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  • 1
    Publication Date: 2021-03-29
    Description: Lambert, cosmological letters, fixed stars, nebulae, island universe, teleology, teleological, enlightenment, enlightened, romanticism, romantic, hypothesis, physical-teleological, speculation, imagination, stability, solar system, cosmology, astronomy, comet, magic, alchemy, pietism, science, arts, philosophy, Newtonian. - Johann Heinrich Lamberts Cosmological Letters was published 1761 in Augsburg. Lambert tried to expose a theory of the structure of the universe as a whole, that is, a theory that was able to involucrate all sorts of observed celestial bodies, like 'fixed stars' und nebulae. Lambert tackles his task mixing two disciplines, which in principle seem to be incompatible: Newtonian physics and teleology. Lambert's speculative and imaginative way to formulate his hypotheses shows resemblances to the way of making science developed during the romantic period, disagreeing with the methods of enlightenment, movement to which Lambert is usually associated. A central aspect of this thesis is to study Lambert's figure in relation to this two traditions, with the finality to deal with the compression of his ideas in depth, in light of the transition between the enlightened vision of the world and the romantic one.
    Description: thesis
    Keywords: 520 ; TA 100 ; TA 400 ; Theoretische Grundlagen {Astronomie} ; Wissenschaftsgeschichte {Astronomie}
    Language: German
    Type: monograph , publishedVersion
    Format: 302 S.
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  • 2
    facet.materialart.
    Unknown
    Univ. Bremen
    Publication Date: 2021-03-29
    Description: The dissolution kinetics of gypsum and anhydrite have been measured under various conditions. For gypsum an almost linear rate equation R=ks1(1-c/ceq)n1 is valid, where R is the surface rate, n1 1 is the kinetics order, c is the total calcium concentration at the surface, and ceq the equilibrium concentration with respect to gypsum. For the determination of the entire dissolution kinetics a batch set-up was used. This batch experiment reveals a dissolution rate equation R=ks1(1-c/ceq)n1 which switch close to equilibrium to a nonlinear rate equation R=ks2(1-c/ceq)n2 with n2 4.5. The experimentally observed dissolution rates from the batch experiment could be fitted by only minor variations with a mixed kinetics model. The rotating disk experiment on anhydrite reveals a surface controlled rate equation. For anhydrite the observed experimentally dissolution rates by a batch experiment are described by R=ks(1-c/ceq})n, where ks is the surface rate constant and n 4.2 is the kinetic order. Furthermore, a method for the determination of the rate equation parameters was developed ...
    Description: thesis
    Keywords: 549 ; VJK 000 ; VHB 600 ; VGC 000 ; Experimentelle Geochemie ; Sulfate, Chromate, Molybdate und Wolframate {Mineralogie} ; Mineralchemie
    Language: German
    Type: monograph , publishedVersion
    Format: 120 S.
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  • 3
    Publication Date: 2021-03-29
    Description: Turbulence, ice ridge, polynja, drag coefficient. - Polarstern (PS) cruise ARK XII led into the Laptev Sea and into the Kara Sea. Measurements of atmospheric processes within the polar surface layer were performed by a turbulence probe mounted at the bow crane of the ship.The meteorological conditions during the cruise were characterised by moderate winds and low temperature differences between the atmosphere and the underlying surface.Detailed information about the variation of meteorological parameters and of the surface fluxes were achieved as a function of the surface characteristics. The measurements are used to analyse ...
