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Northern African Climate Dynamics
Drought in northern Africa routinely impacts millions of people, yet we have an incomplete understanding of the full range of drought in this region. To gain new insights into this drought variability and it’s connections with Atlantic Ocean variability, we have developed a multi-year investigation of Lake Bosumtwi, a small (8 kilometers in diameter), deep (78 meters), hydrologically-closed lake located in the lowland forest zone of southern Ghana in western Africa. The steep-walled crater basin (10.5 km-dia.) was created by an approximately 1.1 million year old meteorite impact into fractured granite that resulted in this small, restricted catchment. Consequently, lake levels are particularly sensitive to subtle changes in the precipitation-evaporation balance. The water column is permanently anoxic below 16 m depth, thereby limiting bioturbation and preserving annually laminated sediments. Former graduate student Tim Shanahan has lead efforts to use newly collected sediments to study drought over the last 2000 years as well as to examine annually-resolved climate variability during earlier periods in the history of the lake. We have already carried out several field investigations at the lake and have received International Continental Drilling Program (ICDP) funding to drill to bedrock. Abrupt
Climate Change
W. Beck, J. Cole, J. King, C. Koberl, J. Peck, C. Scholz, T. Shanahan, W. Wheeler
Scholz, C.A., T.C. Johnson, A.S. Cohen, J.W. King, J.A. Peck, J.T. Overpeck, M.R. Talbot, E.T. Brown, L. Kalindekafe, P.Y.O. Amoako, R.P. Lyons, T.M. Shanahan, I.S. Castañeda, C.W. Heil, S.L. Forman, L.R. McHargue, K.R. Beuning, J. Gomez, and J. Pierson. 2007. East African megadroughts between 135 and 75 thousand years ago and bearing on early-modern human origins. Proceedings of the National Academy of Sciences of the United States of America 10.1073/pnas.0703874104. Koeberl, C., B. Milkereit, J.T. Overpeck, C.A. Scholz, P.Y.O. Amoako, D. Boamah, S. Danuor, T. Karp, J. Kueck, R.E. Hecky, J.W. King, and J.A. Peck. 2007. An international and multidisciplinary drilling project into a young complex impact structure: The 2004 ICDP Bosumtwi Crater Drilling Project - An overview. Meteoritics & Planetary Science 42: 483-511. Koeberl,
C., B. Milkereit, J.T. Overpeck, C.A. Scholz, W.U. Reimold, L. Ferriere,
L. Coney, and J.A. Peck. 2007. Results of the 2004 ICDP Bosumtwi impact
crater, Ghana, drilling project. DOSECC Newsletter 5: 1-4.
Brooks, K., C.A. Scholz, J.W. King, J. Peck, J.T. Overpeck, J.M. Russell, and P.Y.O. Amoako. 2005. Late-Quaternary lowstands of lake Bosumtwi, Ghana: evidence from high-resolution seismic-reflection and sediment-core data. Palaeogeography, Palaeoclimatology, Palaeoecology 216: 235-249. Peck, J.A., R.R. Green, T. Shanahan, J.W. King, J.T. Overpeck, and C.A. Scholz. 2004. A magnetic mineral record of Late Quaternary tropical climate variability from Lake Bosumtwi, Ghana. Palaeogeography, Palaeoclimatology, Palaeoecology 215: 37-57. Peck, J., C. Koeberl, J. King, B. Milkereit, J. Overpeck, and C. Scholz. 2005. The Lake Bosumtwi drilling project: initial report. Limnology Division Newsletter 2: 3-7.
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Studies Laboratory, Department of Geosciences, The University of Arizona Last updated
January 8, 2008
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