Thursday, February 25, 2010

since global warming is in fact global...

How to grow a glacier

BACK in the 13th century, when news of Genghis Khan and his marauding Mongol hordes reached what is now northern Pakistan, the people there came up with an unlikely means of keeping them out. According to local legend, villagers blocked the mountain passes by simply growing glaciers across them.

Whether or not these stories are true, the art of glacier growing - also known as glacial grafting - has been practised for centuries in the mountains of the Hindu Kush and Karakorum ranges. It was developed as a way to improve water supplies to villages in valleys where glacial meltwater tended to run out before the end of the growing season. Now, as these remote mountain communities come under pressure from population growth and climate change, researchers and development agencies are starting to take a serious look at whether growing new glaciers can really stop mountain streams from running dry.

Legends aside, no one really knows when the first glacier was grown in this region. Inayatullah Faizi, assistant professor in social sciences at the Government Degree College at Chitral in Pakistan's North-West Frontier province, cites evidence of a glacier being grown for irrigation purposes as long ago as 1812. However, the first documented reference to the practice does not appear until more than a century later when a British colonial administrator called D.L.R. Lorimer reported it in the 1920s. Though Lorimer described the practice as obsolete, partly thanks to guaranteed food supplies from the British Raj, the traditions of glacier growing survived.

Today, the skills and know-how needed to grow glaciers are kept alive by a handful of village elders. Ghulam Rasool is one of them. At 77, he is resident glacier-growing expert in the village of Hanouchal Haramosh in the Karakoram mountains. Like many communities in the area, Hanouchal Haramosh struggles with an uncertain water supply. Most precipitation falls as snow at altitude, while the inhabited valleys stay largely dry. To irrigate their fields, villagers rely on snow melting up in the mountains, but by the end of the growing season most of the previous winter's snow has gone. The water dries up, and crop yields suffer.

Secure supply

Other villages are luckier. They have a glacier melting into their watershed, and because this is a permanent supply of ice and because ice melts more slowly than fresh snow, the water supply lasts longer and is more predictable. If it really were possible to grow a glacier, this could be a lifeline for communities battling glacier retreat and under pressure to grow more food to feed a growing population. It's a question that prompted Ingvar Tveiten from the Department of International Environment and Development Studies at the Norwegian University of Life Sciences in ├ůs to begin the most comprehensive study so far of the methods and rituals of glacier growing.

In the study, which Tveiten published last year as his master's thesis, he reports that growing a glacier takes a lot more than piling up any old snow and ice and waiting for it to freeze. According to local tradition, Tveiten says, glaciers have a gender. A "male" glacier is one that is covered in stones and soil and moves slowly or not at all. A "female" one is whiter, and grows more quickly, yielding more water. "It is important to have both sexes," a glacier grower from the village of Ghwari in Baltistan, Pakistan-administered Kashmir, told Tveiten, "The ice which we found underneath the rocks in our own valley was only of one sex. Therefore it didn't increase. We had to add the opposite sex to it so it could increase."

Finding the right site is also crucial. Tveiten reviewed 12 sites where glaciers have been grown, and visited five of them. Almost all were located at altitudes above 4500 metres, and most were in a north-west-facing cirque of steep cliffs. Avalanches and rockfall from these cliffs are, according to local people, an important part of the process.

Once the site is selected, ice is brought to rocky areas where there are small boulders about 25 centimetres across. The rocks protect the ice from sunlight, and often have ice trapped in the gaps between them. This seems to be critical to a successful "planting". Common to most of the successful artificial glaciers, Tveiten says, is the existence of ice at the site before work starts, and glacier growers will often dig for a metre or more through talus or scree to find this in-situ "male" ice.

After they have added female to the male ice (traditionally by importing 12 man-loads or about 300 kilograms of the stuff), they cover the area with charcoal, sawdust, wheat husk, nutshells or pieces of cloth to insulate it. Gourds of water placed among the ice and rocks are also critical to a glacier's chances of forming, according to Tveiten. As the glacier grows and squeezes the gourds, they burst, spreading water on the surrounding ice, which then freezes.

Any snowmelt trapped in the budding glacier also freezes, adding more ice. Pockets of cold air moving between the rocks and ice keep the glacier cool. When the mass of rock and ice is heavy enough, it begins to creep downhill, forming a self-sustaining glacier within four years or so. What's produced is hardly a glacier in the proper sense, but growing and flowing areas of ice many tens of metres long have been reported at the sites of earlier grafts.

