Recurring summer and winter droughts from 4.2-3.97 thousand years ago in north India
jats:titleAbstract</jats:title>jats:pThe 4.2-kiloyear event has been described as a global megadrought that transformed multiple Bronze Age complex societies, including the Indus Civilization, located in a sensitive transition zone with a bimodal (summer and winter) rainfall regime. Here we reconstruct changes in summer and winter rainfall from trace elements and oxygen, carbon, and calcium isotopes of a speleothem from Dharamjali Cave in the Himalaya spanning 4.2–3.1 thousand years ago. We find a 230-year period of increased summer and winter drought frequency between 4.2 and 3.97 thousand years ago, with multi-decadal aridity events centered on 4.19, 4.11, and 4.02 thousand years ago. The sub-annually resolved record puts seasonal variability on a human decision-making timescale, and shows that repeated intensely dry periods spanned multiple generations. The record highlights the deficits in winter and summer rainfall during the urban phase of the Indus Civilization, which prompted adaptation through flexible, self-reliant, and drought-resistant agricultural strategies.</jats:p>
Acknowledgements: The authors would like to thank Dr. Giulio Lampronti for assistance with XRD measurements at the University of Cambridge. N.M. received financial support from the German Science Foundation (DFG projects MA4759/9-1 and MA4759/11-1). A.G., D.A.H., and C.A.P. received support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no 648609). A.G., A.H. and S.F.M.B. received support from the European Union’s Horizon 2020 program (QUEST project, grant agreement no 691037), C.A.P. received funding from the Global Challenges Research Fund’s TIGR2ESS project (BB/P027970/1), and A.H. was further supported by Rutherford Discovery Fellowship (RDF-UOW1601) awarded by Royal Society Te Apārangi. Calcium isotope analyses were supported through NERC NE/R013519/1 (H.J.B.). No permissions were required for sampling, but we gratefully acknowledge the support of the local village leaders and accompanying guide.
Funder: DFG projects MA4759/9-1 and MA4759/11-1 ERC Horizon 2020 grant agreement no 648609 ERC Horizon 2020 QUEST project, grant agreement no 691037 Global Challenges Research Fund’s TIGR2ESS project (BB/P027970/1) Rutherford Discovery Fellowship (RDF-UOW1601) NERC NE/R013519/1
European Research Council (648609)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (691037)
Natural Environment Research Council (NE/R013519/1)