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  • Weitere Quellen  (443)
  • AGU (American Geophysical Union)  (247)
  • Wiley  (108)
  • Universität Göttingen,Abteilung Bodenphysik  (39)
  • American Association for the Advancement of Science (AAAS)  (34)
  • Am. Geophys. Un.
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  • 1
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    Unbekannt
    Quantitative Stratigraphic Correlation (1982)
    Wiley
    In:  Chichester, Wiley, vol. 231, no. 3, pp. 2-203, (ISBN 0-470-02298-1)
    Details
    Publikationsdatum: 1982
    Schlagwort(e): Data analysis / ~ processing ; Correlation ; Seismic stratigraphy ; Seismics (controlled source seismology)
    Standort Signatur Erwartet Verfügbarkeit
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    BIBLIOGRAFIE SEISMOLOGIE
  • 2
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    Unbekannt
    Applied Regression Analysis (1981)
    Wiley
    In:  New York, 2nd Edition, 709 pp., Wiley, vol. 75, no. 2, pp. 2-203, (ISBN: 3-7643-7143-9)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Correlation ; Data analysis / ~ processing ; fit ; Textbook of mathematics
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    BIBLIOGRAFIE SEISMOLOGIE
  • 3
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    Unbekannt
    Numerical and Analytical Methods for Scientists and Engineers Using Mathematica (2003)
    Wiley
    In:  Hoboken, NJ, 633 pp., Wiley, vol. 16B, no. 2, pp. 125-169, (ISBN 0-471-26610-8)
    Details
    Publikationsdatum: 2003
    Schlagwort(e): Textbook of mathematics ; Data analysis / ~ processing ; Modelling ; software ; manual ; computer ; algebra ; symbolic ; mathematics
    Standort Signatur Erwartet Verfügbarkeit
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    BIBLIOGRAFIE SEISMOLOGIE
  • 4
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    Unbekannt
    The spatial distribution of earthquakes, focal mechanisms solutions, and subducted lithosphere in the Philippine and northeastern Indonesian islands (1980)
    Am. Geophys. Un.
    In:  Professional Paper, The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands, New York, Am. Geophys. Un., vol. 23, no. 16, pp. 1-35, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publikationsdatum: 1980
    Schlagwort(e): Seismicity ; Fault plane solution, focal mechanism ; Subduction zone ; Plate tectonics
    Standort Signatur Erwartet Verfügbarkeit
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    BIBLIOGRAFIE SEISMOLOGIE
  • 5
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    Unbekannt
    Focal mechanism solutions and their tectonic implications for the eastern Alpine-Himalayan region (1981)
    Am. Geophys. Un.
    In:  Professional Paper, Zagros, Hindu Kush, Himalaya: Geodynamic Evolution, Washington, D. C., Am. Geophys. Un., vol. 65, no. 16, pp. 243-271, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Fault plane solution, focal mechanism ; Tectonics ; Plate tectonics ; Seismology
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    BIBLIOGRAFIE SEISMOLOGIE
  • 6
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    Unbekannt
    The geodynamic evolution of the Himalaya - ten years of research in central Nepal Himalaya and some other regions (1981)
    Am. Geophys. Un.
    In:  Professional Paper, Zagros, Hindu Kush, Himalaya: Geodynamic Evolution, Washington, D. C., Am. Geophys. Un., vol. 37, no. 16, pp. 149-168, (ISBN 0080419208)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): GeodesyY ; Project report/description ; Geol. aspects ; Tectonics ; Plate tectonics
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    BIBLIOGRAFIE SEISMOLOGIE
  • 7
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    The geodynamic history of the Himalaya (1981)
    Am. Geophys. Un.
    In:  Professional Paper, Zagros, Hindu Kush, Himalaya: Geodynamic Evolution, Washington, D. C., Am. Geophys. Un., vol. 24, no. 231, pp. 111-121, (ISBN: 3-540-23712-7)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Tectonics ; Plate tectonics ; GeodesyY ; Geol. aspects
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    BIBLIOGRAFIE SEISMOLOGIE
  • 8
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    Unbekannt
    Microscopic and macroscopic physics of earthquakes (2000)
    Am. Geophys. Un.
    In:  Bull., Polar Proj. OP-O3A4, Geocomplexity and the Physics of Earthquakes, Washington, Am. Geophys. Un., vol. 120, no. 1, pp. 147-163, (ISBN: 3-540-23712-7)
    Details
    Publikationsdatum: 2000
    Schlagwort(e): Stress ; Geothermics ; Non-linear effects ; Fracture ; Seismicity ; Fluids ; AGU ; Modelling ; Rock mechanics ; Friction
    Standort Signatur Erwartet Verfügbarkeit
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    BIBLIOGRAFIE SEISMOLOGIE
  • 9
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    Seismicity and continental subduction in the Himalayan arc (1981)
    Am. Geophys. Un.
    In:  Bull., Open-File Rept., Zagros, Hindu Kush, Himalaya: Geodynamic Evolution, Washington, D. C., Am. Geophys. Un., vol. 5, no. 16, pp. 215-242, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Seismicity ; Subduction zone ; Plate tectonics
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    BIBLIOGRAFIE SEISMOLOGIE
  • 10
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    Tectonics of the central sector of the Himalaya (1981)
    Am. Geophys. Un.
    In:  Professional Paper, Open-File Rept., Zagros, Hindu Kush, Himalaya: Geodynamic Evolution, Washington, D. C., Am. Geophys. Un., vol. 13, no. 16, pp. 87-110, (ISBN 0080419208)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Tectonics ; Plate tectonics ; Geol. aspects
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    BIBLIOGRAFIE SEISMOLOGIE
  • 11
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    Unbekannt
    Some features of medium- and short-term anomalies before great earthquakes (1981)
    Am. Geophys. Un.
    In:  Professional Paper, Open-File Rept., Earthquake Prediction: an International Review, Washington D. C., Am. Geophys. Un., vol. 4, no. 2, pp. 497-509, (ISBN 0080419208)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Earthquake precursor: prediction research ; China
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    BIBLIOGRAFIE SEISMOLOGIE
  • 12
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    Unbekannt
    Flow and Fracture of Rocks (1972)
    Am. Geophys. Un.
    In:  Washington, D. C., Am. Geophys. Un., vol. 16, no. XVI:, pp. 1-14, (ISBN: 1-4020-2968-3)
    Details
    Publikationsdatum: 1972
    Schlagwort(e): Fracture ; Rock mechanics ; Inelastic ; Fluids
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    BIBLIOGRAFIE SEISMOLOGIE
  • 13
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    Unbekannt
    Geocomplexity and the Physics of Earthquakes (2000)
    Am. Geophys. Un.
    In:  Washington, Am. Geophys. Un., vol. 120, no. Publ. No. 12, pp. 81-89, (ISBN 0-444-50971-2)
    Details
    Publikationsdatum: 2000
    Schlagwort(e): Chaotic behaviour ; FractureT ; Fracture ; Seismicity ; SOC ; Pattern recognition ; AGU ; Modelling ; Stress ; Stress drop ; Rock mechanics ; Friction
    Standort Signatur Erwartet Verfügbarkeit
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    BIBLIOGRAFIE SEISMOLOGIE
  • 14
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    Unbekannt
    Status report of the work carried out by Geological Survey of India in the framework of the International Geodynamics Project (1981)
    Am. Geophys. Un.
