Nonuniform Late Pleistocene glacier fluctuations in tropical Eastern Africa

Alexander R Groos,Christof Vockenhuber,Naki Akçar,Serdar Yesilyurt,Heinz Veit,Georg Miehe

doi:10.1126/sciadv.abb6826

Alexander R Groos, Christof Vockenhuber + Show 4 more

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https://doi.org/10.1126/sciadv.abb6826

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Abstract

Today's ice caps and glaciers in Africa are restricted to the highest peaks, but during the Pleistocene, several mountains on the continent were extensively glaciated. However, little is known about regional differences in the timing and extent of past glaciations and the impact of paleoclimatic changes on the afro-alpine environment and settlement history. Here, we present a glacial chronology for the Ethiopian Highlands in comparison with other East African Mountains. In the Ethiopian Highlands, glaciers reached their maximum 42 to 28 thousand years ago before the global Last Glacial Maximum. The local maximum was accompanied by a temperature depression of 4.4° to 6.0°C and a ~700-m downward shift of the afro-alpine vegetation belt, reshaping the human and natural habitats. The chronological comparison reveals that glaciers in Eastern Africa responded in a nonuniform way to past climatic changes, indicating a regionally varying influence of precipitation, temperature, and orography on paleoglacier dynamics.

Highlights

The extant glaciers in Africa are restricted to the summit areas of Mount Kenya, Kilimanjaro, and Rwenzori Mountains [1, 2], but during the cold periods of the Late Pleistocene, several mountain ranges on the continent were extensively glaciated [3,4,5]
Studying the climate and glacial history of the mountains in Eastern Africa is of particular interest since the topography on both sides of the East African Rift along with an amplified regional cooling at high elevations favored the formation of numerous ice caps and valley glaciers [3,4,5,6]
By combining the new 36Cl ages from the Ethiopian Highlands with existing 36Cl and 10Be glacial chronologies from Mount Kenya, Kilimanjaro, and the Rwenzori Mountains [9,10,11,12], this study aims to investigate the response of tropical glaciers in Eastern Africa to Late Pleistocene climate changes and elaborate on the paleoclimatic and paleoecological implications of past glacial fluctuations

Summary

Introduction

The extant glaciers in Africa are restricted to the summit areas of Mount Kenya, Kilimanjaro, and Rwenzori Mountains [1, 2], but during the cold periods of the Late Pleistocene, several mountain ranges on the continent were extensively glaciated (table S1) [3,4,5]. Well-preserved moraine sequences and other glacial landforms testify to multiple glacier advances in the High Atlas, East African Mountains, and Ethiopian Highlands (Fig. 1). Studying the climate and glacial history of the mountains in Eastern Africa is of particular interest since the topography on both sides of the East African Rift along with an amplified regional cooling at high elevations favored the formation of numerous ice caps and valley glaciers [3,4,5,6]. Latest glacial chronological and paleoclimatological studies from the East African Mountains and Ethiopian Highlands indicate distinct climatic and ecological changes at high elevations as they provide evidence for multiple glacier advances, a pronounced cooling, and depression of altitudinal vegetation belts during the Late Pleistocene [7, 9,10,11,12]

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