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https://doi.org/10.5194/cp-2020-13
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2020-13
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 21 Feb 2020

Submitted as: research article | 21 Feb 2020

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This preprint is currently under review for the journal CP.

Late Paleocene – early Eocene Arctic Ocean Sea Surface Temperatures; reassessing biomarker paleothermometry at Lomonosov Ridge

Appy Sluijs1, Joost Frieling1, Gordon N. Inglis2,a, Klaas G. J. Nierop1, Francien Peterse1, Francesca Sangiorgi1, and Stefan Schouten1,3 Appy Sluijs et al.
  • 1Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Princetonlaan 8a, 3584 CB Utrecht, the Netherlands
  • 2Organic Geochemistry Unit, School of Chemistry, School of Earth Sciences, University of Bristol, Bristol, UK
  • 3NIOZ RoyalInstitute for Sea Research, Department of Microbiology and Biogeochemistry, and Utrecht University, PO Box 59, 1790AB Den Burg, the Netherlands
  • apresent address: School of Ocean and Earth Science, University of Southampton, UK

Abstract. The Integrated Ocean Drilling Program Arctic Coring Expedition on Lomonosov Ridge, Arctic Ocean (IODP Expedition 302 in 2004) delivered the first Arctic Ocean sea surface temperature (SST) and land air temperature (LAT) records spanning the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) to Eocene Thermal Maximum 2 (ETM2; ~54 Ma). The distribution of glycerol dialkyl glycerol tetraether (GDGT) lipids indicated elevated SST (ca. 23 to 27 °C) and LATs (ca. 17 to 25 °C). However, recent analytical developments have led to: (i) improved temperature calibrations and (ii) the discovery of new temperature-sensitive glycerol monoalkyl glycerol tetraethers (GMGTs). Here, we have analyzed GDGT and GMGT distributions in the same sediment samples using new analytical procedures, interpret the results following the currently available proxy constraints and assess the fidelity of new temperature estimates in our study site.

The influence of several confounding factors on TEX86 SST estimates, such as variations in export depth and input from exogenous sources, are typically negligible. However, contributions of isoGDGTs from land, which we characterize in detail, complicate TEX86 paleothermometry in the late Paleocene and part of the interval between the PETM and ETM2. The isoGDGT distribution further supports temperature as the likely variable controlling TEX86 values and we conclude that background early Eocene SSTs generally exceeding 20 °C, with peak warmth during the PETM (~26 °C) and ETM2 (~27 °C). We also report high abundances of branched glycerol monoalkyl glycerol tetraethers throughout (branched GMGTs), most likely dominantly marine in origin, and show that their distribution is sensitive to environmental parameters. Further analytical, provenance and environmental work is required to test if and to what extent temperature may be an important factor.

Published temperature constraints from branched GDGTs and terrestrial vegetation also support remarkable warmth in the study section and elsewhere in the Arctic basin, with vegetation proxies indicating coldest month mean temperatures of 6–13 °C. If TEX86-derived SSTs truly represent mean annual SSTs, the seasonal range of Arctic SST was in the order of 20 °C, higher than any open marine locality in the modern ocean. If SST estimates are skewed towards the summer season, seasonal ranges were comparable to those simulated in future ice-free Arctic Ocean scenarios. This uncertainty remains a fundamental issue, and one that limits our assessment of the performance of fully-coupled climate models under greenhouse conditions.

Appy Sluijs et al.

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Latest update: 29 Mar 2020
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Short summary
We revisit 15-year old reconstructions of sea surface temperatures of the Arctic Ocean for the late Paleocene and early Eocene epochs (~57–53 million years ago), based on the distribution of fossil membrane lipids of archaea, preserved in Arctic Ocean sediments. We find that improvements in the methods over the past 15 years do not lead to different results. However, data quality is now higher and potential biases better characterized. Results confirm remarkable Arctic warmth during this time.
We revisit 15-year old reconstructions of sea surface temperatures of the Arctic Ocean for the...
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