    In:  Bull., Polar Proj. OP-O3A4, Zagros, Hindu Kush, Himalaya: Geodynamic Evolution, Washington, D. C., Am. Geophys. Un., vol. 1, no. 2, pp. 169-188, (ISBN 0-87590-532-3, AGU Code: GD0305323)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Geol. aspects ; Project report/description ; GeodesyY ; Tectonics ; Plate tectonics
    Standort Signatur Erwartet Verfügbarkeit
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    BIBLIOGRAFIE SEISMOLOGIE
  • 15
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    Unbekannt
    Faulting and crustal stress at Rangely, Colorado (1972)
    Am. Geophys. Un.
    In:  Bull., Open-File Rept., Flow and Fracture of Rocks, Washington, D. C., Am. Geophys. Un., vol. 16, no. 1, pp. 275-284, (ISBN 0080419208)
    Details
    Publikationsdatum: 1972
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    BIBLIOGRAFIE SEISMOLOGIE
  • 16
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    Unbekannt
    Structure and seismotectonics of the Himalaya-Pamir Hindukush Region and the Indian plate boundary (1981)
    Am. Geophys. Un.
    In:  Bull., Polar Proj. OP-O3A4, Zagros, Hindu Kush, Himalaya: Geodynamic Evolution, Washington, D. C., Am. Geophys. Un., vol. 37, no. 16, pp. 272--293, (ISBN: 3-540-23712-7)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Seismicity ; Tectonics ; Deep seismic sounding (espec. cont. crust)
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    BIBLIOGRAFIE SEISMOLOGIE
  • 17
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    Unbekannt
    State of stress in the northern part of the Indian plate (1981)
    Am. Geophys. Un.
    In:  Bull., Open-File Rept., Zagros, Hindu Kush, Himalaya: Geodynamic Evolution, Washington, D. C., Am. Geophys. Un., vol. 4, no. 16, pp. 307-312, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Stress ; Plate tectonics ; GeodesyY
    Standort Signatur Erwartet Verfügbarkeit
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    BIBLIOGRAFIE SEISMOLOGIE
  • 18
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    Recent ground deformation in continental and oceanic rift zones (1982)
    Am. Geophys. Un.
    In:  Professional Paper, Open-File Rept., Continental and Oceanic Rifts, Washington D.C., Am. Geophys. Un., vol. 8, no. 16, pp. 17-29, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publikationsdatum: 1982
    Schlagwort(e): Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Stress ; GeodesyY ; Plate tectonics ; Iceland
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    BIBLIOGRAFIE SEISMOLOGIE
  • 19
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    Geology and tectonics of the Himalayan region of Ladakh, Himachal, Garwhal-Kummaun and Arunachal Pradesh: A review (1981)
    Am. Geophys. Un.
    In:  Bull., Open-File Rept., Zagros, Hindu Kush, Himalaya: Geodynamic Evolution, Washington, D. C., Am. Geophys. Un., vol. 4, no. 16, pp. 122-148, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Review article ; Geol. aspects ; Tectonics ; Plate tectonics
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    BIBLIOGRAFIE SEISMOLOGIE
  • 20
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    Unbekannt
    Earthquake hazard in the Hellenic arc (1981)
    Am. Geophys. Un.
    In:  Professional Paper, Open-File Rept., Earthquake Prediction: an International Review, Washington D. C., Am. Geophys. Un., vol. 4, no. 2, pp. 153-172, (ISBN 0080419208)
    Details
    Publikationsdatum: 1981
    Schlagwort(e): Earthquake precursor: prediction research ; Seismicity ; Gutenberg-Richter magnitude frequency b-value ; Earthquake hazard ; seismic ; gap
    Standort Signatur Erwartet Verfügbarkeit
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    BIBLIOGRAFIE SEISMOLOGIE
  • 21
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    The History of South American Tropical Precipitation for the Past 25,000 Years (2001)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 291 (5504). pp. 640-643.
    Details
    Publikationsdatum: 2017-01-04
    Beschreibung: Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. Maximum aridity and lowest lake level occurred in the early and middle Holocene (8000 to 5500 cal yr B.P.) during a time of low summer insolation. Today, rising levels of Lake Titicaca and wet conditions in Amazonia are correlated with anomalously cold sea-surface temperatures in the northern equatorial Atlantic. Likewise, during the deglacial and Holocene periods, there were several millennial-scale wet phases on the Altiplano and in Amazonia that coincided with anomalously cold periods in the equatorial and high-latitude North Atlantic, such as the Younger Dryas.
    Materialart: Article , PeerReviewed
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  • 22
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    Submarine landslides around the Canary Islands (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 106 (B3). pp. 3977-3997.
    Details
    Publikationsdatum: 2019-04-08
    Beschreibung: The morphology and structure of the submarine flanks of the Canary Islands were mapped using the GLORIA long-range side-scan sonar system, bathymetric multibeam systems, and sediment echosounders. Twelve young (〈2 Ma) giant landslides have been identified on the submarine flanks of the Canary Islands up to now. Older landslide events are long buried under a thick sediment cover due to high sedimentation rates around the Canary Islands. Most slides were found on the flanks of the youngest and most active islands of La Palma, El Hierro, and Tenerife, but young giant landslides were also identified on the flanks of the older (15–20 Ma) but still active eastern islands. Large-scale mass wasting is an important process during all periods of major magmatic activity. The long-lived volcanic constructive history of the islands of the Canary Archipelago is balanced by a correspondingly long history of destruction, resulting in a higher landslide frequency for the Canary Islands compared to the Hawaiian Islands, where giant landslides only occur late in the period of active shield growth. The lower stability of the flanks of the Canaries is probably due to the much steeper slopes of the islands, a result of the abundance of highly evolved intrusive and extrusive rocks. Another reason for the enhanced slope instability is the abundance of pyroclastic deposits on Canary Islands resulting from frequent explosive eruptions due to the elevated volatile contents in the highly alkalic magmas. Dike-induced rifting is most likely the main trigger mechanism for destabilization of the flanks. Flank collapses are a major geological hazard for the Canary Islands due to the sector collapses themselves as well as triggering of tsunamis. In at least one case, a giant lateral blast occurred when an active magmatic or hydrothermal system became unroofed during flank collapse.
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  • 23
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    Habitat differentiation vs. isolation-by-distance: the genetic population structure of Elymus athericus in European salt marshes (2003)
    Wiley
    In:  Molecular Ecology, 12 (2). pp. 505-515.
    Details
    Publikationsdatum: 2017-07-18
    Beschreibung: We investigated genetic differentiation among populations of the clonal grass Elymus athericus, a common salt-marsh species occurring along the Wadden Sea coast of Europe. While E. athericus traditionally occurs in the high salt marsh, it recently also invaded lower parts of the marsh. In one of the first analyses of the genetic population structure in salt-marsh species, we were interested in population differentiation through isolation-by-distance, and among strongly divergent habitats (low and high marsh) in this wind- and water-dispersed species. High and low marsh habitats were sampled at six sites throughout the Wadden Sea. Based on reciprocal transplantation experiments conducted earlier revealing lower survival of foreign genotypes we predicted reduced gene flow among habitats. Accordingly, an analysis with polymorphic cross-species microsatellite primers revealed significant genetic differentiation between high and low marsh habitats already on a very small scale (〈 100 m), while isolation-by-distance was present only on larger scales (60–443 km). In an analysis of molecular variance we found that 14% of the genetic variance could be explained by the differentiation between habitats, as compared to only 8.9% to geographical (isolation-by-distance) effects among six sites 2.5–443 km distant from each other. This suggests that markedly different selection regimes between these habitats, in particular intraspecific competition and herbivory, result in habitat adaptation and restricted gene flow over distances as small as 80 m. Hence, the genetic population structure of plant species can only be understood when considering geographical and selection-mediated restrictions to gene flow simultaneously.
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  • 24
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    Staining plastic sections (1983)
    Wiley
    In:  Journal of Microscopy, 131 (2). pp. 173-186.
