Collaborative Research: Timing and structure of the last glacial maximum and termination in southern Peru: Implications for the role of the tropics in climate change

热带在气候变化中的作用对于理解轨道尺度和气候突变都具有重要意义。然而，我们评估重大气候事件期间热带行为的能力，如最后一次冰川最大值(LGM)，受到空间覆盖率低和对样本年龄控制不足的限制。该项目将解决这一问题，办法是在秘鲁南部的内瓦多斯、科罗普纳和阿林卡帕克建立从末次冰期到末次冰期和冰后期冰川波动的准确记录，并将这些数据用于冰川物质平衡和当地气候的数值模拟。这些遗址允许研究从干旱(科罗波纳)到潮湿(阿林卡帕克)安第斯山脉的横断面上的冰川变化以及同时代的雪线变化，从而记录了重大气候事件在环境截然不同的地区可能是如何表现出来的。这项工作包括：冰雹的详细测绘；从冰雹峰顶和漂移边缘精心挑选的巨石的精确表面暴露年龄测定(3He和10Be)；散布在冰雹之间的沼泽的基本14C年龄；计算以前的雪线洼地；以及模拟冰川质量平衡变化与气候之间的关系。这项工作将是理解热带行为的重要一步，最终将使人们能够彻底检验米兰科维奇关于热带冰河时代的假说。博士后影响：这项研究教育和培训学生、博士后和最近的女性博士。阿雷基帕大学的生态旅游专业学生有一系列关于当地地质学和全球气候变化的讲座，利马考古系也有讲座。K-12年级的学生通过与缅因州农村地区的教室建立长期的联系而受益，缅因州的农村地区通常经济状况较差。该项目维护了一个网站，并正在探索一个学习模块。此外，这项研究是一项联合倡议的一部分，该倡议旨在了解秘鲁高地上第一批美国人的土地使用和定居模式。

The role of the tropics in climate change has important implications for understanding both orbital-scale and abrupt climate variations. Yet our ability to assess tropical behavior during major climate events, such as the last glacial maximum (LGM), is limited by poor spatial coverage and insufficient control on sample ages. This project will address this problem by developing well-dated records of glacial fluctuations from the LGM through the termination and late-glacial period at Nevados Coropuna and Allinccapac in southern Peru and use these data in numerical simulations of glacier mass balance and local climate. These sites allow an examination of glacier variations, as well as coeval snowline changes, along a transect from the arid (Coropuna) to the humid (Allinccapac) Andes and thus document how major climate events may have been expressed in areas with distinctly different environments. This work consists of detailed mapping of moraines; precise surface-exposure age dating (3He and 10Be) of carefully selected boulders from moraine crests and drift edges; basal 14C ages of bogs interspersed among moraines; calculation of former snowline depression; and modeling of the relationship between glacier mass-balance changes and climate. The work will be an important step towards understanding tropical behavior and will finally allow a thorough testing of the Milankovitch hypothesis of ice ages in the tropics.Broader Impacts: This research educates and trains students, a postdoc, and a recent female Ph.D. There is a lecture series on local geology and global climate change given to eco-tourism students at the University of Arequipa, as well as lectures to the Lima archaeology department. K-12 students benefit through a long-standing associations with classrooms in rural, commonly economically disadvantaged Maine. The project maintains a website and is exploring a learning module. In addition, the research is part of a joint initiative to understand land use and settlement patterns of the first Americans in the Peruvian highlands.