Drought Cycles Over the Last 8,200 Years Recorded in Maar Lake Twintaung, Myanmar

The tropical Asian regions are particularly prone to catastrophic droughts due to high temperature and evaporation and their sensitivity to variable oceanic-atmospheric circulation. The extent to which future global warming may intensify droughts in this populous region is a matter of utmost concern. Palaeoclimatic data can help inform scientists learn more about the temporal patterns and drivers of monsoon change over geological timescales. In this paper, we present a new 8,200 year biomarker record preserved in the annually laminated sediments of Maar Lake Twintaung, Myanmar. The delta C-13(27-35) sedimentary record is mainly derived from leaf wax lipids in the lake catchment, which is presently dominated by C-3 vegetation in the modern lake catchment. The delta C-13(27-35) is mainly regulated by plant physiological and biochemical responses to drought stress and, as such, can be used as a proxy of past changes in moisture. The delta C-13(27-35) record reveals distinct decadal-to-centennial-scale droughts superimposed on a trend of gradually decreasing summer monsoon intensity from the mid-Holocene to late Holocene. Within the limits of the dating uncertainties, these decadal-to-centennial-scale droughts are found to be well correlated with the southward shift of the Intertropical Convergence Zone. It highlights thepimportance of the Intertropical Convergence Zone shift (tropical monsoon trough) in regulating monsoon rainfall in the region. In addition, most of the droughts are likely to be linked with active volcanism and solar minima and suggest a coupled process between external drivers and internal climate dynamics.