    Details
    Publikationsdatum: 2017-07-13
    Beschreibung: Many of the difficulties of staining plastic embedded tissues for light and electron microscopy derive from physical exclusion of hydrophilic staining reagents by hydrophobic embedding media. Structures which stain most intensely with hydrophilic reagents usually contain less hydrophobic plastic than do non-staining structures. Such incomplete infiltration is apparently caused by exclusion of viscous, hydrophobic monomers by physically dense and/or well hydrated tissue elements. In keeping with this, generalized staining of tissues embedded in hydrophobic media does occur when hydrophobic reagents are used. Staining of plastic-free structures with single hydrophilic reagents or with sequences of such reagents, is, however, largely rate-controlled. The surprising similarity of hydrophilic and hydrophobic plastic embedding media is discussed. Limits of this simple model are explored, with a consideration of the roles of fixative and of monomer-tissue reactions
    Materialart: Article , PeerReviewed
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  • 25
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    Microbial Reefs in the Black Sea Fueled by Anaerobic Oxidation of Methane (2002)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 297 (5583). pp. 1013-1015.
    Details
    Publikationsdatum: 2017-07-07
    Beschreibung: Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong 13C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist of densely aggregated archaea (phylogenetic ANME-1 cluster) and sulfate-reducing bacteria (Desulfosarcina/Desulfococcusgroup). If incubated in vitro, these mats perform anaerobic oxidation of methane coupled to sulfate reduction. Obviously, anaerobic microbial consortia can generate both carbonate precipitation and substantial biomass accumulation, which has implications for our understanding of carbon cycling during earlier periods of Earth's history.
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  • 26
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    Paleomagnetism of deep-sea cores (1972)
    AGU (American Geophysical Union)
    In:  Reviews of Geophysics and Space Physics, 10 (1). pp. 213-249.
    Details
    Publikationsdatum: 2017-01-13
    Beschreibung: This review is intended to cover the principal developments that have occurred within the last six years in the paleomagnetic study of marine sediments. Recent work utilizing the reflecting-light microscope indicates that detrital high-temperature Fe-Ti oxides are probably responsible for most of the magnetic remanence in marine sediments. These minerals possess a spectrum of coercivities that makes it necessary to use alternating-field—demagnetization techniques to isolate stable components. It is possible to use the standard magnetic stratigraphy for the last 4 m.y. of earth history derived from terrestrial lavas. Using the ages of the magnetic boundaries from this time scale it is possible by extrapolation and interpolation to better determine the ages of the major events. The ages of these events in increasing age are Jaramillo, 0.87 to 0.92 m.y.; Olduvai, 1.71 to 1.86 m.y.; Kaena, 2.82 to 2.90 m.y.; Mammoth, 3.0 to 3.085 m.y.; Cochiti, 3.72 to 3.82 m.y.; Nunivak, 3.97 to 4.14 m.y.; ‘c’ event of the Gilbert series, 4.33 to 4.65 m.y. Through the use of long cores from the central Pacific and through correlation using fossil datums, it has been possible to extend the magnetic stratigraphy back to the upper middle Miocene to magnetic epoch 5. It is concluded that very short magnetic events are probably short-term excursions of the field and not true magnetic events. It is shown that the field of the earth averages to an axial-dipole field within a period of 27,000 years and that the field over the last two million years has acted as a geocentric axial dipole. The evidence shows that when reversals of the dipole occur, the values of the reversed inclination are not significantly different from the normal values. The use of magnetic stratigraphy in marine geology has opened up a new era in study of sedimentary processes and evolution of marine organisms.
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  • 27
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    Compositional heterogeneity of tephras from the 1980 eruptions of Mount St. Helens (1982)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research - Solid Earth, 87 (B13). pp. 10861-10881.
    Details
    Publikationsdatum: 2017-01-25
    Beschreibung: Samples collected at hourly intervals on May 18–19, 1980, at three sites 200 km downwind from Mount St. Helens, have made possible a detailed reconstruction of the conditions that contribute to the compositional heterogeneity of mineral and glass components observed in distal tephra layers. The air fall tephra deposited at the sites during the first 7 hours of the May 18 eruption is mostly coarse grained, microlite-rich, nonjuvenile glass and feldspar. Grain-size maxima in this initial tephra can be related to the cataclysmic blast at 0832 and a subsequent pulse of the eruption at 1200. Juvenile, microlite-free glass increases in relative abundance at the sampling sites beginning at about 1900. Such a change between nonjuvenile and juvenile tephra can be related to a 5-km increase in column height associated with the last major pulse of the eruption which occurred at 1700 at the volcano. Electron microprobe study of both microlite-rich and microlite-free pumice in the time series samples reveals significant compositional differences. Interstitial glass in nonjuvenile pumice deposited during the first few hours at the sampling sites is enriched in SiO2 and K2O and depleted in TiO2, FeO*, and MgO relative to juvenile glass. By comparison, major element composition of the least evolved juvenile glass sampled during the last several hours of the eruption displays a slight trend toward less evolved composition. Least squares calculations suggest that the more evolved character of the nonjuvenile glass can be explained by greater fractional crystallization brought about by enhanced cooling in a cryptodome prior to eruption, whereas the temporal changes observed in juvenile glass composition during the last several hours of the eruption suggest the presence of a small, slightly zoned magma chamber at depth. Electron microprobe study of glass-coated ilmenites, magnetites, and plagioclases provides the following estimates of the physical conditions in this reservoir: 865°±50°C, PH2O = 2.2 kbar and -log ƒO2 = 11.7. Analyses of bulk pumice, glass and selected mineral phases from May 25, June 12, July 22, and October 16–18 pumices erupted from Mount St. Helens indicate that the bulk pumice (magma) compositions have become slightly more andesitic with time, while mineral and co-existing glass compositions have changed significantly in post-May 18 eruptions with both being more highly evolved than those associated with the May 18 eruption. An application of the magnetite-ilmenite geothermometer to June 12 and July 22 samples indicates temperatures of 919°±30°C and 930°±50°C, respectively. Least squares calculations suggest that such evolved post-May 18 glass and mineral phases can be derived by fractional crystallization of a magma composition like bulk May 18 pumice into approximately 50% crystals and 50% residual liquid. Such partitioning between crystals and residual liquid appears to have occurred on the scale of centimeters and is interpreted as a consequence of accelerated crystallization under reduced water pressure.
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  • 28
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    Parasite Selection for Immunogenetic Optimality (2003)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 301 (5638). p. 1343.
    Details
    Publikationsdatum: 2017-03-31
    Beschreibung: In vertebrates, genes of the major histocompatibility complex (MHC), with their pronounced polymorphism, potentially represent outstanding examples for the selective advantages of genetic diversity (1). Theoretical models predicted that, within an individual, MHC alleles can be subjected to two opposing selective forces, resulting in an optimal number of genes at intermediate individual MHC diversity (2, 3). Diversifying selection increases heterozygosity and enables wider recognition of pathogens (4). This process is opposed by the need to delete T cells that react with self peptide–MHC combinations (5) from the repertoire, which has been proposed as a possible mechanism constraining expansion of MHC genes. Because too high MHC diversity might delimit T cell diversity, it might also impose limitations on the efficiency of pathogen recognition. However, empirical evidence demonstrating fitness benefits in terms of parasite resistance caused by this type of optimal MHC diversity has been lacking. Therefore, we tested whether three-spined sticklebacks (Gasterosteus aculeatus L.) carrying an intermediate level of individual MHC diversity also displayed the strongest level of resistance against parasite infection. Sticklebacks are particularly suited to test MHC optimality, because MHC class II genotypes can differ markedly in the number of MHC class IIB alleles (6). We caught fish from an outbred population and used these to breed six sibships of immunologically naïve fish (i.e., they had no previous contact to parasites). Immunogenetic diversity ranged from three to nine MHC class IIB alleles found in reverse-transcribed messenger RNA (mRNA) [see (6) for details on genotyping]. The MHC genotypes within these sibships segregated above and below the hypothesized optimal number of ∼5 MHC class IIB alleles, which had previously been estimated in an epidemiological field survey (7). In individual infection treatments, fish from all sibships were simultaneously exposed to three of the most abundant parasite species identified in the field (Fig. 1A) (8). After two rounds of infection, separated by an interval of 8 weeks, we found a significant minimal mean infection rate at an intermediate number of individual MHC class IIB variants [i.e., 5.82 expressed alleles (Fig. 1B)]. This result was also confirmed when sibships were considered separately [i.e., 4.96 alleles (Fig. 1C)] (9). The strong pattern only appeared when infection with all three parasites was accounted for simultaneously. This may not be surprising, because single alleles are expected to correlate with single diseases and multiple alleles can contribute to resistance against several infectious agents (2).
