Evaluating isoprenoidal hydroxylated GDGT-based temperature proxies in surface sediments from the global ocean
Varma, D.; Hopmans, E.C.; van Kemenade, Z.R.; Kusch, S.; Berg, S.; Bale, N.J.; Sangiorgi, F.; Reichart, G.-J.; Sinninghe Damsté, J.S; Schouten, S. (2024). Evaluating isoprenoidal hydroxylated GDGT-based temperature proxies in surface sediments from the global ocean. Geochim. Cosmochim. Acta 370: 113-127. https://dx.doi.org/10.1016/j.gca.2023.12.019
In: Geochimica et Cosmochimica Acta. Elsevier: Oxford,New York etc.. ISSN 0016-7037; e-ISSN 1872-9533, more
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| Authors | | Top |
- Varma, D.
- Hopmans, E.C., more
- van Kemenade, Z.R., more
- Kusch, S.
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- Berg, S.
- Bale, N.J., more
- Sangiorgi, F.
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- Reichart, G.-J., more
- Sinninghe Damsté, J.S, more
- Schouten, S., more
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| Abstract |
Recently developed temperature proxies based on hydroxylated isoprenoid Glycerol Dialkyl Glycerol Tetraethers (OH-isoGDGTs), such as %OH, RI-OH, RI-OH′ and OHC, have shown potential for reconstructing past temperature changes. However, progress has been limited by the lack of a global core-top calibration with ample geographical coverage. Here, we compile an extensive global surface sediment dataset of OH-isoGDGTs as well as regular isoprenoid GDGTs (isoGDGTs), with both data generated at NIOZ (n = 575) and previously published data from other laboratories (n = 297). We find interlaboratory differences for proxy indices that incorporate both OH-isoGDGTs and regular isoGDGTs, indicating that care must be taken in compiling large GDGT datasets from multiple laboratories. Our results confirm a strong temperature signal in the isoGDGT distribution, especially for OH-isoGDGT-0 and non-hydroxylated isoGDGTs, but also reveal that water depth might have an impact on the distribution of OH-isoGDGTs with 1 and 2 cyclopentane moieties. This will affect the RI-OH and RI-OH′ indices, particularly in tropical regions, where OH-isoGDGT-0 occurs at low abundance. We explore new proxy indices that combine the temperature dependence of both isoGDGT and OH-isoGDGT distributions and propose the use of TEX86OH, which includes OH-isoGDGT-0 in the denominator of the TEX86 index. This modification leads to a much higher temperature sensitivity of the index, especially in regions with annual mean sea surface temperatures between 5 and 15 °C. Application of this novel paleothermometer to a polar sediment core suggests that this proxy is likely to result in more reliable temperature reconstructions in polar regions where OH-isoGDGTs are abundant. |
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