A global climatic context (6.5 to 5 Ma) for the Mediterranean Messinian Salinity Crisis

地中海墨西拿盐度危机的全球气候背景（6.5 至 5 Ma）

• 批准号: 1930651
• 负责人: Timothy Herbert
• 金额: $ 20.68万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1930651&HistoricalAwards=false
• 关键词: global; climatic; context; 6.5; Ma

The global deep ocean circulation depends on the formation of dense waters that sink in the North Atlantic. Although these waters are not the coldest in the global ocean, they are salty enough to convect, forming a large-scale overturning that is an essential part of the global ocean heat and carbon "conveyor belt". One oceanographic theory posits the important contribution to this circulation of warm, salty water flowing out from the Mediterranean into the deep North Atlantic - the Mediterranean Outflow Water (MOW). Some climate models suggest that interrupting or altering the strength of the MOW would alter ocean heat transport and hence global temperature patterns. In this project, the research team will test the importance of the MOW using a natural geologic experiment when the connection between the Mediterranean and the Atlantic Ocean was completely cut off, a period of time known as the Messinian Salinity Crisis about 6 million years ago when the Mediterranean largely dried up and thick salt deposits were formed. Researchers will for the first time gather high resolution paleotemperature estimates at a number of open ocean sites using sediment sequences that span this time interval. If the MOW hypothesis is correct, the research will find a distinctive pattern of regional temperature responses during the time of Mediterranean isolation, followed by a shift when the connection to the open ocean was again established and MOW production resumed. Alternatively, if the hypothesized pattern of ocean surface temperature does not emerge, the research would suggest that the global importance of MOW has been overestimated.Sites have been selected for this study that span the Messinian and post-Messinian interval in the North Atlantic, central Atlantic, South Atlantic, and equatorial Pacific Oceans. Initial results show that sediment deposition is continuous at all sites through the time interval of interest. The research team will utilize organic alkenone paleothermometry in order to reconstruct ocean surface temperature evolution at approximately 3,000-year time steps from 6.5 to 5 million years ago at each site. This time period covers climate events that precede and post-date Mediterranean isolation. Sediment records will be correlated via oxygen isotope stratigraphy and orbital tuning so that they can be synchronized for comparison. Results will then be compared to climate models that simulate cessation of the MOW in order to verify/falsify the MOW hypothesis. The results will also be used as input for regional climate models of the Messinian interval in the Mediterranean region. This project will provide support for an early career female researcher and foster collaborations with an international community of researchers seeking to resolve the cause and effects of the Messinian Salinity Crisis. As part of the broader impacts of this work, undergraduates from Central Connecticut State University, a non-research institution with a high fraction of first-generation college students, will be recruited and mentored as summer interns.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

全球深海循环取决于北大西洋下沉的密集水的形成。尽管这些水域不是全球海洋中最冷的水，但它们足够咸以对流，形成了大规模推翻，这是全球海洋热和碳“传送带”的重要组成部分。一门海洋学为这种温暖的咸水循环提出了重要的贡献，从地中海流向北大西洋深 - 地中海流出水（MOW）。一些气候模型表明，打断或改变割草强度会改变海洋热传输，从而改变全球温度模式。在该项目中，研究团队将使用自然地质实验测试MOW的重要性，当地中海与大西洋之间的联系完全切断时，这是大约600万年前被称为Messinian Salinity危机的时期，当时地中海很大程度上干燥，形成了浓厚的盐沉积物。研究人员将首次使用跨越此时间间隔的沉积物序列在许多开放海洋地点进行高分辨率古温估计。如果MOW假设是正确的，那么研究将在地中海隔离期间发现区域温度响应的独特模式，然后在再次建立与开阔海洋的连接并恢复割草生产时发生了变化。或者，如果未出现海面温度的假设模式，该研究表明，已选择了MOW的全球重要性。为这项研究选择了跨越弥赛亚和后梅西尼时间隔的北大西洋中心，中大西洋，南大西洋，大西洋和阶梯太平洋海洋的现场。最初的结果表明，通过感兴趣的时间间隔，在所有地点，沉积物沉积都是连续的。研究小组将利用有机烯酮的古温度计，以便以大约3，000年的时间步长从6.5百万到500万年前重建海面温度的演变。这段时间涵盖了在地中海隔离之前和晚期地中海隔离之前的气候事件。沉积物记录将通过氧同位素地层和轨道调整相关，以便将它们同步以进行比较。然后将将结果与模拟割草停止的气候模型进行比较，以验证/伪造MOW假设。结果还将用作地中海地区弥赛亚间隔的区域气候模型的输入。该项目将为早期的职业女性研究人员提供支持，并与寻求解决墨西哥盐度危机的因果关系的国际研究人员促进合作。作为这项工作的更广泛影响的一部分，康涅狄格州立大学中央大学的本科生将作为暑期实习生招募和指导，这是一家非研究机构，该机构将被招募和指导。这一奖项反映了NSF的法定任务，并被认为是通过基金会的知识优点和广泛影响的评估来评估的值得支持的。