Atlantic Forcing of Persistent Drought in West Africa

Publication Type  Journal Article
Year of Publication  2009
Authors  Shanahan, T. M.; Overpeck, J. T.; Anchukaitis, K. J.; Beck, J. W.; Cole, J. E.; Dettman, D. L.; Peck, J. A.; Scholz, C. A.; King, J. W.
Journal Title  Science
Volume  324
Issue  5925
Pages  377-380
Journal Date  Apr 17
ISBN Number  0036-8075
Accession Number  ISI:000265221600039
Key Words  tree-rings; intertropical convergence zone; asian southwest monsoon; el-nino; thermohaline circulation; sahel rainfall; lake bosumtwi; east-africa; time-series; holocene; climate

Although persistent drought in West Africa is well documented from the instrumental record and has been primarily attributed to changing Atlantic sea surface temperatures, little is known about the length, severity, and origin of drought before the 20th century. We combined geomorphic, isotopic, and geochemical evidence from the sediments of Lake Bosumtwi, Ghana, to reconstruct natural variability in the African monsoon over the past three millennia. We find that intervals of severe drought lasting for periods ranging from decades to centuries are characteristic of the monsoon and are linked to natural variations in Atlantic temperatures. Thus the severe drought of recent decades is not anomalous in the context of the past three millennia, indicating that the monsoon is capable of longer and more severe future droughts.


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URL  <Go to ISI>://000265221600039
DOI  DOI 10.1126/science.1166352