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，加勒比腹地以及流入加勒比海的河流的水分供应对气候变化高度敏感。南美洲北部水文循环的变化不仅将影响当地的水收支，而且可能产生深远的后果：加勒比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表面盐度可能最终会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，但尚未尝试以高时间分辨率重建流入加勒比海的全新世和最后一次冰川径流。在拟议的项目中，我们希望通过生成千年尺度的奥里诺科流量的末次冰期至全新世(半)定量估计来缩小这一差距。这项研究的基础将是有孔虫的BA/Ca和δ180海水测量，作为河流输入和奥里诺科三角洲附近岩心盐度变化的当地校准代用品。与亚马逊三角洲、加勒比海、墨西哥湾和北大西洋的记录进行比较，将表明奥里诺科/亚马逊流量的异常高或低正在大规模改变表层海洋盐度，因此代表着海洋/气候系统中以前被低估的因素。

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.