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  • 1
    Online Resource
    Online Resource
    Evidence from Svalbard for near-freezing temperatures and climate oscillations in the Arctic during the Paleocene and Eocene (2009)
    Associated volumes
    Details Availability
    In: Palaeogeography, palaeoclimatology, palaeoecology, Amsterdam [u.a.] : Elsevier Science, 1965, 278(2009), 1/4, Seite 48-56, 0031-0182
    In: volume:278
    In: year:2009
    In: number:1/4
    In: pages:48-56
    Description / Table of Contents: Until recently, the Arctic was assumed to be characterised by relatively warm conditions throughout the Early Cenozoic. However, recent investigations on deep-sea drilling cores from northern high latitudes, including the Arctic Ocean, give apparently contradicting results. Here we report the intermittent occurrence of certain temperature indicators in the Early Tertiary sedimentary sequence on Svalbard, which may represent the first direct northern high-latitude record of cold water temperatures for the early Cenozoic. Glendonites (calcite pseudomorphs after calcium carbonate hexahydrate) and erratics in otherwise fine-grained sediments require near-freezing temperatures and the presence of at least seasonal sea ice. This succession also contains coal seams and other warm climate indicators, but not on the same stratigraphical levels. These results imply the occurrence of cooling phases episodically during the warm background climate of the Paleocene and Eocene, suggesting that Arctic temperature variability was much greater than previously recognized.
    Type of Medium: Online Resource
    Pages: Ill., graph. Darst
    ISSN: 0031-0182
    DOI: 10.1016/j.palaeo.2009.04.012
    Language: English
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  • 2
    Electronic Resource
    Electronic Resource
    Eocene bipolar glaciation associated with global carbon cycle changes (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 436 (2005), S. 341-346 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The transition from the extreme global warmth of the early Eocene ‘greenhouse’ climate ∼55 million years ago to the present glaciated state is one of the most prominent changes in Earth's climatic evolution. It is widely accepted that large ice sheets first appeared on ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03874
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    Paper (German National Licenses)
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  • 3
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    Deconvolving the saturation state and temperature controls on benthic foraminiferal Li/Ca, based on downcore paired B/Ca measurements and coretop compilation (2018)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 236 . pp. 297-314.
    Details
    Publication Date: 2021-02-08
    Description: Li/Ca in calcitic benthic foraminiferal tests has been suggested to co-vary with both temperature and carbonate chemistry, but these two influences have been difficult to disentangle. We use several new downcore records of Li/Ca in Cibicidoides wuellerstorfi and Uvigerina, paired with the carbonate proxy B/Ca, to further elucidate this behavior. We also combine the downcore measurements with a compilation of coretop Li/Ca data. Uvigerina B/Ca presumably records pore water saturation with respect to calcite (ΔCO32−), though downcore data show that it partially reflects bottom water ΔCO32− (inferred from C. wuellerstorfi B/Ca), with a relationship that is consistent with a previous global coretop calibration. Downcore Li/Ca is significantly correlated to B/Ca in both taxa, implying a positive relationship between Li/Ca and carbonate chemistry. This connection breaks down in the coretop compilation however, likely due to the confounding influence of temperature on Li/Ca. We attempt to isolate the temperature influence using a negative exponential equation previously derived from abiotic calcite precipitation experiments, and introduce a new quantity ΔLi/Ca, which is the observed departure from the temperature-based prediction. This transformation brings the downcore and coretop Li/Ca measurements into alignment, with up to 90% of the ΔLi/Ca variance explained by ΔCO32−. Finally, we perform preliminary tests of Li/Ca as a paleo-proxy for both ΔCO32− and temperature.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gca.2018.02.029
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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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
  • 5
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    Constraints on ocean circulation at the Paleocene–Eocene Thermal Maximum from neodymium isotopes (2016)
    Copernicus Publications (EGU)
    In:  Climate of the Past, 12 (4). pp. 837-847.
    Details
    Publication Date: 2019-02-01
    Description: Global warming during the Paleocene-Eocene Thermal Maximum (PETM) ĝ1/4 ĝ€55 million years ago (Ma) coincided with a massive release of carbon to the ocean-atmosphere system, as indicated by carbon isotopic data. Previous studies have argued for a role of changing ocean circulation, possibly as a trigger or response to climatic changes. We use neodymium (Nd) isotopic data to reconstruct short high-resolution records of deep-water circulation across the PETM. These records are derived by reductively leaching sediments from seven globally distributed sites to reconstruct past deep-ocean circulation across the PETM. The Nd data for the leachates are interpreted to be consistent with previous studies that have used fish teeth Nd isotopes and benthic foraminiferal δ13C to constrain regions of convection. There is some evidence from combining Nd isotope and δ13C records that the three major ocean basins may not have had substantial exchanges of deep waters. If the isotopic data are interpreted within this framework, then the observed pattern may be explained if the strength of overturning in each basin varied distinctly over the PETM, resulting in differences in deep-water aging gradients between basins. Results are consistent with published interpretations from proxy data and model simulations that suggest modulation of overturning circulation had an important role for initiation and recovery of the ocean-atmosphere system associated with the PETM.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/cp-12-837-2016
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    13C-18O isotope signatures and ‘clumped isotope’ thermometry in foraminifera and coccoliths (2010)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 74 . pp. 5697-5717.
