Ice Caps In Africa, Tropical South America Likely To Disappear Within 15 Years

Lonnie Thompson, professor of geological sciences, reported that at least one-third of the massive ice field atop Tanzania's Mount Kilimanjaro in Africa has disappeared, or melted, in the last dozen years. About 82 percent of the ice field has been lost since it was first mapped in 1912.

And the Peru's Quelccaya ice cap in the Southern Andes Mountains has shrunk by at least 20 percent since 1963. More troubling however, Thompson said, is the observation that the rate of retreat for one of the main glaciers flowing out from the ice cap, Qori Kalis, has been 32 times greater in the last three years than it was in the period between 1963 and 1978.

Thompson, a researcher with Ohio State's Byrd Polar Research Center, reported the results of two decades of studies by his research team, which has surveyed tropical ice caps and retrieved and analyzed ice cores from South America, Africa, China, Tibet and other locations around the globe. He presented his findings during the annual meeting of the American Association for the Advancement of Science in San Francisco.

"These glaciers are very much like the canaries once used in coal mines," Thompson said. "They're an indicator of massive changes taking place and a response to the changes in climate in the tropics."

The retreat and loss of these massive ice bodies make up part of the evidence Thompson presented that has convinced him global warming has begun to make its mark on the planet. He also looked at the ratio between two oxygen isotopes -- oxygen-16 and oxygen-18 - trapped in ice cores drilled from four sites on the Tibetan Plateau. The higher the oxygen-18 enrichment, the warmer the atmospheric temperatures were when the ice formed from fallen snow. From these, he can extrapolate a history of regional temperatures.

At one site, the Dasuopu Glacier, a two-kilometer-wide ice field that straddles a flat area on the flank of Xixabangma, an 8,014-meter (26,293 feet) peak on the southern edge of the Tibetan Plateau where they drilled in 1997, the cores showed that the last 50 years were the most enriched - and therefore, warmest - in the history of the ice cap. A preliminary look at the isotopes in a core retrieved late last year from Puruogangri, an ice cap in the center of the Tibetan plateau north of Dasuopu, showed a similar enrichment and corresponding warming.

While Thompson's team focused on the records preserved in the ice, his colleagues from the People's Republic of China, have analyzed 30 years of records from 178 weather stations spread across the Plateau. Those records show that between 1969 and 1990, the rate of warming has increased at higher elevation sites. That is consistent with the oxygen isotope measurements from the Tibetan ice cores, Thompson said.

"We have long predicted that the first signs of changes caused by global warming would appear at the few fragile, high-altitude ice caps and glaciers within the tropics," the band extending from 30 degrees North to 30 degrees South. "These findings confirm those predictions," Thompson said.

The retreat of the Kilimanjaro and Quelccaya ice caps are the most dramatic evidence, however. Thompson's photographs documented the retreat of both, as well as that of the glaciers that flow from them.

In the case of Qori Kalis, Quelccaya's main ice tongue, the rate of retreat has reached 155 meters (509 feet) per year, three times faster than the rate measured during the last measurement period from 1995 to 1998. The melting ice has formed a large lake at the front of the glacier which did not exist in 1983 but now covers more than 10 acres. (It is four acres bigger than it was in 1998.) Bare earth has been exposed for the first time in thousands of years.

Thompson and his colleagues drilled their first core from Quelccaya in 1976. "I fully expect to be able to return there in a dozen years or so and see the marks on the rock where our drill bit punched through the ice," he said. If that happens, it means that an ice cap 154 meters (505 feet) thick at that spot has vanished.

For Kilimanjaro, four-fifths of the vast ice field that covered the top of the highest mountain in Africa has disappeared in the last 80 years. "At this rate, all of the ice will be gone between the years 2010 and 2020. "And that is probably a conservative estimate," he said.

African officials worry that the loss of the ice cap atop Kilimanjiro will be devastating to the thriving tourist trade that brings thousands of people to the mountain each year and fuels the country's economy. But for Quelccaya in Peru - and similar ice caps and glaciers in the Andes - the loss represents a much greater threat than lost tourism dollars.

"The loss of these frozen reservoirs threaten water resources for hydroelectric power production in the region, and for crop irrigation and municipal water supplies," he said. The ice in the high-altitude glaciers represents a "bank account" of sorts to feed their power needs. With the melting ice caps, streams have grown and the government is building new dams and hydroelectric plants.

"What they're really doing now is cashing in on a bank account that was built over thousands of years but isn't being replenished. Once it's gone, it will be difficult to reform," he said. In such cases, the countries will probably have to switch to burning fossil fuels to meet their power needs. And by doing so, they'll add more carbon dioxide and water vapor to the atmosphere - two gases that are known to enhance the greenhouse effect and intensify global warming.

Thompson said that other researchers have documented similar ice losses. An ice cap on Mount Kenya has shrunk by 40 percent since 1963. Two glaciers atop mountains in New Guinea are disappearing and should be gone in a decade. And in Venezuela in 1972, there were six such glaciers - now there are only two left and they will have melted in the next 10 years.

"We need to take the first steps to reduce carbon dioxide emissions," he said. "We are currently doing nothing. In fact, as a result of the energy crisis in California - and probably in the rest of the country by this summer - we will be investing even more in fuel-burning power plants.

"That will put more power in the grid but, at the same time it will add carbon dioxide to the atmosphere, amplifying the problem."

Thompson's work is supported in part by the National Science Foundation, the National Aeronautics and Space Administration and the National Oceanic and Atmospheric Administration.

Along with Thompson, other members of the research team include Ellen Mosley Thompson, professor of geography; Henry Brecher, research associate emeritus; Mary Davis, Ping-Nan Lin, Tracy Mashiotta, Zhonqin Li and Victor Zagorodnov, all research associates; and Ph.D candidate Keith Henderson and Deb Bathke.