Millenial Scale Weak Monsoon Intervals over India (WeakMonsoons)

点击翻译按钮获取中文摘要

The Indian Summer Monsoon (ISM) is highly variable and sensitive to global climate change. Modern climate observations suggest that mainly Indian Ocean surface temperatures modulate rainfall intensity and seasonal duration over the Indian continent. Based on the manifold paleoclimatic records for past monsoon changes and supported by earth system modelling monsoon variability at orbital and suborbital timescales must be considered as a response to changes in high and low latitude climate change, in atmosphere and ocean circulation, as well as in greenhouse gas concentrations and ice-sheet growth or melt. The importance of theses processes is still extensively, but often controversely, debated. Under the impression of severe flooding events and their devastating impact on millions of people and economic well-being most of these studies have addressed the causes for intervals of enhanced monsoonal precipitation also at geological time scales. However, more recently the focus of paleoclimate reconstructions is oriented towards periods of very low monsoonal precipitation, so-called Weak Monsoon Intervals (WMIs). At millenial timescales WMIs correspond to abrupt cold climate periods characteristic for northern hemishere high latitudes, However, as for the longer timescales, the forcing mechanisms of WMIs are not well understood due to the scarcity of high-resolution Late Quaternary time series of ISM precipitation. This project aims to generate a new record of past multi-centennial variability in rainfall over India using hydrogen and carbon isotope ratios of specific organic compounds from land plants, transported to and deposited in marine sediments in the Bay of Bengal and recently recently drilled at IODP Leg 353, Site U1446. The main objectives are the determination of the magnitude of hydrological responses to external and internal climate forcing during last Glacial and Holocene and to better identify the most importcontrol mechanisms responsible for rainfall variability over India.