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Branched glycerol dialkyl glycerol tetraethers (brGDGTs) have shown great promise in lacustrine temperature reconstructions across different continents. While brGDGTs have been reported from many different regions and global brGDGT-temperature calibrations have been developed with various methods, southern North America remains an understudied area with little available data. In this study, we analyzed 101 lake surface sediment samples across Mexico and Central America and compared their distributions with those in other lacustrine systems. Nine major brGDGTs were found in all samples. We investigated the relationships between the distribution of the fractional abundances of the nine major brGDGTs and temperature and developed regional calibrations for Mean Annual Temperature using three different approaches, including a novel machine learning method – Ridge Regression. All the regional calibrations provide similar results with very close error ranges (RMSE = 3.1 ◦C). The majority of global brGDGT-temperature calibrations tend to reconstruct lower temperatures when it is below 15 ◦C. Interestingly, regional brGDGT calibrations appear to reduce the “cold bias”, but the various global and regional calibrations tested here are not significantly different in their predictive capability.
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This content will become publicly available on March 1, 2026
The Branched GDGT Isomer Ratio Refines Lacustrine Paleotemperature Estimates
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane-spanning lipids synthesized by bacteria in numerous substrates. The degree of methylation of the five methyl brGDGTs in both soils and lake sediments, described by the MBT′5Me index, is empirically related to surface atmospheric temperature. This relationship in lakes is generally assumed to reflect lake surface temperatures captured by brGDGT production in the water column and exported to lake sediments, and the MBT′5Me index has been applied to brGDGTs in lake sediment successions to reconstruct changes in temperature through time. We analyzed the relationship between MBT′5Me and the isomerization of brGDGTs (IR6Me) in globally distributed surficial lake sediments and demonstrated that the relationship, and calibrations, of MBT′5Me and temperature in middle and high latitude lakes are sensitive to incompletely understood factors related to IR6Me. IR6Me does not appear to track a non-thermal influence of brGDGT methylation in tropical lakes, but this could change as the data set is expanded. We address ongoing challenges in the application of the MBT′5Me paleothermometer in middle and high latitude lakes with new MBT′5Me-temperature calibrations based on grouping lakes by IR6Me. We demonstrate how IR6Me can distinguish samples with a significant non-thermal influence on MBT′5Me by targeting anomalously warm temperatures during the Last Glacial Maximum from newly analyzed piston and gravity core samples from Lake Baikal, Russia.
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- Award ID(s):
- 2202918
- PAR ID:
- 10616559
- Publisher / Repository:
- Geochemistry, Geophysics, Geosystems
- Date Published:
- Journal Name:
- Geochemistry, Geophysics, Geosystems
- Volume:
- 26
- Issue:
- 3
- ISSN:
- 1525-2027
- Page Range / eLocation ID:
- e2024GC012069
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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