TORONTO | Canadian researchers studying the Arctic´s ancient permafrost have discovered 700,000-year-old ice wedges buried in the soil that have survived earlier periods of global warming, adding complexity to predictions about the impact of contemporary climate change.
Duane Froese, an assistant professor in the Department of Earth and Atmospheric Science at the University of Alberta, found what he describes as “the oldest ice in North America” in the Klondike region of Canada’s Yukon Territory about 10 feet below the surface.
Because these ice wedges were found under a layer of volcanic ash, researchers from the University of Toronto and the Geological Survey of Canada were able to use a technique known as “fission track dating” of the ash to date it at roughly 700,000 years old.
This means the ice was older than the ash and older than the previous record holder - 120,000-year-old ice wedges found in Alaska.
“The fact that this ice survived the interglacials about 120,000 and 400,000 years ago, which we think were warmer than present, really illustrates how stubborn permafrost can be in the face of climate warming,” Mr. Froese said.
According to a recent article in Ambio, a journal produced by the Royal Swedish Academy of Sciences, permafrost regions occupy about 25 percent of the Northern Hemisphere, with more than 60 percent in Russia.
Warming, thawing and degradation of permafrost have already been observed, and there are fears that its shrinkage could lead to increased output of greenhouse gases and unstable structures built on what was once ice-hard ground.
Permafrost can vary from almost a mile thick in parts of Siberia to a few feet and turn up over a large region, in scattered regional patches or isolated, the magazine noted.
In Canada, permafrost can be found across half the country, in 80 percent of Alaska, 30 percent of Russia, and 20 percent to 30 percent of China and Mongolia, Mr. Froese said.
“Permafrost is the glue” that holds the Arctic together and widespread thawing could have dramatic effects on the northern environment, he said.
During the life span of the recently discovered ice wedges, the earth´s climate has shifted from long ice ages or glaciations - when woolly mammoths and saber-toothed tigers roamed the Northern Hemisphere - and short warming periods, which may have been much warmer than our current climate.
“This ice is not right at the surface, so it survived several earlier periods of global warming that were longer and warmer than ours,” Mr. Froese said.
So how did this permafrost ice survive when all around it melted from hundreds of thousands of years of warming, cooling and warming?
Brian Moorman, a professor of geography at the University of Calgary, said that although ice can harden with age as it expels gasses, this permafrost is not some kind of “samurai sword” super ice, tempered by climate change.
“Water can exist below 0 degrees [Celsius],” water´s freezing point, “but ice always melts above zero,” he said.
In this case, the ash covering and shadows may have made the difference, he added.
“The thaw didn’t get there,” he said.
So far, only one wedge of permafrost this old has been found, but Mr. Moorman said there may be more, and this could change the way environmentalists look at the effects of climate change.
The current Canadian Arctic is a place of complex and varied temperatures and snowfalls - the Yukon is dry, and the Western Arctic is heating faster than the Eastern Arctic.
Mr. Moorman said that global warming models and grids do not take into account all the complexities of regional variations on the planet, but they are improving.
However, the professor notes that 2007 and 2008 have shown a slight reduction in global temperature averages and that low sunspot activity also point to near-term cooling periods.