    Details
    Publication Date: 2017-09-27
    Description: Accurate constraints on past ocean temperatures and compositions are critical for documenting climate change and resolving its causes. Most proxies for temperature are not thermodynamically based, appear to be subject to biological processes, require regional calibrations, and/or are influenced by fluid composition. As a result, their interpretation becomes uncertain when they are applied in settings not necessarily resembling those in which they were empirically calibrated. Independent proxies for past temperature could provide an important means of testing and/or expanding on existing reconstructions. Here we report measurements of abundances of stable isotopologues of calcitic and aragonitic benthic and planktic foraminifera and coccoliths, relate those abundances to independently estimated growth temperatures, and discuss the possible scope of equilibrium and kinetic isotope effects. The proportions of 13C–18O bonds in these samples exhibits a temperature dependence that is generally similar to that previously been reported for inorganic calcite and other biologically precipitated carbonatecontaining minerals (apatite from fish, reptile, and mammal teeth; calcitic brachiopods and molluscs; aragonitic coral and mollusks). Most species that exhibit non-equilibrium 18O/16O (d18O) and 13C/12C (δ13C) ratios are characterized by 13C–18O bond abundances that are similar to inorganic calcite and are generally indistinguishable from apparent equilibrium, with possible exceptions among benthic foraminiferal samples from the Arctic Ocean where temperatures are near-freezing. Observed isotope ratios in biogenic carbonates can be explained if carbonate minerals generally preserve a state of ordering that reflects the extent of isotopic equilibration of the dissolved inorganic carbon species.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    DOI: 10.1016/j.gca.2010.07.006
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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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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  • 8
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    The Opening of the Arctic-Atlantic Gateway: Tectonic, Oceanographic and Climatic Dynamics - an IODP Initiative (2015)
    Geological Survey of Norway
    In:  EPIC37th International Conference on Arctic Margins - ICAM 2015, Trondheim, Norway, 2015-06-02-2015-06-05Report no. 2015.032, p. 51-52, Geological Survey of Norway
    Details
    Publication Date: 2016-01-21
    Description: The modern polar cryosphere reflects an extreme climate state with profound temperature gradients towards high-latitudes. It developed in association with stepwise Cenozoic cooling, beginning with ephemeral glaciations and the appearance of sea ice in the late middle Eocene. The polar ocean gateways played a pivotal role in changing the polar and global climate, along with declining greenhouse gas levels. The opening of the Drake Passage finalized the oceanographic isolation of Antarctica, some 40 Ma ago. The Arctic Ocean was an isolated basin until the early Miocene when rifting and subsequent sea-floor spreading started between Greenland and Svalbard, initiating the opening of the Fram Strait / Arctic-Atlantic Gateway (AAG). Although this gateway is known to be important in Earth’s past and modern climate, little is known about its Cenozoic development. However, the opening history and AAG’s consecutive widening and deepening must have had a strong impact on circulation and water mass exchange between the Arctic Ocean and the North Atlantic. To study the AAG’s complete history, ocean drilling at two primary sites and one alternate site located between 73°N and 78°N in the Boreas Basin and along the East Greenland continental margin are proposed. These sites will provide unprecedented sedimentary records that will unveil (1) the history of shallow-water exchange between the Arctic Ocean and the North Atlantic, and (2) the development of the AAG to a deep-water connection and its influence on the global climate system. The specific overarching goals of our proposal are to study: (1) the influence of distinct tectonic events in the development of the AAG and the formation of deep water passage on the North Atlantic and Arctic paleoceanography, and (2) the role of the AAG in the climate transition from the Paleogene greenhouse to the Neogene icehouse for the long-term (~50 Ma) climate history of the northern North Atlantic. Getting a continuous record of the Cenozoic sedimentary succession that recorded the evolution of the Arctic-North Atlantic horizontal and vertical motions, and land and water connections will also help better understanding the post-breakup evolution of the NE Atlantic conjugate margins and associated sedimentary basins.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 9
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    Antarctic ice sheet sensitivity to atmospheric CO2variations in the early to mid-Miocene (2016)
    In:  EPIC3Proceedings of the National Academy of Sciences, 113(13), pp. 3453-3458, ISSN: 0027-8424
    Details
    Publication Date: 2018-08-10
    Description: Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23–14 Mya) is a compelling interval to study as global temperatures and atmospheric CO2 concentrations were similar to those projected for coming centuries. Importantly, this time interval includes the Miocene Climatic Optimum, a period of global warmth during which average surface temperatures were 3–4 °C higher than today. Miocene sediments in the ANDRILL-2A drill core from the Western Ross Sea, Antarctica, indicate that the Antarctic ice sheet (AIS) was highly variable through this key time interval. A multiproxy dataset derived from the core identifies four distinct environmental motifs based on changes in sedimentary facies, fossil assemblages, geochemistry, and paleotemperature. Four major disconformities in the drill core coincide with regional seismic discontinuities and reflect transient expansion of grounded ice across the Ross Sea. They correlate with major positive shifts in benthic oxygen isotope records and generally coincide with intervals when atmospheric CO2 concentrations were at or below preindustrial levels (∼280 ppm). Five intervals reflect ice sheet minima and air temperatures warm enough for substantial ice mass loss during episodes of high (∼500 ppm) atmospheric CO2. These new drill core data and associated ice sheet modeling experiments indicate that polar climate and the AIS were highly sensitive to relatively small changes in atmospheric CO2 during the early to mid-Miocene.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
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    Interpreting the Ca isotope record of marine biogenic carbonates (2007)
    In:  EPIC3Geochimica et Cosmochimica Acta.
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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