are having to draw on their own ancestral strengths to adapt to a rapidly changing world.
www.bbc.co.uk: Alaska natives left out in the cold

Methane ices pose climate puzzle
San Francisco, December 13 2006 - Scientists drilling ocean sediments off Canada have discovered methane ices at much shallower depths than expected.
The finding has important implications for climate studies, they believe.
The melting of hydrates, as they are known, is a suspected contributor to past and present increases in atmospheric methane, a greenhouse gas.
news.bbc.co.uk: Methane ices pose climate puzzle

Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming
September 7 2006 - (by K. M. Walter, S. A. Zimov, J. P. Chanton, D. Verbyla & F. S. Chapin, ) - Large uncertainties in the budget of atmospheric methane, an important greenhouse gas, limit the accuracy of climate change projections. Thaw lakes in North Siberia are known to emit methane, but the magnitude of these emissions remains uncertain because most methane is released through ebullition (bubbling), which is spatially and temporally variable.
Here we report a new method of measuring ebullition and use it to quantify methane emissions from two thaw lakes in North Siberia. We show that ebullition accounts for 95 per cent of methane emissions from these lakes, and that methane flux from thaw lakes in our study region may be five times higher than previously estimated.
Extrapolation of these fluxes indicates that thaw lakes in North Siberia emit 3.8 teragrams of methane per year, which increases present estimates of methane emissions from northern wetlands (< 6–40 teragrams per year; by between 10 and 63 per cent).
We find that thawing permafrost along lake margins accounts for most of the methane released from the lakes, and estimate that an expansion of thaw lakes between 1974 and 2000, which was concurrent with regional warming, increased methane emissions in our study region by 58 per cent.
Furthermore, the Pleistocene age (35,260–42,900 years) of methane emitted from hotspots along thawing lake margins indicates that this positive feedback to climate warming has led to the release of old carbon stocks previously stored in permafrost.
www.nature.com: Full article (by payment)

Arctic Ocean Methane Contributes to Global Warming
Anchorage, July 10, 2006 - Global warming and its effects on the environment and human life are being studied by scientists at the International Arctic Research Center. One primary effect of global warming is an increase in the average global temperature due to the greenhouse effect.
Special attention is being given to methane, a greenhouse gas that warms the earth 23 times as much as the same amount of carbon dioxide (for a given weight averaged over a 100 year time period).
In 1998, the average concentration of methane at the Earth's atmosphere was measured at 1.745 ppb with higher concentrations in the northern hemisphere where most sources (both natural and anthropogenic) are larger. Even higher concentrations were registered over the Arctic/Sub-Arctic regions where human activities are considered to be negligible (Figure.1).
It is the widespread opinion that water-saturated terrestrial arctic ecosystems (wetlands) are primarily responsible for the higher concentrations of methane over the Arctic region. During the winter, however, the wetland ecosystems are dormant whereas the concentrations of methane remain high. Scientists from Dr. I. Semiletov's group surmised that there must be another major natural source of methane in the northern hemisphere and considered it might be the Arctic Ocean.
www.iarc.uaf.edu: Arctic Ocean Methane Contributes to Global Warming

The Tipping Point?
December 6, 2005 - (by Jim Hansen) - The Earth's climate is nearing, but has not passed, a tipping point beyond which it will be impossible to avoid climate change with far-ranging undesirable consequences. These include not only the loss of the Arctic as we know it, with all that implies for wildlife and indigenous peoples, but losses on a much vaster scale due to rising seas.
Ocean levels will increase slowly at first, as losses at the fringes of Greenland and Antarctica due to accelerating ice streams are nearly balanced by increased snowfall and ice sheet thickening in the ice sheet interiors.
But as Greenland and West Antarctic ice is softened and lubricated by meltwater, and as buttressing ice shelves disappear because of a warming ocean, the balance will tip toward the rapid disintegration of ice sheets.
The Earth's history suggests that with warming of two to three degrees, the new sea level will include not only most of the ice from Greenland and West Antarctica, but a portion of East Antarctica, raising the sea level by twenty-five meters, or eighty feet. Within a century, coastal dwellers will be faced with irregular flooding associated with storms. They will have to continually rebuild above a transient water level.
This grim scenario can be halted if the growth of greenhouse gas emissions is slowed in the first quarter of this century.
(From a presentation to the American Geophysical Union, December 6, 2005)

Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming
Boulder, December, 2005 - Large uncertainties in the budget of atmospheric methane, an important greenhouse gas, limit the accuracy of climate change projections1, 2. Thaw lakes in North Siberia are known to emit methane3, but the magnitude of these emissions remains uncertain because most methane is released through ebullition (bubbling), which is spatially and temporally variable.
www.nature.com: Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming

Tipping Points in the Tundra
Madison, October, 2005 - Environmental changes in the Arctic may be an early warning system for global climate change, and recent reports from the region are alarming. Several studies have indicated substantial declines in sea ice cover and earlier ice melting, which have led to the lowest level of sea ice in more than a century. And now there is evidence that the warming on the nearby continents may also be accelerating.
In his Perspective, Foley discusses results reported in the same issue by Chapin et al. that suggest that reductions in highly reflective snow cover and expanding shrub and tree cover, both caused by recent warming in the Arctic, are amplifying the temperature changes in the region.
Reduced snow cover and expanded shrubs and tress both act to absorb additional solar radiation (compared to highly reflective snow fields), warming the surface and the atmosphere above. Chapin et al. provide the best empirical evidence for this climate feedback mechanism to date; these results need to be more fully incorporated into models of future climate change.
www.science.com / J. A. Foley: Tipping Points in the Tundra (Abstract)
www.science.com / F. S. Chapin et all: Role of Land-Surface Changes in Arctic Summer Warming
www.heatisonline.org / J. A. Foley: Tipping Points in the Tundra (Full text)
www.heatisonline.org / F. S. Chapin et all: Role of Land-Surface Changes in Arctic Summer Warming (Full text)