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  • 11
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    The DeepMIP contribution to PMIP4: experimental design for model simulations of the EECO, PETM, and pre-PETM (version 1.0) (2017)
    Copernicus Publications (EGU)
    In:  Geoscientific Model Development, 10 (2). pp. 889-901.
    Details
    Publication Date: 2020-02-06
    Description: Past warm periods provide an opportunity to evaluate climate models under extreme forcing scenarios, in particular high ( 〉  800 ppmv) atmospheric CO2 concentrations. Although a post hoc intercomparison of Eocene ( ∼  50  Ma) climate model simulations and geological data has been carried out previously, models of past high-CO2 periods have never been evaluated in a consistent framework. Here, we present an experimental design for climate model simulations of three warm periods within the early Eocene and the latest Paleocene (the EECO, PETM, and pre-PETM). Together with the CMIP6 pre-industrial control and abrupt 4 ×  CO2 simulations, and additional sensitivity studies, these form the first phase of DeepMIP – the Deep-time Model Intercomparison Project, itself a group within the wider Paleoclimate Modelling Intercomparison Project (PMIP). The experimental design specifies and provides guidance on boundary conditions associated with palaeogeography, greenhouse gases, astronomical configuration, solar constant, land surface processes, and aerosols. Initial conditions, simulation length, and output variables are also specified. Finally, we explain how the geological data sets, which will be used to evaluate the simulations, will be developed.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/gmd-10-889-2017
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 12
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    Clay assemblage and oxygen isotopic constraints on the weathering response to the Paleocene-Eocene thermal maximum, east coast of North America (2012)
    Geological Society of America (GSA)
    Details
    Publication Date: 2012-07-01
    Description: The Paleocene-Eocene thermal maximum, a transient global warming event, is characterized by extensive evidence of a more active hydrological cycle. This includes a widespread pulse of kaolinite accumulation on continental margins, viewed as the by-product of either enhanced chemical weathering consistent with much more humid conditions and/or increased erosion of previously deposited laterites. The former would be more consistent with year-round humid conditions, whereas the latter might be indicative of extreme seasonal precipitation patterns. To assess these hypotheses, we present a new high-resolution clay mineral assemblage and oxygen isotope record from Bass River, a site on the New Jersey margin (east coast of North America), which shows a sharp rise in the abundance of kaolinite beginning a few thousand years before the onset of the carbon isotope excursion (CIE). The δ18O of the
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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    PAPER CURRENT
  • 13
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    An astronomically dated record of Earth’s climate and its predictability over the last 66 Million Years (2020)
    AAAS (American Association for the Advancement of Science)
    Details
    Publication Date: 2023-02-08
    Description: Much of our understanding of Earth’s past climate comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the Cenozoic era and to study their dynamics. Here, we present a new, highly resolved, astronomically dated, continuous composite of benthic foraminifer isotope records developed in our laboratories. Four climate states—Hothouse, Warmhouse, Coolhouse, Icehouse—are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume. Statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of Cenozoic climate dynamics.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: other
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 14
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    Toward a Cenozoic history of atmospheric CO 2 (2023)
    AAAS (American Association for the Advancement of Science)
    Details
    Publication Date: 2024-02-23
    Description: The geological record encodes the relationship between climate and atmospheric carbon dioxide (CO 2 ) over long and short timescales, as well as potential drivers of evolutionary transitions. However, reconstructing CO 2 beyond direct measurements requires the use of paleoproxies and herein lies the challenge, as proxies differ in their assumptions, degree of understanding, and even reconstructed values. In this study, we critically evaluated, categorized, and integrated available proxies to create a high-fidelity and transparently constructed atmospheric CO 2 record spanning the past 66 million years. This newly constructed record provides clearer evidence for higher Earth system sensitivity in the past and for the role of CO 2 thresholds in biological and cryosphere evolution. Editor’s summary The concentration of atmospheric carbon dioxide is a fundamental driver of climate, but its value is difficult to determine for times older than the roughly 800,000 years for which ice core records are available. The Cenozoic Carbon dioxide Proxy Integration Project (CenCO2PIP) Consortium assessed a comprehensive collection of proxy determinations to define the atmospheric carbon dioxide record for the past 66 million years. This synthesis provides the most complete record yet available and will help to better establish the role of carbon dioxide in climate, biological, and cryosphere evolution. — H. Jesse Smith
