The ice sheet that capped Kilimanjaro in 1912 was 85 percent smaller by 2007, and since 2000 the existing ice sheet has shrunk by 26 percent, the paleoclimatologists said.
The findings point to the rise in global temperatures as the most likely cause of the ice loss. Changes in cloudiness and precipitation may have also played a smaller, less important role, especially in recent decades, they added.
"This is the first time researchers have calculated the volume of ice lost from the mountain's ice fields," said study co-author Lonnie Thompson, professor of earth sciences at Ohio State University,
"If you look at the percentage of volume lost since 2000 versus the percentage of area lost as the ice fields shrink, the numbers are very close," he said in the study published in the journal Proceedings of the National Academy of Sciences.
While the yearly loss of the mountain glaciers is most apparent from the retreat of their margins, Thompson said an equally troubling effect is the thinning of the ice fields from the surface.
The summits of both the Northern and Southern Ice Fields atop Kilimanjaro have thinned by 1.9 meters (6.2 feet) and 5.1 meters (16.7 feet) respectively. The smaller Furtwangler Glacier, which was melting and water-saturated in 2000 when it was drilled, has thinned as much as 50 percent between 2000 and 2009, the study said.
"It has lost half of its thickness," Thompson said. "In the future, there will be a year when Furtwangler is present and by the next year, it will have disappeared. The whole thing will be gone."
The scientists said they found no evidence of sustained melting anywhere else in the ice core samples they extracted, which date back 11,700 years.
They said their findings show that current climate conditions over Mount Kilimanjaro are unique over the last 11 millennia.