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The Little Ice Age in Southern Tanzania (Africa)
Reference
Garcin, Y., Williamson, D., Bergonzini, L., Radakovitch, O., Vincens, A., Buchet, G., Guiot, J., Brewer, S., Mathe, P.-E. and Majule, A. 2007. Solar and anthropogenic imprints on Lake Masoko (southern Tanzania) during the last 500 years. Journal of Paleolimnology 37: 475-490.

What was done
The authors present new late-Holocene paleoenvironmental data derived from several undisturbed sediment cores retrieved from the deepest central part of Lake Masoko (920.0'S, 3345.3'E), which occupies a maar crater in the Rungwe volcanic highlands of the western branch of Africa's Rift Valley, where it is situated approximately 35 km north of Lake Malawi.

What was learned
In the words of the ten researchers who conducted the work, "magnetic, organic carbon, geochemical proxies and pollen assemblages indicate a dry climate during the 'Little Ice Age' (AD 1550-1850), confirming that the LIA in eastern Africa resulted in marked and synchronous hydrological changes," although "the direction of response varies between different African lakes." In this regard, for example, they report that "to the south (9.5-14.5S), sediment cores from Lake Malawi have revealed similar climatic conditions (Owen et al., 1990; Johnson et al., 2001; Brown and Johnson, 2005)" that are "correlated with the dry period of Lakes Chilwa and Chiuta (Owen and Crossley, 1990)," and they say that "lowstands have been also observed during the LIA at Lake Tanganyika ... from AD 1500 until AD 1580, and from ca. AD 1650 until the end of the 17th century, where the lowest lake-levels are inferred (Cohen et al., 1997; Alin and Cohen, 2003)." In contrast, however, they report that "further north, evidence from Lakes Naivasha (0.7S) and Victoria (2.5S-0.5N) indicates relatively wet conditions with high lake-levels during the LIA, interrupted by short drought periods (Verschuren et al., 2000; Verschuren, 2004; Stager et al., 2005)." Last of all, Garcin et al. state that "inferred changes of the Masoko hydrology are positively correlated with the solar activity proxies."

What it means
In discussing their findings, the African and French scientists note that the Little Ice Age in Africa appears to have had a greater thermal amplitude than it did in the Northern Hemisphere, citing in support of this statement the paleoclimate studies of Bonnefille and Mohammed (1994), Karlen et al. (1999), Holmgren et al. (2001) and Thompson et al. (2002). Nevertheless, the more common defining parameter of the Little Ice Age in Africa was the moisture status of the continent, which appears to have manifested opposite directional trends in different latitudinal bands. In addition, the group of scientists emphasizes that the positive correlation of Lake Masoko hydrology with various solar activity proxies "implies a forcing of solar activity on the atmospheric circulation and thus on the regional climate of this part of East Africa."

References
Alin, S.R. and Cohen, A.S. 2003. Lake-level history of Lake Tanganyika, East Africa, for the past 2500 years based on ostracode-inferred water-depth reconstruction. Palaeogeography, Palaeoclimatology, Palaeoecology 1999: 31-49.

Bonnefille R. and Mohammed, U. 1994. Pollen-inferred climatic fluctuations in Ethiopia during the last 2000 years. Palaeogeography, Palaeoclimatology, Palaeoecology 109: 331-343.

Brown, E.T. and Johnson, T.C. 2005. Coherence between tropical East African and South American records of the Little Ice Age. Geochemistry, Geophysics, Geosystems 6: 10.1029/2005GC000959.

Cohen, A.S., Talbot, M.R., Awramik, S.M., Dettmen, D.L. and Abell, P. 1997. Lake level and paleoenvironmental history of Lake Tanganyika, Africa, as inferred from late Holocene and modern stromatolites. Geological Society of American Bulletin 109: 444-460.

Holmgren, K., Moberg, A., Svanered, O. and Tyson, P.D. 2001. A preliminary 3000-year regional temperature reconstruction for South Africa. South African Journal of Science 97: 49-51.

Johnson, T.C., Barry, S.L., Chan, Y. and Wilkinson, P. 2001. Decadal record of climate variability spanning the past 700 years in the Southern Tropics of East Africa. Geology 29: 83-86.

Karlen, W., Fastook, J.L., Holmgren, K., Malmstrom, M., Matthews, J.A., Odada, E., Risberg, J., Rosqvist, G., Sandgren, P., Shemesh, A. and Westerberg, L.O. 1999. Glacier Fluctuations on Mount Kenya since ~6000 cal. years BP: implications for Holocene climatic change in Africa. Ambio 28: 409-418.

Owen, R.B. and Crossley, R. 1990. Recent sedimentation in Lakes Chilwa and Chiuata, Malawi. Palaeoecology of Africa 20: 109-117.

Owen, R.B., Corssley, R., Johnson, T.C., Tweddle, D., Kornfield, I., Davison, S., Eccles, D.H. and Engstrom, D.E. 1990. Major low levels of Lake Malawi and their implications for speciation rates in Cichlid fishes. Proceedings of the Royal Society of London Series B 240: 519-553.

Stager, J.C., Ryves, D., Cumming, B.F., Meeker, L.D. and Beer, J. 2005. Solar variability and the levels of Lake Victoria, East Africa, during the last millennium. Journal of Paleolimnology 33: 243-251.

Thompson, L.G., Mosley-Thompson, E., Davis, M.E., Henderson, K.A., Brecher, H.H., Zagorodnov, V.S., Mashiotta, T.A., Lin, P.N., Mikhalenko, V.N., Hardy, D.R. and Beer, J. 2002. Kilimanjaro ice core records: evidence of Holocene climate change in tropical Africa. Science 298: 589-593.

Verschuren, D. 2004. Decadal and century-scale climate variability in tropical Africa during the past 2000 years. In: Battarbee, R.W., Gasse, F. and Stickley, C.E. (Eds.), Past Climate Variability Through Europe and Africa. Springer, Dordrecht, The Netherlands, pp.139-158.

Verschuren, D., Laird, K.R. and Cumming, B.F. 2000. Rainfall and drought in equatorial east Africa during the past 1100 years. Nature 403: 410-414.

Reviewed 12 September 2007