Saturday 23 February 2013

The melting Permafrost

The news keeps getting worse, but confirms everything we already know.

Permafrost Melting Rate Could Be Faster And Worse Than We Thought, New Study Finds

22 February, 2013

Nearly a quarter of the Northern Hemisphere’s land surface is covered in permanently frozen soil, or permafrost, which is filled with carbon-rich plant debris — enough to double the amount of heat-trapping carbon in the atmosphere if the permafrost all melted and the organic matter decomposed.
According to a paper published Thursday in Science, that melting could come sooner, and be more widespread, than experts previously believed. If global average temperature were to rise another 2.5°F (1.5°C), say earth scientist Anton Vaks of Oxford University, and an international team of collaborators, permafrost across much of northern Canada and Siberia could start to weaken and decay. And since climate scientists project at least that much warming by the middle of the 21st century, global warming could begin to accelerate as a result, in what’s known as a feedback mechanism.
How much this will affect global temperatures, which are currently projected to rise as much as 9°F by 2100, is impossible to say. It all depends on how quickly the permafrost melts, and how quickly bacteria convert the plant material into carbon dioxide and methane gas, and nobody knows the full answer to that. But since climate scientists already expect a wide range of negative consequences from rising temperatures, including higher sea level, more weather extremes and increasing risks to human health, anything that accelerates warming is a concern.
While the rate at which melting permafrost will add carbon to the atmosphere is largely unknown, a study released February 11 in Proceedings of the National Academy of Sciences at least begins to tackle the problem. It shows that when the permafrost does melt, carbon dissolved in the meltwater decomposes faster after it’s been exposed to the ultraviolet component of sunlight.
In any case, there’s no doubt that the permafrost will melt, at least in part, since it’s already starting to do so. In some parts of the Arctic, trees, buildings and roadways have started listing to one side, or even collapsing, as soil that was once hard as a rock has softened from the warming that’s already taken place.
To get an idea of what might be in store for the future, Vaks and his colleagues searched for evidence from the distant past — specifically, from stalagmites and stalactites formed over hundreds of thousands of years in underground Siberian caves. These spiky mineral deposits, known collectively as speleothems, grow layer by layer as surface water percolates through the ground dissolving limestone as it goes, and finally forms droplets that hang from the ceiling of a cave. If the water evaporates before dropping to the floor, it leaves the limestone behind, and over the centuries those bits of limestone grow into a downward-pointing stalactite. If it drops first, then evaporates, the limestone builds up from the floor, creating a stalagmite.
In places without permafrost, this process happens year-in and year-out. Where there’s permafrost, however, water can only drip when the permafrost melts. So Vaks and his colleagues enlisted members of the Arabica Speleological Club in Irkutsk, Russia — amateur cave explorers — to help identify likely caves in a north-south line across Siberia.
Once they’d found the caves, they carefully removed sample speleothems, “preferably from hidden areas, so we wouldn’t spoil the caves’ natural beauty,” Vaks said. The scientists took their samples back to the lab, sliced them lengthwise, and exposed layers laid down over nearly 500,000 years. “By using uranium/thorium dating,” Vaks said, “we could find the layers’ exact ages with high precision.”
They also found that there were long periods when the speleothems didn’t grow at all — certainly not during ice ages, when permafrost locked the soil across most of Siberia, but not even, in the northernmost caves, during warmer interglacial periods, like the one we’re in now when glaciers went into retreat. The last time these northern speleothems showed any growth, in fact, was during an unusually warm period about 400,000 years ago.
At the time, global average temperatures were some 2.5°F warmer than they are today. That sort of temperature increase by itself wouldn’t make an enormous dent in the permafrost, but the Arctic is likely to warm faster than the rest of the globe — as in fact, it has already started to do.
As for the earlier study on carbon and ultraviolet light, environmental scientist Rose Cory, of the University of North Carolina, focused on sites in Alaska where melting permafrost has caused the soil to collapse into sinkholes or landslides. The soil exposed in this way is “baked” by sunlight, and said Cory in a press release, “(it) makes carbon better food for bacteria.”
In fact, she said, exposed organic matter releases about 40 percent more carbon, in the form of CO2 or methane, than soil that stays buried. “What that means,” Cory said, “ is that if all that stored carbon is released, exposed to sunlight and consumed by bacteria, it could double the amount of this potent greenhouse gas going into the environment.”

