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  • 1
    Publication Date: 2019-01-31
    Description: We present consistent annual mean atmospheric histories and growth rates for the mainly anthropogenic halogenated compounds HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116, which are all potentially useful oceanic transient tracers (tracers of water transport within the ocean), for the Northern and Southern Hemisphere with the aim of providing input histories of these compounds for the equilibrium between the atmosphere and surface ocean. We use observations of these halogenated compounds made by the Advanced Global Atmospheric Gases Experiment (AGAGE), the Scripps Institution of Oceanography (SIO), the Commonwealth Scientific and Industrial Research Organization (CSIRO), the National Oceanic and Atmospheric Administration (NOAA) and the University of East Anglia (UEA). Prior to the direct observational record, we use archived air measurements, firn air measurements and published model calculations to estimate the atmospheric mole fraction histories. The results show that the atmospheric mole fractions for each species, except HCFC-141b and HCFC-142b, have been increasing since they were initially produced. Recently, the atmospheric growth rates have been decreasing for the HCFCs (HCFC-22, HCFC-141b and HCFC-142b), increasing for the HFCs (HFC-134a, HFC-125, HFC-23) and stable with little fluctuation for the PFCs (PFC-14 and PFC-116) investigated here. The atmospheric histories (source functions) and natural background mole fractions show that HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125 and HFC-23 have the potential to be oceanic transient tracers for the next few decades only because of the recently imposed bans on production and consumption. When the atmospheric histories of the compounds are not monotonically changing, the equilibrium atmospheric mole fraction (and ultimately the age associated with that mole fraction) calculated from their concentration in the ocean is not unique, reducing their potential as transient tracers. Moreover, HFCs have potential to be oceanic transient tracers for a longer period in the future than HCFCs as the growth rates of HFCs are increasing and those of HCFCs are decreasing in the background atmosphere. PFC-14 and PFC-116, however, have the potential to be tracers for longer periods into the future due to their extremely long lifetimes, steady atmospheric growth rates and no explicit ban on their emissions. In this work, we also derive solubility functions for HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116 in water and seawater to facilitate their use as oceanic transient tracers. These functions are based on the Clark–Glew–Weiss (CGW) water solubility function fit and salting-out coefficients estimated by the poly-parameter linear free-energy relationships (pp-LFERs). Here we also provide three methods of seawater solubility estimation for more compounds. Even though our intention is for application in oceanic research, the work described in this paper is potentially useful for tracer studies in a wide range of natural waters, including freshwater and saline lakes, and, for the more stable compounds, groundwaters.
    Type: Article , PeerReviewed
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  • 2
    Publication Date: 2019-01-31
    Description: Abstract High-latitude cold-water coral reefs are particularly vulnerable to climate change due to enhanced CO2 uptake in these regions. To evaluate their physiological functioning and potential application as pH archives, we retrieved both recent and fossil samples of Lophelia pertusa along the Norwegian margin from Oslofjord (59°N), over to Trondheimsfjord, Sula and Lopphavet (70.6°N). Boron isotope analyses (δ11B) were undertaken using solution-based and laser ablation multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS; LA-ICP-MS), and secondary ion mass spectrometry (SIMS). Epi-fluorescence microscopy was employed to provide a rapid pre-screening routine for structure-specific subsampling in the coral skeleton. This integrated approach enabled us to assess heterogeneities within single specimens, as well as to investigate the role of local environmental influences including recent and past variations. All three mass spectrometry methods show substantial differences in the δ11B of the theca wall (TW) and the centres of calcification (COC's). Micro-bulk subsamples milled from the theca wall of modern specimens originating from different habitats but with comparable seawater pH (8–8.16) gave consistent δ11B values averaging 26.7 (±0.2‰, 2σ, n = 4), while COC subsamples systematically deviated towards lower B/Ca (by ~40%) and depleted δ11B values (minimum 22.7 ± 0.3‰, 2σ), implying a difference of at least 4‰ between TW and COC. SIMS and LA-ICP-MS measurements identified much larger internal heterogeneities with maximum variation of ~10‰ between the distinct skeletal structures; minimal SIMS δ11B values of ~17.3 ± 1.2‰ (2σ) were associated with the pure COC material. Our findings may be interpreted in terms of the occurrence of two main, but likely different, biomineralisation mechanisms in L. pertusa, with the COC's generally exhibiting minimal pH up-regulation, potentially supporting the use of bicarbonate in the early stages of biomineralisation. Furthermore, we highlight the potential utility of L. pertusa for palaeo-proxy studies if targeting the compositionally homogenous TW zones devoid of COC admixtures, which appear to provide highly reproducible measurements.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 3
    Publication Date: 2019-01-31
    Type: http://purl.org/eprint/type/Thesis
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  • 4
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    In:  Veröffentlichungen / Deutsche Geodätische Kommission. Reihe C, Dissertationen ; Heft Nr. 829
    Publication Date: 2019-01-31
    Type: http://purl.org/eprint/type/Thesis
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  • 5
    Publication Date: 2019-02-01
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
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  • 6
    Publication Date: 2019-01-31
    Language: English
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  • 7
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    Physika-Verlag, Würzburg
    In:  Herausgeberexemplar (Archiv der DGG in Leipzig) | 8 Z NAT 2148
    Publication Date: 2019-01-26
    Description: Inhaltsverzeichnis : Übersichtsartikel: EIDEN, R. und G. ESCHELBACH: Das atmosphärische Aerosol und seine Bedeutung für den Energiehaushalt der Atmosphäre . . . 189 ; MÜLLER, G.: Theoretical Body Wave Seismograms for Media with Spherical Symmetry — Discussion and Comparison of Approximate Methods . . . 229 ; SCHICK, R., and M. RIUSCETTI: An Analysis of Volcanic Tremors at South Italian Volcanoes . . . 247 ; FRÖHLICH, R. K.: Combined Magnetic and Geoelectrical Investigations over Lava Flows in the Volcanic Zone of the Laacher See, West Germany . . . 263 ; MAKRIS, J., J. ZIMMERMANN, H. C. BACHEM, and B. RITTER: Gravity Survey of South AFAR, Ethiopia . . . 279 ; BRÜCKL, E., und W. FÜRLINGER: Ein Vergleich von geologischen Gefügeaufnahmen mit seismischen Messungen . . . 291 ; As, J. A.: The Compensation Method for Measuring the Components of the Earth’s Magnetic Field . . . 303 ; Briefe an den Herausgeber: FUCHS, K.: The Fine Structure of the Lower Lithosphere — a Possible Marker for its Vertical Deformation . . . 313 ; LAUDATIO zur Verleihung der Emil-Wiechert-Medaille an Prof. Dr. LUDWIG BIERMANN . . . 317 ; In memoriom GÜNTER DIETRICH . . . 319 ;
    Description: DGG, DFG, SUB Göttingen
    Description: research
    Keywords: Geophysik ; Physische Geografie ; Atmosphäre ; Deformation ; Ethiopia ; Geoelectrics ; Geomagnetism ; Geomagnetismus ; Germany ; Gravitation ; Gravity ; Italy ; Laacher See ; Lithosphere ; Seismik ; Seismics ; Volcanism ; Vulkanismus ; FID-GEO-DE-7
    Language: German , English
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  • 8
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    Physika-Verlag, Würzburg
    In:  Herausgeberexemplar (Archiv der DGG in Leipzig) | 8 Z NAT 2148
    Publication Date: 2019-01-26
    Description: Inhaltsverzeichnis : STUKENBRÖKER, B.: Ergebnisse von Erdgezeiten-Parallelregistrierungen mit drei ASKANIA-Gravimetern . . . 1 ; DRIMMEL, J., G. GANGL, R. GUTDEUTSCH, M. KOENIG und E. TRAPP: Modellseismische Experimente zur Interpretation makroseismischer Daten aus dem Bereich der Ostalpen . . . 21 ; BORM, G.: Solutions of Boundary Value Problems of Multilayer Analogs of Geoelectrics and Hydrology . . . 41 ; JACOBY, W. R.: Isostasie und Dichteverteilung in Kruste und oberem Mantel . . . . . . 79 ; BUNTEBARTH, G.: Modellberechnungen zur Temperatur-Tiefen-Verteilung im Bereich der Alpen und des Alpenvorlandes . . . 97 ; BUNTEBARTH, G.: Über die Größe der thermisch bedingten Bouguer-Anomalie in den Alpen . . . 109 ; EHRISMANN‚ W.‚ W. LEPPICH, O. LETTAU, O. ROSENBACH und P. STEINHAUSER: Gravimetrische Detail-Untersuchungen in den westlichen Hohen Tauern . . . 115 ; EHRISMANN, W.: Ein allgemeines Verfahren zur digitalen Berechnung der Schwerewirkung von Modellkörpern . . . 131 ; KAHLE, H.-G., and M. TALWANI: Gravimetric Indian Ocean Geoid . . . 167 ;
    Description: DGG, DFG, SUB Göttingen
    Description: research
    Keywords: Geophysik ; Physische Geografie ; Alpen ; Alpenvorland ; Erdmantel ; Geoelectrics ; Geoelektrik ; Gravimetrie ; Gravitation ; Hohen Tauern ; Hydrologie ; Hydrology ; Indian Ocean ; Seismik ; FID-GEO-DE-7
    Language: German , English
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  • 9
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    Springer, Berlin
    In:  SUB Göttingen | 8 Z NAT 2148
    Publication Date: 2019-01-26
