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  • 1
    Online Resource
    Online Resource
    Cham :Springer International Publishing AG,
    Keywords: Paleoclimatology. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (485 pages)
    Edition: 1st ed.
    ISBN: 9783030249823
    Series Statement: Frontiers in Earth Sciences Series
    Language: English
    Note: Intro -- Foreword -- Introduction -- Preface -- Contents -- About the Editors -- 1 The Climate System: Its Functioning and History -- Climate Change -- Definition of Climate -- Climate Changes in the Past -- Climate Mechanisms -- The Radiation Balance of the Earth -- The Greenhouse Effect -- The Water Cycle -- Sun-Related Variability -- Solar Cycles -- Long-Term Variations in the Movement of the Earth Around the Sun -- The Sun's Evolution -- Reconstruction of the History of Atmospheric Composition -- The Atmosphere -- The Main Features of Atmospheric Circulation -- Water Vapor, Clouds and Rainfall -- Reconstructing Changes in Precipitation -- Modes of Variability of the Atmosphere -- The Oceans -- Main Characteristics of the Oceans -- Oceanic Circulation -- Reconstructing Ocean Circulation in the Past -- El Niño, Interplay Between the Atmosphere and the Oceans -- The Terrestrial and Marine Biosphere -- The Geographical Distribution of the Biosphere -- The Role of the Biosphere -- Biosphere of the Past and Paleoclimates -- The Cryosphere -- The Role of the Cryosphere -- The Cryosphere in the Past and Paleoclimates -- The Lithosphere: Over Large Timescales -- The Climate System -- References -- 2 The Changing Face of the Earth Throughout the Ages -- Paleogeographic Reconstructions -- Continental Drift -- The Paleomagnetic Tool, Tests and Uncertainties -- The Topography of the Earth -- The Evidence from Flora -- The Evidence from Erosion Sediment -- Stable Isotope Paleoaltimetry -- Eustatic Variations and Ocean Gateways -- An Overview of the Changing Face of Earth Through the Ages -- Conclusion -- References -- 3 Introduction to Geochronology -- 4 Carbon-14 -- Principles of the Radiocarbon Method -- Discovery of the Method -- Principle of the 14C Dating Method -- Estimation of the Half-Life and the First 14C Dating -- Principle of the Method. , Validity of the Assumptions and Definition of a Reference Standard for the Atmosphere -- Calibration of the 14C Ages -- Methods and Results -- Examples of Precise Calibration of 14C Ages -- The Dating of the Eruption of Santorini -- The Bipolar Seesaw or the North-South Heat Transfer -- Apparent Ages -- Oceanic Environments: The Reservoir Ages -- Continental Environments: The Hard Water and Dead Carbon Effects -- The 14C Exchanges in the Carbon Reservoirs -- Examples of Simulation of Modern Oceanic Circulation -- Oceanic Paleocirculation -- Mineralization of Organic Matter in Soil -- Treatment of Samples and Calculations of 14C Ages -- Physical-Chemical Treatment -- Determination of a 14C Age -- Some Examples of Post-depositional Disturbances of the 14C Ages -- References -- 5 The 40K/40Ar and 40Ar/39Ar Methods -- Principles of the K-Ar Method -- Diagram of Radioactive Decay in 40K -- The Age Equation -- Operation of the Potassium-Argon Clock -- Datable Materials and Age Ranges -- The Unspiked K-Ar Method -- Selection and Preparation of the Samples -- Determining 40Ar* -- Example of a Calculation of Age -- The 40Ar/39Ar Method: General Principles -- The Age Equation -- Corrections for Atmospheric Argon and Interference of Mass -- The Age Spectra -- The Single Grain Method -- The Isochrones -- Selection and Preparation of Samples -- Mass-Spectrometric Analysis -- Calculation of Age -- Advantages and Limitations of the 40K/40Ar and 40Ar/39Ar Methods -- Application: Example of the Dating of the Laschamp Event -- References -- 6 Dating of Corals and Other Geological Samples via the Radioactive Disequilibrium of Uranium and Thorium Isotopes -- Abstract -- Methodology of 230Th/238U Dating -- Principle of 230Th/238U Dating -- Selecting a Coral for 230Th/238U Dating -- Chemical Procedure -- Physical Measurement by Mass Spectrometry. , Limitations of the Method -- The Nuclear Recoil Effect and the 'Open' Dating System -- The Open System: Empirical Model -- Estimating the Change in Sea Level from Tropical Corals -- Other Geological Samples Datable by the U/Th Method -- Conclusions -- References -- 7 Magnetostratigraphy: From a Million to a Thousand Years -- Establishing the Scale of Magnetic Polarities -- First Coupled Measurements: Magnetization of Volcanic Rocks-K/Ar Dating -- the McDougall and Tarling Scale and the Mankinen and Dalrymple Scale for the Plio-Pleistocene -- Magnetic Stratigraphy in Pliocene-Pleistocene Sedimentary Series -- Magnetic Anomalies at Sea and the Heirtzler Scale of Magnetic Polarities -- The Cande and Kent Polarity Scale -- Astronomical Calibration of the Polarity Scale -- Principle and Practice of Magnetostratigraphy -- A High-Quality Magnetostratigraphic Study: The Siwalik Sequences in Pakistan -- Geomagnetic Excursions and the Scale of Magnetic Instabilities (GITS) -- Discovery of Geomagnetic Excursions -- A Scale of Geomagnetic Instabilities? -- Magnetostratigraphy Based on Variations in the Intensity of the Geomagnetic Field -- Introduction -- A Correlation Between Sediment and Polar Ice -- Paleo-Oceanographic Implications of High-Resolution Magnetic-Assisted Stratigraphy -- Conclusions -- References -- 8 Dendrochronology -- A Bit of Botany and Ecology -- Crossdating -- Temporal and Spatial Extension -- Contribution of 14C to Calibration -- References -- 9 The Dating of Ice-Core Archives -- Ice-Air Age Difference -- Introduction -- Modeling the Densification of the Firn -- Application of the 15N and 40Ar Isotopes in the Bubbles -- Synchronization of Two Ice Cores -- The Counting of Annual Layers -- Identification of Dated Horizons -- Volcanic Horizons -- Dansgaard-Oeschger Events -- Variations in the Magnetic Field and in Solar Activity. , Orbital Tuning and Indicators of Local Insolation -- Flow Modeling -- Evaluation of Accumulation on the Surface -- Ice Flow Models -- The Limitations of Modeling -- The Inverse Method: A Collective Approach -- Conclusion -- References -- 10 Reconstructing the Physics and Circulation of the Atmosphere -- Interpretation of Records, Limitations and Uncertainties -- Uncertainties on the Temporal Scale -- Uncertainties Associated with Geochemical Indicators: The Specific Case of the Isotopic Composition of Precipitations -- Uncertainties Associated with Biological Indicators -- References -- 11 Air-Ice Interface: Polar Ice -- Melt Index and Borehole Temperatures -- Stable Isotopes of Water and Temperature -- Stable Isotopes of Air and Temperature -- Conclusions -- References -- 12 Air-Vegetation Interface: Pollen -- From the Production of Pollen to Sediment -- The Pollen Diagram -- Reconstruction of Climate -- References -- 13 Ground-Air Interface: The Loess Sequences, Markers of Atmospheric Circulation -- Abstract -- Overview of Loess -- Paleoclimate Indicators -- Sedimentological Indicators -- Biological Indicators -- Geophysical Indicators -- Geochemical Indicators -- Loess Chronology -- References -- 14 Air-Ground Interface: Reconstruction of Paleoclimates Using Speleothems -- Speleothems: Description, Distribution, Formation and Preservation -- Growth and Chronology of Speleothems -- Paleoclimate Reconstruction: A Qualitative Approach -- Paleoclimate Reconstruction: A Quantitative Approach -- Conclusion -- References -- 15 Air-Interface: δ18O Records of Past Meteoric Water Using Benthic