Testing the Hypothesis: Recurring Century-Length Episodes of Reduced Summer Monsoon Precipitation Are Linked to Ocean/Atmosphere Dynamics in the Tropical Pacific

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This award extends the proxy data base of tropical Pacific ocean-atmospheric variability and monsoon variability in order to investigate whether, on longer time scales, there has been a persistent coupling between the tropical Ocean and monsoons of India and China. The research is a continuation of a project begun two years ago by this group to reconstruct high resolution (decadal resolution) precipitation histories for the monsoon regions through analyses of oxygen isotopes in dated speleothems collected in India and China and compare these to high resolution (multi-decadal resolution) proxy records of sea surface temperature and precipitation variability in Indonesia. The climate thesis at the core of the research is that a centennial and a millennial-length pattern of ocean-atmospheric variability exists within the tropical Pacific and Indian Oceans that involves shifts the locus of warm waters and the strength of atmospheric convection over Indonesia and sea surface temperature gradients in the Indian Ocean and this variability is associated with varying strength of summer precipitation falling on the core monsoon regions of India and China. The researchers are pursuing the following research questions:- Has there been a persistent pattern of centennial-scale climate (SST) variability in the western tropical Pacific and Indian Ocean that is associated with variable precipitation over the monsoon regions of India and China?- Is there a persistent pattern of drought recurrence in the Indian and Asian monsoon rainfall?- Were major cultural events in India and China associated with sustained or exceptional droughts?The researchers will address these questions by expanding the reconstruction of western tropical Pacific and Indian Ocean sea surface temperature changes, developing composite speleothem oxygen isotope records of Indian and Asian monsoon variability, and conducting time series analysis and inter-comparisons of Holocene millennial-scale climate records.The data gained from this research will aid the understanding of the climatology of a large-scale atmospheric feature (Asian monsoon) that has significant impact on a densely populated region. The project has a strong international collaborative education and research component that includes support for research and postdoctoral scholars and active participation by scientists and students in China, India, and Taiwan.