    Description: Inhaltsverzeichnis : Bonjer, K.-P., Gelbke, C., Gilg, B., Rouland, D., Mayer-Rosa, D., Massinon, B.: Seismicity and dynamics of the Upper Rhinegraben . . . 1 ; Zucca, J. J.: The crustal structure of the southern Rhinegraben from re-interpretation of seismic refraction data . . .13 ; Cavaliere, T., Jones, A. G.: On the identification of a transition zone in electrical conductivity between the lithosphere and asthenosphere: a plea for more precise phase data . . . 23 ; Brasse, H., Junge, A.: The influence of geomagnetic variations on pipelines and an application for largescale magnetotelluric depth sounding . . . 31 ; Nevanlinna, H.: Some Characteristics of the horizontal field variations around the geomagnetic jerk of 1970 . . . 37 ; Lühr, H., Klöcker, N., Thürey, S.: Ground-based observations of a very intense substorm-related pulsation event . . . 41 ; Dürschner, H.: Dreidimensionale Seismik in der Exploration auf Kohlenwasserstoff-Lagerstätten . . . 54 ; Varga, P.: Long-term variations recorded by extensometers . . . 68 ; Book reviews . . . 71 ; Preface . . . 75 ; Orr, D.: Magnetospheric hydromagnetic waves: their eigenperiods, amplitudes and phase variations; a tutorial introduction . . . 76 ; Ward, I.A.: ELF intensity levels at geostationary orbit and pulsating aurora . . . 85 ; Gough, H., Orr, D., Wedeken, U.: Ground observations of geomagnetic pulsations during a quiet magnetospheric interval correlated with satellite plasma measurements . . . 92 ; Gardner, M.: Period, phase and resonant structure of a pulsation event seen by the ISEE 1 and 2 spacecraft on 2-3 April 1978 . . . 102 ; Glaßmeier, K.H., Lester, M., Mier-Jedrzejowicz, W. A. C., Green, C. A., Rostoker, G., Orr, D., Wedeken, U., Junginger, H., Amata, E.: Pc5 pulsations and their possible source mechanisms: a case study . . . 108 ; Wedeken, U., Inhester, B., Korth‚ A., Glaßmeier, K.-H., Gendrin, R., Lanzerotti‚ L. J., Gough, H., Green, C. A., Amatas, E., Pedersen, A.‚ Rostoker, G.: Ground-satellite coordinated study of the April 5, 1979 events: flux variations of energetic particles and associated magnetic pulsations . . . 120 ; Inhester‚ B., Wedeken, U., Korth‚ A., Perraut, S., Stokholm, M.: Ground-satellite coordinated study of the April 5, 1979 events: observation of O+ cyclotron waves . . . 134 ; Preface . . . 143 ; Hjelt, S.E.: Deep electromagnetic studies of the Baltic Shield . . . 144 ; Pajunpää, K.: Magnetometer array studies in Finland - determination of single station transfer functions . . . 153 ; Červ, V., Pek, J., Praus, O.: Models of geoelectrical anomalies in Czechoslovakia . . . 161 ; Schwarz, G., Haak, V., Martínez, E., Bannister, J.: The electrical conductivity of the Andean crust in northern Chile and southern Bolivia as inferred from magnetotelluric measurements . . . 169 ; Vanyan, L. L.: Electrical conductivity of the asthenosphere . . . 179 ; Ritz, M.: A high conductivity anomaly on the West African craton (Mali) . . . 182 ; Meloni, A., Gregori, G. P., Lanzerotti‚ L. J., Medford, L. V.: Search for a possible electromagnetic coupling between a transatlantic communication cable and the magma Chamber in the mid-Atlantic ridge . . . 185 ; Schnegg, P.-A., Fischer, G.: A new pulsed audiomagnetotelluric technique . . . 191 ; Heikka, J., Zhamaletdinov, A. A., Hjelt, S. E., Demidova, T. A., Velikhov, Ye. P.: Preliminary results of MHD test registrtions in northern Finland . . . 199 ; Mareschal, M., Vasseur, G.: Bimodal induction in non-uniform thin sheets: do the present algorithms work for regional studies . . . 203 ; Hvoždara, M.: Solution of the stationary approximation for MT fields in the layered Earth with 3D and 2D inhomogeneities . . . 214 ; Hu, W. B., Dosso, H. W., Nienaber, W.: Analogue-model magnetic field responses of an ocean channel, an island and a seamount in the Hainan Island region . . . 222 ; Winch, D. E.: Conductivity modelling of the Earth using solar and lunar daily magnetic variations . . . 228 ;
    Description: DGG, DFG, SUB Göttingen
    Description: research
    Keywords: Geophysik ; Africa ; Asthenosphere ; Aurora ; Baltic Shield ; China ; Czechoslovakia ; Earth’s Crust ; ELAS project ; Electrojets ; Electromagnetic Induction ; ELF waves ; Exploration Seismics ; Geomagnetic Induction Studies ; Geomagnetic Pulsations ; Geomagnetic Secular Variation ; Geomagnetic Variations ; Hydromagnetic Waves ; Ion Cyclotron Waves ; Magnetometer Arrays ; Magnetospheric Plasma ; Magnetotellurics ; MHD generator ; Pipelines ; Refraction Seismology ; Rhinegraben ; Satellite Observations ; Seismicity ; South America ; Transatlantic Cable ; FID-GEO-DE-7
    Language: German , English
    Type: anthology_digi
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  • 10
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    Friedr. Vieweg & Sohn, Braunschweig
    In:  SUB Göttingen | 8 Z NAT 2148
    Publication Date: 2019-01-26
    Description: Inhaltsverzeichnis : Fanselau, G.: Geophysikalische Arbeiten Prof. Filchners in Inner-Asien. . . . S. 1. ; Bartels, J.: Aussprachebemerkung zum Vortrag Fanselau (über Filchner). . . . S. 6. ; Sieberg, A.: Arbeitsgebiete der Reichsanstalt für Erdbebenforschung in ihren Beziehungen zur Geologie und Bergbau. . . . S. 7. ; Krumbach, G.: Über ein Stationsseismometer für optische Registrierung. . . . S. 17. ; Martin, H.: Ein neuer Erschütterungsmesser und die Aufzeichnung nicht-sinusförmiger Bewegungen. . . . S.24. ; Herrmann, A.: Grundsätzliche Betrachtungen über piezoelektrische Beschleunigungsmesser. . . . S. 31. ; Trappe, Fr. und Ruprecht, L.: Die Anwendung der seismischen Reflexionsmethode zur Untersuchung von Salzstöcken im Harzvorland. . . . S. 37. ; Meisser, O.: Zur absoluten Schweremessung. . . . S. 41. ; Jung, K.: Zur Isostasiefrage. . . . S. 47. ; Graf, A.: Über die Bestimmung der Gravimeterkonstante bei einem frei hängenden Federsystem. . . . S. 49. ; Jung. H.: Dichtebestimmung im anstehenden Gestein durch Messung der Schwerebeschleunigung in verschiedenen Tiefen unter Tage. . . . S. 56. ; Rössiger, M.: Diskussionsbemerkung zum Vortrag von H. Jung. . . . S. 65. ; Bock, R.: Über die Magnetische Reichsvermessung II. Ordnung und ihre ersten vorläufigen Ergebnisse. . . . S. 66. ; Reich, H.: Stand der geophysikalischen Reichsaufnahme. . . . S. 73. ; Rössiger, M.: Die experimentellen Grundlagen des Dipol-Induktionsverfahrens. . . . S. 83. ; Paul, M.: Erfahrungen mit einem neuen geothermischen Aufschlußverfahren. . . . S. 88. ; Rössiger, M.: Diskussionsbemerkungen zum Vortrage von M. Paul. . . . S. 93. ; Meinardus, W.: Die Temperaturverhaltnisse der südlichen Halbkugel. . . . S. 94. ; Model, Fr.: Der neue Schreibpegel in Arkona. . . . S. 107. ; Mitteilung für die Mitglieder der Deutschen Geophysikalischen Gesellschaft. Arbeitsgemeinschaft der vier an der Bodenforschung beteiligten Gesellschaften. . . . S. 113. ; Schulz, B.: Wissenschaftliche Ergebnisse der Deutschen Atlantischen Expedition auf dem Forschungs- und Vermessungsschiff „Meteor“ 1925-1927, Bd. VI, 2. Teil, 3. Lieferung. . . . S.114. ; Schulze, G. A.: Veröffentlichungen des Instituts der Deutschen Forschungsgesellschaft für Bodenmechanik (Degebo) an der Technischen Hochschule Berlin, Heft 5. Über Zusammenhänge zwischen Wasserhaushalt der Tonminerale und bodenphysikalischen Eigenschaften bindiger Böden. . . . S. 114. ; Schulze, G. A.: M. Dengler: Erkundung von Verkehrswegen in Neuländern. . . . S. 115. ; Schriel: P. Kukuk: Geologie des Niederrheinisch-Westfälischen Steinkohlengebietes. . . . S. 115. ; Druckfehlerberichtigung. . . . S. 116. ; Graf, A.: Großentfernungsmessungen mit dem Askania-Gravimeter in Texas. . . . S. 117. ; Thyssen, St. v.: Über die Wirkungsweise von einigen feldfähigen Federgravimetern. . . . S. 121. ; Thyssen, St. v. und Rülke, O.: Beschreibung des neuen Gerätes zur Bestimmung der Fortpflanzungsgeschwindigkeit elastischer Wellen in Gesteinsproben und einige Meßergebnisse. . . . S. 130. ; Schmidt, O. v.: Über Kopfwellen in der Seismik. . . . S.141. ; Ramspeck, A.: Der Einfluß eines mit der Tiefe veränderlichen Elastizitätsmoduls auf den Weg elastischer Wellen im Boden. . . . S. 148. ; Bungers, H.: Seismische Untersuchungen des Geophysikalischen Instituts in Göttingen, XXXV. Zur Methodik der Nahbebenbearbeitung. . . . S. 160. ; Jeffreys, H.: Remarks an the Paper of G. Schmerwitz on Central European Earthquakes. . . . S. 168. ; Müller, M.: Die Meßverfahren zur Bestimmung des Dispersionseffektes des Widerstandes von Gesteinsmedien. . . . S. 176. ; Herold, F.: Bemerkung zu Zählrohrmessungen im Gelände. . . . S. 182. ; Hoffrogge, Chr.: Experimentelle Untersuchungen der bodennahen Luftströmungen am Hang und im ebenen Gelände. . . . S. 184. ; Bartels, J.: Potsdamer erdmagnetische Kennziffern. 4. Mitteilung. . . . S. 214. ; Brunner, W.: Tägliche Sonnenflecken-Relativzahlen für das 4. Vierteljahr 1938. . . . S. 222. ; Brunner, W.: Tägliche Sonnenflecken-Relativzahlen für das 1.Vierteljahr 1939. . . . S.223. ; Nachruf auf Oskar Venske. . . . S. 224. ; Schulz, B.: Theodor Stocks: Grundkarte der ozeanischen Lotungen 1: 5 Millionen, Blatt S I 2 mit durchsichtigem Deckblatt. . . . S. 226. ; Müller, M.: Volker Fritsch: Grundzüge der Funkgeologie. . . . S. 226. ; Bungers, K.: K. Jung: Kleine Erdbebenkunde. . . . S. 227. ; Kirsch, G.: Geomechanik. . . . S. 228. ; Druckfehlerberichtigung. . . . S. 228. ; Breyer, Fr.: Die topographische Reduktion der Lotabweichungen am Nanga Parbat mit Hilfe eines Diagramms. . . . S. 229. ; K. Wegener: Bemerkungen zu dem vertikalen Gradienten der Schwere. . . . S. 247. ; Tams, E.: Zur Frage der regionalen Verkoppelung von Erdbeben. II. . . . S. 249. ; Martin, H.: Zur Frage Schwingweg-‚ Geschwindigkeits- oder Beschleunigungsmesser. . . . S. 260. ; Schmerwitz, G.: Berechnung der Dicke der Erdkruste und einiger physikalischer Eigenschaften aus mitteleuropäischen Nahbebenaufzeichnungen. . . . S. 268. ; Trommsdorff, Fro: Seismische Untersuchungen des Geophysikalischen Instituts in Göttingen. XXXVI. Untersuchungen über die natürliche Bodenunruhe (Mikroseismik) mit transportablen Dreikomponentenstationen. . . . S. 304. ; Bungers, R.: Seismische Untersuchungen des Geophysikalischen Instituts in Göttingen. XXXVII. Die Überlagerung zweier Wellen verschiedener Herkunftsrichtung. . . . S. 321 . ; Bartels, J.: Potsdamer erdmagnetische Kennziffern. 5. Mitteilung. . . . S. 333. ; Brunner, W.: Tägliche Sonnenflecken-Relativzahlen für das 2. Vierteljahr 1939. . . . S. 336. ; Balensiefer, E., Büttner, K., Pfleiderer, H. und Wetzel, W.: Untersuchungen über die Bodenunruhe auf Sylt. . . . S. 337. ; Schmerwitz, G.: Die Bedeutung des Ausgleichungsverfahrens für die Auswertung von Nahbeben-Seismogrammen. . . . S. 365. ; Lorenz, H.: Ermittlung des Zustandes des Erdinnern aus dem Energieinhalt. . . . S. 371. ; Becker, L.: Die Bewegung der Kontinente und die Köppen-Wegenersche Polkurve. . . . S. 379. ; Referate : Wegener, K.: Die Laufgeschwindigkeit c der Longitudinalwellen als Funktion der Temperatur. . . . S. 390. ; Suckstorff, G. A.: F. Linke: Meteorologisches Taschenbuch, 3. Ausgabe. . . . S. 394. ; Suckstorff, G. A.: W. G. Kendrew: Climate. . . . S. 394. ; Schneider, W.: A. Ramspeck und G. A. Schulze: Die Dispersion elastischer Wellen im Boden. . . . S. 395. ; Druckfehlerberichtigung. . . . S. 395. ; Geophysikalische Berichte ; Register der Geophysikalischen Berichte ; Namenregister der Geophysikalischen Berichte ;
    Description: DGG, DFG, SUB Göttingen
    Description: research
    Keywords: Geophysik ; Physische Geografie ; Angewandte Geophysik ; Atmosphäre ; Aurora ; Deformationen ; Erdmagnetismus ; Geoelektrik ; Geomagnetismus ; Gezeiten ; Gravimetrie ; Gravitation ; Luftelektrizität ; Physik des Meeres und der Gewässer ; Polarlicht ; Schwere ; Seismik ; Statik ; Strahlung ; Tektonik ; Tiden ; FID-GEO-DE-7
    Language: German , English
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  • 11
    Publication Date: 2019-01-28