Ostracods from Deep Lakes -- Introduction -- Existing Deep-Lake Oxygen-Isotope Records -- Hydro-Meteorological Effects -- The Isotopic Composition of Atmospheric Precipitation -- Catchment Effects -- Lake Water Balance Effects -- Transient Changes and Dynamic Effects. , Isotope Geochemistry of Benthic Freshwater Ostracods -- Vital Effects -- Water Temperature Effects -- The Fossil Ostracod Record -- Calibration Against the Instrumental Air Temperature Record -- The Record of δ18OP in Central Europe Over the Past 15,000 Years -- Late Glacial and Early Holocene Shallow-Water Temperatures -- Quantification of Hydrological Effects -- Conclusions -- Perspectives -- References -- 16 Vegetation-Atmosphere Interface: Tree Rings -- A Dendrochonological Approach -- Dendro-isotopic Analysis -- Isotopic Reconstruction of the Variations in Climate Parameters Over Time -- References -- 17 Air-Vegetation Interface: An Example of the Use of Historical Data on Grape Harvests -- Historical Series of Harvest Dates -- Reconstruction of Spring-Summer Temperatures Based on Grape Harvesting Dates -- Limitations of These Reconstructions: The Anthropic Effects -- References -- 18 Air-Ground Interface: Sediment Tracers in Tropical Lakes -- Intertropical Hydrological Variability in Africa -- Sahara, Kalahari and Arid Zones: Discontinuous Evidence of Hydrological Inversions -- (Sub)Equatorial Zone: Changes in the Activity and Position of the ITCZ -- Recent Anthropological Influence on Climate Archives: Both a Proof and a Tool to Assess the Impacts of Local and Regional Development -- References -- 19 Air-water Interface: Tropical Lake Diatoms and Isotope Hydrology Modeling -- Site Selection and Collection of Samples -- Reconstruction of Paleohydrological Conditions -- Quantification of the Oxygen Isotopic Composition of Lakes -- Hydro-Isotopic Modeling and Paleoclimatic Interpretation -- References -- 20 Air-Ice Interface: Tropical Glaciers -- Paleoclimate Markers -- Some Important Results from the Interpretation of Andean Isotopic Records -- References -- 21 Climate and the Evolution of the Ocean: The Paleoceanographic Data. , Introduction: The Development of Tools and Concepts.
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  • 2
    Keywords: Climate change. ; Paleontology . ; Physical geography. ; Geology. ; Paläoklimatologie ; Geochronologie ; Methode ; Oberproterozoikum ; Eiszeit ; Paläoklima ; Pleistozän ; Treibhausgas ; Klimaänderung ; Phanerozoikum ; Holozän ; Klimaschwankung
    Description / Table of Contents: 1. The climate system: its functioning and history -- 2. The changing face of the Earth throughout the ages -- 3. Introduction to geochronology -- 4. Carbon-14.
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (xxiv, 478 Seiten) , Illustrationen, Diagramme, Karten
    ISBN: 9783030249823
    Series Statement: Frontiers in earth sciences
    Language: English
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  • 3
    Publication Date: 2018-12-17
    Description: Using new high-resolution 10Be measurements in the NGRIP, EDML and Vostok ice cores, together with previously published data from EDC, we present an improved synchronization between Greenland and Antarctic ice cores during the Laschamp geomagnetic excursion  ∼ 41kyr ago. We estimate the precision of this synchronization to be ±20 years, an order of magnitude better than previous work. We discuss the implications of this new synchronization for making improved estimates of the depth difference between ice and enclosed gas of the same age (Δdepth), difference between age of ice and enclosed gas at the same depth (Δage) in the EDC and EDML ice cores, spectral properties of the 10Be profiles and phasing between Dansgaard–Oeschger-10 (in NGRIP) and AIM-10 (in EDML and EDC).
