Collaborative Research: P2C2--What is the Driver of Orbital-Scale Central American Monsoon Variations? Tests of the Insolation and Sea Surface Temperature Hypotheses

该项目的目的是从危地马拉加勒比海岸的一个洞穴中产生跨越14万年或更长时间的最后一个冰川期的轨道时间尺度洞穴沉积物同位素记录。 Rey Marcos洞穴已经产生了概念验证数据，可以从理想的地球化学特征和平衡同位素值中获得高精度的铀系年龄。 来自过去15，000年石笋的初步数据显示，中美洲季风在大约9，200年前加强，与加勒比海海面温度（SST）和危地马拉陆地表面温度的增加相一致。 一个强大而稳定的季风的特点，其余的全新世在对比的季风减弱所产生的减少从Cariaco盆地推断的日照。 研究人员假设，对中美洲季风的主要强迫是SST变化，轨道日射是次要的、不太重要的强迫。该项目将在轨道时间尺度上对SST与轨道强迫假设进行新的测试。 此外，这项工作将记录过去气候事件的时间和持续时间，如当前和最后一次间冰期，海因里希stadials产生的千年尺度变化的影响，大西洋纬向翻转环流的变化，以及高到低纬度表现的Dansgaard/Oeschger事件。概念验证数据不同于其他区域记录，这些记录记录了与轨道和北大西洋来源的千年变化的联系，例如墨西哥中美洲季风的洞穴沉积物记录和Cariaco盆地的海洋沉积物。 重建的季风行为的区域异质性突出了需要额外的高分辨率和精确的日期记录从加勒比海斜坡上的轨道时间尺度。 这些解释将与CMIP 5/6和PMIP 3/4模式运行的模式输出进行比较，以更深入地了解控制中美洲季风的主导机制以及外部强迫和内部产生的变率的相对作用。培训两名来自任职人数不足的少数民族的研究生，（英文/西班牙文）技能，以便利在中美洲的工作;该奖项反映了NSF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进行评估，被认为值得支持的搜索.

This project aims to generate orbital-timescale speleothem isotopic records spanning the last glacial period, 140,000 years or longer, from a cave on the Caribbean coast of Guatemala. Rey Marcos cave has yielded proof-of-concept data that allows for high-precision Uranium-series ages resulting from ideal geochemical characteristics and equilibrium isotopic values. Preliminary data from a stalagmite spanning the last 15,000 years shows that the Central American monsoon strengthened at approximately 9,200 years ago coincident with increased Caribbean Ocean sea surface temperatures (SSTs) and land surface temperatures in Guatemala. A strong and stable monsoon characterizes the rest of the Holocene in contrast to the monsoon weakening over the Holocene arising from decreasing insolation inferred from the Cariaco Basin. The researchers hypothesize that the dominant forcing on the Central American monsoon is SST change and that orbital insolation is a secondary and less important forcing.The project will enable a new test of the SST versus orbital forcing hypotheses on orbital timescales. Further, the work will document the timing and duration of past climate events like the current and last interglacials, the influence of millennial-scale variability arising from Heinrich stadials, changes in the meridional overturning circulation of the Atlantic Ocean, and high-to-low latitude manifestations of Dansgaard/Oeschger events. The proof of concept data differ from other regional records which have documented links to orbital and North Atlantic sourced millennial variability, such as speleothem records of the Mesoamerican monsoon from Mexico and marine sediments from the Cariaco Basin. The regional heterogeneity in reconstructed monsoon behavior highlights the need for additional high-resolution and precisely dated records from the Caribbean slope on orbital timescales. The interpretations will be compared with model output from the CMIP 5/6 and PMIP 3/4 model runs to gain deeper insights about the dominant mechanisms governing the Central American monsoon and about the relative role of externally-forced and internally-generated variability.The potential Broader Impacts include furthering the understanding of natural climate variability; development of educational materials related to caves; training of two graduate students from underrepresented minorities with bi-lingual (English/Spanish) skills to facilitate work in Central America; and stakeholder participation with the local Guatemalan communities hosting the cave sites.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.