    Description: We examine the intra‐arc crustal seismicity of the Southern Andes Volcanic Zone (SVZ). Our aim is to resolve inter‐seismic deformation in an active magmatic arc dominated by both margin‐parallel (Liquiñe‐Ofqui fault system, (LOFS)) and Andean transverse faults (ATF). Crustal seismicity provides information about the schizosphere tectonic state, delineating the geometry and kinematics of high strain domains driven by oblique‐subduction. Here, we present local seismicity based on 16‐months data collected from 34 seismometers monitoring a ~200 km long section of the Southern Volcanic Zone, including the Lonquimay and Villarrica volcanoes. We located 356 crustal events with magnitudes between Mw 0.6 and Mw 3.6. Local seismicity occurs at depths down to 40 km in the forearc and consistently shallower than 12 km beneath the volcanic chain, suggesting a convex shape of the crustal seismogenic layer bottom. Focal mechanisms indicate strike‐slip faulting consistent with ENE‐WSW shortening in line with the long‐term deformation history revealed by structural geology studies. However, we find regional to local‐scale variations in the shortening axes orientation as revealed by the nature and spatial distribution of microseismicity, within three distinctive latitudinal domains. In the northernmost domain, seismicity is consistent with splay faulting at the northern termination of the LOFS; in the central domain, seismicity distributes along ENE‐ and WNW‐striking discrete faults, spatially associated with, hitherto seismic ATF. The southernmost domain, in turn, is characterized by activity focused along a N15°E striking master branch of the LOFS. These observations indicate a complex strain compartmentalization pattern within the intra‐arc crust, where variable strike‐slip faulting dominates over dip‐slip movements.
    Type: Article , PeerReviewed
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  • 12
    Publication Date: 2019-01-28
    Description: Highlights • next to organic matter degradation, bioirrigation and bottom water percolation through permeable surface sediments enhances benthic TPO43- and Fe2+ release • changes in bottom water oxygenation induce slight changes benthic TPO43- and Fe2+ release rates measured in 2011 and 2014 • deoxygenation experiments imply enhanced TPO43- and Fe2+ release at ongoing deoxygenation in the Mauritanian OMZ Abstract Benthic fluxes of total dissolved phosphate (TPO43-), dissolved iron (Fe2+), and dissolved inorganic carbon (DIC) were determined in situ using benthic chambers at nine stations along a depth transect between 47 and 1108 m water depth at 18 °N off Mauritania (NW Africa) during the upwelling season in 2014 (RV Meteor cruise M107). Bottom water oxygen (O2) concentrations were always ≥ 25 µM, and all fluxes (TPO43-, Fe2+, DIC) were consistently directed from the sediments into the bottom water. The highest benthic TPO43- release of 0.2 ± 0.07 mmol m2 d-1 was found at 47 m water depth (50 µM O2). The highest diffusive Fe2+ flux of 0.03 mmol m2 d-1, determined from porewater Fe2+ concentrations, occurred at 67 m water depth (27 µM O2). This was much lower than the detrital Fe supply as indicated by constant Fe/Al ratios along the depth transect. TPO43- release rates decreased concurrently with DIC flux and water depth. A difference of up to one order of magnitude between benthic chamber and diffusive TPO43- fluxes indicated that the total TPO43- release was strongly enhanced by bioirrigation. The observed fluxes were similar to those measured during an earlier cruise in 2011, generally indicating comparable release rates during both upwelling seasons. Furthermore, ex situ oxygen manipulation experiments showed an increase of the nutrient release (e.g. TPO43-, Fe2+) after seven days of anoxic bottom water conditions. The fluxes were enhanced by a factor of 1.4 for P and 7.3 for Fe compared to the measured release under natural conditions and reached values as high as those measured in the anoxic oxygen minimum zone off Peru. Our observations support the hypothesis that increasing deoxygenation of the oceans will likely enhance sedimentary TPO43- and Fe2+ release and thus contribute to a positive feedback mechanism with increasing nutrient levels and increased ocean productivity.
    Type: Article , PeerReviewed
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  • 13
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    Alfred-Wegener-Institut
    In:  Alfred-Wegener-Institut, List auf Sylt, Germany, 2 pp.
    Publication Date: 2019-01-28
    Description: Wochenbericht AL519-1 (23.-27.01.2019) [Alkor]
    Type: Report , NonPeerReviewed
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  • 14
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    In:  Wirtschaftsland . pp. 38-43.
    Publication Date: 2019-01-28
    Description: Zwei Meere vor der Haustür, dazu der Nord-Ostsee-Kanal als meistbefahrene künstliche Wasserstraße - seit Jahrhunderten ist die maritime Wirtschaft in Schleswig-Holstein zu Hause und nach wie vor ein wichtiger Wirtschaftsmotor
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  • 15
    Publication Date: 2019-01-25
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  • 16
    Publication Date: 2019-01-30
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  • 17
    Publication Date: 2019-01-29
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  • 18
    Publication Date: 2019-01-30
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  • 19
    Publication Date: 2019-01-30
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  • 20
    Publication Date: 2019-01-30
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  • 21
    Publication Date: 2019-01-30
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  • 22
    Publication Date: 2019-01-29
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  • 23
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    Springer International Publishing
    In:  Fission-Track Thermochronology and its Application to Geology | Springer Textbooks in Earth Sciences, Geography and Environment
    Publication Date: 2018-09-04
    Description: The geomorphologic evolution of orogens has been a subject of revived interest and accelerated development over the past few decades, thanks to both the increasing availability of high-resolution data and computing power and the realisation that orogenic topography plays a central role in coupling deep-earth and surface processes. Low-temperature thermochronology takes a central place in this revived interest, as it allows us to link quantitative geomorphology to the spatial and temporal patterns of exhumation. In particular, rock cooling rates over million-year timescales derived from thermochronological data have been used to reconstruct rock exhumation histories, to detect km-scale relief changes, and to document lateral shifts in relief. In this chapter, we review how classic approaches of determining exhumation histories have contributed to our understanding of landscape evolution, and we highlight novel approaches to quantifying relief changes that have been developed over the last decade. We discuss how patterns of exhumation in laterally accreting orogens are recorded by low-temperature thermochronology, and how such data can be applied to infer temporal variations in exhumation rates, providing indirect constraints on topographic development. We subsequently review recent studies aimed at quantifying relief development and modification associated with river incision, glacial modifications of landscapes, and shifts in the position of range divides. We also point out how interpretations of some datasets are non-unique, emphasizing the importance of understanding the full range of processes that may influence landscape morphology and how each may affect spatial patterns of thermochronologic ages.
    Language: English
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  • 24
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    Springer
    In:  Karst Water Environment : Advances in Research, Management and Policy | The Handbook of Environmental Chemistry
    Publication Date: 2018-09-11
    Description: Examination of microbial communities within karst aquifers is an important aspect of determining the quality of the drinking water obtained from groundwater. While past work has been based on culture-based assays, a more complete view of the microbial community within karst aquifers can be achieved using molecular approaches based on DNA sequencing. Due to a reduced cell number when compared to surface environments, collecting sufficient microbial cells for analysis in karst aquifers can be problematic. In addition to issues of cell density, particulates due to the geologic location, technological limitations of equipment that can be hand-carried and work for extended periods underground, and even the physical access to some of these subsurface sites, all contribute to making examination of the microbiology in karst aquifers a challenge. This chapter highlights some of the approaches we have used to successfully isolate microbial cells for DNA extraction from an aquifer accessed in a remote cave location. The methods we developed can aid other researchers to evaluate the microbiology of similar isolated karst aquifers.
    Language: English
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  • 25
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    Elsevier
    In:  In: Encyclopedia of Ecology. , ed. by Fath, B. D. Elsevier, Oxford, UK, pp. 108-115. 2. ed. ISBN 978-0-444-63768-0
    Publication Date: 2018-10-16
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  • 26
    Publication Date: 2018-10-23
    Description: Highlights • New 40Ar/39Ar dates from SW Pacific and Zealandia igneous rocks form the basis of a revised tectonic model. • Intraplate lavas erupted onto continental, LIP and oceanic crust from 99 to 78 Ma. • Spreading ridges and transforms adjusted themselves around a collided Hikurangi Plateau. • Kinematically stable Pacific-Antarctic spreading became established from c. 84 Ma. • Osbourn Trough Sea floor spreading possibly ceased at c. 79 Ma. Abstract New 40Ar/39Ar ages of igneous rocks clarify the nature, timing and rates of movement of the oceanic Pacific, Phoenix, Farallon and Hikurangi plates against Gondwana and Zealandia in the Late Cretaceous. With some qualifications, cessation of spreading at the Osbourn Trough is dated c. 79 Ma, i.e. 30–20 m.y. later than 110–100 Ma Hikurangi Plateau-Gondwana collision. Oceanic crust of pre-84 Ma is confirmed to be present at the eastern end of the Chatham Rise, and a 99–78 Ma intraplate lava province erupted across juxtaposed Zealandia, Hikurangi Plateau and oceanic crust. We propose a new regional tectonic model in which a mechanically jammed Hikurangi Plateau resulted in the dynamic propagation of small, kinematically misaligned short-length 110–84 Ma spreading centres and long-offset fracture zones. It is only from c. 84 Ma that geometrically stable spreading became localized at what is now the Pacific-Antarctic Ridge, as Zealandia started to split from Gondwana.