    Type: Article , PeerReviewed
    Format: text
    Format: archive
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  • 4
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , notRev
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  • 5
    Publication Date: 2018-03-19
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
    Publication Date: 2020-04-15
    Description: Stable isotope ratios δ18O and δD in polar ice provide a wealth of information about past climate evolution. Snow-pit studies allow us to relate observed weather and climate conditions to the measured isotope variations in the snow. They therefore offer the possibility to test our understanding of how isotope signals are formed and stored in firn and ice. As δ18O and δD in the snowfall are strongly correlated to air temperature, isotopes in the near-surface snow are thought to record the seasonal cycle at a given site. Accordingly, the number of seasonal cycles observed over a given depth should depend on the accumulation rate of snow. However, snow-pit studies from different accumulation conditions in East Antarctica reported similar isotopic variability and comparable apparent cycles in the δ18O and δD profiles with typical wavelengths of  ∼  20 cm. These observations are unexpected as the accumulation rates strongly differ between the sites, ranging from 20 to 80 mm w. e.  yr−1 ( ∼  6–21 cm of snow per year). Various mechanisms have been proposed to explain the isotopic variations individually at each site; however, none of these are consistent with the similarity of the different profiles independent of the local accumulation conditions. Here, we systematically analyse the properties and origins of δ18O and δD variations in high-resolution firn profiles from eight East Antarctic sites. First, we confirm the suggested cycle length (mean distance between peaks) of  ∼  20 cm by counting the isotopic maxima. Spectral analysis further shows a strong similarity between the sites but indicates no dominant periodic features. Furthermore, the apparent cycle length increases with depth for most East Antarctic sites, which is inconsistent with burial and compression of a regular seasonal cycle. We show that these results can be explained by isotopic diffusion acting on a noise-dominated isotope signal. The firn diffusion length is rather stable across the Antarctic Plateau and thus leads to similar power spectral densities of the isotopic variations. This in turn implies a similar distance between isotopic maxima in the firn profiles. Our results explain a large set of observations discussed in the literature, providing a simple explanation for the interpretation of apparent cycles in shallow isotope records, without invoking complex mechanisms. Finally, the results underline previous suggestions that isotope signals in single ice cores from low-accumulation regions have a small signal-to-noise ratio and thus likely do not allow the reconstruction of interannual to decadal climate variations.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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  • 7
    Publication Date: 2020-09-18
    Description: Understanding climate proxy records that preserve physical characteristics of past climate is a prerequisite to reconstruct long‐term climatic conditions. Water stable isotope ratios (δ18O) constitute a widely used proxy in ice cores to reconstruct temperature and climate. However, the original climate signal is altered between the formation of precipitation and the ice, especially in low‐accumulation areas such as the East Antarctic Plateau. Atmospheric conditions under which the isotopic signal is acquired at Aurora Basin North (ABN), East Antarctica, are characterized with the regional atmospheric model Modèle Atmosphérique Régional (MAR). The model shows that 50% of the snow is accumulated in less than 24 days/year. Snowfall occurs throughout the year and intensifies during winter, with 64% of total accumulation between April and September, leading to a cold bias of −0.86°C in temperatures above inversion compared to the annual mean of −29.7°C. Large snowfall events are associated with high‐pressure systems forcing warm oceanic air masses toward the Antarctic interior, which causes a warm bias of +2.83°C. The temperature‐δ18O relationship, assessed with the global atmospheric model ECHAM5‐wiso, is primarily constrained by the winter variability, but the observed slope is valid year‐round. Three snow δ18O records covering 2004–2014 indicate that the anomalies recorded in the ice core are attributable to the occurrence of warm winter storms bringing precipitation to ABN and support the interpretation of δ18O in this region as a marker of temperature changes related to large‐scale atmospheric conditions, particularly blocking events and variations in the Southern Annular Mode.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
    Publication Date: 2017-09-25
    Description: The oldest ice core records are obtained from the East Antarctic plateau. Water stable isotopes records are key for reconstructions of past climatic conditions both over the ice sheet and at the evaporation source. The accuracy of such climate reconstructions crucially depends on the knowledge of all the processes affecting the water vapour, precipitation and snow isotopic composition. Atmospheric fractionation processes are well understood and can be integrated in Rayleigh distillation and complex isotope enabled climate models. However, a comprehensive quantitative understanding of processes potentially altering the snow isotopic composition after the deposition is still missing, especially for exchanges between vapour and snow. In low accumulation sites such as found on the East Antarctic Plateau, these poorly constrained processes are especially likely to play a significant role. This limits the interpretation of isotopic composition from ice core records, specifically at short time scales. Here, we combine observations of isotopic composition in the vapour, the precipitation, the surface snow and the buried snow from various sites of the East Antarctic Plateau. At