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突变气候变化具有重要意义。然而，我们在重大气候事件（如末次盛冰期）期间评估热带行为的能力受到空间覆盖不足和对样本年龄控制不足的限制。本项目将通过在秘鲁南部的内华达·科罗普纳和阿林卡帕克建立从LGM到冰期终止和晚期的冰川波动的准确年代记录来解决这一问题，并将这些数据用于冰川质量平衡和当地气候的数值模拟。这些地点可以检查冰川变化，以及同时期的雪线变化，沿着从干旱（科罗普纳）到潮湿的安第斯山脉（Allinccapac）的样带，从而记录重大气候事件如何在截然不同的环境中表达。这项工作包括详细绘制冰碛；从冰碛峰和漂移边缘精心挑选的巨石精确地表暴露年龄（3He和10Be）；分布在冰碛间的沼泽的基本14C年龄；原雪线洼地计算；以及冰川质量平衡变化和气候之间关系的建模。这项工作将是理解热带行为的重要一步，并最终允许对米兰科维奇热带冰河期假说进行彻底的测试。更广泛的影响：这项研究教育和培训学生，博士后和最近的女性博士。有一个关于当地地质学和全球气候变化的系列讲座给阿雷基帕大学生态旅游专业的学生，以及利马考古系的讲座。K-12学生通过长期与缅因州农村地区的教室联系而受益，这些地区通常经济上处于不利地位。该项目维护着一个网站，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利用和定居模式。

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.