Frequency, magnitude and character of hyperthermal events at the onset of the Early Eocene Climatic Optimum

Abstract

Abstract. Recent studies have shown that the Early EoceneClimatic Optimum (EECO) was preceded by a series of short-lived global warming events, known as hyperthermals. Here we present high-resolution benthic stable carbon and oxygen isotope records from ODP Sites 1262 and 1263 (Walvis Ridge, SE Atlantic) between ∼ 54 and ∼ 52 million years ago, tightly constraining the character, timing, and magnitude of six prominent hyperthermal events. These events, which include Eocene Thermal Maximum (ETM) 2 and 3, are studied in relation to orbital forcing and long-term trends. Our findings reveal an almost linear relationship between δ 13 C and δ 18 O for all these hyperthermals, indicating that the eccentricity-paced covariance between deep-sea temperature changes and extreme perturbations in the exogenic carbon pool persisted during these events towards the onset of the EECO, in accordance with previous observations for the Paleocene Eocene Thermal Maximum (PETM) and ETM2. The covariance of δ 13 C and δ 18 O during H2 and I2, which are the second pulses of the "paired" hyperthermal events ETM2-H2 and I1-I2, deviates with respect to the other events. We hypothesize that this could relate to a relatively higher contribution of an isotopically heavier source of carbon, such as peat or permafrost, and/or to climate feedbacks/local changes in circulation. Finally, the δ 18 O records of the two sites show a systematic offset with on average 0.2 ‰ heavier values for the shallower Site 1263, which we link to a slightly heavier isotopic composition of the intermediate water mass reaching the northeastern flank of the Walvis Ridge compared to that of the deeper northwestern water mass at Site 1262.

Astronomical calibration of the Ypresian timescale: implications for seafloor spreading rates and the chaotic behavior of the solar system?

“…Published stable isotope data also used in this study have been compiled from Lourens et al (2005), , McCarren et al (2008), Stap et al (2009Stap et al ( , 2010, Sexton et al (2011), Westerhold et al (2012, 2015, Kirtland Turner et al (2014), Littler et al (2014), and Lauretano et al (2015. All data are provided in the Supplement (and PANGAEA) relative to the Site 1263 depth and with the tuned age added.…”

“…High-resolution bulk and benthic stable isotope data for the early (Cramer et al, 2003;Zachos et al, 2010;Stap et al, 2010;Littler et al, 2014;Lauretano et al, 2015Lauretano et al, , 2016, middle (Kirtland Turner et al, 2014), and late Ypresian showed exceptionally strong 100 and 405 kyr eccentricity cycle variations that were partly utilized for age model construction. In order to test the 50 Ma discrepancy and the astronomical age model at ODP Site 1258, high-resolution benthic stable isotope records spanning 54 to 49 Ma were compiled from ODP Site 1262 (Littler et al, 2014;Lauretano et al, 2015) and Site 1263 (Stap et al, 2010;Lauretano et al, 2015Lauretano et al, , 2016 and were astronomically tuned to the La2010d (Laskar et al, 2011a) orbital solution (Lauretano et al, 2016). In theory, the dominant eccentricity-related cyclicity in this interval should enable development of a robust astrochronology.…”

“…The Ypresian stage, from 56.0 to 47.8 Ma, represents the first ∼ 8 million years of the Eocene epoch (Vandenberghe et al, 2012), an interval characterized by the warmest deep-sea temperatures of the Cenozoic era , multiple transient global warming events (Cramer et al, 2003;Lourens et al, 2005;Agnini et al, 2009;Galeotti et al, 2010;Leon-Rodriguez and Dickens 2010;Stap et al, 2010;Zachos et al, 2010;Sexton et al, 2011;Slotnick et al, 2012;Littler et al, 2014;Kirtland Turner et al, 2014;Lauretano et al, 2015Lauretano et al, , 2016, and major faunal turnovers (Thomas and Shackleton, 1996;Gingerich, 2003;Clyde et al, 2007). Climatic records from the Ypresian greenhouse are of special interest because they potentially capture the behavior of Earth's climate system under pCO 2 concentrations likely to be reached in the near future Meinshausen et al, 2011).…”

The 405 kyr and 2.4 Myr eccentricity components in Cenozoic carbon isotope records

“…Particularly distinctive is the imprint of the 405 kyr eccentricity term (Westerhold et al, 2011) on climate and the carbon cycle, under both ice-free (Paleocene-Eocene, Westerhold et al 2011;Lauretano et al 2015) and glaciated (Oligocene-Miocene, Pälike et al 2006;Holbourn et al 2015) climate regimes within the Cenozoic (Fig. 1).…”

“…Assuming a constant sediment methane production, more biogenic methane is derectly mixed into the exogenic carbon pool under relatively warm climates (Dean et al, 2018). Under colder climates, more Lauretano et al 2015Lauretano et al 2015 Figure 1. Long-term high resolution benthic foraminiferal stable carbon and oxygen isotope records show 405 kyr cyclicity.…”