Refining our estimate of atmospheric CO2 across the Eocene-Oligocene climatic transition

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doi: 10.1016/j.epsl.2014.10.036
Author(s): Heureux, Ana M. C.; Rickaby, Rosalind E. M.
Author Affiliation(s): Primary:
University of Oxford, Department of Earth Science, Oxford, United Kingdom
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, Vol.409, p.329-338. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. Includes appendices. 68 refs.; illus., incl. 2 tables, sketch map
Summary: The Eocene-Oligocene transition (EOT) followed by Oligocene isotope event 1 (Oi-1) is a dramatic global switch in climate characterized by deep-sea cooling and the first formation of permanent Antarctic ice. Models and proxy evidence suggest that declining partial pressure of atmospheric carbon dioxide (CO2 atm) below a threshold may explain the onset of global cooling and associated ice formation at Oi-1. However, significant uncertainty remains in the estimated values and salient features of reconstructed CO2 atm across this interval. In this study, we present novel carbon isotope records from size separated diatom associated organic matter (δ 13Cdiatom) preserved in silica frustules. Physical preservation of this material allows concurrent investigation of isotopic and cell size information, providing two input parameters for biogeochemical models and the reconstruction of CO2 atm. We estimate CO2 atm in two ways; first we use size and reaction-diffusion kinetics of a cell to calculate a CO2 atm threshold. Second we use the calibrated relationship between εp(diatom) and carbon dioxide from culture and field studies to create a record of CO2 atm prior to and across the transition. Our study, from site 1090 in the Atlantic sector of the Southern Ocean, shows CO2 atm values fluctuating between 900 and 1700±100 p.p.m.v. across the EOT followed by a drop to values in the order of 700 to 800±100 p.p.m.v. just prior to the onset of Oi-1. Our values and magnitude of CO2 atm change differ from previous estimates, but confirm the overall trends inferred from boron isotopes and alkenones, including a marked rebound following Oi-1. Due to the intricate nature of the climate system and complexities in constraining paleo-proxies, this work emphasizes the importance of a multi-proxy approach to estimating of CO2 atm in order to elucidate its role in the emplacement of Antarctic ice-sheets at the EOT. Abstract Copyright (2015) Elsevier, B.V.
Year of Publication: 2015
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Atlantic Ocean; C-13/C-12; Carbon; Carbon dioxide; Cenozoic; Climate change; Diatoms; Eocene; Glacial environment; Isotope ratios; Isotopes; Leg 177; Microfossils; Models; ODP Site 1090; Ocean Drilling Program; Oligocene; Organic carbon; Paleoatmosphere; Paleoclimatology; Paleogene; Partial pressure; Plantae; Reconstruction; South Atlantic; Southern Ocean; Stable isotopes; Tertiary
Coordinates: S425449 S425449 E0085359 E0085359
Record ID: 2015013789
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands