Impact of surface-water temperature on South American Summer Monsoon dynamics during the past ~850 kyrs

季风带来的降水直接影响到世界上约三分之二人口的生计。因此，预测全球变暖条件下季风系统的未来行为具有重大的社会经济意义。然而，数值模式仍然无法可靠地模拟气候变暖下季风系统复杂的时空降雨变率。这一缺陷在热带海表温度上升对季风降水量和空间分布的影响方面尤为突出。为了更好地了解不同气候边界条件下季风驱动的降水变率，过去的连续代用记录是必要的。在这个项目中，我们建议调查南美夏季风（SASM）在巴西东部更新世中期至晚期的动态，以破译在热带南大西洋西部的SST变化对大陆降水模式的影响。特别是巴西东部受到不同的季节性和年际变化的水分供应，因此，从生态和社会经济的角度来看，一个高度敏感的地区。为了更好地了解热带海洋如何影响季风降雨变率，我们的项目旨在（i）重建热带大西洋西部的水文变化，（ii）将这些变化与巴西东部不同（即，冰川-间冰期）气候状态。为了实现这一目标，我们将研究位于巴西东部靠近Rio Doce和Rio de Contas河口的两个岩心。将根据对南极有孔虫（Globigerinoides ruber，粉红色品种）的Mg/Ca测量值，重建两个岩心的海面温度（SST）。X射线荧光岩心扫描获得的沉积物地球化学数据（如K/Al、Fe/Al比、元素积累率）将提供有关各河流流域的河流径流和风化状况的信息。由于岩心扫描和Mg/Ca-SST将从相同的岩心材料中获得，因此有必要对海洋和陆地环境变异性进行直接比较。综合两个核心的替代数据将允许研究巴西东部降雨的区域尺度变化及其与SST变化的关系。过去约850 kyr）将使巴西东部尚未获得的、通常不连续的降雨变化记录延长至少600 kyr。新的数据将允许限制大陆水分平衡在以前的间冰期与温暖的温度比前工业全新世（例如，MIS 5和11）。因此，我们希望我们的项目的结果作为基准，预测未来的气候变化对降水模式的影响，在热带南美洲东部的所有社会经济相关性。

Monsoon-derived precipitation directly affects the livelihood of about two thirds of the world population. Predicting the future behavior of monsoonal systems under global warming conditions is therefore of great socio-economic relevance. However, numerical models still fail to reliably simulate the complex spatial and temporal rainfall variability of monsoonal systems under a warming climate. This shortcoming is particularly prominent with regard to the impact of rising tropical sea-surface temperatures (SST) on the amount and spatial distribution of monsoonal precipitation. In order to improve the understanding of monsoonally driven precipitation variability under different climatic boundary conditions, continuous proxy records of the past are necessary. In this project we propose to investigate South American Summer Monsoon (SASM) dynamics in E Brazil during the mid to late Pleistocene in order to decipher the impact of SST changes in the western tropical South Atlantic on continental precipitation patterns. Particularly E Brazil is subjected to distinct seasonal and interannual changes in moisture availability and, thus, a highly sensitive area from an ecological and socio-economic perspective. To better understand how the tropical ocean affects monsoonal rainfall variability, our project aims to (i) reconstruct hydrographic changes in the western tropical Atlantic and (ii) to link these changes to reconstructions of continental moisture variability in E Brazil across different (i.e., glacial-interglacial) climate states. To achieve this goal we will study two cores located off E Brazil close to the mouths of the Rio Doce and Rio de Contas. Sea surface temperatures (SST) will be reconstructed for both cores based on Mg/Ca measurements on planktic foraminifera (Globigerinoides ruber, pink variety). Sediment geochemical data (e.g. K/Al, Fe/Al ratios, element accumulation rates) derived from XRF core scanning will provide information about fluvial run-off and weathering state in the respective river catchment. As core scanning and Mg/Ca-SST will be obtained from the same core material a direct comparison of marine and terrestrial environmental variability is warranted. Integrating proxy data from both cores will allow to study the regional-scale variability of rainfall in E Brazil and its relation to SST changes.The entire time interval covered by the new records (i.e., the past ~850 kyr) will extend the yet available, often discontinuous records of rainfall variability in E Brazil by at least 600 kyrs. The new data will allow to constrain the continental moisture balance during previous interglacials with warmer temperatures than the pre-industrial Holocene (e.g., MIS 5 and 11). We therefore expect the results of our project to serve as benchmarks for predicting the influence of future climate change on precipitation patterns in eastern tropical South America with all their socio-economic relevance.