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  • 29
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    Parasite Selection for Immunogenetic Optimality (2003)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 301 (5638). p. 1343.
    Details
    Publikationsdatum: 2017-12-14
    Beschreibung: In vertebrates, genes of the major histocompatibility complex (MHC), with their pronounced polymorphism, potentially represent outstanding examples for the selective advantages of genetic diversity (1). Theoretical models predicted that, within an individual, MHC alleles can be subjected to two opposing selective forces, resulting in an optimal number of genes at intermediate individual MHC diversity (2, 3). Diversifying selection increases heterozygosity and enables wider recognition of pathogens (4). This process is opposed by the need to delete T cells that react with self peptide–MHC combinations (5) from the repertoire, which has been proposed as a possible mechanism constraining expansion of MHC genes. Because too high MHC diversity might delimit T cell diversity, it might also impose limitations on the efficiency of pathogen recognition. However, empirical evidence demonstrating fitness benefits in terms of parasite resistance caused by this type of optimal MHC diversity has been lacking. Therefore, we tested whether three-spined sticklebacks (Gasterosteus aculeatus L.) carrying an intermediate level of individual MHC diversity also displayed the strongest level of resistance against parasite infection. Sticklebacks are particularly suited to test MHC optimality, because MHC class II genotypes can differ markedly in the number of MHC class IIB alleles (6). We caught fish from an outbred population and used these to breed six sibships of immunologically naïve fish (i.e., they had no previous contact to parasites). Immunogenetic diversity ranged from three to nine MHC class IIB alleles found in reverse-transcribed messenger RNA (mRNA) [see (6) for details on genotyping]. The MHC genotypes within these sibships segregated above and below the hypothesized optimal number of ∼5 MHC class IIB alleles, which had previously been estimated in an epidemiological field survey (7). In individual infection treatments, fish from all sibships were simultaneously exposed to three of the most abundant parasite species identified in the field (Fig. 1A) (8). After two rounds of infection, separated by an interval of 8 weeks, we found a significant minimal mean infection rate at an intermediate number of individual MHC class IIB variants [i.e., 5.82 expressed alleles (Fig. 1B)]. This result was also confirmed when sibships were considered separately [i.e., 4.96 alleles (Fig. 1C)] (9). The strong pattern only appeared when infection with all three parasites was accounted for simultaneously. This may not be surprising, because single alleles are expected to correlate with single diseases and multiple alleles can contribute to resistance against several infectious agents (2).
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  • 30
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    Late Wisconsin-Weichselian Mountain Glaciers and Small Ice Caps (1981)
    Wiley
    In:  In: The last great ice sheets. , ed. by Denton, G. H. and Hughes, T. J. Wiley, New York, pp. 179-206. ISBN 0-471-06006-2
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    Publikationsdatum: 2017-04-10
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  • 31
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    Caldera development during the Minoan eruption, Thira, Cyclades, Greece (1984)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research - Solid Earth, 89 (B10). pp. 8441-8462.
    Details
    Publikationsdatum: 2017-05-04
    Beschreibung: The well-known caldera of Thira (Santorini), Greece, was not formed during a single eruption but is composed of two overlapping calderas superimposed upon a complex volcanic field that developed along a NE trending line of vents. Before the Minoan eruption of 1400 B.C., Thira consisted of three Java shields in the northern half of the island and a flooded depression surrounded by tuff deposits in the southern half. Andesitic lavas formed the overlapping shields of the north and were contemporaneous with and, in many places, interbedded with the southern tuff deposits. Although there appears to be little difference between the composition of magmas erupted, differences in eruption style indicate that most of the activity in the northern half of the volcanic field was subaerial, producing lava flows, whereas in the south, eruptions within a flooded depression produced a sequence of mostly phreatomagmatic tuffs. Many of these tuffs are plastered onto the walls of what appears to have been an older caldera, most probably associated with an eruption of rhyodacitic tephra 100,000 years ago. The Minoan eruption of about 1400 B.C. had four distinct phases, each reflecting a different vent geometry and eruption mechanism. The Minoan activity was preceded by minor eruptions of fine ash. (1) The eruption began with a Plinian phase, from subaerial vent(s) located on the easternmost of the lava shields. (2) Vent(s) grew toward the SW into the flooded depression. Subsequent activity deposited large-scale base surge deposits during vent widening by phreatomagmatic activity. (3) The third eruptive phase was also phreatomagmatic and produced 60% of the volume of the Minoan Tuff. This activity was nearly continuous and formed a large featureless tuff ring with poorly defined bedding. This deposit contains 5–40% lithic fragments that are typical of the westernmost lava shield and appears to have been erupted when caldera collapse began. (4) The last phase consisted of eruption of ignimbrites from vent(s) on the eastern shield, not yet involved in collapse. Collapse continued after eruption of the ignimbrites with foundering of the eastern half of the caldera. Total volume of the collapse was about 19 km3, overlapping the older caldera to form the caldera complex visible today. Intracaldera eruptions have formed the Kameni Islands along linear vents concomitant with vents that may have been sources for the Minoan Tuff.
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  • 32
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    A new green-tide-forming alga, Ulva ohnoi Hiraoka et Shimada sp. nov. (Ulvales, Ulvophyceae) from Japan (2004)
    Wiley
    In:  Phycological Research, 52 (1). pp. 17-29.
    Details
    Publikationsdatum: 2017-11-24
    Beschreibung: Ulva ohnoi Hiraoka et Shimada sp. nov. (Ulvales, Ulvophyceae) is described from southern and western Japan and is characterized by the following combination of features: (i) the large, fragile, easily torn thalli, which are 30–55 μm thick in the upper and middle regions and often have microscopic marginal teeth; (ii) the production of zoids in the upper marginal region; (iii) a regular alternation of dioecious gametophytes and a sporophyte; (iv) the production of free-floating thalli from torn-off attached thalli, which reproduce vegetatively by fragmentation and form green tides in summer to autumn; (v) disorderly arranged cells that are polygonal or quadrangular in the upper and middle regions; and (vi) the chloroplast covering the outer face of cell, with 1–3 pyrenoids. Ulva ohnoi differs from U. armohcana Dion et al., U. fasciata Delile, U. reticulata Forsskal, U. scandinavica Eliding and U. spiulosaOkamura et Segawa, which all possess microscopic marginal serrations, in thallus shape, cell shape or life history pattern. It is also distinguished from morphologically similar species by sequences of the nuclear encoded internal transcribed spacers and the 5.8S ribosomal RNA gene and the plastid encoded large subunit of ribulose-l,5-bisphosphate carboxylase/oxgenase gene. Furthermore, crossing tests demonstrate that there is a reproductive boundary between U. ohnoi and the most closely related species, U. fasciata and U. reticulata.
