Millennial-scale reconstruction of Orinoco run-off strength and its impact on the Atlantic Meridional Overturning Circulation (MORA)

气候模型和古环境研究表明，加勒比内陆地区的湿度以及流入加勒比海的河流径流对气候变化非常敏感。南美洲北方水文循环的变化不仅会影响当地的水收支，而且可能产生深远的后果：加勒比海的地表水是墨西哥湾流盐分收支的重要媒介，因此是高纬度深水形成的先决条件。因此，由于淡水输入的变化而改变的加勒比海表面盐度可能最终影响大西洋经向翻转环流的强度，从而影响全球气候。尽管这一现象具有明显的相关性，但没有人试图以高时间分辨率重建全新世和末次冰期流入加勒比海的主要河流径流。在拟议的项目中，我们希望通过生成末次冰期至全新世（半）定量估计奥里诺科河流量的千年尺度分辨率来缩小这一差距。研究的基础将是有孔虫Ba/Ca和δ 18 O海水测量值，作为奥里诺科河三角洲附近岩心中河流输入和盐度变化的当地校准代理。与亚马逊三角洲、加勒比海、墨西哥湾和北方大西洋的记录进行比较，将显示奥里诺科河/亚马逊河的排放量过高或过低是否正在大规模地改变表层海洋的盐度，从而表明海洋/气候系统中以前被低估的一个因素。

Climate models as well as paleoenvironmental studies demonstrate that moisture availability in the hinterland of the Caribbean and, hence, river run-off into the Caribbean Sea is highly sensitive to climatic changes. Changes of the hydrological cycle in northern South America will not only impact the local water budget but might have far-reaching consequences: Caribbean surface water is an important mediator of the salt budget of the Gulf Stream and thereby preconditions high-latitude deep water formation. Caribbean surface salinities altered by changes in the freshwater input might therefore ultimately affect the strength of the Atlantic Meridional Overturning Circulation and, consequently, global climate. Despite the clear relevance of this phenomenon, no attempts have been made to reconstruct Holocene and Last Glacial runoff of major rivers into the Caribbean Sea in high temporal resolution. In the proposed project we want to close this gap by generating Last Glacial to Holocene (semi)quantitative estimates of Orinoco discharge in millennial-scale resolution. The base of the study will be foraminiferal Ba/Ca and δ18Oseawater measurements as locally calibrated proxies for river input and salinity changes in cores located close to the Orinoco Delta. A comparison with records from the Amazon Delta, Caribbean, Gulf of Mexico and Northern Atlantic will show whether anomalously high or low Orinoco/Amazon discharge is changing surface ocean salinity on a large scale and thereby represents a previously underestimated factor within the ocean/climate system.