By Paul Homewood
Someone sent me this BBC article from a few months ago:
Near the Yana river basin, in a vast area of permafrost, there is a dramatic tadpole-shaped hole in the ground: the Batagaika crater.
The crater is also known as a "megaslump" and it is the largest of its kind: almost 0.6 miles (1km) long and 282ft (86m) deep. But these figures will soon change, because it is growing quickly.
Locals in the area avoid it, saying it is a "doorway to the underworld". But for scientists, the site is of great interest.
Looking at the layers exposed by the slump can give indications of how our world once looked – of past climates. At the same time, the acceleration of the growth gives an immediate insight into the impact of climate change on the increasingly fragile permafrost.
There are two types of permafrost. One is from glacier ice, left over from the last Ice Age and now buried underground. The other type, the one present around the Batagaika crater, is ice that has formed in the ground itself. Often, this ice is trapped beneath a layer of sediment and has been frozen for at least two years.
The Batagaika crater opens up a vast area of previously buried permafrost, some of which first formed many thousands of years ago.
The trigger that led to the crater started in the 1960s. Rapid deforestation meant that the ground was no longer shaded by trees in the warmer summer months. This incoming sunlight then slowly warmed the ground. This was made worse by the loss of cold "sweat" from trees as they transpire, which would have kept the ground cool.
"This combination of less shading and less vapid transpiration led to warming of the ground surface," says Julian Murton of the University of Sussex in the UK.
As the ground surface warmed up, it caused the layer of soil right above the permafrost to warm. This caused the permafrost itself to thaw. Once this process started and the ice was exposed to warmer temperatures, melting escalated.
So far, so good.
But, of course, someone has to mention global warming!
Frank Günther of the Alfred Wegener Institute in Potsdam, Germany, and colleagues have been monitoring the site for the last decade, using satellite images to measure the rate of change.
During their study, the head wall of the crater has grown by an average of 33ft (10m) per year. In warmer years, the changes have been even greater, sometimes up to 98ft (30m) per year. Günther announced these findings at the American Geophysical Union meeting in December 2016.
He also has reason to believe that the side wall of the growing crater will reach a neighbouring eroding valley in the coming summer months. This in turn will "very likely" be a new trigger for more growth.
"On average over many years, we have seen that there’s not so much acceleration or deceleration of these rates, it’s continuously growing," says Günther. "And continuous growth means that the crater gets deeper and deeper every year."
This has other worrying consequences.
Many of the ice deposits that are now being exposed formed during the last Ice Age. This ground ice contains a lot of organic matter, including plenty of carbon that has been locked away for thousands of years.
"Global estimations of carbon stored in permafrost is [the] same amount as what’s in the atmosphere," says Günther.
As more permafrost thaws, more and more carbon is exposed to microbes. The microbes consume the carbon, producing methane and carbon dioxide as waste products. These greenhouse gases are then released into the atmosphere, accelerating warming further.
"This is what we call positive feedback," says Günther. "Warming accelerates warming, and these features may develop in other places. It’s not only a threat to infrastructure. Nobody can stop this development. There’s no engineering solution to stop these craters developing."
There is no indication that the erosion of this crater will slow down any time soon, as it continues to grow year on year.
That makes the future of Siberia’s permafrost look very wobbly indeed.
But there is absolutely no evidence that the crater has anything to do with local temperatures, never mind global ones.
The 1960s, when the hole first appeared were relatively cold years in the local area. Although there were a couple of warm years in 1997 and 2008, most years recently are only slightly less cold than the 1930s and 40s.
Much more important though are the summer temperatures, which are much higher than one would maybe intuitively expect. Again, there is no evidence of any untoward warming.
The BBC report actually gives the clue to what actually happened – deforestation. As the scientists themselves say, cutting down trees allowed the sun to do its work.
Furthermore, it also increased the effects of erosion.
There is, however, one aspect of the scientific work going on which the BBC forgot to mention, but which the Siberian Times reported on:
The director of the Research Institute of Applied Ecology of the North, Gregory Savvinov, said: ‘In the 1960s there was a road between the village of Batagai and some industrial facilities. The forest was cut down, and this led to the formation of the ravine. In recent years, against the backdrop of climatic changes, due to the warming, the ravine grew to the size of crater.’
In 2009 the carcass of an Holocene era foal – some 4,400 years old – was discovered, and a mummified carcass of a bison calf. Remains of ancient bison, horses, elks, mammoths, and reindeer were also found here.
So we learn that the region was at least as warm as now 4400 years ago, and probably much warmer for horses to survive then. Yet we did not get runaway warming caused by the release of methane, which is now predicted.
There are many other such holes scattered around Siberia and northern Canada, albeit much smaller. But we have only recently possessed satellites and aircraft to film these, so we cannot say there is anything remotely unusual about them.
But it appears highly unlikely deforestation is the key behind many of them.
via NOT A LOT OF PEOPLE KNOW THAT
October 9, 2017 at 01:30PM
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