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ICE CAPS IN AFRICA, TROPICAL SOUTH
AMERICA LIKELY TO DISAPPEAR WITHIN 15 YEARS
Ohio State
University, COLUMBUS, Ohio
- Many glaciers and ice caps atop mountains in Africa and South America
will probably have melted within the next 15 years because of global
warming and little can be done to save them, an Ohio State University
researcher explained .
Lonnie
Thompson
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.
In
1978, the Qori Kalis Glacier looked like this, flowing out from the
Quelccaya Ice Cap in the Peruvian Andes Mountains
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.
In
2000, the view of Qori Kalis has changed dramatically with a massive
10-acre lake forming at the ice margin
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.
Map
showing drill sites spread across the Tibetan Plateau
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.
Xixabangma,
an 8,014-meter (26,293 feet) peak on the southern edge of the Tibetan
Plateau
"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.
Mt.
Kilimanjaro’s Receding Glaciers
Space
Shuttle Photograph
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.
Mount
Kilimanjaro
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.
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