Glacier fluctuations on Mount Kenya since similar to 6000 cal. years BP: Implications for holocene climatic change in Africa

Radiocarbon-dated lacustrine sedimentary evidence indicates that glaciers o f variable size occupied the southwestern cirques on Mount Kenya during muc h of the last 6000 years. Pro-glacial lacustrine sediments obtained from Ha usberg Tarn reveal distinct variations in rock-flour content whereas the se diments in Oblong Tarn, a nearby non-pro-glacial lake of similar size and a ppearance to Hausberg Tarn show no such variations. The lamination is there fore likely to be directly related to erosion by the glaciers draining into the upper lake in Hausberg Valley. Six major periods of glacier advances h ave been dated to shortly before 5700, 4500-3900, 3500-3300, 3200-2300, 130 0-1200, and 600-400 cat. years BP. Radiocarbon dating of the bottom sedimen ts from both Naro Moru and Hausberg Tarn, is consistent with a marked glaci er expansion that occurred shortly before 5700 cal. years BP. This advance reached approximately 1 km farther downvalley compared with the advances of the Little Ice Age. Modelling of the climate conditions required for this mid-Holocene Mount Kenya advance shows that a lowering of the equilibrium l ine altitude (ELA) by 100 m for a few hundred years could cause a glacier a dvance of the inferred magnitude. The glacier advances are attributed prima rily to changes in temperature because several independent paleoclimatic st udies from East Africa and other areas affected by the Indian monsoon indic ate a relatively dry climate at times of glacier advance on Mount Kenya.