Indian rainfall variability in a warmer world: Unraveling the Miocene-Pliocene enigmatic onset and evolution of the Indian monsoon in unparalleled sedimentary archives from IODP Expedition 353
Final Report Abstract
The orbitally-tuned, high resolution isotope records generated from the continuous upper Miocene sedimentary successions drilled at Sites U1447 and U1448 in the Andaman Sea spanning the interval from 9 to 5 Ma contribute to the following primary objectives of the iMonsoon Expedition 353: (1) to monitor changes in sea surface temperature and salinity as well as terrigenous discharge as proxies for the intensity of Indian summer monsoon rainfall in its core area; (2) to determine the evolution of paleoproductivity in response to changes of monsoonal wind patterns over the equatorial Indian Ocean; (3) to validate and extend the astronomical calibration of the geological timescale using orbitally forced variations in benthic and planktic oxygen and carbon isotopes. The spliced stable isotope and Mg/Ca data of Sites U1447 and U1448 provide the first complete millennial resolution sea mixed layer temperature and salinity record in the core area of the Indian Monsoon over the critical interval between 9 and 5 Ma, when major changes in the Indian-Asian-Australian monsoon-system occurred. This record can be linked to comparable records of the East Asian Monsoon in the South China Sea and the Australian Monsoon offshore Northwestern Australia (IODP Expedition 363 Site U1482), which are currently being analyzed by our working group in cooperation with colleagues in the US, China and Australia. The outcome of this joined effort will allow a direct comparison and synthesis of the early evolution of these three major marine components of the global monsoon system in relation to changing gobal boundary conditions (Southern and Northern Hemisphere glaciation, atmospheric CO2 and topography/vegetation changes in central Asia and Australia). Our results will, thus, contribute to planned global monsoon synthesis papers, will guide future ocean drilling efforts in the Andaman Sea and Bay of Bengal and will also help to constrain modeling experiments of past and future monsoonal climate.
