December 22, 2009 – Original Source: Nature, Harvey Leifert
Just when we thought you knew all of the dangers facing the people of Afghanistan, here comes one more: catastrophic flooding from high altitude glaciers. Afghanistan’s glaciers are located in the narrow eastern Wakhan Panhandle of the country, wedged between Pakistan, China, and several former Soviet republics. They drain southwestward via system of streams, providing surface water and recharging aquifers through most of the country.
For four years, the US Geological Survey has been studying satellite imagery of the region, using data collected by various instruments, including ASTER and Landsat 7. At the American Geophysical Union’s annual Fall Meeting in San Francisco, USGS glacial geologist Bruce Molnia presented the findings thus far.
I asked Molnia the difference between a glaciologist and a glacial geologist. “Glacial geologists focus on what glaciers do to the landscape,” he explained, “whereas glaciologists are more focused on the ice and its physics.” It was only 8:30 a.m., and I had learned something I should have known years ago. Catastrophic outburst floods from glaciers are called jökulhlaups, an Icelandic word meaning “glacier flood,” Molnia said (adding another word to my vocabulary), because the phenomenon was first described there.
USGS is under contract to the US Agency for International Development, which is seeking to help Afghanistan prepare for its future, both agriculturally and industrially, and for that it is necessary to understand its water resources, Molnia said. The majority of the country’s precipitation falls in the higher mountains in the east, and many Afghan and Pakistani cities get much of their water as glacial and snowpack runoff from those mountains.
The first step was to map the location of the glaciers. The second was to look at them systematically to measure their response to changing climate, Molnia said. ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) a Japanese-NASA instrument aboard the Terra satellite, has provided the highest resolution images for this purpose, said Molnia.
“What we discovered is that for elevations below about 4,000 metres, almost every small cirque showed evidence that there had been a glacier there, and most of them were showing evidence that the glaciers had completely disappeared,” said Molnia. Cirques, he explained, are small basins high in the mountains. From 4,000 to 6,000 metres, glaciers showed signs of recent thinning and evidence of liquid water for a good part of the year, suggesting that the temperature in estern Afghanistan was milder than elsewhere in the world at similar altitude.
In fact, temperatures have been warming in the panhandle “for a significant number of years,” notes Molnia. Snowfall starts later and begins melting earlier. Scientists do not have good data on the volume of precipitation, but they know that glaciers are melting faster than in the past, he said. Lower altitude glaciers may disappear completely, just as Afghanistan’s industrial development is getting underway and the demand for water is going up.
The worst case scenario, said Molnia, citing US government intelligence estimates, involves a significant population displacement, should the Afghan glaciers disappear. People would move into areas where water is already a scarce commodity, potentially parking local strife that could expand into international conflict.
What can be done to avert disaster? The climate is changing, says Molnia, so the answer must lie in water management, including, perhaps, impoundment dams, changes in agricultural land use, and education for long term planning. So far, there have been no known jökulhlaups in Afghanistan, but such events have occurred recently in China and Pakistan, and Molnia says that a catastrophic flood down the Wakhan panhandle cannot be ruled out.
Are the Himalayan glaciers all disappearing? The latest IPCC report gave 2035 as the year most of them may be gone, Molnia told me, and this has provoked understandable concern. But, he says, that was an unfortunate typographical error, citing a decade-old Russian report that gave the date as 2350. The glaciers above 4,000 metres will survive, even with significant climate warming, but those below that level are problematic. “What that will mean in terms of available water, we just don’t know. It is certainly something to think about,” he concluded.