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  • 33
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    Leg 4 of the Deep Sea Drilling Project (1971)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 172 (3989). pp. 1197-1205.
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    Publikationsdatum: 2017-01-05
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  • 34
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    Seasonal phytoplankton distribution along the Peruvian coast (1981)
    AGU (American Geophysical Union)
    In:  In: Coastal Upwelling. , ed. by Richards, F. A. Coastal and estuarine sciences, 1 . AGU (American Geophysical Union), Washington, USA, pp. 348-356.
    Details
    Publikationsdatum: 2017-08-10
    Beschreibung: During a 10-year study more than 2,000 phytoplankton samples were collected from the entire coast of Peru and analyzed. In general, diatoms were the most abundant group of organisms in all seasons. Predominant species were Rhizosolenia delicatula, Skeletonema costatum Thalassiosira subtilis, Thalassionema nitzschioides and several species of the genus Chaetooeros. Dinoflagellates and flagellates were observed frequently during summer. The mean distribution of the phytoplankton concentration during the 10 years shows the existence of several centers with higher cell densities along the coast, coinciding with the areas of more intense and persistent upwelling. Four major centers have been identified: Pimentel (˜6°S), Chimbote (˜9°S), Callao (˜12°S), and Tambo de Mora-Pisco (˜15°S); and two minor centers, Talara (˜4°S) and Ilo (˜17°S). The relative importance of each center seems to change according to the season. The highest phytoplankton concentration tended to be in the northern part of the coast during fall and winter and in the south through spring and summer.
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  • 35
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    Do commonly used indices of β-diversity measure species turnover? (2001)
    Wiley
    In:  Journal of Vegetation Science, 12 (4). pp. 545-552.
    Details
    Publikationsdatum: 2017-09-15
    Beschreibung: Indices of β-diversity are of two major types, (1) those that measure among-plot variability in species composition independently of the position of individual plots on spatial or environmental gradients, and (2) those that measure the extent of change in species composition along predefined gradients, i.e. species turnover. Failure to recognize this distinction can lead to the inappropriate use of some β-diversity indices to measure species turnover. Several commonly-used indices of β-diversity are based on Whittaker's βW (βW = γ/α, where γ is the number of species in an entire study area and α is the number of species per plot within the study area). It is demonstrated that these indices do not take into account the distribution of species on spatial or environmental gradients, and should therefore not be used to measure species turnover. The terms ‘β-diversity’ and ‘species turnover’ should not be used interchangeably. Species turnover can be measured using matrices of compositional similarity and physical or environmental distances among pairs of study plots. The use of indices of β-diversity and similarity-distance curves is demonstrated using simulated data sets.
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  • 36
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    The strength and rheology of methane clathrate hydrate (2003)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 108 (B4). p. 2182.
    Details
    Publikationsdatum: 2018-04-11
    Beschreibung: Methane clathrate hydrate (structure I) is found to be very strong, based on laboratory triaxial deformation experiments we have carried out on samples of synthetic, high‐purity, polycrystalline material. Samples were deformed in compressional creep tests (i.e., constant applied stress, σ), at conditions of confining pressure P = 50 and 100 MPa, strain rate 4.5 × 10−8 ≤ equation image ≤ 4.3 × 10−4 s−1, temperature 260 ≤ T ≤ 287 K, and internal methane pressure 10 ≤ PCH4 ≤ 15 MPa. At steady state, typically reached in a few percent strain, methane hydrate exhibited strength that was far higher than expected on the basis of published work. In terms of the standard high‐temperature creep law, equation image = Aσne−(E*+PV*)/RT the rheology is described by the constants A = 108.55 MPa−n s−1, n = 2.2, E* = 90,000 J mol−1, and V* = 19 cm3 mol−1. For comparison, at temperatures just below the ice point, methane hydrate at a given strain rate is over 20 times stronger than ice, and the contrast increases at lower temperatures. The possible occurrence of syntectonic dissociation of methane hydrate to methane plus free water in these experiments suggests that the high strength measured here may be only a lower bound. On Earth, high strength in hydrate‐bearing formations implies higher energy release upon decomposition and subsequent failure. In the outer solar system, if Titan has a 100‐km‐thick near‐surface layer of high‐strength, low‐thermal conductivity methane hydrate as has been suggested, its interior is likely to be considerably warmer than previously expected.
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  • 37
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    Regulation of gas vesicle content and buoyancy in light- or phosphate-limited cultures of Aphanizomenon flos-aquae (Cyanophyta) (2004)
    Wiley
    In:  Journal of Phycology, 23 (1). pp. 70-78.
    Details
    Publikationsdatum: 2018-07-20
    Beschreibung: Measurements of the gas vesicle space in steady‐state light or phosphate‐limited cultures of Aphanizomenon flos‐aquae Ralfs, strain 7905 showed that gas vesicle content decreased as energy‐limited growth rate increased hut was the same at several phosphate‐limited growth rates. Upon a decrease in growth irradiance, gas vesicle content did increase in phosphate‐limited cultures, hut the cultures remained nonbuoyant as long as P was limiting. Buoyant, energy‐limited cultures lost their buoyancy in less than 2 h when exposed to higher irradiances. The primary mechanism for buoyancy loss was the accumulation of polysaccharide as ballast. Collapse of gas vesicles by turgor pressure played a minor role in the loss of buoyancy. When cultures were exposed to higher irradiances, cells continued to synthesize gas vesicles at the same rate as before the shift for at least 1 generation time. The amount of ballast required to make individual filaments in the population sink varied 4‐fold. This variation appears to be due to differences in gas vesicle content among individual filaments.
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  • 38
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    Nautilus Growth and Longevity: Evidence from Marked and Recaptured Animals (1984)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 224 (4652). pp. 990-992.
    Details
    Publikationsdatum: 2019-03-19
    Beschreibung: Study of Nautilus belauensis i its natural habitat in Palau, West Caroline Islands, shows that growth is slow (0.1 millimeter of shell per day on the average) and decreases as maturity is approached and that individuals may live at least 4 years beyond maturity. Age estimates for seven animals marked and recaptured between 45 and 355 days after release range from 14.5 to 17.2 years. These data indicate that the life-span of Nautilus may exceed 20 years and that its life strategy is very different from that of other living cephalopods.
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  • 39
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    Volcanism and geochemistry in Central America: Progress and problems (2003)
    AGU (American Geophysical Union)
    In:  In: Inside the Subduction Factory. , ed. by Eiler, J. Geophysical Monograph, 138 . AGU (American Geophysical Union), Boulder, pp. 153-174.
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    Publikationsdatum: 2017-03-01
    Beschreibung: Most Central American volcanoes occur in an impressive volcanic front that trends parallel to the strike of the subducting Cocos Plate. The volcanic front is a chain, made of right-stepping, linear segments, 100 to 300 Km in length. Volcanoes cluster into centers, whose spacing is random but averages about 27 Km. These closely spaced, easily accessible volcanic centers allow mapping of geochemical variations along the volcanic front. Abundant back-arc volcanoes in southeast Guatemala and central Honduras allow two cross-arc transects. Several element and isotope ratios (e.g. BalLa, Uffh, B/La, IOBe/9Be, 87Sr/86Sr) that are thought to signal subducted marine sediments or altered MORB consistently define a chevron pattern along the arc, with its maximum in Nicaragua. BalLa, a particularly sensitive signal, is 130 at the maximum in Nicaragua but decreases out on the limbs to 40 in Guatemala and 20 in Costa Rica, which is just above the nominal mantle value of 15. This high amplitude regional variation, roughly symmetrical about Nicaragua, contrasts with the near constancy, or small gradient, in several plate tectonic parameters such as convergence rate, age of the subducting Cocos Plate, and thickness and type of subducted sediment. The large geochemical changes over relatively short distances make Central America an important margin for seeking the tectonic causes of geochemical variations; the regional variation has both a high amplitude and structure, including flat areas and gradients. The geochemical database continues to improve and is already adequate to compare to tectonic models with length scales of 100 Km or longer.
