Side effects of global warming

Thawing permafrost can render railroad tracks useless, as seen in this photo from the northern Tibetan Plateau taken in the early 1960s. Credit: Tingjun Zhang

The problem could be particularly acute for urban and suburban places in the far North, such as Barrow and Fairbanks, Alaska. Nelson notes, however, the problem can be mitigated if engineers look ahead.

Zhang is helping the builders of an ambitious Tibetan railroad do just that.

The Qinghai-Xizang railroad will be 695 miles (1, 118 kilometers) long when completed in 2007. Most of it is above 13, 000 feet (4 kilometers), and about half of it is being built on permafrost, much of which is likely to melt in coming years, Zhang said.

So Zhang has helped the engineers devise an insulation system - a thick layer of crushed rock over the permafrost.

All of Nature can't be insulated, however.

Mountain makeovers

Antoni Lewkowicz of the University of Ottawa has studied several northern landslides and rockslides that he says can be at least partially attributed to thinning and weakening of ice or permafrost caused by climate warming. In one case, an earthquake broke off a weakening glacier in the Yukon. About 500, 000 tons of ice raced down a mountain.

"By the time it reached the bottom it would have been going about 140 mph, " Lewkowicz said.

At other remote catastrophe sites, Lewkowicz has documented a bizarre situation in which thin permafrost sits atop unfrozen sand containing groundwater under pressure. The system is stable until the icy overlay gets slushy. The whole mess then gives way.

Some of these events expose a layer of earth - perhaps a very salty layer - on which nothing can grow for years, resulting in "profound ecological effects, " Lewkowicz said.

And landslides like this could become common if the climate grows warmer, as many scientists expect it will.

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