EGU21-8362, updated on 03 Jan 2024
https://doi.org/10.5194/egusphere-egu21-8362
EGU General Assembly 2021
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Revised brGDGT fractional abundances and warm-season temperatures strengthen relationships between brGDGTs and environmental variables

Jonathan H. Raberg1,2, Aria Blumm1, David J. Harning1,2, Sarah E. Crump1, Greg de Wet1, Nadia Dildar1, Sebastian Kopf1, Áslaug Geirsdóttir2, Gifford H. Miller1, and Julio Sepúlveda1
Jonathan H. Raberg et al.
  • 1Institute of Arctic and Alpine Research, University of Colorado, Boulder, United States of America
  • 2Faculty of Earth Sciences, University of Iceland, Reykjavík, Iceland

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are an important tool for reconstructing terrestrial paleotemperatures from lake sediments. In addition to temperature, however, the distribution of these bacterial membrane lipids is influenced by other environmental variables such as pH, conductivity, and dissolved oxygen. Furthermore, though most brGDGT calibrations are performed against mean annual air temperature (MAT), there is considerable evidence that their distributions are more closely tied to warm-season conditions. Here, we present a new method for analyzing brGDGT data that deconvolves the influences of temperature, conductivity, and pH. Additionally, we measure brGDGT distributions in surface sediments from 43 high-latitude lakes with low MAT and high seasonality. In combination with a globally compiled lake sediment dataset, these samples show a clear warm-season bias in brGDGT-derived temperatures. They also show lake water conductivity to be the second-most important variable in controlling brGDGT distributions. We use the compiled dataset and new fractional abundances to generate brGDGT calibrations for warm-season air temperatures and lake water conductivity and pH for use in lake sediments globally.

How to cite: Raberg, J. H., Blumm, A., Harning, D. J., Crump, S. E., de Wet, G., Dildar, N., Kopf, S., Geirsdóttir, Á., Miller, G. H., and Sepúlveda, J.: Revised brGDGT fractional abundances and warm-season temperatures strengthen relationships between brGDGTs and environmental variables, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8362, https://doi.org/10.5194/egusphere-egu21-8362, 2021.

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