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  • 27
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    Taylor & Francis Group
    In:  The Anthropocene Debate and Political Science | Routledge Research in Global Environmental Governance
    Publication Date: 2018-10-23
    Language: English
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  • 28
    Publication Date: 2018-10-26
    Description: After Rock-Eval & TOC screening and heterogeneity evaluation on 91 Palaeogene source rock samples from a well drilled in the Austrian Molasse Basin, ten shale samples were selected for detailed investigations by means of pyrolysis-gas chromatography, bulk kinetics and biomarker identification and quantification. Afterwards, 2-D biplots based on principal component analysis were applied to unravel the palaeo-environmental control on the development of petroleum source rocks. All samples are immature source rocks with good petroleum generation potentials. The redox environment during deposition was generally reducing, and palaeosalinity is suggested to be the main factor causing the differences in organic carbon contents among the samples. The hydrogen index values, the gas generation preferences and the aromaticity of the products are controlled by both depositional environment and precursors, and the product of a salinity indicator (MTTC) and the oleanane index is introduced as predictive proxy to evaluate these features. The maturity indicator (Tmax) is revealed as dominated by the stability of the kerogen structure which is controlled by the proportion of organic sulphur compounds in the kerogen. The global Eocene-Oligocene climate change from a greenhouse to an icehouse world is suggested to play an important role in changing the palaeoenvironment and further in influencing the development of petroleum source rocks by triggering upwelling, increasing the palaeo-sea water salinity and decreasing the deposition of carbonate-minerals. The chemometric method suggested here acts as a powerful tool in identifying the controlling factors for the petroleum generation potential among many variables, and can be applied more widely in petroleum geology when multi-parameters are involved to get quick and meaningful correlations.
    Language: English
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  • 29
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    In:  CASI
    Publication Date: 2018-10-17
    Description: NASA has developed and commercialized high temperature coatings and bearings for extreme conditions. These technologies are now under consideration by industry for automotive applications such as turbochargers, fuel cell compressors and exhaust gas path mechanism applications. In this presentation, a review of Oil-Free technologies and their current state-of-development is introduced. Key NASA contributions to the field as documented by patents, research papers and technology demonstrations is also presented.
    Keywords: Mechanical Engineering
    Type: GRC-E-DAA-TN50940 , Schaeffler International Bearing Meeting; 25 Jan. 2018; Herzogenaurach; Germany
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  • 30
    Publication Date: 2018-11-02
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  • 31
    Publication Date: 2018-10-30
    Description: Highlights • New 40Ar/39Ar age and geochemical (major, trace element, Sr-Nd-Pb-Hf isotope) data are presented from the Walvis Ridge, belonging to the Tristan-Gough hotspot track in the South Atlantic. • The entire Tristan-Gough hotspot system, including Walvis Ridge, display a spatially continuous age progression. • The Gough-type component is the dominant geochemical flavor of the Tristan-Gough plume and has also been identified in the Discovery and Shona hotspot systems. • The geochemical heterogeneity in the South Atlantic DUPAL region can be reproduced by mixing of Gough-type enriched mantle with continental crust and a FOZO/PREMA-like component. • The HIMU-type alkalic lavas on the Walvis Ridge and older part of Shona hotspot track are ∼30 Ma younger in age than the EMI-type primarily tholeiitic basement lavas at a given locality. Abstract Long-lived spatial geochemical zonation of the Tristan-Gough and Discovery hotspot tracks and temporal variations from EMI-type basement to HIMU-type late-stage volcanism at the Walvis Ridge and Shona hotspot tracks point to a complex evolution and multiple source areas for the South Atlantic hotspots. Here we report 40Ar/39Ar age and geochemical (major and trace element, Sr-Nd-Pb-Hf isotope) data for samples from 16 new sites on the Walvis Ridge. This aseismic ridge is the oldest submarine expression of the Tristan-Gough mantle plume and represents the initial reference locality of the EMI end member in the South Atlantic Ocean. The EMI-type lavas display an excellent age progressive trend of ∼31 mm/a along the entire Tristan-Gough hotspot track, indicating constant plate motion over a relatively stationary melt anomaly over the last ∼115 Ma. The Gough-type EMI composition of the Tristan-Gough hotspot track is the dominant composition on the 〉70 Ma part of the Walvis Ridge, the Etendeka and Parana flood basalts, and along the Gough sub-track, extending from DSDP Site 525A on the SW Walvis Ridge to Gough Island, whereas Tristan-type EMI dominates on the Tristan Track, extending from DSDP Sites 527 and 528 to Tristan da Cunha Island. Gough-type EMI is also the dominant composition of the northern Discovery and Shona hotspot tracks, suggesting that these hotspots tap a common source reservoir. The continuous EMI-type supply over ≥132 Ma, coupled with high 3He/4He (〉10 RA), points to a deep-seated reservoir for this mantle material. The Tristan and Southern Discovery EMI-type flavors can be reproduced by mixing of the Gough-type component with (1) FOZO/PREMA to produce Tristan-type lavas, and (2) marine sediments or upper continental crust to generate the Southern Discovery-type composition. South Atlantic hotspots with EMI-type compositions overlie the margin (1 % ∂Vs velocity contour) of the African Large Low Shear Velocity Province (LLSVP), which may promote the emergence of geochemical “zonation”. The St. Helena HIMU-type volcanism, however, is located above internal portions of the LLSVP, possibly reflecting a layered LLSVP.
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  • 32
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    Elsevier
    In:  Journal of Petroleum Science and Engineering, 172 . pp. 855-877.
    Publication Date: 2018-10-29
    Description: Gas hydrates are crystalline ice-like structures formed from water and gas molecules at high pressure and low temperature conditions. They are considered as near-future energy resources. Recently, there have been many drilling activities in gas hydrates in both permafrost regions (mainly Mallik wells, Canada; Ignik Sikumi #1 well, Alaska; Mount Elbert #1, Alaska) and marine sediments (the wells drilled in Gulf of Mexico and India drilling expeditions). In this study, it is aimed to evaluate and analyze logging-while drilling data (LWD) and other drilling data of these drilling activities. Initially, all drilling parameters (i.e. rate of penetration, weight on bit, torques, mud logs, etc.) of these wells were collected and drawn to see the change in parameters with depths. In order to indicate the changes in drilling parameters in the sediments containing gas hydrates, gas hydrate saturations were estimated from resistivity logs and NMR logs in this study. High resistivity log values and methane peaks in drilling fluid were good indicators of gas hydrate existence. During the drilling of permafrost formations and gas hydrates deposited in coarse sands as pore filling, the rate of penetration generally decreased. Differently, there was not almost any change in the rate of penetration during the drilling of fracture-filling gas hydrates within silts/clay in India. Borehole enlargements (washouts) were commonly seen in the wells drilled in marine sediments (Gulf of Mexico and Indian expeditions). However, this effect was minimum during the drilling of the wells in permafrost regions. This difference is due to the loose sediments in marine environment. Furthermore, gamma and density logs were seriously affected by washouts, mainly in marine sediments. It was observed that pore-filling gas hydrates affect the rate of penetration and keep the sediments stable because well collapses mainly occurred in the sediments without any gas hydrates. However, the temperature of drilling fluid should be close to the temperature of gas hydrate zones to reduce the effect of drilling on gas hydrate dissociation for the wells both in permafrost and marine sediments. In Gulf Mexico and Indian drilling expeditions, riser and wellhead equipment were not used. However, the usage of surface casing might decrease the risk of borehole collapses due to very loose sediments close to sea floor. Another important outcome of this study is that the pressure gradient follows hydrostatic pressure gradients according to the pressure analysis within gas hydrate stability zones of marine sediments. Finally, the analyses of drilling parameters revealed that drilling through gas hydrate bearing strata is not as risky as it might have been considered. The key is hidden in appropriate drilling design.
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  • 33
    Publication Date: 2018-10-29
    Description: Highlights • Thermodynamic and kinetic influences of NaCl on HFC-125a hydrate were investigated. • NaCl enrichment in the unconverted solution resulted in a lower conversion. • The presence of NaCl had little effect on the ΔH of HFC-125a hydrate. • The hydrate dissociation was retarded due to the formation of NaCl⋅2H2O. In this study, HFC-125a was selected as a hydrate-forming guest for gas hydrate-based desalination. The thermodynamic and kinetic effects of NaCl on HFC-125a hydrates were investigated with a primary focus on phase equilibria, gas uptake, dissociation enthalpy, and dissociation behavior. The equilibrium curve of HFC-125a hydrate shifted to higher pressure regions at any given temperature depending on the concentration of NaCl. The presence of NaCl also reduced the gas uptake and conversion to hydrates, because of the enrichment of NaCl in the solution during gas-hydrate formation. Even though NaCl did not affect the dissociation enthalpy of the HFC-125a hydrate, the thermograms obtained using a high-pressure micro-differential scanning calorimeter (HP μ-DSC) demonstrated that HFC-125a + NaCl hydrates started to dissociate at lower temperatures due to NaCl in unconverted solutions. Rietveld refinement of powder X-ray diffraction (PXRD) patterns indicated that the HFC-125a hydrate (sII) was transformed into Ih as it dissociated. The dissociation of HFC-125a + NaCl hydrates was retarded and completely ended at higher temperatures compared to the pure HFC-125a hydrate by the sodium chloride dihydrate (NaCl⋅2H2O). Overall, these results could facilitate a better understanding of HFC-125a hydrates in the presence of NaCl; further, they might also be useful in the design and operation of hydrate-based desalination plants using HFC-125a.
