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By Juan Ramon Romero EFE
WASHINGTON—
South America was already a wet region some 25,000 years
ago—not dry as formerly thought—when glaciers
from the last Ice Age covered most of the Earth, according
to the results of a study of sediments in Lake Titicaca
in Bolivia and Peru.
Lake
Titicaca, which is relatively close to the Amazon River,
the world's largest source of fresh water, is also one of
the best registers of global climate.
According
to Paul Baker, professor of geology at Duke University's
Nicolas School for the Environment and Earth Sciences in
North Carolina, “Lake Titicaca is a beautiful rain
gauge.”
The
study of the lake's sediment core samples revealed that
most books on paleoclimatology—the study of ancient
climates—are wrong, because they claim South America
was a dry region during the last Ice Age.
While
climates cooled as glaciers advanced in the rest of the
world, the Andean region was wet and temperate, asserted
Baker, who has published the results of the study in Science
magazine.
Researchers
from five U.S. universities, and Bolivian and Peruvian doctoral
students in the United States, were among those who contributed
to the study of Lake Titicaca sediments.
The
scientists used “Neecho,” a research ship from
the U.S. Geological Service in Woods Hole, Massachusetts,
to drill core samples measuring up to 15 meters long (some
49 feet) in three different areas of the lake, at depths
of 50, 100 and 200 meters (some 164, 328, and 656 feet).
The
researchers studied the magnetic values, fossilized diatoms—a
type of tiny silica-encased aquatic algae - calcium carbonate
concentrations and the oxygen isotope ratios of the core
samples.
Based
on this geological evidence, “the study's results suggest
that the South American tropics were wet during cold eras
and advancing ice in the Northern Hemisphere,” the
article, published in Science magazine, noted.
The
Lake Titicaca region was not only wet during the last Ice
Age, which began some 25,000 years ago and lasted until
some 15,000 years ago, but also during the last cold periods
of the North Atlantic Ocean region.
Although
the study of fossil sediments can explain some of the climate
changes of the past, Baker cautioned against
forecasting future climate patterns because of the influence
of human-caused climate change.
“Human
influence is so dominant now that whatever is going to go
on in the tropics has much less to do with sea surface temperatures
and Earth's orbital parameters and much more to do with
deforestation, increasing atmospheric carbon dioxide, and
global warming,” the researcher explained.
Lake
Titicaca, which measures 195 kilometers (121 miles) by 80
kilometers (some 50 miles), has undergone a series of drastic
changes since the last Ice Age, some 250 centuries ago.
The
Altiplano, a 12,000-foot plateau below the Andean Mountains
in Bolivia and Peru, and the Amazon River basin were wetter
than they are now, researchers found.
One
of the most dramatic changes observed in Lake Titicaca was
a notable decrease in the water table 6,000 years ago, but
scientists have not been able to find its cause.
The
researchers noted that the fact that alternate wet and dry
periods occur in cycles of 1,000 years or more could be
influenced by the Earth's movement around the Sun.
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