Glaciers Melting Worldwide, Study Finds
Robert S. Boyd
Contra Costa Times
|August 21, 2002|
New surveys from satellites and aircraft document an alarming
acceleration in the melting of glaciers around the world.
The swift retreat of these great ice streams is helping to raise ocean levels and is threatening significant changes in human, animal, and plant lifesome good, but mostly bad.
Like a canary in a coal mine, the dwindling of the glaciers is visible evidence that the earth really is getting hotter.
"Receding and wasting glaciers are a chief telltale sign that global climate change is real and accelerating," said Jeffrey Kargel, a glacier expert with the U.S. Geological Survey in Flagstaff, Arizona.
Most of Earth's 160,000 glaciers have been slowly shrinking and thinning for more than a century as the climate warms up from both natural causes and human activity.
But scientists say the melt rate has accelerated dramatically since the mid-1990s, which was the hottest decade in a thousand years, according to data from ancient ice cores and tree rings.
A glacier in the Peruvian Andes, Qori Kalis, is losing as much ice in one week as it used to surrender in a year, according to Lonnie Thompson, a geologist at the Byrd Polar Research Center at Ohio State University in Columbus.
"You can literally sit there and watch it retreat," Thompson told a meeting of the American Association for the Advancement of Science.
"As the Peruvian ice fields disappear, sources of irrigation and hydroelectric power will dry up," he said. Other consequences include a more rapid rise in sea levels, speeding the flooding or even destruction of low-lying islands and coastal areas.
Glaciers are shrinking not only in area but also in thickness. In Alaska, they are losing an average of 6 feet (1.8 meters) of thickness a year, Anthony Arendt, a glaciologist at the University of Alaska, Fairbanks, reported last month in the journal Science. That's more than twice the annual rate observed from the 1950s to the mid-1990s.
By the middle of this century, the Rockies, the Cascades, and Glacier National Park will have lost almost all their ice, Kargel predicted.
"I expect to see absolutely no glaciers in the Swiss or European Alps by the end of the century," he added. "The huge valleys of the Himalayas will be completely deglaciated."
Even the snows of Africa's Mount Kilimanjaro, made famous by Ernest Hemingway, will be gone within a dozen years, Thompson predicted after a 1999 expedition to the top of the storied mountain.
To measure the dwindling of the world's glaciers, the U.S. Geological Survey and NASA are collaborating on a new satellite project called GLIMS, for Global Land Ice Measurements from Space.
GLIMS monitors the planet with a stereoscopic imaging system aboard the Terra spacecraft, which was launched in December 1999 as part of NASA's Earth Observing System.
The satellite is supposed to take three to five images every year of all permanent land ice except for the interiors of Greenland and Antarctica. Data from the images are collected in a computer database, revealing any changes that have occurred.
Arendt's group at the University of Alaska is measuring the thinning of glaciers in a project supported by NASA, the National Science Foundation, and the National Oceanic and Atmospheric Administration.
The scientists use a laser rangefinder mounted on a small plane to compare the heights of 67 glaciers in Alaska and nearby Canada to older topographic maps made from aerial photographs in the 1950s and '60s.
By Arendt's calculation, about 12 cubic miles (50 cubic kilometers) of glacial ice now disappears in Alaska each year, the equivalent of an enormous ice cube 2.5 miles (4 kilometers) on each side.
"During the past five to seven years, glacier thinning was more than twice as fast as that measured on the same glaciers from the mid-1950s to the mid-1990s," Arendt reported.
"We now have [thickness] data for an additional 30 glaciers [which] will provide us with an even better picture of the changes across Alaska," Arendt said.
Counting losses in both area and thickness, Mark Dyurgerov, an expert at the Institute for Arctic and Alpine Research in Boulder, Colo., estimated that glaciers around the world are losing 22 cubic miles (92 cubic kilometers) of ice per year. That's as much water as America's homes, farms and factories use every four months, according to the USGS.
The U.S. Environmental Protection Agency estimates that the global sea level rose 6 to 12 inches (15 to 30 centimeters) over the last 100 years. One or 2 inches (3 to 5 centimeters) of that rise is blamed on glaciers melting; the rest is due to the fact that seawater expands as it gets warmer.
In the coming century, sea levels are expected to rise another 12 to 24 inches (30 to 60 centimeters), enough to cause devastating flooding.
Researchers say there is a bright side, at least temporarily, to glacial melting.
Kargel pointed out that large amounts of land now covered by ice will be available for agriculture and mining. A melting glacier in Alaska is exposing what may be the richest lode of copper ever found in the state.
While the glaciers last, they supply fresh water for drinking, irrigation and hydropower.
In parts of northern India and western China, Kargel said, economic development and the well-being of the populace depend partly on melting glaciers. When the glaciers are gone, some decades from now, the water supply will be diminished.
Copyright 2002 Contra Costa Times. All Rights Reserved.
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