    Description: thesis
    Keywords: 551.5 ; VAQ 990 ; TYZ 400 ; TVH 500 ; Meereis {Glaziologie} ; Nordpolarmeer {Meteorologie und Klimatologie} ; Temperatur der Wasseroberfläche als meteorol. Element
    Language: German
    Type: monograph , publishedVersion
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  • 4
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; VAQ 990 ; Meereis {Glaziologie}
    Language: German
    Type: monograph , publishedVersion
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  • 5
    Publication Date: 2021-03-29
    Description: Photooxidants play an important role for the oxidation capacity of the troposphere. The presented work deals with seasonal changes of atmospheric photooxidants like hydrogen peroxide (H2O2), methylhydroperoxide (MHP) and formaldehyde (HCHO). The principal purpose was to follow and quantify the mixing-ratios of these photochemical species for the first time over a complete annual cycle in Antarctica. During two field campaigns at the German Antarctic station Neumayer (overwintering campaign from January 1997 until March 1998 and a shorter campaign from January to March 1999) continuous measurements of atmospheric mixing-ratios were performed. A continuous wet-chemical technique was used for peroxides and formaldehyde sampling and analysis. Species were quantified by fluorescence detection. In order to compare the results and measurements with well-known reaction mechanisms a photochemical box model was applied. The obtained time series show a pronounced seasonal variation with higher values during summer. For the first time atmospheric concentrations of H2O2, MHP and HCHO were documented during polar night in winter. The mixing-ratios were significantly higher than expected due to missing actinic radiation essential for photochemical production. Trajectory analyses and calculations with a three-dimensional model showed that during winter the mixing-ratios of photooxidants are mainly affected by long-range transport in the free troposphere. Investigations during the Antarctic ó́zone hole period ́́show no significant impact of the increased UV-B radiation on the photooxidants. The findings of this work contribute to a better understanding of the photochemistry of the investigated trace gases in the clean troposphere of Antarctica and provide a useful data record for further photochemical modeling.
    Description: thesis
    Keywords: 551.5 ; 551.9 ; 550 ; TYY 200 ; TVA 210 ; Antarktis {Meteorologie und Klimatologie} ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: German
    Type: monograph , publishedVersion
    Format: 176 S.
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  • 6
    Publication Date: 2021-03-29
    Description: Besides measurements of atmospheric trace gases and laboratory studies of chemical reactions, modelling has been recognised to be of increasing importance to improve our knowledge of the atmosphere and the capabilities of photochemical models. Main scope of this work was the development of a photochemical atmospheric model, which was especielly designed for the interpretation of Differential Optical Absorption measurments (DOAS). This model has been used to improve our knowledge of atmospheric chemistry. For example, for the first time it was possible to demonstrate that a significant amount of IO in a range of 0.65 to 0.8 pptv is present in the stratosphere in the polar region (Ny-Alesund,Spitzbergen). Moreover it has been shown that such amounts of stratospheric IO lead to an additional Ozone loss in the range of 10 % in cold arctic winters.
    Description: thesis
    Keywords: 551.5 ; 550 ; TUA 700 ; TVA 210 ; Verfahren zur Untersuchung der freien Atmosphäre {Meteorologie} ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: German
    Type: monograph , publishedVersion
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  • 7
    Publication Date: 2021-03-29
    Description: Ozone profile retrieval, ERS-2, GOME, FURM, ozone decline, Northern hemisphere. - Measurements of stratospheric ozone over the Northern hemisphere forthe winter/spring periods of 1997 to 2000 taken with the GOMEinstrument were used to derive the chemical ozone depletion inside thepolar vortex. GOME onboard the ERS-2 satellite measures radiationcoming from the Earth in the UV/vis spectral range.To discern the chemical depletion from dynamical influences, a modelwas developed to calculate vortex averaged diabatic descent ratesusing the radiative transfer model MIDRAD and the FURM ozoneprofiles. The permeability of the Arctic vortex was analysed by usingthe trajectory model TANGO in conjunction with a reverse domainfilling algorithm, developed within the framework of this thesis.The chemical ozone ...
    Description: thesis
    Keywords: 551.5 ; 550 ; TUA 850 ; TVA 210 ; TY 100 ; Satellitenmeteorologie ; Chemische Zusammensetzung der Atmosphäre {Meteorologie} ; Nördliche Hemisphäre {Meteorologie und Klimatologie}
    Language: German
    Type: monograph , publishedVersion
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  • 8
    Publication Date: 2021-03-29
    Description: Ozone chemistry, tracer measurements, radiometry, airborne,submillimeterwave, Arctic, stratosphere. - The Airborne Submillimeter Radiometer (ASUR) is a passive heterodyne instrument using a superconducting detector with an instrumental frequency range from 604.3 to 662.3 GHz.Operating onboard an aircraft to avoid absorption by tropospheric water vapor key species of the stratospheric ozone chemistry can be detected for a vertical altitude range from 15 to 55 km. In the winter 1999/2000 the ASUR instrument participated in the THESEO 2000/SOLVE project onboard the NASA research aircraft DC-8. Three deployments were carried ...
