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Last Glacial Maximum Tropical Pacific Thermocline Structure and Wind Field: A Data Synthesis

末次盛冰期热带太平洋温跃层结构和风场：数据综合

基本信息

批准号：
2002297
负责人：
Jean Lynch-Stieglitz
金额：
$ 44.97万
依托单位：
Georgia Tech Research Corporation
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-15 至 2024-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2002297&HistoricalAwards=false
关键词：
Last Glacial Maximum Tropical Pacific

项目摘要

The spatial pattern of wind and rainfall in the tropics is not fixed, but changes with time. The changes can be driven by the amount of greenhouse gasses in the atmosphere, changes in seasonality, or the presence of large expanses of ice outside of the tropics. By looking at these patterns during the height of the last ice age, ideas about the links between these drivers and the tropical climate can be tested. It would be difficult to directly deduce the patterns of the ice age winds. But when the winds blow on the upper ocean, they pile up warm water in some areas and bring cold water closer to the sea surface in others. In this project, the investigators will use tiny shells (foraminifera) that contain information about the temperature of seawater at different depths. These shells accumulate on the sea-floor and preserve a history of ocean temperature. The upper ocean temperature reconstructed from shells that fell to the seafloor during the height of the last ice age can then be used to deduce the wind patterns. The project would support two graduate students (one of whom is a woman from an underrepresented minority), as well as providing support for undergraduate summer researchers.The PIs proposes a plan of database development and analysis that will use the information about the thermocline structure recorded in the oxygen isotope composition of surface and subsurface planktonic foraminifera in the tropics to reconstruct the tropical thermocline and winds during the Last Glacial Maximum. The isotopic composition of the tests of different species will reflect the surface and subsurface density and can be used to reconstruct thermocline structure. The tight coupling between winds and thermocline structure will be exploited to infer changes in the winds through the thermocline reconstructions provided from the foraminifera proxy data. The PIs will first create a global database of tropical planktonic foraminifera oxygen isotope data from recent sediments. Using this data, models for foraminifera calcification habitat will be constructed and the uncertainty in the calcification habitat quantified. A variety of statistical approaches will then be explored in order to determine how to project the sparse information about the vertical structure of the water column from the foraminiferal proxy data into estimates of the tropical thermocline structure, and to determine how to optimally estimate the long-term mean winds associated with a given mean thermocline state. These analytical approaches will include Empirical Orthogonal Functions, Optimal Linear Estimators, and Inverse Methods. Finally, existing Last Glacial Maximum oxygen isotope data will be compiled for these same species. The database will be augmented in the Tropical Pacific with new measurements, as guided by the data analysis effort. Once the Last Glacial Maximum foraminiferal database is complete the data will be directly compared to results from isotope-enabled general circulation model simulations of ice age climate, and also used to produce an estimate of Tropical Pacific thermocline structure and winds using the data analysis tools developed as described above.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.

热带地区的风和雨的空间格局不是固定的，而是随时间而变化的。这种变化可能是由大气中温室气体的数量、季节性的变化或热带地区以外大片冰层的存在所驱动的。通过观察上一个冰河期高峰时期的这些模式，关于这些驱动因素与热带气候之间联系的想法可以得到检验。直接推断冰河时期风的模式是很困难的。但是，当风吹向上层海洋时，它们会在一些地区积聚温暖的海水，并在其他地区将冷水带到离海面更近的地方。在这个项目中，研究人员将使用含有不同深度海水温度信息的微小贝壳（有孔虫）。这些贝壳堆积在海底，保存着海洋温度的历史。在最后一个冰河时期，从落到海底的贝壳中重建的上层海洋温度可以用来推断风的模式。该项目将资助两名研究生（其中一名是来自少数族裔的女性），并为本科生暑期研究员提供支持。PIs提出了利用热带表层和地下浮游有孔虫氧同位素组成记录的温跃层结构信息重建末次盛冰期热带温跃层和风的数据库开发和分析计划。不同物种的同位素组成可以反映地表和地下密度，可以用来重建温跃层结构。利用风与温跃层结构之间的紧密耦合，通过有孔虫代用资料提供的温跃层重建来推断风的变化。pi将首先建立一个热带浮游有孔虫氧同位素数据的全球数据库，这些数据来自最近的沉积物。利用这些数据，建立有孔虫钙化生境模型，量化钙化生境的不确定性。然后将探索各种统计方法，以确定如何从有孔虫代理数据中投影有关水柱垂直结构的稀疏信息到热带温跃层结构的估计中，并确定如何最佳地估计与给定平均温跃层状态相关的长期平均风。这些分析方法将包括经验正交函数、最优线性估计和逆方法。最后，将对这些物种的末次盛冰期氧同位素数据进行汇编。在数据分析工作的指导下，热带太平洋地区将增加新的测量数据。一旦末次冰期极大期有孔虫数据库完成，这些数据将直接与同位素支持的冰期气候环流模式模拟的结果进行比较，并使用上述开发的数据分析工具对热带太平洋温跃层结构和风进行估计。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。