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  • 34
    Publication Date: 2018-11-06
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  • 35
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    Elsevier
    In:  Multiple stressors in river ecosystems. Status, impacts and prospects for the future
    Publication Date: 2018-11-07
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  • 36
    Publication Date: 2018-11-12
    Description: We present a transport-reaction model (TRACTION) specifically designed to account for non-ideal transport effects in the presence of thermodynamic (e.g. salinity or temperature) gradients. The model relies on the most fundamental concept of solute diffusion, which states that the chemical potential gradient (Maxwell’s model) rather than the concentration gradient (Fick’s law) is the driving force for diffusion. In turn, this requires accounting for species interactions by applying Pitzer’s method to derive species chemical potentials and Onsager coefficients instead of using the classical diffusion coefficients. Electrical imbalances arising from varying diffusive fluxes in multicomponent systems, like seawater, are avoided by applying an electrostatic gradient as an additional transport contribution. We apply the model to pore water data derived from the seawater mixing zone at the submarine Mercator mud volcano in the Gulf of Cadiz. Two features are particularly striking at this site: (i) Ascending halite-saturated fluids create strong salinity (NaCl) gradients in the seawater mixing zone that result in marked chemical activity, and thus chemical potential gradients. The model predicts strong transport-driven deviations from the mixing profile derived from the commonly used Fick’s diffusion model, and is capable of matching well with the profile shapes observed in the pore water concentration data. Even better agreement to the observed data is achieved when ion pairs are transported separately. (ii) The formation of authigenic gypsum (several wt%) occurs in the surface sediments, which is typically restricted to evaporitic surface processes. Very little is known about the gypsum paragenesis in the subseafloor and we first present possible controls on gypsum solubility, such as pressure, temperature, and salinity (pTS), as well as the common ion and ion pairing effects. Due to leaching of deep diapiric salt, rising fluids of the MMV are saturated with respect to gypsum (as well as celestite and barite). Several processes that could drive these fluids towards gypsum supersaturation and hence precipitation were postulated and numerically quantified. In line with the varied morphology of the observed gypsum crystals, gypsum paragenesis at the MMV is likely a combination of two temperature-related processes. Gypsum solubility increases with increasing temperature, especially in strong electrolyte solutions and the first mechanism involves the cooling of saturated fluids along the geothermal gradient during their ascent. Secondly, local temperature changes, i.e. cooling during the transition from MMV activity towards dormancy results in the cyclic build-up of gypsum. The model showed that the interpretation of field data can be majorly misguided when ignoring non-ideal effects in extreme diagenetic settings. While at first glance the pore water profiles at the Mercator mud volcano would indicate strong reactive influences in the seawater mixing zone, our model shows that the observed species distributions are in fact primarily transport-controlled. The model results for SO4 are particularly intriguing, as SO4 is shown to diffuse into the sediment along its increasing (!) concentration gradient. Also, a pronounced gypsum saturation peak can be observed in the seawater mixing zone. This peak is not related to the dissolution of gypsum but is simply a result of the non-ideal transport forces acting on the activity profile of SO4 and Ca profiles.
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  • 37
    Publication Date: 2018-11-20
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  • 38
    Publication Date: 2018-11-20
    Description: Atlantic cod (Gadus morhua) is an important recreational and commercial fisheries target species in the Northern hemisphere. Release rates are high in the recreational fishery due to regulatory and voluntary catch-and-release practice. Although post-release mortality of cod is relatively low, there is potential for further reductions. The most effective way to reduce post-release mortality is to minimize the catch of sublegal fish or non-target species and to reduce hooking injuries by using more selective fishing methods. This study investigated the influence of the lure/bait type on: (1) size of fish, (2) catch and harvest, (3) proportion of bycatch, (4) hooking location, and (5) injury (bleeding) in the western Baltic Sea recreational cod fishery. Data were collected via random onboard sampling of 35 charter vessel angling trips (778 anglers) and during two supplementary studies in the western Baltic Sea. Overall, the median total length was significantly higher for cod caught on artificial lures (39 cm) than for cod caught on natural bait (28 cm), leading to a 43% higher proportion of sublegal (〈38 cm) cod for bait than for lure. Median catch-per-unit-efforts (number of captured cod per angling hour) did not differ significantly between lure and bait angling (both: 0.49 cod per hour), whereas the median harvest-per-unit-effort (number of captured cod ≥ minimum landing size (38 cm) per angling hour) was significantly higher for lure (0.24 cod ≥38 cm per hour) than for bait angling (0.06 cod ≥38 cm per hour). The incidence of deep hooking and severe bleeding was significantly higher for bait angling. Furthermore, bait angling significantly increased bycatch of other species dominated by whiting (Merlangius merlangus) and European flounder (Platichthys flesus). Cod anglers can reduce the catch of sublegal cod and non-target species and minimize hooking injuries of released fish by using lures instead of bait in the western Baltic Sea. Thus, voluntary terminal gear recommendations may be an effective tool for anglers and managers to increase selectivity in recreational cod fisheries.
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  • 39
    Publication Date: 2018-11-21
    Description: Non-classical nonlinear elasticity in micro-inhomogeneous materials such as rocks and cracked or granular materials leads to a number of phenomena ranging from hysteresis and memory to a transient response of elastic properties to perturbations in dynamic or quasi-static experiments. Dynamic acousto-elastic testing (DAET) provides very detailed observations of some of these phenomena that are still not fully understood in terms of their physical origin. We suggest that the observations of non-classical nonlinear elasticity can be related to the physics of friction. We propose a conceptual model for the nonlinear elasticity based on friction of internal interfaces and the process of contact aging that leads to an increase of friction with increasing contact time. The central element of the model is the continuous interplay between (1) softening that occurs as small-scale damage due to shear motion of internal contacts and (2) stiffening (healing) as a thermally activated process of establishing connections across the contact at the current strain state. Chemical bonds, mineral fibres or capillary bridges are the most likely candidates for the physical nature of these connections. Our model qualitatively describes dynamic softening, hysteresis, slow dynamics and the shape of DAET loops including the absence of cusps and the loop orientation that leads to a stiffening at both maxima and minima of the dynamic strain
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  • 40
    Publication Date: 2018-11-27
    Description: The neodymium isotope proxy has become a valuable tool for the reconstruction of past ocean water mass provenance and mixing. For its accurate application, knowledge about the origin and preservation of Nd in sedimentary archives is crucial. Recently, concerns have emerged regarding the applicability of neodymium isotopes as a conservative palaeo water mass tracer, given potential Nd fluxes from sediments into bottom waters (Abbott et al., 2015a) and inferred relabelling of ocean waters by settling detrital material (Roberts and Piotrowski, 2015). Consequently, a decoupling of water mass provenance and proxy variations may arise. We investigate the mobility of Nd around extreme detrital sedimentation events such as glacial ice rafting pulses and turbidite deposition in the Northeast Atlantic. The constructed records from sediment leachates span extreme Nd isotope variations including volcanic (εNd ∼ 0) and Laurentian (εNd ∼ −27) sources. We find that Nd was released into pore waters from reactive detritus inside some detrital layers during early diagenesis, thereby overprinting any archived bottom water Nd signature and precluding the reconstruction of past water mass provenance during the affected time intervals. However, we do not observe any definite indication of diffusive vertical migration of Nd into adjacent layers. Furthermore, bottom water Nd isotope signatures were not modified to a measurable degree by any potential benthic flux of Nd during the deposition of these detrital sediment layers. Consequently, the Nd isotope composition of the pelagic glacial Northeast Atlantic water masses were resilient to such episodic large detrital fluxes. Apart from extreme local sedimentation events, we confirm the presence of detritally overprinted deep waters north of 47°N during the peak glacial from comparison of Northeast Atlantic depth transects. We furthermore suggest that the sensitivity of deep waters to this overprinting effect increased during periods of reduced Atlantic Meridional Overturning Circulation and elevated ice rafting. Overall, our study demonstrates that a thorough evaluation of the proportion of Nd originating from physical water mass advection versus in situ chemical inputs is crucial for the reliable application of Nd isotopes as a water mass tracer.
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  • 41
    Publication Date: 2018-11-27
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  • 42
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    Springer
    In:  Natural Gas Engines: For Transportation and Power Generation | Energy, Environment, and Sustainability
    Publication Date: 2018-11-29
    Description: Lean-burn natural gas engines can be used to reduce exhaust emissions significantly. However, as the mixture is leaned out, the occurrence of extinction and incomplete combustion increases, resulting in poor performance and stability, as well as elevated levels of unburned hydrocarbon (UHC) and nitrogen oxides (NOx) emissions. The partially stratified charge (PSC) method can be used to mitigate these issues, while extending the lean misfire limit (LML) beyond its equivalent, homogeneous level. In this chapter, the PSC ignition and combustion processes are examined following a comprehensive experimental and numerical approach. Experiments are conducted in an idealized PSC configuration, using a constant volume combustion chamber (CVCC), to identify the principle enabling mechanisms of the PSC methodology. Engine tests conducted in a single-cylinder research engine (SCRE) demonstrate the feasibility of various PSC implementations in improving performance and emission characteristics in real-world settings. Complementary numerical analyses for the CVCC are obtained through large eddy simulations (LES), while Reynolds-averaged Navier–Stokes (RANS) simulations are conducted for SCRE with reduced chemical kinetics. The corresponding simulated results provide additional insights in characterizing the effect of fuel stratification on flame kernel maturation and flame propagation, the interplay between chemistry and turbulence at different overall air–fuel ratios, as well as formation of major pollutant species.
    Language: English
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  • 43
    Publication Date: 2018-11-29
    Description: This paper investigates the interplay between the German incentive regulation and renewable capacity integration. A comprehensive review of the current incentive regulation scheme and its 2016 amendment is first presented. Then, results of ten representative interviews with large-scale distribution system operators are analyzed. Firstly, all necessary grid integration measures could so far be implemented. Secondly, creating proper incentives for intelligent operating equipment to partly substitute conventional grid expansion remains a challenge. Thirdly, the new curtailment regulation of 2016 is welcome, but will not become a substitute for grid expansion as long as renewable integration rates are high. Moreover, the discussions on further improvements to the incentive regulation scheme reveal a distribution conflict between grid operators and grid users.
    Language: English
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  • 44
    Publication Date: 2018-11-28
    Description: Protodunes emerge from a flat sand bed at the upwind margin of White Sands Dune Field, and, over several hundred meters, transition into fully developed dunes. Here, we investigate spatial and temporal changes in topography across this transition from 2007 to 2016 using lidar-derived topography, structure-from-motion-derived topography, and RTK GPS. We characterize the deposits present in 2015 using ground penetrating radar. Symmetric protodunes give way downwind to an asymmetric protodune at the transition to slipface development. Between 2007 and 2016, protodune amplitude increased from 0.2 m to 4.0 m, migration rate increased from 3.2 m/yr to 6.1 m/yr, and wavelength increased from 76 m to 122 m. Ground-penetrating radar surveys show strata between flat and 15° make up the stratigraphic architecture of the protodunes. Strata increase in steepness commensurate with an increase in amplitude. Decimeter accumulations of low-angle strata associated with initial protodune stages give way to 4 m of accumulation composed of sets up to 1 m thick prior to slipface development. Topsets present in the thickest sets indicate near critical angles of bedform climb. Growth and slipface development occur by aerodynamic sand trapping and protodune merging. Changes in asymmetry erase initial slipfaces prior to permanent slipface development, after which efficient sand trapping and scour promotes the transition to a dune across 20 m in 5 years. Protodune stratification has hallmarks of sandsheet stratification and can be appreciated within the greater suite of processes that create low-angle eolian stratification found in modern and ancient environments.
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  • 45
    Publication Date: 2018-11-29
    Description: Germany’s ambition to promote sustainable energy globally, on the basis of its own “Energiewende,” has led to the development of a multi-faceted international energy transition policy with various activities and an agenda to promote renewables and energy efficiency abroad. While domestic energy policy developments in Germany have received substantial attention in research and public debate, this is still less true for the country’s international energy transition policy. With the new German government’s program now having taken shape and implementation starting, it is time to assess the foundations and likely direction of and the most relevant challenges for Germany’s efforts to promote sustainable energy internationally. This perspective article takes a look at the aspects shaping Germany’s outreach to partner countries outside the EU to promote sustainable energy and addresses open questions related to its agenda. Germany’s international energy transition policy builds on a longstanding track record, but in order to maintain credibility and visibility in leadership for sustainable energy, two key challenges remain: setbacks in domestic climate mitigation efforts are putting into question claims for climate leadership and struggles to expand the Energiewende beyond the electricity sector require a new spin to international collaboration efforts, more and more directed toward bidirectional exchange and mutual learning.