    Description: thesis
    Keywords: 551.5 ; 550 ; TUA 800 ; TVA 210 ; TYY 100 ; Radarmeteorologie ; Chemische Zusammensetzung der Atmosphäre {Meteorologie} ; Arktis {Meteorologie und Klimatologie}
    Language: German
    Type: monograph , publishedVersion
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  • 9
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.5 ; 550 ; TUA 850 ; TUA 500 ; TVA 210 ; Satellitenmeteorologie ; Meteorologische Modelle ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: German
    Type: monograph , publishedVersion
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  • 10
    Publication Date: 2021-03-29
    Description: WSDW, water mass spreading, numerical model, lagrangian trajectories, Weddell Scotia Confluence. - The deep Scotia Sea is filled with ventilated Weddell Sea Deep Water (WSDW). This in turn is an essential contributor to the ventilation of the World Ocean abyss. A primitive equation, hydrostatic, ocean general circulation model (BRIOS1.1) with terrain-following coordinate is used to investigate the water mass export from the Weddell Sea. The model is circumpolar focusing on the Weddell Sea, with particularly high resolution (2̃0 km) in the DOVETAIL area. The northern limb of the Weddell Gyre exhibits an eastward Weddell Sea Deep Water transport across 44ʿW of 24 Sv. Export rates of Weddell Sea Deep Water through gaps in theSouth Scotia Ridge are estimated to be 6.4 Sv with a semi-annual cycle of ± 0.6 Sv, which can be correlated to atmospheric cyclone activity and Weddell Gyre strength. Sensitivity studies considering extreme sea ice conditions in the Weddell Sea show higher (lower) exports in years of minimum (maximum) winter sea ice extent. This can be attributed to the local change of the surface stress achieved by wind and ice. Lagrangian ...
    Description: thesis
    Keywords: 910 ; QGZ 420 ; UKG 200 ; Physische Geographie der Antarktis ; Teilfragen {Regionale Ozeanologie, Südpolarmeer}
    Language: German
    Type: monograph , publishedVersion
    Format: 142 S.
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  • 11
    Publication Date: 2021-03-29
    Description: Thermohaline circulation, variability, energy and moisture balance model, paleoceanography. - Freshening of high latitude surface water can change the large scale oceanic transport of heat and salt. Consequently, atmospheric and sea ice perturbations over the deep water production sites excite a large scale response establishing an oceanic t̀̀eleconnection'' with time scales of years to centuries. To study these feed-backs, an atmospheric energy and moisture balance model (EMBM), predicting the heat and fresh water fluxes at the surface, and a thermodynamic sea ice model were constructed and coupled to the GFDL ocean model MOM2. The heat and moisture transports by transient eddies in the EMBM are parameterized by diffusion. The coupled model reproduces many aspects of today's oceanic circulation. The most interesting features of the coupled model are the sensitivity of the thermohaline circulation to changes in the configuration, the multidecadal variability in the ocean-sea ice system, and the behaviour of the thermohaline circulation during transitions between glacial and interglacial periods. A very strong thermohaline circulation develops in the coupled system that is not evident in the stand-alone ocean model. An interesting aspect of this behaviour is the existence of a maximum strength in the overturning. Beyond this maximum, evaporation in the subtropics cannot balance the northward salt-transport. As a result, the watermasses over the deep water production sites become fresher, leading to a collapse of the thermohaline circulation. The associated changes in the sea ice cover prevent the system to recover. ...
    Description: thesis
    Keywords: 551.6 ; 550 ; QDC 200 ; Synoptische Klimageographie ; Wärme- und Strahlungshaushalt der Atmosphäre {Meteorologie} ; Statistische Klimatologie und Klimatologische Modelle ; Klimaänderungen
    Language: German
    Type: monograph , publishedVersion
    Format: 132 S.
