Sensitivity of ocean circulation to warming during the Early Eocene greenhouse.

Autor:	Kirtland Turner S; Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521., Ridgwell A; Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521., Keller AL; Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521., Vahlenkamp M; Center for Marine Environmental Sciences (MARUM), University of Bremen, Bremen 28359, Germany., Aleksinski AK; Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521.; Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, IN 47906., Sexton PF; School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom., Penman DE; Department of Geosciences, Utah State University, Logan, UT 84322., Hull PM; Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06511., Norris RD; Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093.
Jazyk:	angličtina
Zdroj:	Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2024 Jun 11; Vol. 121 (24), pp. e2311980121. Date of Electronic Publication: 2024 Jun 03.
DOI:	10.1073/pnas.2311980121
Abstrakt:	Multiple abrupt warming events ("hyperthermals") punctuated the Early Eocene and were associated with deep-sea temperature increases of 2 to 4 °C, seafloor carbonate dissolution, and negative carbon isotope (δ 13 C) excursions. Whether hyperthermals were associated with changes in the global ocean overturning circulation is important for understanding their driving mechanisms and feedbacks and for gaining insight into the circulation's sensitivity to climatic warming. Here, we present high-resolution benthic foraminiferal stable isotope records (δ 13 C and δ 18 O) throughout the Early Eocene Climate Optimum (~53.26 to 49.14 Ma) from the deep equatorial and North Atlantic. Combined with existing records from the South Atlantic and Pacific, these indicate consistently amplified δ 13 C excursion sizes during hyperthermals in the deep equatorial Atlantic. We compare these observations with results from an intermediate complexity Earth system model to demonstrate that this spatial pattern of δ 13 C excursion size is a predictable consequence of global warming-induced changes in ocean overturning circulation. In our model, transient warming drives the weakening of Southern Ocean-sourced overturning circulation, strengthens Atlantic meridional water mass aging gradients, and amplifies the magnitude of negative δ 13 C excursions in the equatorial to North Atlantic. Based on model-data consistency, we conclude that Eocene hyperthermals coincided with repeated weakening of the global overturning circulation. Not accounting for ocean circulation impacts on δ 13 C excursions will lead to incorrect estimates of the magnitude of carbon release driving hyperthermals. Our finding of weakening overturning in response to past transient climatic warming is consistent with predictions of declining Atlantic Ocean overturning strength in our warm future. Competing Interests: Competing interests statement:The authors declare no competing interest.
Databáze:	MEDLINE
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