Fossil plant stomata indicate decreasing atmospheric CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; prior to the Eocene–Oligocene boundary

Steinthorsdottir, Margret; Porter, Amanda S.; Holohan, Aidan David; Kunzmann, Lutz; Collinson, Margaret E.; McElwain, Jennifer C.

doi:10.5194/cp-12-439-2016

Cited by 55 publications

(64 citation statements)

References 101 publications

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“…Long-term CO2 decline likely provided the required underlying preconditioning for the EOT (DeConto and Pollard, 2003) and cool summers due to the coincidence of an eccentricity minimum and low amplitude obliquity at ~34 Ma provided a tipping point for sustained major Antarctic glaciation (Coxall et al, 2005). We conclude from the Prydz Bay record that in East Antarctica an EOT-1 ice sheet formed during a time of declining pCO 2 (Pagani et al, 2011;Pearson et al, 2009;Steinthorsdottir et al, 2016). The onset of diamict deposition, the prograding clinoforms in seismic data, the declining values of the CIA, and enhanced erosion and glacial weathering rates (Scher et al, 2011;Tochilin et al, 2012) all suggest that high-latitude climate deterioration and ice growth in the hinterland of Prydz Bay intensified 0.5 Myr prior to Oi-1 with major ice growth coincident with Eocene-Oligocene precursor glaciaton (Figure 8).…”

Section: Antarctic Warm Events Ice Growth and The Global Carbon Cyclementioning

confidence: 77%

“…Superimposed transient Eocene warming events are generally attributed to releases of atmospheric greenhouse gases from tectonic, metamorphic, ocean ventilation, methane hydrate (Dickens, 2003), or permafrost (DeConto et al, 2012 sources. Marine and terrestrial proxies show declining concentrations of atmospheric pCO 2 through the mid-to-late Eocene (Beerling and Royer, 2011;Pearson et al, 2009;Pagani et al, 2011;Anagnostou et al, 2016;Steinthorsdottir et al, 2016), but short-term fluctuations are not yet well represented due to the low temporal resolution of the records.…”

Section: Antarctic Warm Events Ice Growth and The Global Carbon Cyclementioning

confidence: 99%

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An Antarctic stratigraphic record of stepwise ice growth through the Eocene-Oligocene transition

Passchier

Ciarletta

Miriagos

et al. 2016

Geological Society of America Bulletin

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Earth's current icehouse phase began ~34 million years ago with the onset of major Antarctic glaciation at the Eocene-Oligocene Transition (EOT). Changes in ocean circulation and a decline in atmospheric greenhouse gas levels were associated with step-wise cooling and ice growth at southern high latitudes.The Antarctic cryosphere plays a critical role in the ocean-atmosphere system, but its early evolution is still poorly known. With a near-field record from Prydz Bay, Antarctica, we demonstrate that Antarctic ice growth was stepwise and had an earlier onset than previously suggested. Prydz Bay lies downstream of a major East Antarctic ice-sheet drainage system and its sedimentary records uniquely constrain the timing of ice-sheet advance onto the continental shelf. We investigate a detrital record extracted from three Ocean Drilling Program drill holes within a new depositional and chronological framework spanning the late Eocene to early Oligocene (~36-33 Ma). The chemical index of alteration (CIA) and the S-index, calculated from the major element geochemistry of bulk samples, yield estimates of chemical weathering intensities and mean annual temperature (MAT) on the East Antarctic continent. We document evidence for late Eocene mountain glaciation along with transient warm events at 35.8-34.8 Ma. From 34.4 Ma, associated with the EOT-1  18 O excursion, glaciers advanced into Prydz Bay, coincident with a decline in chemical weathering and temperature. We conclude that Antarctic continental ice growth commenced with the EOT-1 "precursor" glaciation, during a time of Subantarctic surface ocean cooling and a decline in atmospheric pCO 2 . These results call for dynamic high-latitude feedbacks that are currently poorly represented in Earth system models and emphasize the need for additional near-field glaciosedimentological, high-latitude SST, and pCO2 records across the EOT.

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Section: Antarctic Warm Events Ice Growth and The Global Carbon Cyclementioning

confidence: 77%

Section: Antarctic Warm Events Ice Growth and The Global Carbon Cyclementioning

confidence: 99%

An Antarctic stratigraphic record of stepwise ice growth through the Eocene-Oligocene transition

Passchier

Ciarletta

Miriagos

et al. 2016

Geological Society of America Bulletin

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“…Stomatal proxy pCO 2 reconstructions currently offer the highest-resolution record of Eocene pCO 2 , with almost 50 data points, compared to ∼10 each derived from marine alkenone and boron isotopes, and ∼20 from paleosols. The numerous studies, using various fossil angiosperms as well as the fossil gymnosperms Ginkgo and Metasequoia, in the three stomatal proxy methods currently in use mostly agree that the Eocene pCO 2 was more moderately elevated compared to what marine proxies and climate modeling suggest (McElwain, 1998;Kürschner et al, 2001;Royer et al, 2001;Greenwood et al, 2003b;Retallack, 2009;Smith et al, 2010;Doria et al, 2011;Grein et al, 2011;Roth-Nebelsick et al, 2012;Franks et al, 2014;Maxbauer et al, 2014;Liu et al, 2016;Steinthorsdottir et al, 2016;Wolfe et al, 2017). The discrepancy between the marine isotope and stomatal proxy pCO 2 results is considerable, with the marine isotopes recording pCO 2 currently assumed to be more consistent with the elevated Eocene temperatures recorded by numerous proxies and the workings of the Earth's climate system (Cramwinckel et al, 2018).…”

