A dynamic climate and ecosystem state during the Paleocene-Eocene Thermal Maximum: inferences from dinoflagellate cyst assemblages on the New Jersey Shelf

A Sluijs,H Brinkhuis

doi:10.5194/bg-6-1755-2009

Abstract

Abstract. Late Paleocene and Early Eocene climates and ecosystems underwent significant change during several transient global warming phases, associated with rapidly increasing atmospheric carbon concentrations, of which the Paleocene-Eocene Thermal Maximum (PETM; ~55.5 Ma) is best studied. While biotic response to the PETM as a whole (~170 kyrs) has been relatively well documented, variations during the PETM have been neglected. Here we present organic dinoflagellate cyst (dinocyst) distribution patterns across two stratigraphically expanded PETM sections from the New Jersey Shelf, Bass River and Wilson Lake. Many previously studied sites show a uniform abundance of the thermophilic and presumably heterotrophic taxon Apectodinium that spans the entire carbon isotope excursion (CIE) of the PETM. In contrast, the New Jersey sections show large variations in abundances of many taxa during the PETM, including the new species Florentinia reichartii that we formally propose. We infer paleoecological preferences of taxa that show temporal abundance peaks, both qualitative and absolute quantitative, from empirical as well as statistical information, i.e., principle (PCA) and canonical correspondence analyses (CCA). In the CCAs, we combine the dinocyst data with previously published environmental proxy data from these locations, such as TEX86 paleothermometry, magnetic susceptibility and sedimentary size fraction. The combined information supports previous inferences that sea level rose during the PETM, but also indicates a (regional) increase in fresh-water runoff that started ~10 kyr after the onset of the CIE, and perhaps precession-paced cycles in sea surface productivity. The highly variable dinocyst assemblages of the PETM contrast with rather stable Upper Paleocene assemblages, which suggests that carbon input caused a dynamic climate state, at least regionally.

Highlights

That almost everyone expects a certain amount of global warming by the end of the century (IPCC, 2007), interest to climate change as a whole is increasing
Dinocyst assemblages are very similar in both relative and absolute abundances between Bass River and Wilson Lake, and generally comprise taxa commonly recorded in midlatitude marginal marine lower Paleogene sediments
The biotic response of dinocysts to the Paleocene-Eocene Thermal Maximum (PETM) is interesting because it includes a quasi-global acme of Apectodinium spp., thereby comprising usually >40% of the dinocyst assemblage (Heilmann-Clausen, 1985; Powell et al, 1996; Bujak and Brinkhuis, 1998; Heilmann-Clausen and Egger, 2000)

Summary

Introduction

That almost everyone expects a certain amount of global warming by the end of the century (IPCC, 2007), interest to climate change as a whole is increasing. Global and regional climate models expect an increase in year-to-year variability of weather resulting from increasing CO2 concentrations (e.g., Diffenbaugh et al, 2008). One may expect increasing variability in climate over the coming centuries, millennia and even longer time scales, because carbon concentrations in the atmosphere are expected to remain high for several hundreds of thousands of years (Archer, 2005; Archer et al, 2009). One way to assess climate dynamics in a rapidly warming world is to perform high-resolution paleoenvironmental reconstructions on high-accumulation rate sediment sections deposited during a past analogue, such as the Paleocene-Eocene Thermal Maximum (PETM). The onset of the PETM is marked by a pronounced negative stable carbon

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