July 3, 2007
Study: Northern Canada Ponds Drying Up
WASHINGTON -- Ponds that have provided summertime water in the high arctic for thousands of years are drying up as global warming advances, Canadian researchers say.
Falling water levels and changes in chemistry in the ponds first were noticed in the 1990s, and by last July some of the ponds that dot the landscape were dry, according to a report in Tuesday's Proceedings of the National Academy of Sciences.
John P. Smol of Queens University in Kingston, Ontario, and Marianne S. V. Douglas of the University of Alberta in Edmonton have been studying about 40 ponds on Ellesmere Island in northern Canada since 1983.
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.
On the Net:
Proceedings of the National Academy of Sciences: http://www.pnas.org