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

项目技术说明本项目的主要目标是在秘鲁南部的Cordillera Vilcabamba确定准确和精确的冰碛年龄，并量化全新世冰川对气候变化的敏感性，最终目的是阐明热带地区全新世气候变化和控制。在比尔卡班巴的初步工作已经确定了在全新世早期和“小冰期”间隔期间的突出冰川进展，揭示了一系列与欧洲冰川记录广泛相关的事件。这些试验结果表明热带和北大西洋地区之间的气候遥相关，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。该项目将在初步调查结果的基础上，利用冰碛物的宇宙成因10 Be表面暴露测年法，重建比尔卡班巴其他山谷的冰川历史，并利用最新的方法学进展，确定极年轻（200年）和精确的同位素年龄。补充14 C年龄和古气候代用数据将获得从位于10 Be-定年冰碛之间的沼泽中回收的沉积物岩心。独立的14 C年龄控制这些冰碛提供了一个新的本地校准的10 Be生产率的潜力。古冰川物质平衡对特定气候变量的规定变化的敏感性将通过使用冰川表面能量-物质平衡模型进行模拟来量化，从而能够估计温度、降水和太阳辐射等主要作用力对冰川范围的相对作用。气候变化的定位机制将评估其程度的一致性与综合年龄控制和建模结果，使识别可能的驱动程序全新世冰川和气候变率在热带安第斯山脉。更广泛的意义和importanceThe热带地区的作用，在触发，放大和传递全球气候信号仍然是一个激烈的辩论在气候科学的话题。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%的港口？它是现今的热带冰川，并包含了丰富的地质证据，以前的冰川扩张。然而，该地区过去冰川波动的年表很少，特别是在全新世时期（过去约11，700年）。该项目的新成果将大大有助于了解秘鲁全新世冰川事件的时间和对冰川作用的主要气候影响。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兴冰川历史发展的过去气候记录，有助于更全面地描述区域气候变化及其环境后果。因此，研究结果将有助于对全新世期间热带气候变化的根本原因进行严格的研究，包括与理解现代和未来气候变化相关的最近气候变化，对过去安第斯冰川的更好理解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该地区古代文明的环境影响至关重要，包括印加和前印加社会。本研究将为新罕布什尔州大学和哥伦比亚大学的本科生和研究生提供现场技术、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。这个多国项目小组的组装将加强每个参与机构的研究计划，设施和推广活动的发展。研究活动还将通过改进旨在提高广泛使用的同位素测年方法的精确度的实验室方法，促进技术发展。

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.