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  • 12
    Publication Date: 2021-03-29
    Description: Sea-ice, Finite Element Sea-Ice Model, Kalman Filter, Data Assimilation. - The Arctic region is sensitive to climate change. Since the Arctic sea-ice cover influences the surface heat budget of the Earth the observed sea-ice decline is seen as an indication of global warming. Furthermore, the dynamics of sea ice plays an important role for the sea-ice mass distribution in the Arctic, for the production of dense, cold, and salty water in the Arctic Ocean, which contributes to the thermohaline circulation, and also for the freshwater budget of the Nordic Seas. Thus, a realistic description of sea-ice motion is important to draw conclusions for the mass transport and sea-ice mass distribution. The Finite-Element Sea-Ice Model simulates the large-scale physical sea-ice processes like the sea-ice growth and circulation realistically. The model domain covers the entire Arctic Ocean and its marginal seas. Together with the Singular Evolutive Interpolated Kalman (SEIK) Filter and remotely sensed sea-ice drift observations this sea-ice model is applied for data assimilation to investigate details of the sea-ice dynamics. So far, drift assimilation has been carried out to analyze and modify only the drift field with subsequent computation of the advection or redistribution of ice mass which corresponds more to the physical model behavior than a statistical analysis that the SEIK Filter provides. The sea-ice drift data assimilation with the SEIK Filter achieves drift modification and furthermore changes in the two other sea-ice variables concentration and thickness. The modifications of these "unobserved variables" (within the meaning of data assimilation) are validated and it is found that they are in good agreement for at least 2 months for the sea-ice thickness and even 4 months for the sea-ice concentration which is the longest period examined. The drift improvement is achieved due to the sea-ice concentration and ...
    Description: thesis
    Keywords: 551 ; 550 ; VAQ 990 ; VAQ 500 ; TVH 100 ; TOY 000 ; Meereis {Glaziologie} ; Gletscherbewegung und Gletscherschwankungen ; Wärme- und Strahlungshaushalt der Atmosphäre {Meteorologie} ; Energiebilanzen in der Geodynamik {Geophysik}
    Language: German
    Type: monograph , publishedVersion
    Format: 141 S.
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  • 13
    Publication Date: 2021-03-29
    Description: Tectonics, marine geophysics, plate-tectonic reconstruction, new zealand, antarctica, seismic refraction/wide-angle reflection, Gondwana break-up. - The last supercontinent fell into pieces with the break-up of Gondwana. In this context, the separation of the microcontinent of New Zealand from Antarctica is a jigsaw puzzle of many pieces. Its parts lay at the convergent margin of East Gondwana, which changed into a divergent margin within a geologically short time. That is why the microcontinent of New Zealand experienced different tectonic regimes and phases of the Wilson cycle. Although it is a good object of investigation due to its changing history, remarkably little is known about the submerged parts of the microcontinent. Knowledge of the magmatic-tectonic development of the submarine plateaux such as Campbell Plateau and Chatham Rise will improve the understanding of the processes that led to the late Gondwana break-up, and, in turn, lead to better reconstructions of East Gondwana, as Zealandia is a key piece in plate-kinematic reconstructions of this part of Gondwana. The central part of this thesis deals with the separation process of Zealandia from Antarctica leading to an improved reconstruction of New Zealand with emphasis on the submarine plateaux. Bounty Trough separating Chatham Rise from Campbell Plateau, and the Great South Basin separating Campbell Plateau from the South Island are investigated with seismic refraction and reflection methods. They are interpreted jointly with magnetic and gravity data. The results of crustal thickness modelling based on satellite gravity data are combined with existing information about crustal thickness of Zealandia. With these data ...
    Description: thesis
    Keywords: 551.136 ; 550 ; TST 000 ; Ozeanien {Geophysik} ; Pazifischer Ozean {Geophysik} ; Geotektonische Entwicklung der Erdkruste {Tektonik}
    Language: German
    Type: monograph , publishedVersion
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  • 14
    Publication Date: 2021-03-29
    Description: Dinoflagellate cysts, paleoceanography, paleoenvironment, Late Quaternary, Norwegian-Greenland Sea. - Dinoflagellate cysts have been investigated in nine short sediment cores as well as two long sediment cores from the Norwegian-Greenland Sea and the North Atlantic to reconstruct the surface water paleoenvironment of the last climatic cycle and the Holocene. Holocene sea-surface temperatures and salinities during summer and winter and the extent of sea-ice cover were reconstructed. On the Rockall Plateau, higher cyst concentrations indicating favourable conditions and increased productivity only occur during parts of stage 5, 4-2, and the Holocene. Only sparse occurrences of dinocysts have been observed in the Norwegian-Greenland Sea before 10000 yr BP. Later, high abundances of O. centrocarpum and N. labyrinthus indicate the increased inflow of relatively warm Atlantic. A change in dominance of these species as well as a distinct increase in cyst concentrations marks the onset of the recent circulation system. In the Norwegian Sea, O. centrocarpum dominates the assemblages since about 7000 yr BP, while assemblages in the Iceland and the Greenland Sea are more complex due to the influence of different surface currents.
