Temperature and water depth effects on brGDGT distributions in sub-alpine lakes of mid-latitude North America

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1016/j.orggeochem.2020.104174. This is version 4 of this Preprint.

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Authors

Ioana Cristina Stefanescu, Bryan N Shuman, Jessica E. Tierney

Abstract

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) in lake sediments are increasingly being used to reconstruct past temperatures. However, recent studies suggest that brGDGT distributions and concentrations vary with lake size and environmental conditions such as seasonality and its effects on water column temperature and chemistry. To test their use as a paleothermometer in high-altitude environments of mid-latitude North America, we analyzed brGDGT distributions in lake surface sediments across a range of lake depths and elevations in the Rocky Mountains of Wyoming and Colorado. Our results suggest that brGDGT distributions and the MBT’5Me index correlate with water column temperatures, which are sensitive to both lake water depth and air temperatures. Based on these relationships, we developed a calibration to mean summer air temperatures using a Bayesian regression model that incorporates the MBT’5Me index and lake water depth. We applied our calibration to lake sediments from Lower Paintrock Lake in northern Wyoming to test its use as a paleothermometer. Reconstructed temperature trends are consistent with pollen-inferred temperatures at the same site and with known regional climate history, demonstrating that our calibration can be successfully applied to infer temperatures in high-altitude environments of mid-latitude North America.

DOI

https://doi.org/10.31223/X5188H

Subjects

Earth Sciences, Environmental Sciences, Physical Sciences and Mathematics

Keywords

5- and 6-methyl brGDGTs, temperature calibration, mid-latitude

Dates

Published: 2021-02-01 01:12

Last Updated: 2021-02-06 06:04

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License

CC BY Attribution 4.0 International

Additional Metadata

Data Availability (Reason not available):
http://dx.doi.org/10.15786/20.500.11919/7164

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