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    • Fulltext

       

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      Permanent link:
      https://www.ias.ac.in/article/fulltext/jess/126/06/0087

    • Keywords

       

      Paleoclimate; polar cold reversals; ITCZ; Indian monsoon; Arabian Sea; sediment core.

    • Abstract

       

      The deglacial transition from the last glacial maximum at $\sim$20 kiloyears before present (ka) to the Holocene (11.7 ka to Present) was interrupted by millennial-scale cold reversals, viz., Antarctic Cold Reversal ($\sim$14.5–12.8 ka) and Greenland Younger Dryas ($\sim$12.8–11.8 ka) which had different timings and extent of cooling in each hemisphere. The cause of this synchronously initiated, but different hemispheric cooling during these cold reversals (Antarctic Cold Reversal $\sim$3∘C and Younger Dryas $\sim$10∘C) is elusive because CO2, the fundamental forcing for deglaciation, and Atlantic meridional overturning circulation, the driver of antiphased bipolar climate response, both fail to explain this asymmetry. We use centennial-resolution records of the local surface water $\delta ^{18}\hbox {O}$ of the Eastern Arabian Sea, which constitutes a proxy for the precipitation associated with the Indian Summer Monsoon, and other tropical precipitation records to deduce the role of tropical forcing in the polar cold reversals. We hypothesize a mechanism for tropical forcing, via the Indian Summer Monsoons, of the polar cold reversals by migration of the Inter-Tropical Convergence Zone and the associated cross-equatorial heat transport.

    • Author Affiliations

       

      Virupaxa K Banakar1 2 Sweta Baidya1 2 Alexander M Piotrowski3 D Shankar1

      1. CSIR-National Institute of Oceanography, Dona Paula, Goa 403004, India.
      2. Academy of Scientific and Innovative Research (AcSIR), CSIR-NIO, Goa, India.
      3. Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.

    • Dates

       
      Published
      31 August 2017
      Manuscript received
      5 December 2016
      Manuscript revised
      17 March 2017
      Accepted
      24 March 2017

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