Indian Summer Monsoon Variability during the Last Millennium

ORAL

Abstract

The seasonal rainfall associated with the Indian summer monsoon during the instrumental period ($\sim$last 150 years) is characterized by a biennial oscillation, such that monsoon precipitation varied between singularly strong and weak years but rarely deviated far from its mean state for consecutive years. This observation has led to a hypothesis that monsoon is a self-regulating system, regulated by the annual cycle of the heat balance in the Indian Ocean, mediated by the cross-equatorial ocean heat transport from the summer hemisphere through wind-driven Ekman transport. Consequently, the present day water resource infrastructure and the contingency planning in the region does not take into account the possibility of protracted failures of the monsoon or drastic shifts in its spatial patterns. Here we present new millennial-length speleothem-based reconstructions of Indian monsoon variability from a number of sites across India that challenges the underlying physics of the aforementioned hypothesis. Our proxy records of Indian monsoon provide clear evidence for type of low frequency and high amplitude variability in rainfall that have not been observed during the short instrumental period.

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Authors

  • Mary Rooker

    CSU Dominguez Hills

  • G.V. Brown

    Department of Physics at CSU, Fresno, Lawrence Livermore National Laboratory, Stanford University, Advanced Light Source, Lawrence Berkeley National Lab, Nanoelectronics Research Institute, Japan Atomic Energy Agency, University of Tokyo, Cornell University, Tokyo Institute of Technology, Suranaree University of Technology, Shandong University, Stanford Synchrotron Radiation Lightsource, UC Davis, CSU Dominguez Hills, Thomas Jefferson National Accelerator Facility, UC Berkeley, ANL, UChicago/ANL, UManitoba, Northwestern U/ANL, LLNL, UCB/LLNL, McGill U, McGill U/ANL, University of Nevada, Reno, Hitachi Global Storage Technology, Advanced Light Source, Stanford Synchrotron Radiation Laboratory, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Materials Science and Engineering, Stanford University, Radiation Oncology, Stanford University School of Medicine, Missouri University of Science and Technology, International Institute of Physics, University of Missouri, University of Notre Dame du Lac, Department of Physics, California State University, Fresno, California, California State University Long Beach, BNL, IWF Dresden, Department of Physics, University of California, Davis, CA 95616, USA, University of California, Merced, Laboratoire Univers et Particules de Montpellier, IN2P3 (France), SLAC National Accelerator Laboratory/Stanford University/KIPAC, University of Perugia, University of Washington, CEA/Saclay, UNR, UNM, UCSD, RAL, ILE, MIT, LANL, LLE, NRL, SLAC National Accelerator Laboratory, Technische Universitaet Berlin, Max Born Institut, Hiroshima University, Western Michigan University, MPIK