Development of Precipitation, Evaporation and Temperature Records from Tropical Lake Sediments and Cave Deposits for the last 700,000 years

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).The influence of increasing global temperatures on people and ecosystems varies across the world. In tropical regions, the impact is felt mostly in terms of water availability. Deposits preserved in caves and lakes provide key insights into how tropical environments responded to past climate change. This study will build a 700 thousand year-long record from cave deposits and lake sediments in Peru to understand how a changing global climate affects precipitation, temperature and humidity in the upper reaches of the Amazon Basin. The findings from this work will apply to understanding the impacts of climate change in this region and extend globally, as the Amazon is home to the world’s largest rainforest and an important regulator of the global carbon cycle. This project will integrate researchers at three research universities and one undergraduate liberal arts college. Undergraduate students will interface with graduate students through all aspects of the proposed work, and a postdoctoral fellow will be based at the liberal arts institution and will work with teams at the research universities. In addition, scientists will collaborate with faculty and students in Peru to establish a monitoring program for regional caves, lakes and precipitation, and on a public outreach program aimed at climate change education led by community members. Researchers will expand participation of underrepresented minority students in the Earth sciences through development of a hands-on hydrology and climate change module as part of the University of Michigan Earth Camp, an experiential learning program for high school students.Researchers will combine analyses of a suite of paleoclimate proxies using both the 700,000 year-long Lake Junín sediment record and deposits from nearby caves, to produce a near-continuous, composite record of precipitation-evaporation balance and temperature for the upper Amazon Basin for the last 700,000 years. The National Science Foundation and the International Continental Drilling Program funded the successful collection of the Lake Junín drill core in 2015, and the cave deposits were collected in 2019 using university funds. Researchers will combine the well-dated Lake Junín drill core with a composite speleothem (cave) record dated by precise U-Th geochronology, and will use these archives to build records of precipitation, evaporation, and temperature, that will enable synthesis of our new data with existing records to investigate coupled climate systems in the Amazon Basin (monsoon strength and Atlantic meridional overturning circulation), climate sensitivity under different boundaryconditions, and hydrologic change during periods of large and rapid changes in forcing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.