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  • 40
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    Alaskan earthquake of 1964 and Chilean earthquake of 1960: Implications for arc tectonics (1972)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research, 77 (5). pp. 901-925.
    Details
    Publikationsdatum: 2017-05-04
    Beschreibung: The 1964 Alaskan earthquake (Ms ≈ 8.4) involved a segment of the eastern Aleutian arc 800 gm long; the 1960 Chilean earthquake sequence (Ms ≈ 8.5) affected roughly 100 km of the southern Peru-Chile arc. These two major events are strikingly similar in that (1) seismicity was shallow (〈70 km), the earthquake focal regions and most of the associated tectonic deformation being between the oceanic trenches and volcanic chains of the two arcs; (2) regional vertical displacements were characterized by broad asymmetric downwarps elongate parallel to the arcs with flanking zones of marked uplift on the seaward sides and minor, possibly local, uplift on the landward sides; and (3) horizontal displacements, where determined by retriangulation, involved systematic shifts in a generally seaward direction and transverse tensile strains across the zones of subsidence. Surface displacements and seismicity for both events are compatible with dislocation models involving predominantly dip-slip movement of 20 meters or more on major complex thrust faults (megathrusts) inclined at average angles of about 9° beneath the eastern Aleutian arc and perhaps 20° beneath the Peru-Chile arc. The thrust-fault mechanism deduced for both the Alaskan and Chilean earthquakes is broadly consistent with the concept that the sectors of the Pacific rim in which they occurred are major zones of convergence along which the oceanic plates progressively underthrust the less mobile America plate. Directions of convergence between lithospheric plates at these arcs as deduced primarily from paleomagnetic data are in reasonably good agreement with the observed earthquake-related deformation; the deduced rates of convergence, however, appear to be too high in the eastern Aleutian arc and too low in the southern Peru-Chile arc. Despite gross similarities in tectonic setting and the present style of earthquake-related deformation, the geologies of the continental margins in the eastern Aleutian arc and southern Peru-Chile arc differ significantly. This difference suggests that Mesozoic and Cenozoic sediments and volcanic rocks conveyed into the eastern Aleutian trench have progressively accreted to the Alaskan continental margin, whereas most or all of the material carried into the southern Peru-Chile trench has disappeared beneath the Chilean continental margin.
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  • 41
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    Taxonomy and Ecology of Sponge-AssociateMarionina spp. (Clitellata : Enchytraeidae) from the Horomatangi Geothermal System of Lake Taupo, New Zealand (2004)
    Wiley
    In:  International Review of Hydrobiology, 89 (1). pp. 58-67.
    Details
    Publikationsdatum: 2017-06-28
    Beschreibung: The dissection of Heterorotula sponges collected in an area of geothermal activity at 126–145 m depth on the floor of Lake Taupo (de Rondeet al., 2002) revealed a dense population of associated Enchytraeidae. They represent three species of Marionina, two of which known but exotic (the Palaearctic M. ripariaBretscher, 1899 and the Chinese M. seminudaXie and Rota, 2001), and one new to science, M. spongicola sp. n. This is the first report of an ecological association between enchytraeids and poriferans in the lake profundal zone. The possible nature of such relationship (casual contact for feeding or dwelling for food and shelter) is discussed.
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  • 42
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    The North Atlantic Oscillation: Climate Significance and Environmental Impact (2003)
    AGU (American Geophysical Union)
    In:  , ed. by Hurrell, J. W., Kushnir, Y., Ottersen, G. and Visbeck, M. Geophysical Monograph Series, 134 . AGU (American Geophysical Union), Washington, DC, 279 pp.
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    Publikationsdatum: 2012-03-13
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  • 43
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    The Oceanic Sink for Anthropogenic CO〈sub〉2〈/sub〉 (2004)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 305 . pp. 367-371.
    Details
    Publikationsdatum: 2016-09-09
    Beschreibung: Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 ± 19 petagrams of carbon. The oceanic sink accounts for ∼48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO2 to the atmosphere of about 39 ± 28 petagrams of carbon for this period. The current fraction of total anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential.
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  • 44
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    Microearthquake seismicity of the Mid-Atlantic Ridge at 5°S: A view of tectonic extension (2004)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 109 . B06102.
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    Publikationsdatum: 2018-04-25
    Beschreibung: We report measurements made with an ocean bottom array which was operated for 10 days on the Mid-Atlantic Ridge just south of the 5°S transform fault/fracture zone. A total of 148 locatable earthquakes with magnitudes ∼0.5–2.8 were recorded; seismic activity appears to be concentrated within the western half of the median valley. The median valley seismic zone is bounded in along-axis direction by the transform fault to the north and the tip of the axial volcanic ridge to the south. A few scattered events occurred within the inside corner high, on the transform fault, and in the western sidewall close to the segment center. Earthquakes reach a maximum depth of 8 km below the median valley floor and appear to be predominantly in the mantle, although a few crustal earthquakes also occurred. The presence of earthquakes in the mantle indicates that it is not strongly serpentinized. We infer the median valley seismic activity to primarily arise from normal faulting.
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  • 45
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    Impact of atmospheric CO〈sub〉2〈/sub〉 and galactic cosmic radiation on Phanerozoic climate change and the marine d18O record (2004)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 5 (1). Q06004.
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    Publikationsdatum: 2019-09-23
    Beschreibung: [1] A new model is developed and applied to simulate the Phanerozoic evolution of seawater composition (dissolved Ca, Sr, dissolved inorganic carbon, alkalinity, pH, δ18O), marine carbonates (Sr/Ca, 87Sr/86Sr, δ13C, δ18O), atmospheric CO2 and surface temperature. The marine carbonate records (Sr/Ca, 87Sr/86Sr, δ13C) are used to reconstruct changes in volcanic/tectonic activity and organic carbon burial over the Phanerozoic. Seawater pH is calculated assuming saturation with respect to calcite and considering the changing concentration of dissolved Ca documented by brine inclusion data. The depth of calcite saturation is allowed to vary through time and the effects of changing temperature and pressure on the stability constants of the carbonate system are considered. Surface temperatures are calculated using the GEOCARB III approach considering also the changing flux of galactic cosmic radiation (GCR). It is assumed that GCR cools the surface of the Earth via enhanced cloud formation at low altitudes. The δ18O of marine carbonates is calculated considering the changing isotopic composition of seawater, the prevailing surface temperatures and seawater pH. Repeated model runs showed that the trends observed in the marine δ18O record can only be reproduced by the model if GCR is allowed to have a strong effect on surface temperature. The climate evolution predicted by the model is consistent with the geological record. Warm periods (Cambrian, Devonian, Triassic, Cretaceous) are characterized by low GCR levels. Cold periods during the late Carboniferous to early Permian and the late Cenozoic are marked by high GCR fluxes and low pCO2 values. The major glaciations occurring during these periods are the result of carbon cycling processes causing a draw-down of atmospheric CO2 and a coevally prevailing dense cloud cover at low-altitudes induced by strong GCR fluxes. The two moderately cool periods during the Ordovician - Silurian and Jurassic - early Cretaceous are characterized by both high pCO2 and GCR levels so that greenhouse warming compensated for the cooling effect of low-altitude clouds. The very high Jurassic δ18O values observed in the geological record are caused by low pH values in surface waters rather than cold surface conditions.
