P2C2: Collaborative Research: Transient forcing of the Local Last Glacial Maximum in the tropical Peruvian Andes

热带冰川的地质历史可以为科学家提供一个重要的视角，从过去的地球气候系统如何响应人类活动。该项目将研究安第斯山脉热带冰川的地质记录，以了解过去冰川范围的变化，以及这些变化如何与气候突变期间大气条件变化的记录有关。这些冰川活动的记录将有助于将热带地区冰缘快速退缩的现状置于一个长期的背景下，远远超出仪器记录的范围。最后，通过整合过去气候的多个档案并模拟热带高海拔气候变化的原因，这项工作将提高我们对全球气候突变的理解，因为这些地区过去有更大的冰川。通过确定古代冰川搬运的岩石的年龄，并结合对冰川下连续沉积的湖泊沉积物的分析，这项研究将提供冰川变化程度和时间的详细记录。研究小组将结合气候模型模拟来测试热带气候变化的原因以及它们与高纬度变暖和变冷事件的关系。本项目将培养3名研究生，至少4名本科生。项目团队将通过地球仪计划（全球学习和观察以造福环境），让教师和学生（本地和国外）参与研究，从而改善K-12科学教育和参与。该团队还将与秘鲁的INAIGEM合作，扩大项目影响，并帮助完成教育能力建设的使命。该项目将评估当地末次盛冰期（LLGM）期间的热带冰川变化，以更好地了解低纬度温度变化和水文循环如何受到海洋和大气过程的调制。这项研究有以下目标：1）使用陆地宇宙成因放射性核素（TCN）测年方法确定冰碛的可靠年龄，以提供有关多个LLGM冰限的时间和范围的信息; 2）使用最近获得的胡宁湖钻孔岩芯记录的高分辨率地球化学档案，严格评估冰粉通量的百年尺度记录; 3）利用气候模式模拟测试LLGM气候变率的尺度和气候强迫; 4）利用能量和质量平衡模式测试LLGM冰川变率对气候强迫响应的尺度。这项研究将产生秘鲁山区冰川作用的多代理、百年尺度记录，其规模和分辨率尚未达到LLGM。这一分辨率将足以与格陵兰、南极和热带安第斯山脉的冰芯以及同一流域（胡宁湖）水文气候变化的十年尺度洞穴沉积稳定同位素记录进行比较。这将允许对山区冰川档案和过去大气变化的其他区域记录进行集体评估，这将提高我们对热带地区在千年时间尺度上全球突变事件中的作用的理解。这些记录将提供有关热带冰川对一系列气候条件（包括大气和海洋）的敏感性的见解，特别是热带气候系统如何对融水强迫作出反应。最终，这些记录将告知热带水文循环如何驱动低纬度和高纬度地区的冰川-间冰期循环。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标准进行评估，被认为值得支持。

The geological history of tropical glaciers can provide scientists an important perspective from the past on how Earth’s climate system responds to human activity. This project will look to the geological record of tropical glaciers in the Andes Mountains for a perspective on past changes in the glacial ice extent and how these changes may relate to records of changes in the atmospheric conditions during periods of abrupt climate change. These records of glacial activity will help place the current state of rapidly retreating ice margins in the tropics in a longer-term context that extends well beyond the instrumental record. Finally, by integrating multiple archives of past climates and modeling the causes of tropical high elevation climate changes, this work will improve our understanding of abrupt global climate changes because these regions had much larger glaciers in the past. By determining ages on the rocks that were transported by the ancient glaciers and combining analyses of lake sediments deposited continuously below the glaciers, this research will provide a detailed record of how much the glaciers changed and when. The research team will incorporate climate model simulations to test the causes of tropical climate changes and how they relate to high latitude warming and cooling events. This project will train 3 graduate students, and at least 4 undergraduate students. The project team will improve K-12 science education and engagement by exposing teachers and students (both local and abroad) to research through the GLOBE program (Global Learning and Observation to Benefit the Environment). The team also will partner with INAIGEM in Peru to broaden project impact, and help with the mission of educational capacity building. This project will evaluate tropical glacial variability during the local Last Glacial Maximum (LLGM) to better understand how low latitude temperature variability and the hydrologic cycle were modulated by ocean and atmospheric processes. This research has the following objectives: 1) determine robust ages of moraines using terrestrial cosmogenic radionuclide (TCN) dating methods to provide information about both the timing and extent of multiple LLGM ice limits; 2) rigorously evaluate centennial-scale records of glacial flour flux using high-resolution geochemical archives from the recently acquired Lake Junín drill-core record; 3) test the scale and climatic forcing of LLGM climate variability using climate model simulations; 4) test the scale of LLGM glacier variability responses to climatic forcing using energy and mass-balance models. This research will produce multi-proxy, centennial-scale records of mountain glaciation in Peru spanning the LLGM, at a scale and resolution that has not yet been achieved. This resolution will be sufficient to make comparisons with ice cores from Greenland, Antarctica, and the tropical Andes, as well as decadal-scale speleothem-based stable isotope records of hydroclimate changes from the same (Lake Junín) catchment. This will allow for a collective evaluation of mountain glacier archives and other regional records of past atmospheric variability that will improve our understanding of the role of the tropics in abrupt global change events on millennial timescales. These records will provide insight on the sensitivity of tropical glaciers to a range of climate conditions, both atmospheric and oceanic, and particularly how the tropical climate system responds to meltwater forcing. Ultimately, these records will inform how the tropical hydrologic cycle drives glacial-interglacial cycles in both the low and high latitudes.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.