Glacier fluctuations on Mount Kenya since ~ 6000 cal. years BP: Implications for Holocene climatic change in Africa

Radiocarbon-dated lacustrine sedimentary evidence indicates that glaciers of variable size occupied the southwestern cirques on Mount Kenya during much of the last 6000 years. Pro-glacial lacustrine sediments obtained from Hausberg Tarn reveal distinct variations in rock-flour content whereas the sediments in Oblong Tarn, a nearby non-pro-glacial lake of similar size and appearance to Hausberg Tarn show no such variations. The lamination is therefore likely to be directly related to erosion by the glaciers draining into the upper lake in Hausberg Valley. Six major periods of glacier advances have been dated to shortly before 5700, 4500-3900, 3500-3300, 3200-2300, 1300-1200, and 600-400 cal. years BP. Radiocarbon dating of the bottom sediments from both Naro Moru and Hausberg Tarn, is consistent with a marked glacier 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 line altitude (ELA) by 100 m for a few hundred years could cause a glacier advance of the inferred magnitude. The glacier advances are attributed primarily to changes in temperature because several independent paleoclimatic studies from East Africa and other areas affected by the Indian monsoon indicate a relatively dry climate at times of glacier advance on Mount Kenya.