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  • 46
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    Elastic properties of marine sediments (1971)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research, 76 (2). pp. 579-604.
    Details
    Publikationsdatum: 2016-03-07
    Beschreibung: This report includes discussions of elastic and viscoelastic models for water-saturated porous media, and measurements and computations of elastic constants including compressibility, incompressibility (bulk modulus), rigidity (shear modulus), Lamé's constant, Poisson's ratio, density, and compressional- and shear-wave velocity. The sediments involved are from three major physiographic provinces in the North Pacific and adjacent areas: continental terrace (shelf and slope), abyssal plain (turbidite), and abyssal hill (pelagic). It is concluded that for small stresses (such as from a sound wave), water-saturated sediments respond elastically, and that the elastic equations of the Hookean model can be used to compute unmeasured elastic constants. However, to account for wave attenuation, the favored model is ‘nearly elastic,’ or linear viscoelastic. In this model the rigidity modulus μ and Lamé's constant λ in the equations of elasticity, are replaced by complex Lamé constants (μ + iμ′) and (λ + iλ′), which are independent of frequency; μ and λ represent elastic response (as in the Hookean model), and iμ′ and iλ′ represent damping of wave energy. This model implies that wave velocities and the specific dissipation function 1/Q are independent of frequency, and attenuation in decibels per unit length varies linearly with frequency in the range from a few hertz to the megahertz range. The components of the water-mineral system bulk modulus are porosity, the bulk modulus of pore water, an aggregate bulk modulus of mineral grains, and a bulk modulus of the structure, or frame, formed by the mineral grains. Good values of these components are available in the literature, except for the frame bulk modulus. A relationship between porosity and dynamic frame bulk modulus was established that allowed computation of a system bulk modulus that was used with measured values of density and compressional-wave velocity to compute other elastic constants. Some average laboratory values for common sediment types are given. The underlying methods of computation should apply to any water-saturated sediment. If this is so, values given in this paper predict elastic constants for the major sediment types.
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  • 47
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    Continental margin subsidence: A Comparison between the east and west coasts of Africa (1982)
    AGU (American Geophysical Union)
    In:  In: Dynamics of Passive Margins. , ed. by Scrutton, R. A. Geodynamics series, 6 . AGU (American Geophysical Union), Washington, DC, pp. 59-71.
    Details
    Publikationsdatum: 2016-04-11
    Beschreibung: Sedimentation rates (corrected for compaction) from along the passive continental margin of Africa between the Equatorial Fracture Zone and Somalia are used to compare the rates of subsidence of the continental crust since early Mesozoic time. Three distinctive subsidence histories can be identified which correspond with basinal areas that have different structural styles: rifted (west coast), sheared (Equatorial and Agulhas fracture zones) and sunk (zones of vertical tectonics in eastern Africa). A comparison of subsidence rates with other tensional margins (NE USA and the North Sea) and a consideration of the plate tectonic history of the African margins leads to the proposal of a geo and thermodynamic model that takes cognizance of the worldwide mid-Cretaceous rheological discontinuity between taphrogenic and epeirogenic basin formation recognized by Kent, and the more generally accepted, purely plate tectonic driven model of margin subsidence. The new suggestion involves a lower Mesozoic worldwide rise in the geothermal gradient in the lithosphere which produces metamorphism of the base of the continental crust and initiates taphrogenesis along lineaments throughout Gondwanaland. A lowering of the geothermal gradient in the lower Cretaceous produces a switch to epeirogenic subsidence, driven solely by sediment loading and thermal contraction, by Aptian/Albian times. The thermal event facilitated continental separation, and sea floor spreading commenced locally at various times along the active taphrogenic belts. Local thermal and tectonic aberrations associated with this phenomenon over print onto the worldwide pattern of marginal basin subsidence. A further rise in the geothermal gradient may have been responsible for renewed taphrogenesis in eastern Africa in Tertiary times.
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  • 48
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    Nonuniform response of the major surface currents in the Nordic Seas to insolation forcing: Implications for the Holocene climate variability (2004)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 19 (PA2003).
    Details
    Publikationsdatum: 2016-04-15
    Beschreibung: High-resolution sediment cores from the Vøring Plateau, the North Iceland shelf, and the East Greenland shelf have been studied to investigate the stability of major surface currents in the Nordic Seas during the Holocene. Results from diatom assemblages and reconstructed sea-surface temperatures (SSTs) indicate a division of the Holocene into three periods: the Holocene Climate Optimum (9500–6500 calendar (cal) years BP), the Holocene Transition Period (6500–3000 cal years BP) and the Cool Late Holocene Period (3000–0 cal years BP). The overall climate development is in step with the decreasing insolation on the Northern Hemisphere, but regional differences occur regarding both timing and magnitude of SST changes. Sites under the direct influence of the Norwegian Atlantic Current and the Irminger Current indicate SST cooling of 4–5°C from early Holocene to present, compared to 2°C recorded under the East Greenland Current. Superimposed on the general Holocene cooling trend, there is a high-frequency SST variability, which is in the order of 1–1.5°C for the Vøring Plateau and the East Greenland shelf and 2.5–3°C on the North Iceland shelf.
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  • 49
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    The use of Fick's First Law for predicting porewater nutrient fluxes under diffusive conditions (2001)
    Wiley
    In:  Hydrological Processes, 15 (13). pp. 2435-2451.
    Details
    Publikationsdatum: 2020-07-29
    Beschreibung: Porewater fluxes into or out of the sediments in aquatic systems are frequently estimated using Fick's First Law. This assumes that diffusive processes control the transport of nutrients. As a corollary, advection, bioturbation and chemical processes are assumed not to be significant. Through a series of sediment core incubations, this paper seeks to quantify the uncertainties involved in such assumptions. Duplicate sediment cores were collected from 28 sites along the Swan–Canning Estuary, returned to the laboratory and incubated under oxic or anoxic conditions. Porewater nutrient concentrations, sediment porosity and initial nutrient concentrations in the overlying water were measured. These parameters were used to estimate the expected nutrient fluxes via Fick's First Law. The estimated fluxes were then compared with measured fluxes of nutrients out of the sediments over the incubation period. Severe bioturbation occurred in several of the anoxic treatments, resulting in large releases of nutrients into the overlying water. Aside from these bioturbated cores, phosphate and ammonium fluxes under anoxic conditions are well predicted by Fick's First Law. Nitrate fluxes are predicted well under oxic conditions. For coarse sediments (D10 averaging 0·3 mm) and under redox conditions favourable for nutrient release, Fick's First Law predicted close to 100% of the observed fluxes. For finer grain sediments (D10 〈 0·01 mm), Fick's First Law overestimated the observed flux by up to 40%. Under unfavourable oxygen conditions, chemical retardation processes are likely to dominate fluxes, and the error associated with using Fick's First Law is increased. These results confirm the usefulness of using Fick's First Law for a baseline estimate of nutrient fluxes under favourable redox conditions. Much greater care must be taken when using Fick's First Law to estimate nutrient fluxes under unfavourable redox conditions, or under conditions when bioturbation is likely to be severe.
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  • 50
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    Electrical conductivity, temperatures, and fluids in the lower crust (1983)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research - Solid Earth, 88 (B11). p. 9475.
