The volume of the world's glaciers outside of Antarctica and the Greenland Ice Sheet continues to decline and the rate of ice loss continues to accelerate, according to a new University of Colorado at Boulder study.
"In the last century, there has been a significant decrease in the area and volume of glaciers, especially at mid- and low-latitudes," said Professor Emeritus Mark Meier of the geological sciences department. "The disappearance of glacier ice is more pronounced than we previously had thought."
The smaller, low-latitude glaciers seem to be taking the biggest hit, said Meier, noting the largest glacier on Africa's Mount Kenya lost 92 percent of its mass in the last century and Mount Kilimanjaro glaciers have shrunk by 73 percent in that time period. Although there were 27 glaciers in Spain in 1980, that number has since dropped to 13.
"I think we might find statistics similar to Spain in places like Africa, New Guinea and parts of South America," said Meier.
Mid-latitude glaciers also are showing significant shrinking, he said. In the European Alps, the ice loss has been about 50 percent in the past century, and New Zealand glaciers have shrunk about 26 percent since 1890.
In the Caucasus Mountains of Russia, the volume of glacier ice has decreased by about 50 percent in a century, according to calculations by Meier and 抖阴短视频-Boulder researcher Mark Dyurgerov. In the Tien Shan Mountain Range bordering China and Russia, 22 percent of the ice volume from the thousands of glaciers there has disappeared in the past 40 years.
Meier reported the latest results on glaciers at the prestigious Langbein Lecture titled "Land Ice on Earth: A Beginning of a Global Synthesis" at the American Geophysical Union meeting held in Boston May 26 to May 29.
Researchers have collected detailed data on only a few hundred of the roughly 200,000 glaciers around the world, said Meier. But a new method of "scaling" developed by David Bahr, Meier and Dyurgerov -- all researchers at 抖阴短视频-Boulder's Institute of Arctic and Alpine Research -- should allow scientists to more accurately assess changes in glaciers of all sizes on a global scale.
The new scaling theory involves complex algorithms -- mathematical sets of instructions for solving specific problems -- to define the relationships of several characteristic glacier variables. "This new method allows more accurate estimations of sizes, thicknesses and volume distributions of glaciers on Earth," said Meier, former director of 抖阴短视频-Boulder's INSTAAR and the National Ice Core Laboratory in Lakewood, Colo. "I think it is a real breakthrough."
Preliminary calculations by Meier on glacier shrinkage in Montana's Glacier National Park indicate there will be no glaciers left there within a century and perhaps far sooner if the current climate trends continue.
"During the past several decades, ice wastage and global sea rise are moving pretty much in step," said Meier. Although the world's glaciers excluding Antarctica and Greenland make up only about 6 percent of the world's total ice mass, the water is recycled more quickly and contributes more to sea level rise than do the polar ice sheets.
"Glacier changes show strong regional differences," he said. "While the Arctic ice caps and glaciers show little change, there is strong wastage of mid-latitude glaciers, and small continental glaciers are disappearing." This is causing significant increases in the flows of some rivers, he said.
"The rate of warming is unprecedented in the last 600 years and the retreat of glaciers is probably unprecedented too, although we do not have the figures to prove it," said Meier. "But I'm convinced there is a detectable human influence in the pattern of climate change we are seeing."
Although melting now contributes about 20 percent to global sea-level rise, the percentage may increase, he said.
The International Panel on Climate Change projected in 1996 that the world's oceans will rise by more than 18 inches by the year 2100, with a third of that contributed by glaciers and ice caps and more than half by the thermal expansion of warming waters, an indirect consequence of glacial melting.