    Language: English
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  • 46
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    Elsevier
    In:  Earth and Planetary Science Letters, 506 . pp. 381-387.
    Publication Date: 2018-12-04
    Description: Highlights • A small fraction of corrugated detachment fault surfaces is eventually exposed at the seafloor. • Seafloor slopes indicate effective friction of ∼0.2 on shallow part of detachments. • Moderate-offset detachment faults may be largely blanketed by hanging wall material. • Seafloor-shaping processes profoundly alter the morphology of oceanic core complexes. Abstract While oceanic detachment faults have been proposed to account for the accretion of ∼40% of new seafloor in the North Atlantic ocean, clear exposures of large-offset, often-corrugated fault surfaces remain scarce and spatially limited. To help resolve this paradox, we examine the conditions under which detachment fault growth may or may not lead to extensive exposure of corrugated fault planes at the seafloor. Using high-resolution bathymetry from four detachment faults at the northern Mid-Atlantic Ridge, we investigate the rafting of hanging wall-derived debris over emerging fault scarps, which can lead to covering shallow-dipping corrugated fault surfaces. We model this process using critical taper theory, and infer low effective friction coefficients (∼0.2) on the shallowest portion of detachment faults. A corollary to this result is that detachments emerging from the seafloor at angles 〈13° are more likely to become blanketed under an apron of hanging wall material. We generalize these findings as a simple model for the progressive exposure and flexural rotation of detachment footwalls, which accounts for the continued action of seafloor-shaping processes. Our model suggests that many moderate-offset, hidden detachment faults may exist along slow mid-ocean ridges, and do not feature an exposed fault surface.
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  • 47
    Publication Date: 2018-12-04
    Description: Highlights • Increased glacial sedimentation rates do not generate sufficient overpressure to trigger a landslide. • Simulated overpressures for different sedimentation scenarios do not significantly differ. • A glacimarine layer underneath rapidly-deposited sediments is important for overpressure build-up. • An earthquake of M6.9 or larger at a short distance from the Tampen Slide headwall could have triggered the Tampen Slide. Abstract Trough mouth fans are environments characterized by high sediment supply during glacial stages and the occurrence of large-scale instabilities. The geological record indicates that several of these environments have failed repeatedly resulting in large submarine landslides. The roles of sedimentation rate, weak layers, glacial loading and unloading as well as seismic activity on triggering megaslides in trough-mouth-fan systems is still unclear. A better understanding of the preconditioning factors, triggers and consequences of these landslides is crucial due to the hazard they pose to coastal communities and offshore industries. In this paper, we focus on the North Sea Trough Mouth Fan, which is the result of massive glacial sediment input delivered to the shelf edge through the Norwegian Channel, southeast Nordic Seas margin. The Tampen Slide, one of several large paleo-landslides that have happened within the North Sea Trough Mouth Fan, took place at c. 130 ka (end of MIS 6), and removed an estimated 1800 km3 of sediment. Here, we use boundary conditions from the Tampen Slide and 2D Finite Element Modeling (Abaqus software from Simulia) to evaluate the effects of variations in sedimentation rates as well as sediment properties on the generation of excess pore pressure, fluid flow, and slope stability along the axis of the trough-mouth-fan system. The model domain, 40 km in length and 2 km in height, is dominated by glacigenic debris flows and glacimarine sediment deposits. We use geotechnical data measured on samples of glacigenic and glacimarine sediment deposits from the nearby Ormen Lange gas field area to constrain the model. We evaluate the stability of the slope under various scenarios, including constant sediment loading, episodic changes in sedimentation rates and abrupt pulses in sediment delivery for a 61 kyr period (MIS 6). The models show that increased sedimentation rates during glacial stages do not generate sufficient excess pore pressure to set off a landslide. Furthermore, the simulated overpressures for the different sedimentation scenarios do not significantly differ at the end of the model runs. The results also highlight the importance of a basal glacimarine sediment layer underneath the rapidly-deposited sediments for the build-up of overpressure. Consequently, this glacimarine sediment layer has the inherited potential to act as a weak layer facilitating instability. However, as overpressure due to sediment deposition alone does not result in slope failure, we couple the preconditioned slope with earthquake ground shaking. Based on attenuation models, an earthquake of approximately M6.9 or larger at a short distance from the Tampen Slide headwall could have triggered the landslide. Therefore, we suggest glacial sedimentation and a glacimarine sediment layer to represent preconditioning factors, and seismic shaking as the final trigger mechanism for the Tampen Slide, i.e. similar to the situation that lead to the development of the Storegga Slide in the same area.
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  • 48
    Publication Date: 2018-12-04
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  • 49
    Publication Date: 2018-12-04
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  • 50
    Publication Date: 2018-12-04
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  • 51
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    Elsevier
    In:  Geochimica et Cosmochimica Acta, 245 . pp. 406-425.
    Publication Date: 2018-12-06
    Description: Stable isotopes (15,14N, 18,16O) of dissolved inorganic nitrogen (N) were measured in sediment porewaters and benthic flux chambers across the Peruvian oxygen minimum zone (OMZ) from 74 to 1000 m water depth. Sediments at all locations were net consumers of bottom water NO3−. In waters shallower than 400 m, this sink was largely attributed to dissimilatory nitrate reduction to ammonium (DNRA) by filamentous nitrate-storing bacteria (Marithioploca and Beggiatoa) and to denitrification by foraminifera. The apparent N isotope effect of benthic NO3− loss (15εapp) was 7.4 ± 0.7‰ at microbial mat sites and 2.5 ± 0.9‰ at the lower fringe of the OMZ (400 m) where foraminifera were abundant. The OMZ sediments were a source of 15N-enriched NO2− (28.9 to 65.5‰) and NH4+ (19.4–20.5‰) to the bottom water. Model simulations generally support a previous hypothesis attributing the 15NH4+ enrichment to a coupling between DNRA and anammox (termed DAX) using biologically-stored NO3− from Marithioploca and NH4+ from the porewater. The model predicts that 40% of NO3− that is actively transported into the sediment by Marithioploca is reduced to N2 by this pathway. DAX enhances N2 fluxes by a factor of 2–3 and accounts for 70% of fixed N loss to N2. Moreover, because most of the ambient porewater NH4+ is generated by DNRA, up to two-thirds of biologically-transported NO3− could end up being lost to N2. This challenges the premise that Marithioploca-dominated sediments tend to conserve fixed N. By limiting the flux of 15NH4+ back to the ocean, DAX also tends to decrease benthic N fractionation. Tracking the fate of NH4+ once it leaves the sediment is critical for understanding how the benthos contributes to N isotope signals in the water column.
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  • 52
    Publication Date: 2018-12-07
    Description: This study presents new high resolution sedimentary δ15N records from piston cores collected within and outside the present-day eastern south Pacific oxygen minimum zone along a latitudinal transect from 3.5°S to 15°S. Radiocarbon dating of foraminifera and organic matter show that the cores cover the Holocene and the last deglaciation with high sedimentation rate allowing interpretations at millennial to centennial timescale. High δ15N values, reaching 10‰ and large amplitude changes, with a magnitude of ~4‰, are observed in the southern part of the studied area during the last 18 ka BP. In contrast, the northern Peruvian cores located on the edge of the OMZ show low δ15N values varying from 4 to 6‰ with amplitude of only 1‰, during the same time period. δ15N values decrease in all the studied cores from the last deglaciation to the early Holocene (17 to 8.5 ka BP) and reach a minimum value during the mid-Holocene. The δ15N variations are attributed to microbial N-loss to N2, e.g. denitrification and/or anammox, and the characteristic 15N-enriched signal that is recorded in the underlying sediments under suboxic to anoxic conditions where denitrifiers thrive. Surprisingly, δ15N values from cores located within the OMZ show similar values as the more northern cores located outside the OMZ between 5 and 8.5 ka BP. This minimum is not related to local changes in export production, reconstructed from sedimentary organic carbon, total nitrogen and bromine, but appears to be controlled by changes in the ventilation of the area. The low δ15N values recorded between 8.5 and 5 ka BP are well correlated with more arid conditions developed along the Peruvian margin and an increase of the sea surface temperature gradient along the Peruvian margin and between the West and East Pacific along the equator, implying an intensification of the Hadley circulation and climatic conditions similar to La Niña-like state. Consequently, these mid-Holocene conditions led to greater ventilation of subsurface waters that deepened the Peruvian oxycline then revealing similar conditions as observed today in the northern part of the study area.
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  • 53
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    Springer
    In:  In: Oceanographic and Biological Aspects of the Red Sea. , ed. by Rasul, N. M. A. and Stewart, I. C. F. Springer Oceanography Series . Springer, Cham, pp. 185-194.
    Publication Date: 2018-12-11
    Description: The deep-sea brines of the Red Sea are unusual extreme environments and form characteristically steep gradients across the brine-seawater interfaces. Due to their unusual nature and unique combination of physical-chemical conditions these interfaces provide an interesting source of new findings in the fields of geochemistry, geology, microbiology, biotechnology, virology, and general biology. The current chapter summarizes recent and new results in the study of geochemistry and life at the interfaces of brine-filled deeps of the Red Sea.
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  • 54
    Publication Date: 2018-12-11
    Description: Hydrate dissociation equilibrium conditions for the mixture of carbon dioxide (CO2), nitrogen (N2), and water (H2O) are measured in the temperature range of 274.15–280.15 K. The relative molar composition of carbon dioxide in the feed gas mixture varies between 0.05 and 0.25 which is the interesting range of composition when it comes to production of methane, and sequestration of carbon dioxide, from methane hydrate reservoirs. A thermodynamic model is presented based on the classical van der Waals and Platteeuw (vdW-P) solid solution theory for the hydrate phase combined with the Equation of State (EoS) for combustion gas and combustion gas-like mixtures (CG-EoS). The results of this model are compared to the dissociation data measured here, along with all available data from the experimental literature. The predicted results from two thermodynamic software programs, CSMGem, and Multiflash (which use Peng-Robinson (PR) and Cubic Plus Association (CPA) EoSs respectively), are also statistically evaluated. A Clausius-Clapeyron type equation was used to derive the enthalpy of dissociation at 279.15 K, and the values were found to converge for mixtures containing 0.1–0.25 mol fraction of carbon dioxide.
