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.

全球深海环流依赖于在北大西洋沉没的稠密水域的形成。虽然这些水域不是全球海洋中最冷的，但它们的盐度足以对流，形成了一场大规模的倾覆，这是全球海洋热能和碳传送带的重要组成部分。一种海洋学理论认为，对这种温暖的咸水从地中海流入北大西洋深处的循环做出了重要贡献--地中海外流水(MOW)。一些气候模型表明，干扰或改变MOW的强度将改变海洋热量输送，从而改变全球温度模式。在这个项目中，研究团队将通过一项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梅西尼亚盐度危机，当时地中海基本上干涸，形成了厚厚的盐矿。研究人员将首次使用跨越这一时间间隔的沉积物序列收集一些开阔海域的高分辨率古温度估计。如果MOW假说是正确的，研究将发现地中海孤立期间区域温度响应的独特模式，然后在与开阔海洋的连接再次建立和恢复MOW生产时发生变化。或者，如果没有出现假设的海洋表面温度模式，这项研究将表明最低气温的全球重要性被高估了。这项研究的地点选择在北大西洋、中大西洋、南大西洋和赤道太平洋的梅西尼和后梅西尼期。初步结果表明，在感兴趣的时间间隔内，所有地点的泥沙淤积都是连续的。研究小组将利用有机烯酮古测温法，在每个地点重建大约3000年的时间步长，从650万年前到500万年前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。沉积物记录将通过氧同位素地层学和轨道调整进行对比，以便同步进行比较。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假说。这些结果还将被用作地中海地区梅西尼亚间隔期区域气候模型的输入。该项目将为一名职业生涯早期的女研究人员提供支持，并促进与寻求解决梅西尼亚盐度危机的原因和影响的国际研究人员社区的合作。作为这项工作更广泛影响的一部分，中康涅狄格州立大学的本科生将作为暑期实习生被招募和指导。中康涅狄格州立大学是一所非研究型机构，第一代大学生的比例很高。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。