Earth Equity News

Permafrost May Not Thaw Even During Global Warming. By Henry Fountain, NYTimes, September 19, 2008. "A study published in Science suggests that the impact of warming on the permafrost may not be as bad as forecast [by some]. The evidence comes in the form of a wedge of ancient ice found at an old mining site in the Yukon in Canada. Ice wedges form in permafrost when the ground cracks because of cold, and spring meltwater seeps in and freezes. Over hundreds of years, the wedge builds up, like an in-ground icicle... The top of [this] wedge was a couple of yards deep in the permafrost, and the researchers found volcanic ash on its top surface. By dating the ash (which presumably came from eruptions in what is now southeastern Alaska), Dr. Froese and his colleagues were able to say how long the ice has been there: about 740,000 years. Because the ash had to have been deposited after the wedge formed, that's 'very clear proof,' Dr. Froese said, that the ice is at least that old. That means the ice survived through several warming periods, including the last major one, 120,000 years ago. 'The general view is that everything would have melted out back then,' Dr. Froese said. The new finding suggests that wasn't the case, and that models of future melting need to be rethought. 'But I don't want people to think we don't have to worry about global climate change,' Dr. Froese said. The top couple of yards of permafrost are still likely to melt as temperatures warm, and there's plenty of carbon stored in them. 'But the deeper part of the permafrost is probably relatively stable,' he said."