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Kilimanjaro snow may soon vanish: thinning rate suggests ice caps may disappear by 2022.

The famed snows of Kilimanjaro may soon appear only in old tourist photos and a short story by Ernest Hemingway if current rates of melting persist, a new study suggests.

Warming in recent decades has caused high-altitude glaciers worldwide, especially in tropical areas, to shrink substantially (SN: 10/4/03, p. 215). Recent studies atop Tanzania's Mount Kilimanjaro show ice loss to be proceeding apace on the African peak: More than a quarter of the ice cover in the year 2000 had disappeared by late 2007, says Lonnie Thompson, a glaciologist at Ohio State University in Columbus.

At current melting rates, permanent ice fields could disappear from Kilimanjaro by 2022, he and his colleagues report online November 2 in the Proceedings of the National Academy of Sciences. Data from aerial surveys supplement the team's field studies, which show that Kilimanjaro's melting has dramatically accelerated in recent decades. From 1912 to 1953, ice coverage declined by 1.1 percent per year. Between 1953 and 1989, the annual rate of ice loss jumped to 1.4 percent. From 1989 to the most recent survey in 2007, the ice-covered area dropped, on average, a whopping 2.4 percent per year, the researchers report.

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Not only are the ice masses of Kilimanjaro receding farther up the peak, they're thinning considerably--a trend detectable only by improved ground observations made in recent years. The thickest part of the peak's 50-meter-thick Northern Ice Field thinned by 1.9 meters between 2000 and 2007, Thompson says. Kilimanjaro's Southern Ice Field--which was about 21 meters thick in 2000--lost about 5.1 meters by 2007. It's unclear whether the ice loss stems from melting due to global warming or from increased sublimation because of a climate shift that starved the peak of precipitation.

As Kilimanjaro's glaciers retreat and break into smaller pieces, the dark rocks surrounding the remaining ice will absorb more sunlight and heat up, accelerating the melting, says Thompson.

Lessons learned from the Kilimanjaro studies could help scientists better predict when glaciers elsewhere in the tropics--many of which people depend on for water--will eventually disappear, says Tad Pfeffer, a glaciologist at the University of Colorado in Boulder.

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Title Annotation:Earth; Tanzania's Mount Kilimanjaro
Author:Perkins, Sid
Publication:Science News
Geographic Code:1USA
Date:Dec 5, 2009
Words:361
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