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，但在地球最强的水文系统中，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第353次考察（iMonsoon）的目标是重建其核心地理影响区域（孟加拉湾边缘）中新世至更新世的季风降水信号。从这一关键地区检索的新的核心将允许评估印度季风的相对敏感性，太阳辐射强迫和气候边界条件，如全球冰量和温室气体浓度的程度，以及季风环流的启动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构造发展和青藏高原上升之间的密切联系这一假设也将是至关重要的。我们建议开发高分辨率的温度和盐度重建（从成对的稳定同位素和Mg/Ca）和季风径流记录（从XRF扫描元素数据），侧重于时间间隔16-14 Ma，10-7 Ma和5-3 Ma。对这些关键时间窗的比较将使人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新的认识：（1）在中新世气候最佳时期（16- 14.5Ma），南极冰盖处于高度动态状态，青藏高原的主要隆升和扩张阶段尚未发生，（2）10 ~ 7 Ma，地球单极冰川作用，青藏高原主要隆升扩张阶段;（3）5 ~ 3 Ma，北方冰川作用开始。

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.