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

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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.