Collaborative Research: P2C2--Evaluating Controls on Holocene Glacier Fluctuations and Climate Variability in the Southern Peruvian Andes

该项目的主要目标是在秘鲁南部的科迪勒拉Vilcabamba地区建立准确的冰碛年龄，并量化全新世冰川对气候变化的敏感性，最终目标是阐明全新世热带地区的气候变化及其控制。在Vilcabamba的初步工作已经确定了全新世早期和“小冰期”期间显著的冰川推进，揭示了一系列与欧洲冰川记录广泛相关的事件。这些初步结果表明，热带和北大西洋地区之间存在气候遥相关，但需要更广泛的数据来确定区域冰川模式和全新世气候控制。该项目将在初步发现的基础上，利用宇宙成因10Be冰碛地表暴露年代法，重建Vilcabamba其他山谷的冰川历史，利用最近的方法进步，可以确定极年轻（200年）和精确的同位素年龄。补充14C年龄和古气候代理数据将从位于10万年冰碛之间的沼泽中恢复的沉积物岩心中获得。这些冰碛的独立14C年龄控制提供了开发10Be生产速率的新本地校准的潜力。古冰川物质平衡对特定气候变量规定变化的敏感性将通过冰川表面能量-物质平衡模式进行模拟来量化，从而可以估计温度、降水和太阳辐射等主要强迫对冰川范围的相对作用。将评估假定的气候变化机制与综合年龄控制和模拟结果的一致性程度，从而确定热带安第斯山脉全新世冰川和气候变率的可能驱动因素。更广泛的意义和重要性热带在触发、放大和传递全球气候信号中的作用仍然是气候科学中一个激烈争论的话题。对气候敏感的热带山地冰川过去波动的准确日期记录是反映过去气候变化及其原因的区域趋势的最佳指标之一。秘鲁拥有世界71%的人口？它包含了丰富的以前冰川扩张的地质证据。然而，该地区过去冰川波动的年表很少，特别是在全新世（过去~11,700年）。该项目的新结果将对理解秘鲁全新世冰川事件的时间和主要气候对冰川作用的影响作出重大贡献。重要的是，新的冰川年表将增加从附近冰芯、湖泊和海洋遗址以及其他新出现的冰川历史中发展出来的过去气候记录，有助于更全面地描述区域气候变化及其环境后果。因此，结果将允许对全新世期间热带气候变率的潜在原因进行严格的检查，包括与理解现代和未来气候变化相关的近期气候变化。更好地了解过去的安第斯冰川对于预测冰川对未来气候变化的反应和对当地水资源的影响，以及确定对该地区古代文明（包括印加和前印加社会）的环境影响至关重要。这项研究将为新罕布什尔大学和哥伦比亚大学的本科生和研究生提供实地技术、实验室方法和数值模拟方面的培训。该项目还将扩大美国早期职业科学家与加拿大和秘鲁合作者之间富有成效的合作。这个多国项目团队的集合将加强每个参与机构的研究计划、设施和外展活动的发展。研究活动还将通过改进实验室方法来促进技术发展，这些方法旨在提高广泛使用的同位素定年方法的精度。

Technical description of the projectThe main objectives of this project are to develop accurate and precise moraine ages in the Cordillera Vilcabamba of southern Peru, and to quantify the sensitivity of Holocene glaciers to climate changes, with the ultimate goal of elucidating Holocene climate variability and controls in the tropics. Initial work in the Vilcabamba has identified prominent glacial advances during the early Holocene and the 'Little Ice Age' interval, revealing a sequence of events that is broadly correlative with glacial records in Europe. These pilot results suggest climate teleconnections between the tropics and the North Atlantic region, but a more extensive array of data is needed to confidently identify regional glacial patterns and Holocene climate controls. This project will build substantially on initial findings by reconstructing glacial histories in additional valleys in the Vilcabamba using cosmogenic 10Be surface exposure dating of moraines, taking advantage of recent methodological advances that allow determination of extremely young (200 year) and precise isotopic ages. Supplementing 14C ages and paleoclimate proxy data will be obtained from sediment cores recovered from bogs situated between 10Be-dated moraines. Independent 14C age control for these moraines offers the potential to develop a new local calibration of the 10Be production rate. The sensitivity of paleo-glacier mass balances to prescribed changes in specific climatic variables will be quantified by performing simulations with a glacier surface energy-mass balance model, thus allowing an estimation of the relative roles of major forcings such as temperature, precipitation, and solar radiation on glacier extent. Posited mechanisms of climate change will be assessed for their degree of consistency with the integrated age control and modeling results, enabling identification of likely drivers of Holocene glaciations and climate variability in the tropical Andes.Broader significance and importanceThe role of the tropics in triggering, amplifying, and transmitting global climate signals remains a topic of vigorous debate in climate science. Accurately dated records of past fluctuations in climatically sensitive tropical mountain glaciers are among the best indicators of regional trends in past climate changes and their causes. Peru harbors 71% of the world?s present-day tropical glaciers, and contains abundant geologic evidence of former glacier expansions. However, chronologies of past glacier fluctuations in this region are scarce, particularly during the Holocene epoch (the past ~11,700 years). New results from this project will contribute significantly toward an understanding of both the timing of Holocene glacier events in Peru and the predominant climatic influences on glaciation. Importantly, the new glacier chronologies will augment records of past climates developed from nearby ice core, lake, and marine sites as well as other emerging glacial histories, contributing to a more comprehensive characterization of regional climate changes and their environmental consequences. Results will thus allow for a rigorous examination of the underlying causes of tropical climate variability during the Holocene, including recent climate shifts relevant to understanding modern and future climate change.An improved understanding of past Andean glaciations is crucial for predicting glacier responses to future climate change and consequences for local water resources, and for identifying environmental impacts on ancient civilizations in the region, including Inca and pre-Inca societies. This study will provide training in field techniques, laboratory methods, and numerical modeling for undergraduate and graduate students at the University of New Hampshire and Columbia University. The project will also expand on a productive collaboration between early career U.S. scientists and collaborators in Canada and Peru. Assembly of this multinational project team will enhance the development of research programs, facilities, and outreach activities at each participating institution. Research activities will also contribute to technique development by refining laboratory methods aimed at increasing the precision of widely used isotopic dating methods.