Some of the earliest signs of climate change are evident in the highest, coldest parts of the globe, where Arctic sea ice is reaching record low levels and glaciers calve dramatically off Greenland's frozen ice sheet.
In northern Canada, researchers are seeing another signal that is likely connected to global warming. Shallow lakes in the tundra are drying up.
There are two reasons for this, according to Frédéric Bouchard, an earth scientist at Laval University and lead author of a study on the lakes recently accepted in the journal Geophysical Research Letters.
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"You have longer ice-free seasons because of the climate warming in the north, so you have more chance of evaporation," Bouchard said. The other reason, he said, is lack of snow in the winters. Snow feeds the shallow lakes, which are about 3 feet deep.
"So if you have less precipitation in the winter, you have less snowmelt runoff in the spring," he said.
Added up, it's a recipe for a drying lake.
While climate models have difficulty agreeing on regional precipitation trends, snow cover in the Hudson Bay region is expected to decrease over the next hundred years, Bouchard said.
Other researchers, such as John Smol, a paleoecologist at Queen's University, have also found drying in shallow ponds in other parts of the Arctic. The drying is significant in part because, Smol said, "these ponds are all over the Arctic."
Multiple studies
This research adds to those findings by using different methods and studying two very different parts of Canada.
One study area, called Old Crow Flats, is high in northwest Yukon. The other area is in northern Manitoba, in the Hudson Bay lowlands.
In their research, the scientists took water samples and used the ratio of different isotopes of oxygen to find lakes that were vulnerable to evaporation.
Sometimes this can be seen visually, but the water samples allowed the researchers to find vulnerable lakes even if they did not appear to be drying up, Bouchard said.
The researchers also took sediment samples of a dried-up lake in the Hudson Bay lowlands, which allowed them to look at evaporation going back for two centuries. Their analysis of the oxygen isotope ratios in that sediment core showed them the lake had not experienced extreme evaporation in those 200 years.
Yet now it is dry. "It appears at least from this one lake that this type of extreme drying has not occurred in the past 200 years. Of course, this needs to be tested with more lakes," said Brent Wolfe, a co-author of the study and a northern hydrologist at Wilfrid Laurier University in Ontario.
Consequences for humans and wildlife
The researchers hope to use sediment samples from more lakes to see what that can tell them about past evaporation.
They also hope to extend the sediment record in the lakes further back, to periods such as the Medieval Climate Anomaly, a warm period about 1,000 years ago, to see what was happening with the lakes back then, Bouchard said.
The consequences for wildlife and indigenous communities that depend on those ponds could be significant.
Wolfe said part of the research was driven by the First Nations communities in the Yukon, who are concerned that climate change is altering water levels in the lakes.
The lakes provide important habitat to birds and other species in the area.
Smol, who praised the researchers for doing an "excellent job," said this was an example of how climate change is altering an ecosystem. There will be winners and losers as the shifts continue, he said.
"We're reshuffling the deck. We're changing an awful lot of things; it's quite serious," he added.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500