    Description: thesis
    Keywords: 560
    Language: German
    Type: monograph , publishedVersion
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  • 15
    Publication Date: 2021-03-29
    Description: Reflection seismics, sediment drifts, bottom currents. - The region south of South Africa has been a crucial gateway for large scale Thermohaline Circulations since late Eocene times. Here, three of the most important currents for maintaining the global heat exchange, namely the warm and surface related Agulhas Current (AC), and the cold and denser North Atlantic Deep Water (NADW) as well as the Atlantic Bottom Water (AABW), flow around South Africa. Due to the special tectonic and geologic situation, a huge amount of the deep and bottom water masses that flow around South Africa have to pass the narrow Agulhas Passage, located between the South African continental shelf and the submarine Agulhas Plateau. As a result, the sedimentary infill of the Transkei Basin, which is located east of the Agulhas Plateau, has been predominantly influenced by NADW and AABW activity since ~36 Ma. Via the analysis of this sedimentary infill, a palaeo current reconstruction of (proto-) NADW and (proto-) AABW revealed changing flow paths and flow strengths since then. These variations in current attributes were triggered by large scale effects, such as the opening of the Tasman Gateway and the Drake Passage in the Late Eocene, or the closure of the Isthmus of Panama in the Pliocene. A more detailed analysis of the Transkei Basin's depocentre locations and interface outlines resulted in a palaeo flow path reconstruction for this region. Moreover, palaeo climate conditions from the Late Cretaceous were partially reconstructed ...
    Description: thesis
    Keywords: 551.462 ; 551.69 ; 550 ; TSZ 100 ; Atlantischer Ozean {Geophysik}
    Language: German
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  • 16
    facet.materialart.
    Unknown
    Univ. Bremen
    Publication Date: 2021-03-29
    Description: Ice, microstructures, subgrain boundaries, recrystallization, flow, deformation. - The primary objective of this thesis is the investigation of microstructures obtained from samples from the EPICA Dronning Maud Land ice core from Antarctica. The goal is to gain understanding of deformation processes an deformation-related recrystallization mechanisms using these structures. The structures are visualized with the new microstructure mapping method using the preferred sublimation along defect regions in the crystal. This method enables observation in high resolution as well as overview over a significant sample volume. In order to provide unambiguous proof of their deformational origin and to offer interpretation and characterization, experimental reproduction of the microstructural features are performed using creep tests. Subgrain boundaries and grain-boundary morphology are identified as the most direct effects of deformation and recrystallization processes, which are still easily observable. They can be used additionally to the conventional parameters (grain size, crystal-orientation distribution) to determine these mechanisms. Different sbugrain-boundary types observed in experimentally deformed samples as well as in natural ice indicate several formation processes. Results obtained from this new and novel data suggest a profound reconsideration of the classical tripartition of recrystallization regimes described in the literature in ice sheets. Instead, dynamic recrystallization in two of its forms (rotation recrystallization and strain-induced migration recrystallization) dominates the microstructure evolution in all depth regions of the EDML ice core. Results of systematic microstructure analysis of creep-test samples demonstrate ...
    Description: thesis
    Keywords: 551.312 ; 548.842 ; 551 ; 550 ; VAE 140 ; VAQ 100 ; Gesteinsdeformation {Strukturgeologie} ; Gletscheruntersuchungen im Allgemeinen
    Language: German
    Type: monograph , publishedVersion
    Format: 129 S.