Cold comfort

So does it work? There is no shortage of anecdotal accounts of successful grafts. The Aga Khan Rural Support Programme (AKRSP), an NGO based in Baltistan, cites several examples of long-lasting artificial glaciers. One has been providing water since the 1940s, and another is claimed to have been grafted in the 16th century. The AKRSP has found these accounts convincing enough to fund the grafting of 17 new glaciers to improve water supply in villages with limited access to meltwater. It also recently signed a memorandum of understanding with the Pakistani government to extend its activities to more villages in Baltistan and in the nearby Gilgit region. The Parbat Social Welfare Organisation, a community group based in Chilas, south of Gilgit, has funded at least 10 more since 2003.

Local people are convinced that it's worth the effort. When Tveiten visited, Ghulam Rasool's village in eastern Gilgit, 18 of the 20 people he interviewed claimed that a glacier planted in the 1950s, and still in place today, increased water supply later in the season. Many people believed that the glacier had allowed them to cultivate up to 50 per cent more land, and that it has increased water flows in the critical period late in the growing season when crops mature. Local people also say the new glacier has grown to the point where it now stretches some 800 metres down from where it was planted.

Locals believe that growing a glacier allowed them to cultivate 50 per cent more land and increased yields late in the growing season

The AKRSP is also claiming success with its more recent glacier plantings. Sher Khan, a water and environmental engineer with the AKRSP, reported in 2005 that five of 15 communities reported increased water flows late in the season, with other glaciers also growing. Since then two more glaciers have been planted, and Nazir Ahmad of the AKRSP says villagers continue to report that this has boosted their water supplies.

Tveiten is more sceptical: he suspects that in many cases, similar quantities of ice would have developed without any human intervention. "Glacier growing is conducted at locations which are already very prone to ice accumulation," he observes. He also suggests that "planting" a glacier on a frozen talus slope that is already advancing may give a false impression that human intervention has had an impact.

Calling the accumulated ice a "glacier" may also be an exaggeration at times. Tveiten visited one site in the valley above the village of Balghar, where grafting took place in 2000. This was done by placing 300 kilograms of ice, water, coal and sawdust under a 15-metre boulder inside a cave in a position where the ice was shielded from sunlight. Tveiten says he saw a metre-thick mass of ice under the entire length of the boulder. That's quite an accumulation of ice, but hardly a glacier, and it's questionable whether such accumulations could significantly increase the amount water that is available.

But as Tveiten also points out, analysing glacier growing only in technical terms may miss an important point. The practice is associated with many traditional ceremonies and rituals that help bind the community together. For people living in such a harsh environment, the experience gives them an important sense of control of their future.

Others, however, are convinced there is more to it than that. Hermann Kreutzmann, a glaciologist at the Free University of Berlin in Germany, witnessed a ceremony in Hunza, near Gilgit, in 1985. "It seemed very plausible to me to search for a specific location at the appropriate altitude with a tolerable temperature regime and to place ice there," he says. As ice can absorb and retain water, he reckons that "a substantial amount of ice in a proper location might indeed augment water supplies".

Kenneth Hewitt from the Cold Regions Research Centre at Wilfrid Laurier University in Waterloo, Ontario, Canada, witnessed a glacier planting in Baltistan in 1961, making him possibly the first westerner to do so. "In literal, western terms I don't think they grow glaciers," he says. "It would be very easy to say this is all hokum, mumbo-jumbo, but I don't believe that either," he adds. "The people involved are, on their own terms, extremely practical and knowledgeable about their environment."

Hewitt agrees with Tveiten that the social value of glacier growing is important, particularly as a way to help ease communal anxiety during periods of climatic stress. But he is also interested in working out a physically plausible basis for the practice. "It would have to be about enhanced freezing or capture of available moisture in solid form," he says. This could occur through cold air drainage, evaporative cooling, and possibly deposition of rime or frost. "Given the exact setting and practices of glacier planting, I suspect they are designed to reproduce conditions known to involve evaporative cooling across the freezing point."

Khan hopes that the work being done by the AKRSP will encourage more researchers to investigate whether glacier growing can be used to provide water for expanding communities - not just in Pakistan, but also in mountain communities in other parts of the world. Researchers as far away as the Andes, where the terrain is similar, have already shown some interest. As more studies get under way, we may soon find out if the legend can survive scrutiny by modern science.

Ed Douglas is a science writer based in Sheffield, UK

http://www.newscientist.com/article/mg19726412.000-how-to-grow-a-glacier.html?page=1

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