"NATO and the United States should change their policy because the time when they dictate their conditions to the world has passed," Ahmadinejad said in a speech in Dushanbe, capital of the Central Asian republic of Tajikistan

Melting Permafrost:
Scientists Warn of Dangers of Trapped Carbon
By Christoph Seidler

26 January, 2013

Research published Thursday in the journal Science says that even slightly warmer temperatures could start melting permafrost, which in turn threatens to trigger the release of huge amounts of greenhouse gases trapped in ice.

The frosty dungeon hides a dark secret. At least a quarter of the Northern Hemisphere's landmass is frozen and, like a vault, it holds 1,700 gigatonnes of carbon. This unimaginably high quantity of carbon comes from countless generations of creatures that have lived and died in the area over millions of years.

A portion of those dead plants and animals weren't decomposed by microorganisms because, at a certain point, it was simply too cold for that. But the permafrost is slowly melting. If large areas of ground underneath were to thaw one day, the bacterial decomposition process would pick up where it left off, releasing huge amounts of greenhouse gases. In total, permafrost contains twice as much carbon as what is currently billowing through the Earth's atmosphere.

If major portions of that carbon become released, the world's climate would suffer fatal consequences. For this reason, scientists have for some time now been asking the frightening question of just how strongly global warming affects permafrost areas. Using ingenious measuring methods, they are meticulously monitoring the fate of the planet. A new study, published in the professional journal Science on Thursday, suggests that it's possible that even slightly higher temperatures could thaw out significant portions of the region's permafrost areas.

A team of researchers led by Anton Vaks at the University of Oxford examined calcareous deposits from a total of six Siberian caves. Specifically, they looked at so called speleothems, which are mineral deposits -- including stalactites and stalagmites -- that form in limestone and other caves. "Speleothems only grow when rain and meltwater can seep through cracks into the caves," Vaks told SPIEGEL ONLINE. "And that process only occurs when temperatures are above the freezing point."

Precise Climate Records

Since water from the frozen earth can't reach cracks deep within the caves, the mineral deposits are precise records of the climate. In warmer times, the so-called interglacial periods, stalactites and stalagmites form. In colder phases, so called glacial periods, they don't. So there is a pattern similar to how tree rings can be used to tell their age.

A total of 36 speleothems were dated using the uranium-thorium method. Over time, uranium decays into thorium. The uranium isotopes dissolve in water that penetrates into the speleothems, while thorium does not and thus remains in the deposits.

Researchers can look back about 500,000 years in the past using this method. Speleothems in today's permafrost areas must have come from a significantly warmer period in which water was flowing. Vaks and his colleagues have been able to show that stalactites in the northern-most Lenskaya Ledyanaya Cave only grew in a very warm part of an interglacial period about 400,000 years ago.

At that time, average temperatures were about 1.5 degrees Celsius higher than they are today. Traces of this particularly warm period were also proven with pollen deposits and residue of algae found in the sediment of Elgygytgyn Lake, in northeastern Siberia, as well as from other sources of evidence. During this time, there were probably even numerous trees in southern Greenland.

On the Border

In periods with higher tempatures, the permafrost retreats further north. The Lenskaya Ledyanaya Cave lies at 40 degrees north latitude, in an area currently on the border of continuous permafrost. If the temperatures rise another one or two degrees, to approach something like what they were in the interglacial period 400,000 years ago, the situation would most likely look differently. "That is probably the threshold where continuous permafrost becomes vulnerable," says Vaks.

The research is "well-argued and conclusive, the data is great, and it's very diligent," says Hanno Meyer, at the Alfred Wegener Institute for Polar and Marine Research (AWI) in Potsdam, outside Berlin. It was the first time that speleothems have been used to prove the changing areas of southern permafrost borders, he says.

Meyer also said the is currently little information about older warm periods in this region. However, he adds, the research method used by the Oxford University team is not appropriate for other permafrost landscapes because these areas have been frozen for longer than 500,000 years and are therefore too old for the dating method to measure.

The frozen earth varies in thickness from a couple of meters to 1.5 kilometers, depending on the area. And a large portion of the permafrost areas lie farther north than Vaks and his team have studied until now, with pieces even in the ocean floor. So what does this newly released research now mean for these areas in the high Arctic? "We understand that we must go further to the North," admits Vaks. Over the next two years, Vaks and his team will look for more northern caves -- and for speleothems that can be dated.

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