Orbitally Paced Carbon and Deep‐Sea Temperature Changes at the Peak of the Early Eocene Climatic Optimum

Abstract

The late Paleocene to early Eocene warming trend was punctuated by a series of orbitally paced transient warming events, associated with the release of isotopically light carbon into the ocean-atmosphere system. These events occurred throughout the early Eocene, critically persisting during onset, peak, and termination of the early Eocene climatic optimum (EECO) and the onset of the middle Eocene cooling. Here we present a~5.2-Myr-long high-resolution benthic foraminiferal stable-isotope record spanning the peak of the early Eocene "hothouse" from Ocean Drilling Program Leg 208 Site 1263. Our new oxygen isotope record confirms the presence of short-term warming events during the peak and termination of the EECO, previously described in coeval bulk carbonate records. The degree of change between deep-sea temperature and concurrent carbon release during these events is consistent with previous findings for Eocene thermal maximum 2 to 3, suggesting that the orbitally forced processes that triggered these perturbations in the exogenic carbon pool were similar. Additionally, the long-term background carbon isotope signature reveals a rapid enrichment of up to~1.0‰ across the peak warmth of the EECO,~51.6 Ma, without a corresponding shift in the oxygen record, suggesting a decoupling from climate. We speculate that this carbon shift reflects a non-recurrent adjustment in the mean (steady) state of the deep-ocean carbon reservoir due to a significant change in carbon source/sink, the biological pump, and/or ocean circulation during the extreme greenhouse conditions of the EECO.

The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database

“…3). This is consistent with the global benthic δ 18 O record, in which cooling begins at ~50 Ma (Zachos et al, 2008;Cramer et al, 2009;Kirtland-Turner et al, 2014;Lauretano et al, 2015Lauretano et al, , 2018. At mid-Atlantic ODP Site 1258, the termination of the EECO is placed at the base of a positive shift in benthic δ 18 O that follows a hyperthermal event identified as CIE C22nH3 (Sexton et al, 2011).…”

EoceneAraucariaSect.Eutactafrom Patagonia and floristic turnover during the initial isolation of South America

“…Conifer taxa previously described from the Eocene fossil caldera‐lake deposits of Laguna del Hunco (~52.2 Ma), Chubut, Argentina, and Río Pichileufú (~47.7 Ma), Río Negro, Argentina (Fig. ; Berry, ; Wilf et al., , ; Wilf, ; Wilf et al., 2017a, b), illustrate a complex biogeographic history of Old World (mostly Australasian/SE Asian) and New World survival patterns following the early Cenozoic isolation of Antarctica and onset of global cooling (Zachos et al., ; Lauretano et al., ).…”

“…Laguna del Hunco preserves a highly diverse late Gondwanan flora (Wilf et al., , ; Appendix S1) from the early Eocene climatic optimum (EECO), the longest period of sustained warmth in the Cenozoic (~53–49 Ma; Zachos et al., ; Lauretano et al., ). In that greenhouse world, the westernmost edge of a frost‐free, trans‐Antarctic, mesothermal rainforest biome reached into southern South America via a close connection between Patagonia and Antarctica (e.g., Hill, ; Wilf et al., ; Kooyman et al., ).…”

Astronomical Time Keeping of Earth History: An Invaluable Contribution of Scientific Ocean Drilling

“…Paleoclimate records from the Paleogene greenhouse world provide a unique opportunity to constrain Earth's climate system behavior under similar atmospheric CO 2 concentrations projected for the year 2100, and to investigate in detail the causal relationships between astronomical forcing and climatic/cryospheric and carbon cycle responses. Within the Paleogene, the Paleocene and Eocene Epochs (~66-34 million years ago) were generally characterized by warm "greenhouse" climates, reaching peak temperatures during the Early Eocene Climatic Optimum (EECO; Zachos et al, 2008;Lauretano et al, 2018) and punctuated by orbitally paced "hyperthermals" (i.e., strong, short-lived heating events) such as the Eocene Thermal Maximum 2 (~54 million years ago; e.g., Stap et al,…”