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

热带地区风和降水的空间格局不是固定的，而是随时间变化的。这些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以外大片冰层的存在推动的。通过观察上一个冰河时代高峰期的这些模式，可以检验这些驱动因素与热带气候之间的联系。很难直接推断出冰河时代的风的模式。但当风吹到上层海洋时，它们在一些地区堆积温暖的水，在另一些地区使冷水更接近海面。在这个项目中，研究人员将使用包含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，保存了海洋温度的历史。从上一次冰河时代高峰时期落到海底的贝壳重建的上层海洋温度，然后可以用来推断风型。该项目将支持两名研究生(其中一名是来自代表性不足的少数民族的女性)，并为本科生夏季研究人员提供支持。PIS提出了一项数据库开发和分析计划，将利用热带表层和表层下浮游有孔虫的氧同位素组成中记录的关于温跃层结构的信息来重建热带温跃层和最后一次冰盛期期间的风。不同物种测试的同位素组成将反映地表和地下密度，并可用于重建温跃层结构。风和温跃层结构之间的紧密耦合将被用来通过由有孔虫代理数据提供的温跃层重建来推断风的变化。PIS将首先建立一个全球数据库，记录最近沉积物中的热带浮游有孔虫的氧同位素数据。利用这些数据，将建立有孔虫钙化生境模型，并对钙化生境的不确定性进行量化。然后将探讨各种统计方法，以确定如何将来自有孔虫替代数据的有关水柱垂直结构的稀少信息投射到热带温跃层结构的估计中，并确定如何以最佳方式估计与给定平均温跃层状态有关的长期平均风。这些分析方法将包括经验正交函数、最优线性估计器和逆方法。最后，将为这些相同物种汇编现有的最后一次冰川最大氧同位素数据。在数据分析工作的指导下，热带太平洋的数据库将用新的测量数据加以扩充。一旦最后一次冰川最大有孔虫数据库完成，这些数据将被直接与冰河时代气候的同位素启用的大气环流模型模拟的结果进行比较，还将被用来使用如上所述开发的数据分析工具来估计热带太平洋温跃层结构和风。该奖项反映了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。

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.