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  • 17
    Publication Date: 2021-03-29
    Description: GIS, Geoinformatik, Spatial Theory, Face Intersection, Polygon Clipping, Diagramatic Reasoning. - A Geographic Information System (GIS) is used to handle, analyse and visualize ‘facts’ of the ‘real world’. These ‘facts’ are assumed to be spatial in the sense that they are located at the earth’s surface. The first chapter outlines that the recent success of applied GIS is based on this ‘real world’ approach, which conforms to the tradition of geography as a scientific discipline. While most GIS-applications are pragmatically oriented in solving ‘real-world-problems’, each attempt to implement ‘spatial theories’ of GIS ends up in the well known geographical dilemma ...
    Description: thesis
    Keywords: 910 ; QBD 700 ; Geoinformationssysteme {Geographie}
    Language: German
    Type: monograph , publishedVersion
    Format: 162 S.
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  • 18
    Publication Date: 2021-03-29
    Description: Deep-sea fan, early diagenesis, susceptibility, anaerobic oxidation of methane, black shale, anoxia, oceanic anoxic event, trace elements, iron, phosphorus, sediment source, redox changes, enrichment factors, sequential extraction. - In the context of present-day changes of atmo-, hydro-, geo- and biosphere processes, there is growing interest to decipher rapid paleoenvironmental changes in the geological past. Marine deposits provide valuable insights into paleoenvironmental conditions that prevailed during their deposition, if we know how to read the respective signals in the sedimentary record. However, caution is demanded as primary signals of past environmental conditions can be altered by postdepositional diagenetic processes. In the presented work, we will show the potentials, but also limitations of inorganic geochemical proxies to record signals of abrupt paleoenvironmental shifts in the terrestrially dominated Late Quaternary deposits of the Zambesi deep-sea fan (SE African margin), and in a fully marine Late Cretaceous black shale succession on Demerara Rise (NW South American margin).
    Description: thesis
    Keywords: VAT 200 ; VJB 322 ; VAT 200 ; VJB 322 ; Meeresablagerungen {Geologie} ; Geochemie der ozeanischen Sedimente
    Language: German
    Type: monograph , publishedVersion
    Format: 127 S.
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  • 19
    Publication Date: 2021-03-29
    Description: Im ersten Kapitel erfolgt nach der Zielsetzung und Motivation für die vorliegende Dissertation eine kurze geographische Beschreibung des Arktischen Ozeans und dessen tektonischer Entwicklung.Das Augenmerk gilt dabei dem ca. 1800 km langen Gakkel-Rücken, der sich von der Nordküste Grönlands bis zum Schelf der Laptewsee erstreckt und die Grenze zwischen Nordamerikanischer und Eurasischer Platte bildet. Die Spreizungsgeschwindigkeiten dieses Rückensystems, welche für geowissenschaftliche Untersuchungen von besonderer Bedeutung sind, betragen nur etwa einen Zentimeter pro Jahr und sind damit die langsamsten weltweit. Eine kurze Vorstellung von geophysikalischen und geodätischen Messverfahren zeigt, wie man zu solchen präzisen Spreizungsraten gelangt. Im Anschluss erfolgt eine kurze Beschreibung der Arctic Mid-Ocean Ridge Expedition (AMORE), welche die Forschungsschiffe Healy (USA) und Polarstern (Deutschland) im Sommer 2001 in den zentralen Arktischen Ozean und zum Nordpol führte. Die Sonarmessdaten und Bodenproben, die auf der AMORE-Expedition gesammelt und in dieser Arbeit ausgewertet wurden, stammen hauptsächlich aus dem ca. 32 000 km2 großen Gebiet entlang des Gakkel-Rückens (7°W85°E, 82°N87°N), zum Teil aber auch aus dem Amundsen- und Nansen-Becken. In Kapitel Zwei werden hydroakustische Grundlagen erläutert, die für das Verständnis dieser Arbeit unabdingbar sind und auf die später zurückgegriffen wird. Nach der Beschreibung von physikalischen Größen und Verhältnissen, der Wellengleichung, der Ausbreitung von Unterwasserschall und der Reflexion und Rückstreuung von Schallwellen am Meeresboden erfolgt eine Formulierung der Sonargleichung ...
    Description: thesis
    Keywords: 551.46 ; TQD 800 ; TSZ 100 ; VAT 300 ; Georadar {Geophysik} ; Atlantischer Ozean {Geophysik} ; Geologie des Meeresboden
    Language: German
    Type: monograph , publishedVersion
    Format: 231 S.
