Extreme deep-sea warmth supports high climate sensitivity in the early Eocene hothouse

This is a Preprint and has not been peer reviewed. This is version 2 of this Preprint.

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Authors

Tobias Agterhuis, Martin Ziegler, Lucas Joost Lourens

Abstract

The early Eocene (56–48 Ma) hothouse experienced the highest CO2 levels of the Cenozoic, as well as the occurrence of multiple transient global warming events, so-called hyperthermals. The deep ocean constitutes a stable and vast heat reservoir in the climate system, and hence compromises a robust setting to estimate past global mean temperatures. However, available deep-sea temperature reconstructions rely on uncertain assumptions of non-thermal influences. Here, we apply for the first time the carbonate clumped isotope paleothermometer (Δ47), a proxy not governed by these uncertainties, on early Eocene benthic foraminifera to evaluate South Atlantic deep-sea temperatures across two hyperthermal events (ETM2 and H2; ~54 Ma). In comparison to the conventional δ18O-based estimates, our new temperature reconstructions indicate two and a half degrees warmer deep water conditions, i.e. 13.2±1.9 °C (95% Confidence Interval) for background state, and average deep-sea warming of 3.3±2.9 °C (95% CI) during these hyperthermal events. These findings imply a reassessment of the assumed isotope composition of the ancient seawater and of a potential pH effect on foraminiferal oxygen isotopes. On a broad scale, our Δ47-based overall warmer deep-sea temperatures provide new evidence for high climate sensitivity during the early Eocene hothouse.

DOI

https://doi.org/10.31223/X5NC9H

Subjects

Earth Sciences, Geochemistry

Keywords

clumped isotopes, oxygen isotopes, paleoclimate, hyperthermals, deep-sea temperatures, benthic foraminifera

Dates

Published: 2021-06-08 20:31

Last Updated: 2021-06-09 03:31

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License

CC BY Attribution 4.0 International

Additional Metadata

Data Availability (Reason not available):
Data will be made available upon publication of the pre-print in the respective or another journal

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