Section: Comparison To Existing Pco 2 Records and Implicationsmentioning

confidence: 99%

Moderate levels of Eocene pCO2 indicated by Southern Hemisphere fossil plant stomata

Steinthorsdottir

Vajda

Pole³

et al. 2019

Geology

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Reducing the uncertainty in predictions of future climate change is one of today’s greatest scientific challenges, with many significant problems unsolved, including the relationship between pCO2 and global temperature. To better constrain these forecasts, it is meaningful to study past time intervals of global warmth, such as the Eocene (56.0–33.9 Ma), serving as climatic analogues for the future. Here we reconstructed pCO2 using the stomatal densities of a large fossil Lauraceae (laurel) leaf database from ten sites across the Eocene of Australia and New Zealand. We show that mostly moderate pCO2 levels of ∼450–600 ppm prevailed throughout the Eocene, levels that are considerably lower than the pCO2 forcing currently needed to recreate Eocene temperatures in climate models. Our data record significantly lower pCO2 than inferred from marine isotopes, but concur with previously published Northern Hemisphere Eocene stomatal proxy pCO2. We argue that the now globally consistent stomatal proxy pCO2 record for the Eocene is robust and that climate sensitivity was elevated and/or that additional climate forcings operated more powerfully than previously assumed.

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“…A recent global study of vegetation and terrestrial temperature change across the EOCT found a heterogeneous response in vegetation with cooling being well before the EOCT and being most prevalent in coastal areas (Pound and Salzmann). Another study using stomatal indices in fossil leaves recently found a decrease in CO2 levels, and implied cooling, beginning 1 to 2 million years before the EOCT (Steinthorsdottir et al, 2016). Thus, climate change preceding the EOCT is not unreasonable, and is a potential cause for the abundance changes reported here.…”

Section: Discussionmentioning

confidence: 52%

Changes in Mammalian Abundance Through the Eocene-Oligocene Climate Transition in the White River Group of Nebraska, Usa

Gillham¹,

Secord²

2019

Geological Society of America Abstracts With Programs

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Marine records show major cooling during the Eocene-Oligocene Climate Transition (EOCT). Most proxy studies in the White River Group suggest drying across the EOCT, and some suggest cooling. The lower resolution continental record has hindered a direct correlation of the marine climate record to Nebraska. I explore various correlation schemes and what they imply for faunal changes. This study compiles and analyzes data from 4,875 specimens in the University of Nebraska State Museum (UNSM) collection to test the hypothesis that climate change across the Eocene-Oligocene (E-O) boundary caused significant abundance changes in mammals. A series of binning schemes was created. One binning scheme followed previously established lithological zones, two schemes were based on average sediment accumulation rates, and three more were created by applying a cubic spline curve to published 206 Pb/ 238 U zircon ash dates. For the purpose of correlating the marine and Toadstool sections, I constructed a high-resolution (±0.5 m) carbon isotope stratigraphy across the E-O boundary using fossil enamel from the oreodont Merycoidodon. Results show that turnover in taxonomic abundance occurs throughout the study interval and is not concentrated across the EOCT. The largest pulse of faunal change and largest abundance changes for the most common taxa, Merycoidodon and the horse Mesohippus, slightly predate the EOCT. This raises the possibility that climate change began earlier in the continental interior than indicated by the marine benthic oxygen isotope record. Chord distance analyses reveal that the faunal composition of Orellan zones are more similar to one another than they are to the faunas of Chadron zones. This similarity is likely caused by the extinction, or near extinction, of Chadron taxa like Megacerops around the EOCT. Despite the lack of significant change in evenness, numerous taxa underwent extended changes in relative abundance through time. Archaeotherium, a water-dependent artiodactyl, decreased in relative abundance through time just as Poebrotherium, a water-independent camelid, increased in abundance through time. Changes in the relative abundances of Poebrotherium and Archaeotherium are consistent with a drier environment beginning in EOCT. The level of waterdependence in other taxa is less clear, and their changes in abundance cannot be confidently explained through diet, dentition, body mass, or locomotion.

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Fossil plant stomata indicate decreasing atmospheric CO<sub>2</sub> prior to the Eocene–Oligocene boundary

Cited by 55 publications

References 101 publications

An Antarctic stratigraphic record of stepwise ice growth through the Eocene-Oligocene transition

An Antarctic stratigraphic record of stepwise ice growth through the Eocene-Oligocene transition

Moderate levels of Eocene pCO2 indicated by Southern Hemisphere fossil plant stomata

Changes in Mammalian Abundance Through the Eocene-Oligocene Climate Transition in the White River Group of Nebraska, Usa

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