Influence of Mediterranean oceanographic and environmental conditions on molecular proxy‐based sea surface temperature reconstructions during the last interglacial
Obreht, I.; Wörmer, L.; Varma, D.; De Vleeschouwer, D.; Schulz, H.; Kucera, M.; Hinrichs, K.-U. (2025). Influence of Mediterranean oceanographic and environmental conditions on molecular proxy‐based sea surface temperature reconstructions during the last interglacial. Paleoceanography and Paleoclimatology 40(4): e2024PA004951. https://dx.doi.org/10.1029/2024pa004951
In: Paleoceanography and Paleoclimatology. American Geophysical Union: Washington DC. ISSN 2572-4525; e-ISSN 2572-4525, more
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| Author keywords |
GDGTs; UK´37; sapropel S5; mass spectrometry imaging; paleoclimate; SST; biomarkers |
| Authors | | Top |
- Obreht, I.
- Wörmer, L.
- Varma, D., more
- De Vleeschouwer, D., more
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- Schulz, H.
- Kucera, M.
- Hinrichs, K.-U.
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| Abstract |
We investigated the variability and phase relationship of two annually to subdecadally resolved sea surface temperature (SST) proxy records from the Mediterranean sapropel S5 deposited during the Last Interglacial. We compared our recently published alkenone-based SST record, considered to reliably represent surface temperature, with a newly generated record of archeal glycerol dialkyl glycerol tetraether (GDGTs). GDGT-based SST reconstruction in the Mediterranean Sea has been suggested to be affected by other parameters besides SST, and presumably represents subsurface temperature. Our investigation unveils notable differences between the two proxies; throughout most of the record, SST reconstructions derived from GDGTs and alkenones exhibit an anti-phase relationship in the multicentennial time band. This suggests that during sapropel deposition, centennial-scale alterations in the upper-ocean temperature gradient, plausibly due to water column stratification, influenced both compound classes. While we expect a direct, thermal driver for the alkenone ratio, the effect on the GDGT-based SST signal might have been mediated by ammonia oxidation rates that were positively correlated with changes in SST. A multidecadal comparison between GDGT- and alkenone-based SSTs reveals distinct behaviors of the two proxies under different oceanographic conditions, indicating that changing oceanographic and environmental dynamics significantly impacted short-term proxy variability. We demonstrate that during sapropel deposition in the Last Interglacial oceanographic, environmental and ecological factors played a crucial role in modulating the GDGT cyclization on both multidecadal and multicentennial time-scales, suggesting strong non-thermal forcing on GDGT-based SST reconstruction during Mediterranean sapropel deposition. |
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