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

全球深海环流取决于北大西洋下沉的稠密沃茨的形成。尽管这些沃茨不是全球海洋中最冷的，但它们的盐度足以对流，形成大规模的翻转，是全球海洋热量和碳“传送带”的重要组成部分。一种海洋学理论认为，从地中海流入北大西洋深处的暖盐水--地中海外流水（MOW）对这种环流有重要贡献。一些气候模型表明，中断或改变MOW的强度将改变海洋热传输，从而改变全球温度模式。在这个项目中，研究小组将使用一个自然地质实验来测试MOW的重要性，当时地中海和大西洋之间的联系被完全切断，大约600万年前的一段时间被称为墨西拿盐度危机，当时地中海大部分干涸，形成了厚厚的盐层。研究人员将首次利用跨越这一时间间隔的沉积物序列在一些开阔海洋地点收集高分辨率的古温度估计值。如果MOW假设是正确的，研究将发现地中海隔离期间区域温度响应的独特模式，然后当再次建立与开放海洋的连接并恢复MOW生产时发生转变。或者，如果海洋表面温度的假设模式没有出现，研究将表明MOW的全球重要性被高估了。本研究选择了北大西洋、中大西洋、南大西洋和赤道太平洋的梅西尼期和后梅西尼期。初步结果表明，沉积物沉积是连续的，在所有地点通过感兴趣的时间间隔。该研究小组将利用有机烯酮古温度测量法，以重建每个地点从650万年到500万年前大约3,000年时间步长的海洋表面温度演变。这段时间涵盖了地中海孤立之前和之后的气候事件。将通过氧同位素地层学和轨道调整使沉积物记录相互关联，以便能够同步进行比较。然后将结果与模拟MOW停止的气候模型进行比较，以验证/证伪MOW假设。研究结果还将用于地中海区域麦西尼期区域气候模型的输入。该项目将为早期职业女性研究人员提供支持，并促进与国际研究人员社区的合作，以解决墨西拿盐度危机的原因和影响。作为这项工作的更广泛影响的一部分，来自中央康涅狄格州立大学的本科生将被招募和指导为暑期实习生。中央康涅狄格州立大学是一所非研究机构，第一代大学生的比例很高。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

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.