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  • 55
    Publication Date: 2018-12-10
    Description: Highlights • Seafloor geomorphology was important in the structuring of abyssal megafauna. • Differences in megafaunal community ecology were found between all landscape types. • Lower megafauna density & diversity in a bathymetric valley than flat and ridge areas. • Large samples, collected by AUV, were required to make robust ecological conclusions. The potential for imminent polymetallic nodule mining in the Clarion Clipperton Fracture Zone (CCZ) has attracted considerable scientific and public attention. This concern stems from both the extremely large seafloor areas that may be impacted by mining, and the very limited knowledge of the fauna and ecology of this region. The environmental factors regulating seafloor ecology are still very poorly understood. In this study, we focus on megafaunal ecology in the proposed conservation zone ‘Area of Particular Environmental Interest 6′ (study area centred 17°16′N, 122°55′W). We employ bathymetric data to objectively define three landscape types in the area (a level bottom Flat, an elevated Ridge, a depressed Trough; water depth 3950–4250 m) that are characteristic of the wider CCZ. We use direct seabed sampling to characterise the sedimentary environment in each landscape, detecting no statistically significant differences in particle size distributions or organic matter content. Additional seafloor characteristics and data on both the metazoan and xenophyophore components of the megafauna were derived by extensive photographic survey from an autonomous underwater vehicle. Image data revealed that there were statistically significant differences in seafloor cover by nodules and in the occurrence of other hard substrata habitat between landscapes. Statistically significant differences in megafauna standing stock, functional structuring, diversity, and faunal composition were detected between landscapes. The Flat and Ridge areas exhibited a significantly higher standing stock and a distinct assemblage composition compared to the Trough. Geomorphological variations, presumably regulating local bottom water flows and the occurrence of nodule and xenophyophore test substrata, between study areas may be the mechanism driving these assemblage differences. We also used these data to assess the influence of sampling unit size on the estimation of ecological parameters. We discuss these results in the contexts of regional benthic ecology and the appropriate management of potential mining activities in the CCZ and elsewhere in the deep ocean.
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  • 56
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    Springer
    In:  In: Geological Setting, Palaeoenvironment and Archaeology of the Red Sea. , ed. by Rasul, N. M. A. and Stewart, I. C. F. Springer, Cham, pp. 37-52.
    Publication Date: 2018-12-14
    Description: Continental rifting and ocean basin formation can be observed at the present day in the Red Sea, which is used as the modern analogue for the formation of mid-ocean ridges. Competing theories for how spreading begins—either by quasi-instantaneous formation of a whole spreading segment or by initiation of spreading at multiple discrete “nodes” separated by thinned continental lithosphere—have been put forward based, until recently, on the observations that many seafloor features and geophysical anomalies (gravity, magnetics) along the axis of the Red Sea appeared anomalous compared to ancient and modern examples of ocean basins in other parts of the world. The latest research shows, however, that most of the differences between the Red Sea Rift (RSR) and other (ultra)slow-spreading mid-ocean ridges can be related to its relatively young age and the presence and movement of giant submarine salt flows that blanket large portions of the rift valley. In addition, the geophysical data that was previously used to support the presence of continental crust between the axial basins with outcropping oceanic crust (formerly named “spreading nodes”) can be equally well explained by processes related to the sedimentary blanketing and hydrothermal alteration. The observed spreading nodes are not separated from one another by tectonic boundaries but rather represent “windows” onto a continuous spreading axis which is locally inundated and masked by massive slumping of sediments or evaporites from the rift flanks. Volcanic and tectonic morphologies are comparable to those observed along slow and ultra-slow spreading ridges elsewhere and regional systematics of volcanic occurrences are related to variations in volcanic activity and mantle heat flow. Melt-salt interaction due to salt flows, that locally cover the active spreading segments, and the absence of large detachment faults as a result of the nearby Afar plume are unique features of the RSR. The differences and anomalies seen in the Red Sea still may be applicable to all young oceanic rifts, associated with plumes and/or evaporites, which makes the Red Sea a unique but highly relevant type example for the initiation of slow rifting and seafloor spreading and one of the most interesting targets for future ocean research.
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  • 57
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    Springer
    In:  In: Geological Setting, Palaeoenvironment and Archaeology of the Red Sea. , ed. by Rasul, N. M. A. and Stewart, I. C. F. Springer, Cham, pp. 221-232.
    Publication Date: 2018-12-14
    Description: Hydrothermal circulation at mid-ocean ridges and assimilation of hydrothermally altered crust or hydrothermal fluids by rising magma can be traced by measuring chlorine (Cl) excess in erupted lavas. The Red Sea Rift provides a unique opportunity to study assimilation of hydrothermally altered crust at an ultra-slow spreading ridge (maximum 1.6 cm yr−1 full spreading rate) by Cl, due to its saline seawater (40–42‰, cf. 35‰ in open ocean water), the presence of (hot) brine pools (up to 270‰ salinity and 68 °C) and the thick evaporite sequences that flank the young rift. Absolute chlorine concentrations (up to 1300 ppm) and Cl concentrations relative to minor or trace elements of similar mantle incompatibility (e.g., K, Nb) are much higher in Red Sea basalts than in basalts from average slow spreading ridges. Mantle Cl/Nb concentrations can be used to calculate the Cl-excess, above the magmatic Cl, that is present in the samples. Homogeneous within-sample Cl concentrations, high Cl/H2O, the decoupling of Cl-excess from other trace elements and its independence of the presence of highly saline seafloor brines at the site of eruption indicate that Cl is not enriched at the seafloor. Instead we find basaltic Cl-excess to be spatially closely correlated with evidence of hydrothermal activity, suggesting that deeper assimilation of hydrothermal Cl is the dominant Cl-enrichment process. A proximity of samples to both evaporite outcrops and bathymetric signs of volcanism on the seafloor enhance Cl-excess in basalts. The basaltic Cl-excess can be used as a tracer together with new bathymetric maps as well as indications of hydrothermal venting (hot brine pools, metalliferous Hydrothermal circulation at mid-ocean ridges and assimilation of hydrothermally altered crust or hydrothermal fluids by rising magma can be traced by measuring chlorine (Cl) excess in erupted lavas. The Red Sea Rift provides a unique opportunity to study assimilation of hydrothermally altered crust at an ultra-slow spreading ridge (maximum 1.6 cm yr−1 full spreading rate) by Cl, due to its saline seawater (40–42‰, cf. 35‰ in open ocean water), the presence of (hot) brine pools (up to 270‰ salinity and 68 °C) and the thick evaporite sequences that flank the young rift. Absolute chlorine concentrations (up to 1300 ppm) and Cl concentrations relative to minor or trace elements of similar mantle incompatibility (e.g., K, Nb) are much higher in Red Sea basalts than in basalts from average slow spreading ridges. Mantle Cl/Nb concentrations can be used to calculate the Cl-excess, above the magmatic Cl, that is present in the samples. Homogeneous within-sample Cl concentrations, high Cl/H2O, the decoupling of Cl-excess from other trace elements and its independence of the presence of highly saline seafloor brines at the site of eruption indicate that Cl is not enriched at the seafloor. Instead we find basaltic Cl-excess to be spatially closely correlated with evidence of hydrothermal activity, suggesting that deeper assimilation of hydrothermal Cl is the dominant Cl-enrichment process. A proximity of samples to both evaporite outcrops and bathymetric signs of volcanism on the seafloor enhance Cl-excess in basalts. The basaltic Cl-excess can be used as a tracer together with new bathymetric maps as well as indications of hydrothermal venting (hot brine pools, metalliferous sediments) to predict where hydrothermal venting or now inactive hydrothermal vent fields can be expected. Sites of particular interest for future hydrothermal research are the Mabahiss Deep, the Thetis-HadarbaHatiba Deeps and Shagara-Aswad-Erba Deeps (especially their large axial domes), and Poseidon Deep. Older hydrothermal vent fields may be present at the Nereus and Suakin Deeps. These sites significantly increase the potential of hydrothermal vent field prospection in the Red Sea.
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  • 58
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    Springer
    In:  In: Oceanographic and Biological Aspects of the Red Sea. , ed. by Rasul, N. M. A. and Stewart, I. C. F. Springer, Cham, Switzerland, pp. 401-418. ISBN 978-3-319-99416-1
    Publication Date: 2018-12-14
    Description: Coral reefs in the Red Sea belong to the most diverse and productive reef ecosystems worldwide, although they are exposed to strong seasonal variability, high temperature, and high salinity. These factors are considered stressful for coral reef biota and challenge reef growth in other oceans, but coral reefs in the Red Sea thrive despite these challenges. In the central Red Sea high temperatures, high salinities, and low dissolved oxygen on the one hand reflect conditions that are predicted for ‘future oceans’ under global warming. On the other hand, alkalinity and other carbonate chemistry parameters are considered favourable for coral growth. In coral reefs of the central Red Sea, temperature and salinity follow a seasonal cycle, while chlorophyll and inorganic nutrients mostly vary spatially, and dissolved oxygen and pH fluctuate on the scale of hours to days. Within these strong environmental gradients micro- and macroscopic reef communities are dynamic and demonstrate plasticity and acclimatisation potential. Epilithic biofilm communities of bacteria and algae, crucial for the recruitment of reef-builders, undergo seasonal community shifts that are mainly driven by changes in temperature, salinity, and dissolved oxygen. These variables are predicted to change with the progression of global environmental change and suggest an immediate effect of climate change on the microbial community composition of biofilms. Corals are so-called holobionts and associate with a variety of microbial organisms that fulfill important functions in coral health and productivity. For instance, coral-associated bacterial communities are more specific and less diverse than those of marine biofilms, and in many coral species in the central Red Sea they are dominated by bacteria from the genus Endozoicomonas. Generally, coral microbiomes align with ecological differences between reef sites. They are similar at sites where these corals are abundant and successful. Coral microbiomes reveal a measurable footprint of anthropogenic influence at polluted sites. Coral-associated communities of endosymbiotic dinoflagellates in central Red Sea corals are dominated by Symbiodinium from clade C. Some corals harbour the same specific symbiont with a high physiological plasticity throughout their distribution range, while others maintain a more flexible association with varying symbionts of high physiological specificity over depths, seasons, or reef locations. The coral-Symbiodinium endosymbiosis drives calcification of the coral skeleton, which is a key process that provides maintenance and formation of the reef framework. Calcification rates and reef growth are not higher than in other coral reef regions, despite the beneficial carbonate chemistry in the central Red Sea. This may be related to the comparatively high temperatures, as indicated by reduced summer calcification and long-term slowing of growth rates that correlate with ocean warming trends. Indeed, thermal limits of abundant coral species in the central Red Sea may have been exceeded, as evidenced by repeated mass bleaching events during previous years. Recent comprehensive baseline data from central Red Sea reefs allow for insight into coral reef functioning and for quantification of the impacts of environmental change in the region.
