Abstract
Abstract. Late Paleocene and early Eocene hyperthermals are transient warming events associated with massive perturbations of the global carbon cycle, and are considered partial analogues for current anthropogenic climate change. Because the magnitude of carbon release varied between the events, they are natural experiments ideal for exploring the relationship between carbon cycle perturbations, climate change and biotic response. Here we quantify marine biotic variability through three million years of the early Eocene that include five hyperthermals, utilizing a method that allows us to integrate the records of different plankton groups through scenarios ranging from background to major extinction events. Our long time-series calcareous nannoplankton record indicates a scaling of biotic disruption to climate change associated with the amount of carbon released during the various hyperthermals. Critically, only the three largest hyperthermals, the Paleocene–Eocene Thermal Maximum (PETM), Eocene Thermal Maximum 2 (ETM2) and the I1 event, show above-background variance, suggesting that the magnitude of carbon input and associated climate change needs to surpass a threshold value to cause significant biotic disruption.
Highlights
Late Paleocene through early Eocene hyperthermals occurred against a backdrop of long-term climate warming between ∼60 and ∼50 million years ago (Ma) (e.g. Cramer et al, 2003; Lourens et al, 2005; Quillevereet al., 2008; Zachos et al, 2010)
All are characterized by negative carbon isotope excursions (CIEs) and deep-sea carbonate dissolution (Lourens et al, 2005; Zachos et al, 2005), indicating the release and/or redistribution of massive amounts of 13Cdepleted carbon between carbon reservoirs (e.g. Cramer et al, 2003; Lourens et al, 2005; Sexton et al, 2011; Lunt et al, 2011)
Loss may occur if all the species co-varied, or if abundance changes occurred at a frequency that cancelled each other out
Summary
Late Paleocene through early Eocene hyperthermals occurred against a backdrop of long-term climate warming between ∼60 and ∼50 million years ago (Ma) (e.g. Cramer et al, 2003; Lourens et al, 2005; Quillevereet al., 2008; Zachos et al, 2010). The PETM (∼56 Ma) was the largest and most abrupt of these hyperthermals with a marine CIE of 2.5– 4.0 ‰, accompanying lysocline shoaling of more than two kilometers and global warming of 5 to 8 ◦C (Sluijs et al, 2007a; Zachos et al, 2005) This climate event was accompanied by dramatic biotic changes, including migration of terrestrial mammals, extinction of benthic foraminifera and a global expansion of tropical plankton (e.g. Sluijs et al, 2007a; McInerney and Wing, 2011). Suggesting that the isotopic composition and release mechanism of the injected carbon were similar across these events (Stap et al, 2010; Abels et al, 2012) These closely spaced CIEs/climate change events of different magnitudes provide enormous potential for quantifying biological sensitivity to carbon cycle perturbations. We apply a modified coefficients of variation technique to quantify levels of variation in a long time-series record of calcareous nannoplankton abundance across multiple hyperthermals, and compare these results with data from other plankton groups and from the mass extinction event at the Cretaceous–Paleogene boundary
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