New evidence for a reduced water balance in East Africa during the Last Glacial Maximum: implication for model-data comparison |
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| Institution: | 1. Natural Resources Canada, Canadian Forest Service, Victoria, British Columbia, Canada;2. Departments of Biology and Earth and Environmental Science, University of British Columbia, Kelowna, Canada;3. Department of Marine Geology and Glaciology, Geological Survey of Denmark and Greenland, Copenhagen, Denmark;4. Royal British Columbia Museum, Victoria, British Columbia, Canada;5. Department of Water Management, Delft University of Technology, Delft, The Netherlands |
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| Abstract: | Some syntheses of lake-level data for the Last Glacial Maximum (LGM) in East Africa (10°N and 30°S, East of 25°E) show apparently wetter conditions than present for some basins, whereas palaeovegetation reconstruction indicates a generally dry climate. PMIP GCM simulations for the LGM support both scenarios for this region when run under different boundary conditions. Here, we compare three new records from lakes in the data-poor southern part of East Africa; Lake Malawi, Lake Massoko, and Lake Rukwa. We also re-assess previously published lake-level data and apply a salinity transfer function to the diatom record from Lake Manyara. Our results show that in contrast to previous interpretations, these lakes were at least as low as today at the LGM and are thus in agreement with the palaeovegetation data. Relative drought across East Africa is best simulated by GCMs that use computed SSTs rather than the higher CLIMAP values. Lower SSTs and the presence of the Northern Hemisphere ice sheets must have been dominant over any monsoon precipitation rise caused by astronomically induced summer insolation enhancement in the southern African tropics. |
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