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 15
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    Two-stepping into the icehouse: East Antarctic weathering during progressive ice-sheet expansion at the Eocene-Oligocene transition (2011)
    Geological Society of America (GSA)
    Details
    Publication Date: 2011-04-01
    Description: In conjunction with increasing benthic foraminiferal {delta}18O values at the Eocene-Oligocene transition (EOT; ca. 34 Ma), coarse-grained ice-rafted debris (IRD; 〉425 {micro}m) appears abruptly alongside fossil fish teeth with continentally derived neodymium (Nd) isotope ratios ({varepsilon}Nd) in Kerguelen Plateau (Southern Ocean) sediments. Increased Antarctic weathering flux, as inferred from two steps to less radiogenic {varepsilon}Nd values, coincides with two steps in benthic foraminiferal {delta}18O values. These results indicate that two distinct surges of weathering were generated by East Antarctic ice growth during the EOT. Weathering by ice sheets during a precursor glaciation at 33.9 Ma did not produce significant IRD accumulation during the first {varepsilon}Nd shift. Glacial weathering was sustained during a terrace interval between the two steps, probably by small high-elevation ice sheets. A large increase in weathering signals the rapid coalescence of small ice sheets into an ice sheet of continental proportions ca. 33.7 Ma. Rapid ice sheet expansion resulted in a suppression of weathering due to less exposed area and colder conditions. Parallel changes in Antarctic weathering flux and deep-sea carbonate accumulation suggest that ice-sheet expansion during the EOT had a direct impact on the global carbon cycle; possible mechanisms include associated changes in silicate weathering on the East Antarctic craton and enhanced fertilization of Southern Ocean waters, both of which warrant further investigation.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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    PAPER CURRENT
  • 16
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    An astronomically dated record of Earth's climate and its predictability over the last 66 million years (2021)
    AAAS
    Details
    Publication Date: 2023-10-26
    Description: Much of our understanding of Earth's past climate comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the Cenozoic era and to study their dynamics. Here, we present a new, highly resolved, astronomically dated, continuous composite of benthic foraminifer isotope records developed in our laboratories. Four climate states-Hothouse, Warmhouse, Coolhouse, Icehouse-are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume. Statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of Cenozoic climate dynamics.
    Description: Published
    Description: 1383–1387
    Description: 5A. Ricerche polari e paleoclima
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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    PAPER (OA)
  • 17
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    Supplementary material of IODP Site 342-U1410 and COSMOS model (2018)
    PANGAEA
    In:  Supplement to: Vahlenkamp, Maximilian; Niezgodzki, Igor; De Vleeschouwer, David; Bickert, Torsten; Harper, Dustin T; Kirtland Turner, Sandra; Lohmann, Gerrit; Sexton, Philip F; Zachos, James C; Pälike, Heiko (2018): Astronomically paced changes in deep-water circulation in the western North Atlantic during the middle Eocene. Earth and Planetary Science Letters, 484, 329-340, https://doi.org/10.1016/j.epsl.2017.12.016
    Details
    Publication Date: 2023-03-03
    Description: North Atlantic Deep Water (NADW) currently redistributes heat and salt between Earth's ocean basins, and plays a vital role in the ocean-atmosphere CO2 exchange. Despite its crucial role in today's climate system, vigorous debate remains as to when deep-water formation in the North Atlantic started. Here, we present datasets from carbonate-rich middle Eocene sediments from the Newfoundland Ridge, revealing a unique archive of paleoceanographic change from the progressively cooling climate of the middle Eocene. Well-defined lithologic alternations between calcareous ooze and clay-rich intervals occur at the ~41-kyr beat of axial obliquity. Hence, we identify obliquity as the driver of middle Eocene (43.5-46 Ma) Northern Component Water (NCW, the predecessor of modern NADW) variability. High-resolution benthic foraminiferal d18O and d13C suggest that obliquity minima correspond to cold, nutrient-depleted, western North Atlantic deep waters. We thus link stronger NCW formation with obliquity minima. In contrast, during obliquity maxima, Deep Western Boundary Currents were weaker and warmer, while abyssal nutrients were more abundant. These aspects reflect a more sluggish NCW formation. This obliquity-paced paleoceanographic regime is in excellent agreement with results from an Earth system model, in which obliquity minima configurations enhance NCW formation.
