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Orbital precession modulates interannual rainfall variability, as recorded in an Early Pleistocene speleothem

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posted on 2023-05-10, 05:46 authored by Philip J Hopley, Graham P Weedon, Chris M Brierley, Christopher Thrasivoulou, Andrew HerriesAndrew Herries, Ada Dinckal, David A Richards, Dan C Nita, Randall R Parrish, Nick MW Roberts, Diana Sahy, Claire L Smith

Interannual variability of African rainfall impacts local and global communities, but its past behavior and response in future climate projections are poorly understood. This is primarily due to short instrumental records and a lack of long high-resolution palaeoclimate proxy records. Here we present an annually resolved 91,000 year Early Pleistocene record of hydroclimate from the early homininbearing Makapansgat Valley, South Africa. Changes in speleothem annual band thickness are dominated by precession over four consecutive orbital cycles with strong millennial-scale periodicity. The frequency of interannual variability (2.0-6.5 yr oscillations) does not change systematically, yet its amplitude is modulated by the orbital forcing. These long-term characteristics of interannual variability are reproduced with transient climate model simulations of water balance for South Africa from the Late Pleistocene to Recent. Based on these results, we suggest that the frequency of interannual variations in southern African rainfall is likely to be stable under anthropogenic warming, but that the size of year-to-year variations may increase. We see an orbitally forced increase in the amplitude of interannual climate variability between 1.8 Ma and 1.7 Ma coincident with the first evidence for the Acheulean stone tool technology.


Funding was provided to Hopley by the Natural Environment Research Council (NERC, UK), awards NE/J00443X/1 and IP/1065/1108. Weedon was supported by the Joint UK DECC/Defra Met Office Hadley Climate Centre Programme (GA01101). Herries was supported by Australian Research Council Future Fellowship FT120100399.


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4p. (p. 731-734)


Geological Society of America



Rights Statement

© 2018 The Authors. This paper is published under the terms of the CC-BY license.

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