Testing amino acid paleothermometry in radiocarbon-dated lake sediment

Northern Arizona University, Flagstaff AZ

Investigators

Abstract

Testing amino acid paleothermometry in radiocarbon-dated lake sediment Climate change poses a major challenge for society. More information is needed to put recent climate changes into a long-term context of natural climate variability. This information helps to foresee possible future climate trends, especially those that involve slow-moving features of the climate system, which will continue to evolve over hundreds to thousands of years to come. A variety of geological evidence can be used to extend observations of temperature and other climate variables back in time. This project focuses on developing a new method of estimating temperature changes extending back thousands of years by using amino acids contained in lake sediment. The extent to which these molecules have been degraded depends largely on the temperature of the environment in which they have been stored and the length of time since they were formed. This project will use laboratory experiments to determine the temperature sensitivity of different degradation reactions coupled with radiocarbon dating to determine the age of the enclosing lake sediment. Funding will also be used to sustain the shared use of the Amino Acid Geochronology Laboratory at Northern Arizona University, which is the only one of its type in the United States. The project will also prepare undergraduate and graduate students for careers in the STEM workforce. Developing new methods to quantify past temperature is a high priority for climate science. The extent to which amino acids (AAs) in geologic settings have been chemically altered is primarily determined by the length of time elapsed since the molecules formed and by the ambient post-depositional temperature. Coupled with independent age control though radiocarbon (14C) dating, chemical reactions involving AAs can been used to quantify the timing and magnitude of past temperature changes. AAs are abundant in lake sediment, which has generally accumulated continuously in lakes over thousands of years, and thereby can be analyzed in detailed time series from widely distributed sites. This project will generate the first major AA dataset on 14C-dated and laboratory heated lake sediment. This project builds on a growing number of studies of AAs in lake sediment and it takes advantage of NSF-supported lake-core community resources. This award will sustain the Amino Acid Geochronology Laboratory as research infrastructure, enabling it to continue its long tradition of training users, offering pilot-study analyses, and assisting with data interpretation and curation. This project will also support STEM graduate and undergraduate students. 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.