Science 17 April 2009:
Vol. 324. no. 5925, pp. 377 - 380
Atlantic Forcing of Persistent Drought in West Africa
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.1 Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA.
2 Jackson School of Geosciences, University of Texas–Austin, Austin, TX 78705, USA.
3 Institute for the Environment and Society and Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA.
4 Lamont Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.
5 Department of Physics, University of Arizona, Tucson, AZ 85719, USA.
6 Department of Geology, University of Akron, Akron, OH 44325, USA.
7 Department of Earth Sciences, Syracuse University, Syracuse, NY 13244, USA.
8 Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA.
最后更新 (2009-09-24 16:09)