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Study Indicates that Africa
May
Be Overdue for Drought
Tom Johnson, UMD Large Lakes Observatory and Department of Geological Sciences,
and J.M. Russell, (former UMD grad student) Brown University, had an article
published in this month's Geology, the magazine of the Geological
Society of America. The article is entitled, "Little Ice Age drought
in equatorial Africa: Intertropical Convergence Zone migrations and El Niño
Southern Oscillation variability." New research by Russell and Johnson,
using geochemical analyses of well-dated sediments from Lake Edward, shows
that central Africa experienced severe drought during the Little Ice Age.
The results suggest that the climate of central equatorial Africa has been
wetter and more stable over the past century than at any time during the
preceding millennium. This finding implies that central Africa is overdue
for a return to prolonged drought that would severely disrupt developing
East African economies.
Climate researchers have long known that northern Europe experienced
exceptionally cool conditions during much of 1500-1800 A.D. This time
interval, often referred to as the ‘Little Ice Age’ also appears
to have been marked by significant climate anomalies in tropical regions;
however, scientists are only beginning to understand the mechanisms by
which climate anomalies in these regions are linked. Russell and Johnson
used geochemical analyses of well-dated sediments from Lake Edward (a
central African rift lake) to determine that central Africa experienced
severe drought during the Little Ice Age.
This finding contrasts with paleoclimate records from further east in
tropical Africa, and suggests significant regional variations in climate
during the Little Ice Age. By comparing paleoclimate records that extend
through the Little Ice Age at sites throughout the tropics, Russell and
Johnson argue that tropical climate anomalies during the Little Ice Age
resemble the pattern of tropical rainfall and temperature anomalies experienced
during an El Niño event in the Pacific Ocean. This finding suggests
that coupled ocean-atmosphere variability in the tropical Pacific Ocean
may play an important role in connecting tropical and polar climate anomalies.
The results of suggest that the climate of central equatorial Africa has
changed over the past century compared to the preceding millennium and
it implies that central Africa is overdue for a drought that would severely
disrupt developing East African economies. Top image
courtesy of Earth Science World Image Bank http://www.earthscienceworld.org/images.
Bottom image: Tom Johnson.
Geology
Magazine Article
UMD home page editor, Cheryl Reitan, creitan@d.umn.edu
NEW RELEASES, UMD media contact,
Susan Latto, slatto@d.umn.edu,
218-726-8830
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Africa
Study Published in Geology Magazine
