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Published November 2017 | Supplemental Material
Journal Article Open

Climatic and in-cave influences on δ^(18)O and δ^(13)C in a stalagmite from northeastern India through the last deglaciation

Abstract

Northeastern (NE) India experiences extraordinarily pronounced seasonal climate, governed by the Indian summer monsoon (ISM). The vulnerability of this region to floods and droughts calls for detailed and highly resolved paleoclimate reconstructions to assess the recurrence rate and driving factors of ISM changes. We use stable oxygen and carbon isotope ratios (δ^(18)O and δ^(13)C) from stalagmite MAW-6 from Mawmluh Cave to infer climate and environmental conditions in NE India over the last deglaciation (16–6ka). We interpret stalagmite δ^(18)O as reflecting ISM strength, whereas δ^(13)C appears to be driven by local hydroclimate conditions. Pronounced shifts in ISM strength over the deglaciation are apparent from the δ^(18)O record, similarly to other records from monsoonal Asia. The ISM is weaker during the late glacial (LG) period and the Younger Dryas, and stronger during the Bølling-Allerød and Holocene. Local conditions inferred from the δ^(13)C record appear to have changed less substantially over time, possibly related to the masking effect of changing precipitation seasonality. Time series analysis of the δ^(18)O record reveals more chaotic conditions during the late glacial and higher predictability during the Holocene, likely related to the strengthening of the seasonal recurrence of the ISM with the onset of the Holocene.

Additional Information

© 2017 University of Washington. Published by Cambridge University Press. Received April 3, 2017; Accepted August 2, 2017, Published online 21 September 2017. We gratefully acknowledge financial support from the Swiss National Fond (SNF Sinergia grant CRSI22 132646/1 and grant P2EZP2_172213), the German Science Foundation (DFG project MA4759/8-1--Impacts of uncertainties in climate data analysis [IUCliD]: approaches to working with measurements as a series of probability distributions--and grant no. RE3994-1/1), the National Natural Science Foundation of China (NSFC) grants 4123054 and 2013CB955902, the U.S. National Science Foundation grant 1103403, and the European Union's Horizon 2020 Research and Innovation program under the Marie Skłodowska-Curie grant agreement no. 691037 (QUEST). We thank our Indian colleagues Bijay Mipun and Gregory Diengdoh for their logistic help. We thank Daniel Gebauer for support during fieldwork. We also thank Lydia Zehnder and Stewart Bishop (both at ETH Zürich) for assistance during XRD and stable isotope analysis, respectively. Tim Eglinton is acknowledged for financial support of F.A.L. We thank Ashish Sinha, Max Berkelhammer, James Baldini, Yanjun Cai, and two anonymous reviewers for constructive feedback and fruitful discussions on this and earlier versions of this manuscript. We thank the editors, Matthew Lachniet and Lewis Owen, for feedback and handling of the manuscript.

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Supplemental Material - urn_cambridge.org_id_binary_20171101120743425-0354_S0033589417000722_S0033589417000722sup001.docx

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August 22, 2023
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October 17, 2023