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  • 20
    Publication Date: 2021-03-29
    Description: Antarctica, Dronning Maud Land, anisotropy, seismic anisotropy, shear wave splitting, receiver functions, moho, moho depth, crust, upper mantle, refraction seismic, gravity, 3D-gravity, igmas, bouguer anomaly, seismology. - The area of investigation, Dronning Maud Land (DML), comprises with the Weddell Sea and the Lazarev Sea approximately the region between 15 degrees W and 15 degrees E longitude and 68 degrees and 75 degrees latitude - a surface area of more than 1.500.000 qkm. Three major events formed the present-day geology and tectonic settings of DML: (1) the Grenvillian Orogeny, ca. 1.1 Ga ago, caused by the formation of the supercontinent Rhodinia, (2) the Panafrican Orogeny 500 Ma ago, forming the supercontinent Gondwana due to the collison of West and East Gondwana, and (3) the break-up of Gondwana 180 Ma ago, which started in the present-day Lazarev Sea. Seismological, refraction seismic and aerogravity data-sets form the basis of this thesis. The combination of these data-sets allows to investigate the structural composition and the spatial variation of the lithospheric thickness. The latter is essential for the determination of the regional geoid, which is the main objective of the VISA-project. Within the framework of this project airborne measurements of the potential field as well as ice-penetrating radar and GPS-measurements have been carried out. Moreover, seismographic stations were temporarily deployed in various parts of DML. Despite their very short operation time, applications of seismological methods to the recorded teleseismic events yielded conclusions about the structure and dynamic of the deeper subsurface. By analyses of seismic anisotropy, which investigates the splitting of shear waves traversing an anisotropic medium (so-called shear wave splitting) conclusions ...
    Description: thesis
    Keywords: 551.1 ; 550 ; TSY 200 ; Antarktis {Geophysik}
    Language: German
    Type: monograph , publishedVersion
    Format: 150 S.
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  • 21
    Publication Date: 2021-03-29
    Description: Radiocarbon, reservoir age, ocean circulation, projection age, top-to-bottom age, B-P age. - In paleoceanography and paleoclimatology radiocarbon is frequently used to date carbonaceous samples of the past 50,000 years and as a proxy to reconstruct circulation states of the ocean. Temporal variations of the atmospheric radiocarbon concentration, caused by a varying radiocarbon production rate or changes in the global carbon cycle, lead to dating uncertainties and also limit the usability of radiocarbon as an oceanographic proxy. In order to analyze and correct the influence of varying atmospheric radiocarbon on the ocean, radiocarbon has been included as a tracer to a global climate model (University of Victoria Earth System Climate Model). This model was forced by the reconstructed atmospheric radiocarbon production rate, to predict differences between atmospheric and marine radiocarbon age, the so-called reservoir age, spatially and temporally.
    Description: thesis
    Keywords: 551.701 ; 550 ; Geochronologie einzelner Regionen ; Holozän ; Isotopengeologie ; Geochemische Kreislaufmodelle
    Language: German
    Type: monograph , publishedVersion
    Format: 124 S.
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  • 22
    Publication Date: 2021-03-29
    Description: Sediment transport, high productivity, submarine canyon, submarine slide, excess pore-pressure, weak layers, slope failure. - The study investigates processes of mass sediment transport in two geologically unique Atlantic margins influenced by high primary productivity, i.e. the Mauritanian and Uruguayan margins. Whereas the Mauritanian margin is dominated by hyper-arid conditions, the Uruguayan margin, on the other hand, is dominated by fluvial sediment inputs. Investigations of the Mauritanian margin are centred on two major features, i.e. the Cap Timiris Canyon and the Mauritania Slide Complex, using combined analyses of hydroacoustic and high resolution multi-channel seismic (MCS) data. An area offshore Uruguay, which is dominated by extensive slope instabilities and mass sediment transport, was also investigated with high resolution MCS data. Results of the study suggest ...
    Description: thesis
    Keywords: 551 ; 551 ; 550 ; Atlantischer Ozean {Geophysik} ; Marine Sedimentation {Geologie}
    Language: German
    Type: monograph , publishedVersion
    Format: 130 S.
    Format: application/pdf
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