On the horizon: news from the frontiers of science

Walden Pond and global warming, truckers don their skirts, and how Arctic flow can snowball.

Walden Pond and Global Warming

College professors continually go back to Henry David Thoreau's "Walden Pond" for lessons on self-reliance and Transcendentalism. But conservation biologist Richard Primack is using the 150-year-old work to study climate change.

Thanks to Thoreau's keen eye and meticulous record-keeping, the Boston University professor has used "Walden Pond" as a field guide to Massachusetts' past. Several times a week, Mr. Primack and his team of students trek to Concord, Mass., and wander the town's parks. They track when flowers bloom and when birds return from their winter vacations down south.

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Comparing notes, Primack found that the signs of spring occur a week earlier than they did in the 1850s. Warmer average temperatures have accelerated the natural timetable, he says. Early blooms can throw off seasonal pollination and seeding, which might then further warp nature's schedule in future years. With Walden as his living laboratory, Primack hopes to suss out which flowers are most susceptible to the effects of global warming and find ways to protect those species. – Chris Gaylord

Truckers don their skirts

Those cool-looking aerodynamic cowlings atop the cabs of 18-wheelers may soon have company – aerodynamic skirts along the base of the trailers and odd-shaped "boat tails" for a trailer's stern.

It's all in the name of improving fuel economy – and reducing greenhouse gases and other emissions – by smoothing air currents along and behind a trailer.

Aerospace engineers at Delft Technical University in the Netherlands conducted wind-tunnel tests on the skirts and estimated that they would reduce wind resistance by 14 to 18 percent. That translated into a 7 to 9 percent increase in fuel economy.

Field tests on trucks operated by one of the country's largest freight haulers showed that the skirts improved fuel economy by 10 percent. And while the tails haven't been road-tested yet, wind-tunnel experiments pointed to additional gains. Working in tandem, these aerodynamic additions could boost fuel economy by up to 15 percent.

The team, led by Michel van Tooren, notes that since many trucks use skirts now to prevent other vehicles from "under-running" the trailers in an accident, it would be fairly straightforward to replace many existing skirts with more aerodynamic models. They could pay for themselves within two years, the team estimates. – Peter N. Spotts

How Arctic flow can snowball

For several years, scientists have worried that meltwater plunging from the surface of Greenland's ice sheet to the bedrock below has in effect greased the skids – accelerating the rate at which Greenland is losing ice.

Now, a team of researchers from the US and Britain suggests that while water under the ice is an important lubricant, it's unlikely to cause a catastrophic loss of Greenland ice as the climate warms. The more significant mass loss is likely to come from the speedup of glaciers that bring ice to the ocean. For the glaciers, lubricating of the underside appears to be less important than the loss of ice shelves along the coast that were grounded on the seafloor and acted as a brake on glacier movement.

Still, the team from the University of Washington, the Woods Hole Oceanographic Institution, and Newcastle University in Britain got a first-hand look at how powerful a lubricant icecap meltwater can be.

Their instruments recorded the loss of a lake covering some 2 square miles of icecap surface to a depth of up to 40 feet. Once water began working its way down a crevasse, the crack grew until it reached the ground a half mile below. The entire lake drained in less than two hours, with a peak flow higher than the average gush over Niagara Falls. The results of these studies appear at Sciencexpress, the online edition of the journal Science. – P.N.S.

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