    Keywords: Center for Marine Environmental Sciences; Integrated Ocean Drilling Program / International Ocean Discovery Program; IODP; MARUM
    Type: Dataset
    Format: application/zip, 7 datasets
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    DATA PANGAEA
  • 18
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    Carbonate, stable isotope data, abundance of pyrite and siderite, pyrite alteration and nannofossil Whole Shield Index during the PETM (2018)
    PANGAEA
    In:  Supplement to: Bralower, Timothy J; Kump, Lee R; Self-Trail, Jean; Robinson, Marci M; Lyons, Shelby; Babila, Tali L; Ballaron, Edward; Freeman, Katherine H; Hajek, Elizabeth; Rush, William; Zachos, James C (2018): Evidence for shelf acidification during the onset of the Paleocene-Eocene Thermal Maximum. Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2018PA003382
    Details
    Publication Date: 2023-01-13
    Description: A transect of paleoshelf cores from Maryland and New Jersey contains an ~0.19 m to 1.61 m thick interval with reduced percentages of carbonate during the onset of the Paleocene‐Eocene Thermal Maximum (PETM). Outer paleoshelf cores are barren of nannofossils and correspond to two minor disconformities. Middle paleoshelf cores contain a mixture of samples devoid of nannofossils and those with rare specimens characterized by significant dissolution (i.e., etching). The magnitude of the decrease in carbonate cannot be explained by dilution by clastic material or dissolution resulting from the oxidation of organic matter during early diagenesis. The observed preservation pattern implies a shoaling of the calcite compensation depth (CCD) and lysocline to the middle shelf. This reduced carbonate interval is observed during the onset of the PETM on other continental margins raising the possibility that extreme shoaling of the CCD and lysocline was a global signal, which is more significant than in previous estimates for the PETM. An alternative scenario is that shoaling was restricted to the northwest Atlantic, enhanced by regional and local factors (eutrophication from rivers, microbial activity associated with warming) that exacerbated the impact of acidification on the shelf.
    Type: Dataset
    Format: application/zip, 8 datasets
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    DATA PANGAEA
  • 19
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    Compilation of PETM carbonate and isotope data from PETM sections (2018)
    PANGAEA
    Details
    Publication Date: 2023-01-13
    Type: Dataset
    Format: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet, 15.6 kBytes
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    DATA PANGAEA
  • 20
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    Shelf ecosystems along the U.S. Atlantic Coastal Plain prior to and during the Paleocene-Eocene Thermal Maximum (2022)
    PANGAEA
    Details
    Publication Date: 2023-01-30
    Description: The Paleocene-Eocene Thermal Maximum (PETM) is the most pronounced climate event of the early Paleogene. It is characterized by negative δ18O and δ13C excursions recorded in sedimentary archives and a transient disruption of the marine biosphere. Bulk carbonate and foraminiferal δ13C records from Paleocene-Eocene core sections from the U.S. Atlantic Coastal Plain show an additional small, but distinct δ13C excursion below the onset of the PETM, coined the “pre-onset excursion” (POE). This study focuses on the South Dover Bridge (SDB) core in Maryland, where the Paleocene-Eocene transition is stratigraphically constrained by calcareous nannoplankton and stable isotope data, and in which the POE is well-expressed. The site was situated in a shallow marine shelf setting near a major outflow of the paleo-Potomac River system (38°44′49″N latitude, 76°00′25″W longitude, Talbot County). We generated high-resolution benthic foraminiferal assemblage, stable isotope, trace-metal, grain size and clay mineralogy data. Data collection was done via core-sampling, and successive preparation of the samples according to each proxy. Foraminifera underwent wet sieving (〉63 μm), picking and mounting on Plummer slides. For geochemistry analysis Cibicidoides alleni (Paleocene) and Anomalinoides acutus (PETM) were used. Grain size data was collected with a Laser Diffraction Particle Analyzer. Stable isotope samples were analyzed with a Kiel Mat 253 gas source mass spectrometer system. All carbon isotope values are given in δ13C notation, relative to the PeeDee belemnite Standard (PDB). Trace elemental analyses were carried out on a Thermo Scientific Element XR Sector Field Inductively Coupled Plasma Mass Spectrometer (SF-ICP-MS). For clay mineral analysis, after Jackson treatment, a Philips PW 1380 diffractometer equipped with CuKalpha radiation, 45kV and 30mA graphite monochromator and was quantified through Rietveld Refinement for clay content.
    Keywords: Benthic foraminifera; CaCO3 content; grainsize; kaolinite; Maryland; Mg/Ca; Mg/Ca paleothermometry; Paleocene; Paleocene-Eocene Thermal Maximum; PETM; POE; Pre-onset excursion; South Dover Bridge; Stable isotope; Taxonomy; U.S. Atlantic Coastal Plains
    Type: Dataset
    Format: application/zip, 10 datasets
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    DATA PANGAEA
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