the seasonal scale, we highlight a significant impact of metamorphism on surface snow isotopic signal compared to the initial precipitation isotopic signal. In particular, in summer, exchanges of water molecules between vapour and snow are driven by the sublimation/condensation cycles at the diurnal scale. Using highly resolved isotopic composition profiles from pits in five East Antarctic sites, we identify a common 20 cm cycle which cannot be attributed to the seasonal variability of precipitation. Altogether, the smaller range of isotopic compositions observed in the buried and in the surface snow compared to the precipitation, and also the reduced slope between surface snow isotopic composition and temperature compared to precipitation, constitute evidences of post-deposition processes affecting the variability of the isotopic composition in the snow pack. To reproduce these processes in snow-models is crucial to understand the link between snow isotopic composition and climatic conditions and to improve the interpretation of isotopic composition as a paleoclimate proxy.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , notRev
    Format: application/pdf
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  • 9
    Publication Date: 2018-03-26
    Description: Improving the representation of the hydrological cycle in atmospheric general circulation models (AGCMs) is one of the main challenges in modeling the Earth’s climate system. One way to evaluate model performance is to simulate the transport of water isotopes. Among those available, tritium is an extremely valuable tracer, because its content in the different reservoirs involved in the water cycle (stratosphere, troposphere, and ocean) varies by order of magnitude. Previous work incorporated natural tritium into Laboratoire de Météorologie Dynamique Zoom (LMDZ)-iso, a version of the LMDZ general circulation model enhanced by water isotope diagnostics. Here for the first time, the anthropogenic tritium injected by each of the atmospheric nuclear bomb tests between 1945 and 1980 has been first estimated and further implemented in the model; it creates an opportunity to evaluate certain aspects of LDMZ over several decades by following the bomb tritium transient signal through the hydrological cycle. Simulations of tritium in water vapor and precipitation for the period 1950–2008, with both natural and anthropogenic components, are presented in this study. LMDZ-iso satisfactorily reproduces the general shape of the temporal evolution of tritium. However, LMDZ-iso simulates too high a bomb tritium peak followed by too strong a decrease of tritium in precipitation. The too diffusive vertical advection in AGCMs crucially affects the residence time of tritium in the stratosphere. This insight into model performance demonstrates that the implementation of tritium in an AGCM provides a new and valuable test of the modeled atmospheric transport, complementing water stable isotope modeling.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Format: application/zip
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  • 10
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    Copernicus GmbH
    In:  EPIC3EGU General Assembly, Vienne, Austria, 2018-04-08-2018-04-13Copernicus GmbH
    Publication Date: 2020-06-08
    Description: Oxygen and hydrogen isotope ratios in polar ice typically show variations over a large range of timescales. Since the isotope ratios are interpreted as a proxy for atmospheric temperatures, their variations can provide essential information about the natural climate variability and cycles. Nowadays high-resolution isotope samplings corresponding to depth intervals below or around the local accumulation of snow per year are routinely performed, and observed variations in the isotopic composition at a given site have frequently been interpreted as the reflection of the seasonal cycle in temperature and also to indicate multi-year quasi-periodic climatic cycles. However, studies from strongly different accumulation conditions in East Antarctica reported similar isotopic variability and comparable apparent cycles in isotope profiles with typical wavelengths of around 20 cm, which is inconsistent with a climatically driven origin. Here we show, based on spectral analysis, that these features do not correspond to truly or quasi-periodic cycles. In addition, the typical wavelengths increase with depth for most East Antarctic sites, which is inconsistent with the effect of burial and compression on a climatic cyclic signal. We explain these results by isotopic diffusion acting on a noise-dominated isotope signal. The firn diffusion length is rather stable across the Antarctic Plateau, leading to similar power spectral densities of the isotopic variations, and increases with depth in the near-surface firn. Since the first moments of the spectral density govern the characteristic spacing of the extrema of a time series – a fundamental relationship known as Rice’s law – the similar isotope spectra in turn imply similar average distances between the isotopic minima and maxima that get larger with increasing depth. Our results bear important implications for the interpretation of isotope records in terms of cyclical climate variability. They underline that simply counting isotopic extrema is not sufficient to detect periodicities, instead robust spectral analyses have to be applied in order to differentiate between true climate cycles and the apparent cycles created in the diffusion process. This has consequences for the dating of ice-core records, which is often based on or underpinned by counting isotopic maxima, but also for the detection and interpretation of quasi-periodic climate phenomena on longer timescales. Finally, the general implications of our findings are not restricted to ice cores but likely also apply to other paleo-climate archives, as other smoothing processes, e.g. the bioturbational smoothing of proxy records from marine sediments, might lead to similar apparent cycles.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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