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  • 59
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    Springer
    In:  Springer Oceanography Book series . Springer, Cham, Switzerland, 550 pp. ISBN 978-3-319-99417-8
    Publication Date: 2018-12-14
    Description: This book includes invited contributions presenting the latest research on the oceanography and environment of the Red Sea. In addition to covering topics relevant to research in the region and providing insights into marine science for non-experts, it is also of interest to those involved in the management of coastal zones and encourages further research on the Red Sea
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  • 60
    Publication Date: 2018-12-14
    Description: Highlights • Northern Hispaniola Margin is studied with new high-resolution bathymetry and vintage seismic data. • Northern Hispaniola Deformed Belt forms an active N-verging fold-and-thrust imbricate system. • Gravity failures are frequent features in the Northern Hispaniola Margin and Bahamas Banks slope. • Oblique collision accelerates the Bahamas Carbonate Province collapse and retreat. • New observations help the assessment of tsunami hazards in the Northern Caribbean region. Abstract The northern margin of Hispaniola records the oblique collision/underthrusting of the Bahamas Carbonate Province with the island-arc. Due to the collision, northern Hispaniola has suffered several natural disasters caused by major earthquakes and tsunamis, such as the historic earthquake of 1842, the tsunami caused by earthquake-driven slumping in 1918 in the Mona Passage, the seismic crisis of 1943–1953 with five events of M 〉 7.0 or the seismic crisis of 2003 with a main shock of M6.3 and a large aftershock of M5.3. Using new swath multibeam bathymetry data and vintage single- and multi-channel seismic profiles, we have performed a regional scale analysis and interpretation of the shallow surface and active processes along the northern margin of the Dominican Republic. We have identified three morphostructural provinces: a) the Bahamas Banks, b) the Hispaniola Trench and c) the Insular Margin, which are divided into two tectonic domains, the Collision Domain and Underthrusting Domain. The southern slope of the Bahamas Carbonate Province shows a very irregular morphology produced by active erosive processes and normal dip-slip faulting, evidence of an extensional tectonic regime and margin collapse. This collapse is of major extent in the Oblique Collision Domain where there are erosive and fault escarpments with higher dip-slip fault throws. The Hispaniola Trench, is formed by the Caicos and Hispaniola basins in the underthrusting domain, and by the Santisima Trinidad and Navidad basins in the Oblique Collision Domain. They have a flat seafloor with a sedimentary filling of variable thickness consisting of horizontal or sub-horizontal turbiditic levels. The turbiditic fill mostly proceeds from the island arc through wide channels and canyons, which transports sediment from the shelf and upper slope. The Insular Margin comprises the Insular Shelf and the Insular Slope. The active processes are generated on the Insular Slope where the Northern Hispaniola Deformed Belt is developed. This Deformed Belt shows a very irregular morphology, with a WNW-ESE trending N verging imbricate thrust-and fold system. This system is the result of the adjustment of the oblique collision/underthrusting between the North American plate and the Caribbean plate. In the Oblique Underthrusting Domain the along-strike development of the imbricate system is highly variable forming salients and recesses. This variability is due to along-strike changes in the sediment thickness of the Hispaniola Trench, as well as to the variable topography of the underthrusting Bahamas Carbonate Province. In the Oblique Collision Domain, the morphology of the Insular Slope and the development of the Deformed Belt deeply change. The imbricate system is barely inferred and lies upslope. These changes are due to the active collision of Bahamas Carbonate Province with the Insular Margin where the spurs are indented against the Insular Margin. Throughout the entire area studied, gravitational instabilities have been observed, especially on the Insular Margin and to a lesser extent on the southern slope of the Bahamas Carbonate Province. These instabilities are a direct consequence of the active underthrusting/collision process. We have mapped large individual slumps north of Puerto Plata in the Oblique Underthrusting Domain and zones of major slumps in the Oblique Collision Domain. These evidences of active processes must be considered as near-field sources in future studies on the assessment of tsunami hazards in the region.
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  • 61
    Publication Date: 2018-12-10
    Description: In Nepal, majority of households still burn solid fuels in inefficient cook stoves inside poorly ventilated kitchens, which results in very high levels of indoor pollutants, including black carbon (BC). Previous studies have not yet reported BC concentrations in typical kitchen configurations in rural Nepal. In this study, fine particulate matter (PM) and BC concentrations were monitored continuously inside two types of kitchens (separated from and attached to the main house) under actual cooking practices. Prior to monitoring of pollutants, a field survey was conducted to gain insight into the types of kitchens, cook stoves and fuels used. Indoor PM and BC concentrations were monitored using biomass fuels in traditional cook stoves (TC) and improved cook stoves (ICS). Clear diurnal variations of the pollutants were observed in both kitchens, with the highest concentrations during cooking times. BC and PM concentrations during cooking and non-cooking periods demonstrated clear reductions in the concentrations during non-cooking periods. It was observed that the concentrations rose steeply during the first half hour of cooking, then decreased slightly and finally leveled off to the non-cooking period concentrations. 24-hour average indoor PM concentrations in both kitchens frequently exceeded Nepal's indoor air quality standards and the WHO PM2.5 guidelines, by a factor of ~8 to ~28. We found that the specific type of ICS used in this study, a commonly used ICS in Nepal and other developing countries might help in PM emission reductions but not necessarily BC emission reduction.
    Language: English
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
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  • 62
    Publication Date: 2018-12-10
    Description: Based on diatom, aquatic pollen and non-pollen palynomorph (NPP), lake sediment microfacies, and X-ray fluorescence (XRF) analyses we define three main phases of lake basin development including a marshy phase (ca. 16,600–9400 cal. yr BP), lagoon phase (ca. 9400–5900 cal. yr BP) and freshwater lake phase (since ca. 5900 cal. yr BP). Marine influence on the lake system linked to global sea-level rise and the Holocene marine transgression reached a maximum between ca. 8000 and 6000 cal. yr BP. An increase of Aulacoseira subarctica at 5530 cal. yr BP marks the end of the Holocene Thermal Optimum (i.e. onset of Middle Holocene cooling) in the study region. Our results further suggest that freshwater Lake Kushu had a significant effect on the initial habitation of Rebun Island by sedentary hunter-gatherer populations. The reconstructed onset of stable freshwater conditions (ca. 5100 cal. yr BP) coincided with the appearance of the earliest permanent settlements during the Middle Jomon culture phase (ca. 5000–4000 cal. yr BP). On the other hand, there is evidence for human-induced changes in the limnological conditions. This includes enhanced sediment and nutrient input into Lake Kushu resulting in high eutrophication levels that caused strongly reduced diatom productivity and enhanced green algae growth, which can be attributed to human activities apparently associated with the Okhotsk (ca. 1450–950 cal. yr BP) and Classic Ainu (ca. 350–100 cal. yr BP) culture periods.
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
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  • 63
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    In:  Journal of Structural Geology
    Publication Date: 2018-12-10
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
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  • 64
    Publication Date: 2018-12-10
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
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  • 65
    Publication Date: 2018-12-10
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
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  • 66
    Publication Date: 2018-12-11
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
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  • 67
    Publication Date: 2018-12-11
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  • 68
    Publication Date: 2018-12-12
    Description: Highlights The increase in volcanic activity after the last glacial maximum observed on Iceland has led to one of the most fascinating hypothesis in science in the last decades: that deglaciation may force volcanism. We: - Re-analyzed four longer tephra records with the same statistical method and demonstrated that all contain the ∼41 kyr and ∼100 kyr Millankovitch periodicities. - The frequency spectra of the tephra and δ18O records are significantly correlated supporting the hypothesis that orbital-driven global climate changes interact with the volcanic eruption frequency regionally and globally. - However, the simultaneous analysis of the four best-characterized tephra records shows that correlations and associated time lags suffer from a number of uncertainties including the nature and quality of tephra time series, a wide range in geographic latitudes and geological settings, as well as applied statistical methods Therefore more precise tephra time series (preservation and age optimized) from different regions (glaciated versus non-glaciated) and geological settings (island arcs, continental arcs, intraplate) are needed together with standardized statistical analysis to decipher the impact of these factors on a global perspective of how climate may control volcanism. Abstract The increase in volcanic activity after the last glacial maximum observed on Iceland has led to one of the most fascinating hypothesis in science in the last decades: that deglaciation may force volcanism. Consequently, tephrostratigraphic records of sufficient length that cover multiple glacial cycles have been used to test whether such relationships hold systematically through the Quaternary. Here we review such tephra records that have been linked with climate proxy records such as δ18O in marine sediments, which is a measure of sea-level change and which is thought to be orbitally forced, as it exhibits the characteristic Milankovitch periodicities of precession (∼23 kyr), obliquity (∼41 kyr) and eccentricity (∼100 kyr). Statistical analyses have identified these periodicities also in long tephra records from different latitudes and geotectonic settings, as well as in compiled semi-global records. These studies detect Milankovitch periods in their tephra record, and also a phase shift relative to the δ18O record in such that periods of increased eruption frequencies coincide with the deglaciation period at the glacial/interglacial transition when ice and water loads on the lithosphere change most rapidly. However, there are also disparities in results and interpretations, which may be attributable to the different methods of analysis applied by the studies. We have therefore re-analyzed the four best-characterized tephra records by the same methods. We distinguish between analysis in the frequency domain, a novel approach, and analysis in the time domain, which has been used in previous studies. Analysis in the frequency domain identifies harmonic frequencies that arise from the binary nature of the tephra records and complicate the identification of primary frequencies. However, we show that all four records show spectral density peaks near the main Milankovitch periodicities of 41 and 100 kyr, and that they produce meaningful and significant statistical correlations with each other and the global δ18O record but not with random time series. Although the time-domain correlations with δ18O roughly confirm phase shifts implying peak volcanism during deglaciation, correlation coefficients arising from very noisy records are generally too low for precise constraints on the relative timing. These deficiencies presently hamper the recognition of the physical mechanisms through which global climate changes affect volcanism at both, high-latitude glaciated regions and low-latitude non-glaciated regions.
    Type: Article , PeerReviewed
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  • 69
    Publication Date: 2018-12-12
    Type: inbook
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  • 70
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    Elsevier
    In:  Earth and Planetary Science Letters, 506 . pp. 255-267.
    Publication Date: 2018-12-18
    Description: Highlights • Tungsten isotopes reveal vertical structure in mantle plumes. • Plume heads and tails each sample a distinct ancient mantle reservoir. • ULVZs contribute material to OIBs. • LLSVPs may contribute to both OIBs and LIPs. • Chemical heterogeneity in the mantle may be restricted to the base of LLSVPs. Abstract The lowermost mantle is driven to Earth's surface by mantle plumes, providing a volcanic record of its structure and composition. Plumes comprise a head and tail, which melt to form large igneous provinces (LIPs) and ocean island basalts (OIBs), respectively. Recent analyses have shown that LIPs and OIBs exhibit tungsten (W) isotope heterogeneity that was created in the first ∼60 million years of our solar system's evolution. Moreover, the isotopic signature found in LIPs differs to that found in OIBs, revealing that the melt products of plume heads must be dominated by a different ancient mantle reservoir to that of plume tails. However, existing geodynamical studies suggest that plume heads and tails sample the same deep-mantle source region and, therefore, cannot account for any systematic differences in composition. Here, we present a suite of numerical simulations of thermo-chemical plumes and an isotopic model for W sources in the mantle. Our results demonstrate that the W isotope systematics of LIPs and OIBs can, under certain conditions, arise as a dynamical consequence of plumes forming in a heterogeneous, thermo-chemical boundary layer. We find that ultra low-velocity zones (ULVZs), which sit on the core–mantle boundary (CMB), likely contribute to the chemical diversity observed in OIBs but not LIPs, while any dense components residing inside large low shear-wave velocity provinces (LLSVPs) may contribute to both. This study places geochemical observations from Earth's surface in a geodynamically consistent framework and illuminates their relationship with seismically imaged features of the deep mantle.
    Type: Article , PeerReviewed
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  • 71
    Publication Date: 2018-12-17
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
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