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

尽管进行了半个世纪的深入研究，在地球最强大的水文系统中，驱动季风降水短期和长期变化的过程仍然是一个激烈争论的问题。IODP远征353 （iMonsoon）的目标是重建其核心地理影响区域中新世至更新世的季风降水信号，即孟加拉湾边缘。从这一关键区域获取的新岩心将有助于评估印度季风对日照强迫和气候边界条件（如全球冰量和温室气体浓度的范围）的相对敏感性，以及季风环流开始和演变的时间和条件。这些新记录对于检验南亚气候演变与喜马拉雅山脉的构造发展和青藏高原的上升之间存在密切联系的假设也至关重要。我们建议建立高分辨率的温度和盐度重建（来自配对的稳定同位素和Mg/Ca）和季风径流记录（来自xrf扫描元素数据），重点关注时间间隔为16-14 Ma， 10-7 Ma和5-3 Ma。对这些关键时间窗的比较，将使我们对在边界条件差异很大的气候变暖期间，季风降雨与高纬度气候变化之间的联系有了新的认识：(1)中新世气候最适期（16 ~ 14.5 Ma），南极冰盖处于高度动力状态，青藏高原尚未出现主要隆升扩张期；(2)10 ~ 7 Ma，地球处于单极冰期，青藏高原出现主要隆升扩张期；(3)5 ~ 3 Ma，北半球开始冰川作用。

Despite half a century of intense research, the processes that drive the short- and long-term variability of monsoonal precipitation within the Earths strongest hydrological regime are still a matter of intense debate. IODP expedition 353 (iMonsoon) targeted the reconstruction of the monsoonal precipitation signal through the Miocene to Pleistocene in its core geographic region of influence, the margins of the Bay of Bengal. The new cores retrieved from this critical region will allow to assess the relative sensitivity of the Indian Monsoon to insolation forcing and climate boundary conditions such as the extent of global ice volume and greenhouse gas concentrations, and the timing and conditions under which monsoonal circulation initiated and evolved. These new records will also be crucial to test the hypothesis of a close linkage between the climatic evolution of South Asia and the tectonic development of the Himalayans and the rising of the Tibetan Plateau. We propose to develop high-resolution temperature and salinity reconstructions (from paired stable isotopes and Mg/Ca) and monsoonal run off records (from XRF-scanning elemental data), focusing on the time intervals 16-14 Ma, 10-7 Ma and 5-3 Ma. The comparison of these crucial time windows will allow new insights into the linkages between monsoonal rainfall and high-latitude climate change during intervals of warmer climate with widely differing boundary conditions: (1) during the Miocene Climate Optimum (16-14.5 Ma), when Antarctic ice sheets behaved in a highly dynamic manner and the main uplift and expansion phase of the Tibetan plateau had not yet taken place, (2) between 10 and 7 Ma, when Earth was unipolarly glaciated and the main uplift and expansion phase of the Tibetan plateau occurred, and (3) between 5 to 3 Ma when northern hemisphere glaciation was initiated.