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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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