Ancient Arctic ponds evaporating
Reuters News Service, July 3, 2007
Ancient ponds in the
They say the evaporation of these ponds - some of which have existed for thousands of years - illustrates the rapid effects of global warming, threatening bird habitats and breeding grounds and reducing drinking water for animals.
For 24 years, researchers at the
Last year, when they went back to check, some of these 6000-year-old ponds had vanished.
"We were surprised. We arrived in early to mid-July and the ponds we had been monitoring were dry. Some of them had dried up completely. Some were just about to lose the last remaining centimetres of water," Marianne Douglas, director of the Canadian Circumpolar Institute at the
"It's really interesting to see how quickly it is happening. We could see this trend had started a while ago but at no time did we expect it to accelerate," she said in work published in the journal Proceedings of the National Academy of Sciences.
She said a study of the fossilised sediments in these pools of water - which are less than 2m deep - showed climate changes beginning as long as 150 years ago.
The researchers had thought these ponds were permanent. But change has come rapidly.
"It is a bit of a tipping point. We don't know how far this warming or drying will go," she said.
The researchers took water samples to measure the concentration of minerals and sediments in the water. They compared it to data from the 1980s and found a significant change.
Evaporation had made the sediments much more concentrated.
They also discovered that ponds that formerly remained frozen until mid-July were free of ice as early as late May.
The changes will have significant impact on the birds and animals that rely on these sources of fresh water to survive and breed.
"The ecological ramifications of these changes ... will cascade throughout the Arctic ecosystem. Lower water levels will have many indirect environmental effects, such as further concentration of pollutants," the team wrote.
Global warming seen evaporating eons-old arctic ponds
The Associated Press, July 3, 2007
Falling water levels and changes in chemistry in the ponds were first noticed in the 1990s, and by last July some of the ponds that dot the landscape were dry, according to a report in today's Proceedings of the National Academy of Sciences.
John P. Smol of
The ponds are habitat for algae and invertebrates such as insect larvae, and waterfowl use them.
Smol likens the warming conditions to a pot of soup on a stove.
"If you take the lid off, it is similar to what we are observing in these ponds. The soup will slowly decrease in volume and it will get saltier and saltier as the water evaporates, leaving the salts behind."
That same evaporation process is taking place with these ponds, he said.
Weather records show there has been no decline in rain and snowfall in the region and, while some arctic ponds have drained when the permafrost melted beneath them, these ponds sit above bedrock.
Douglas and Smol were able to use paleological techniques to trace the history of the ponds back thousands of years. "We basically followed them from cradle to the grave," Smol said.
Changes set in about a century ago, he said, with more mosses growing and shorter periods of ice, followed by lowering water levels and increasing salinity until some dried up completely.
In addition to the ponds, the researchers also reported a drying of nearby wetlands.
In the 1980s they often needed to wear hip waders to make their way to the ponds, they noted, while by 2006 the same areas were dry enough to burn.