Reconstructing hydrological changes in (sub)tropical South America over the last 36 kyrs: insights into the low-latitude expressions of high-latitude climate forcing

南美洲热带地区的水文循环在很大程度上取决于南美洲夏季风（SASM）的强度和热带辐合带（ITCZ）的纬度迁移。特别是在巴西东部，降水季节性极强，3月至10月为长达8个月的旱季，11月至2月为相对雨季。特别漫长的旱季使该地区对降雨量的变化非常敏感。这不仅使该区域的陆地生态系统极易受到长期干旱的影响，而且通过对农业和水力发电的影响，产生了严重的社会后果。由于巴西东北部目前正经历着历史性的干旱，因此必须限制该地区的自然气候变化，从而评估未来气候变化对大陆水分供应的潜在影响。考虑到预期的全球变暖速度只在地球历史的少数时期出现，该项目特别旨在通过研究末次冰期和冰川消退期间气候变化极其迅速的类似时期，评估南美洲的水文变化。本研究旨在通过重建河流径流，在过去的36 kyr期间，在南美洲热带气候高度敏感的地区关闭。该项目依赖于在METEOR 78/1（2009年3月）和最近的M125（2016年3月/4月，PI参与）期间获得的战略位置的海洋岩心。岩心M78/1-235-1记录了奥里诺科河的流出，从而反映了受ITCZ日照驱动变化影响的北方区域的气候变率。相比之下，M125-35-3岩芯记录了巴西东部南部南帕拉伊巴河的流出，位于ITCZ影响以南，但受到SASM和南美辐合带（SACZ）的影响。重建将基于高分辨率的多代理数据，包括有孔虫Ba/Ca，Mg/Ca，d18 O，XRF和彩色扫描。重点将放在气候变化率高的关键时间间隔，即晚更新世/早全新世过渡期，末次冰期最大期和海洋同位素阶段3与Dansgaard-Oeschger周期5-7。由于这两个网站的强烈影响，突然的气候变化，从高纬度的北部和南部高纬度地区，将获得新的见解大陆水文循环的敏感性，在气候高度动态的时期。

The hydrological cycle in tropical South America depends strongly on the intensity of the South American Summer Monsoon (SASM) and the latitudinal migration of the Intertropical Convergence Zone (ITCZ). Particularly in eastern Brazil, precipitation is extremely seasonal, with an eight-months-long dry season between March and October and a relatively rainy season between November and February. The exceptionally long dry season makes this region highly sensitive to changes in the amount of the rainfall received. This does not only entail a very high vulnerability of the region's terrestrial ecosystems to prolonged draughts, but has also severe societal consequences via its effects on agriculture and the availability of hydroelectric power. As NE Brazil currently experiences historic droughts, it is essential to constrain the natural climatic variability in that region, thereby assessing the potential impacts of future climate change on continental moisture availability. Considering that the expected rate of global warming is paralleled by only few periods of earth's history, this project particularly aims to assess the hydrological variability in South America by studying analogue periods of extremely rapid climatic shifts during the last glacial and the deglaciation.To achieve this goal, this study aims to disentangle the impact of insolation and abrupt oceanic forcing on continental moisture availability via reconstructing river run-off in climatically highly sensitive regions of tropical South America during the last 36 kyr. The project relies on marine cores from strategically located positions that have become available during METEOR cruises 78/1 (March 2009) and, very recently, M125 (March/April 2016, with participation of the PI). Core M78/1-235-1 captures the outflow of the Orinoco River, thereby reflecting climate variability in the northern extent of the area influenced by the insolation-driven shifts of the ITCZ. In contrast, core M125-35-3 records the outflow of the Paraíba do Sul River in southern East Brazil, south of the ITCZ influence, but affected by the SASM and the South American Convergence Zone (SACZ). Reconstructions will be based on high- resolution multi-proxy data comprising foraminiferal Ba/Ca, Mg/Ca, d18O, XRF- and color-scanning. Focus will be on critical time intervals with high rates of climate change, i.e. the late Pleistocene/early Holocene transition, the Last Glacial Maximum and Marine Isotope Stage 3 with Dansgaard-Oeschger cycles 5-7. As both sites are strongly influenced by abrupt climate shifts originating from the high-northern and high-southern latitudes, novel insights will be gained about the sensitivity of the continental hydrological cycle during climatically highly dynamic periods.