    Details
    Publikationsdatum: 2016-03-02
    Beschreibung: We have compiled both laboratory and worldwide field data on electrical conductivity to help understand the physical implications of deep crustal electrical profiles. Regional heat flow was used to assign temperatures to each layer in regional electrical conductivity models; we avoided those data where purely conductive heat flow suggested temperatures more than about 1000°C, substantially higher than solidus temperatures and outside the range of validity of heat flow models. The resulting plots of log conductivity σ versus 1/T demonstrate that even low-conductivity layers (LCL) have conductivities several orders of magnitude higher than dry laboratory samples and that the data can be represented by straight line fits. In addition, technically active regions show systematically higher conductivities than do shield areas. Because volatiles are usually lost in laboratory measurements and their absence is a principal difference between laboratory and field conditions, these materials probably account for the relatively higher conductivities of rocks in situ in the crust; free water in amounts of 0.01–0.1% in fracture porosity could explain crustal conductivities. Other possibilities are graphite, hydrated minerals in rare instances, and sulfur in combination with other volatiles. As most of the temperatures are less than 700°C, partial melting seems likely only in regions of highest heat flow where the conductive temperature profiles are inappropriate. Another result is that at a given temperature, crustal high-conductivity layers (HCL) are more conductive by another order of magnitude and show more scatter than do LCL's. Because the differences between HCL's and LCL's are independent of temperature, we must invoke more than temperature increases as a cause for large conductivity increases; increased fluid concentration in situ seems a probable cause for enhanced conductivities in HCL's. From the point of view of these observations, it does not matter whether the fluids are in communication with the surface or trapped at lithostatic pressures.
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  • 51
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    Crude oil and natural gas in the Federal Republic of Germany: development and prospects (1982)
    Wiley
    In:  Journal of Petroleum Geology, 4 (3). pp. 235-266.
    Details
    Publikationsdatum: 2020-07-20
    Beschreibung: Before making a critical evaluation of the crude oil and natural gas prospects for the years to the end of the century, it is necessary to review the geology and structure of the three German hydrocarbon-producing provinces. Furthermore, past exploration, production and reserves should be discussed. The three hydrocarbon-producing provinces are: the NW German Basin, the Upper Rhine Graben and the Molasse Basin, which together make up about 41% of West German territory (Fig. 1). The NW German Basin contains a sedimentary sequence over 8,000 m thick ranging in age from Permian to Quaternary. Gas and oil, the two natural hydrocarbons, are generally confined to separate lower and higher stratigraphic levels respectively (Fig. 2). The NW German Basin is the most important prospective area in West Germany. It extends into the North Sea. The tectonic rift feature of the Upper Rhine Graben originated in the Eocene. The Tertiary fill is over 4,000 m thick. Oil is found mainly in Mesozoic, Eocene and Oligocene rocks; the Miocene and Pliocene reservoir rocks contain natural gas almost exclusively (Fig. 3). The Molasse Basin is part of the foredeep north of the Alpine and Carpathian mountain ranges. The basin is filled with Upper Eocene to Pliocene and Quaternary sediments which, near the Alpine nappes, reach a thickness of over 5,000m (Fig. 4). During this century there were peaks in annual oil-production in 1910, 1940 and 1968 (see Fig. 5). The 1910 peak was the result of drilling activity in the Wietze oilfield. During the period 1934–1945, government financial aid was made available for drilling exploration wells. The success of this collaboration is demonstrated by the oil output in 1940 of 1 × 106 t. After World War II, many different types of oil-bearing structure were found, particularly by reflection seismic techniques in conjunction with detailed stratigraphical and palaeogeographical investigations. The success achieved can be seen by the peak of 8 × 106 t oil production for 1968 (Fig. 5) and in the growth of oil reserves (Fig. 7). Intensive exploration also enabled many new gasfields to be developed, especially in the deeper horizons of the NW German Basin. In 1971, estimated gas reserves reached 360 × 109 m3 (Fig. 11), and annual gas production in 1979 was 20.7 × 109 m3 (731 Bcf) (Fig. 9). There is, no doubt, still scope for the discovery and exploitation of oil and gas in Germany, especially in the NW German Basin where the best prospects for the future lie. This is borne out by two recent offshore oil discoveries and also by the successful application of enhanced recovery methods in the oilfields. The chances of finding more gas at the lower stratigraphic levels are promising now that gas has been discovered in the deeper parts of the Permian basin. The results of massive-hydraulic-fracturing tests in low-permeability pay-horizons are also encouraging. The deeper parts of oil- and gas-producing basins contain interesting prospects and have yet to be tested by ultra-deep wells. Provided that the economic climate remains favourable, there should be no difficulty in finding and supplying German oil and gas in the future. Geologically and technically possible reserves should be converted into proven and/or probable reserves. German crude oil will be available for several years beyond the year 2000, and German natural gas for a far longer time. A production rate of 19 to 20 × 109 m3 of gas per annum is feasible over the next twenty years, and oil production will probably not sink below 3 × 106 t/a in this period.
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  • 52
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    Calcium Carbonate Hexahydrate from Organic-Rich Sediments of the Antarctic Shelf: Precursors of Glendonites (1982)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 216 (4550). pp. 1128-1131.
    Details
    Publikationsdatum: 2018-03-08
    Beschreibung: Large euhedral crystals of calcium carbonate hexahydrate were recovered from a shelf basin of the Bransfield Strait, Antarctic Peninsula, at a water depth of 1950 meters and sub-zero bottom water temperatures. The chemistry, mineralogy, and stable isotope composition of this hydrated calcium carbonate phase, its environment of formation, and its mode of precipitation confirm the properties variously attributed to hypothetical precursors of the glendonites and thereby greatly expand their use in paleoceanographic interpretation.
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  • 53
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    Reply to Comment on "Cosmic rays, carbon dioxide, and climate" (2004)
    AGU (American Geophysical Union)
    In:  Eos, Transactions American Geophysical Union, 85 (48). p. 511.
    Details
    Publikationsdatum: 2020-03-19
    Beschreibung: In our analysis [Rahmstorf et al., 2004], we arrived at two main conclusions: the data of Shaviv and Veizer [2003] do not show a significant correlation of cosmic ray flux (CRF) and climate, and the authors' estimate of climate sensitivity to CO2 based on a simple regression analysis is questionable. After careful consideration of Shaviv and Veizer's comment, we want to uphold and reaffirm these conclusions. Concerning the question of correlation, we pointed out that a correlation arose only after several adjustments to the data, including shifting one of the four CRF peaks and stretching the time scale. To calculate statistical significance, we first need to compute the number of independent data points in the CRF and temperature curves being correlated, accounting for their autocorrelation. A standard estimate [Quenouille, 1952] of the number of effective data points is urn:x-wiley:00963941:media:eost14930:eost14930-math-0001 where N is the total number of data points and r1, r2 are the autocorrelations of the two series. For the curves of Shaviv and Veizer [2003], the result is NEFF = 4.8. This is consistent with the fact that these are smooth curves with four humps, and with the fact that for CRF the position of the four peaks is determined by four spiral arm crossings or four meteorite clusters, respectively; that is, by four independent data points. The number of points that enter the calculation of statistical significance of a linear correlation is (NEFF− 2), since any curves based on only two points show perfect correlation; at least three independent points are needed for a meaningful result.
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  • 54
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    Cosmic rays, carbon dioxide, and climate (2004)
    AGU (American Geophysical Union)
    In:  Eos, Transactions American Geophysical Union, 85 (4). pp. 38-41.
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    Publikationsdatum: 2017-02-10
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  • 55
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    Methane cycling in the Weddell Sea determined via stable isotope ratios and CFC-11 (2004)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 18 (2). GB2012.
    Details
    Publikationsdatum: 2018-03-16
    Beschreibung: The physical, chemical/biological processes that control the methane dynamics in the Weddell Sea are revealed by the distributions of methane (CH4), its stable carbon isotope ratio, δ13C-CH4, and the conservative transient tracer, chlorofluorocarbon-11 (CFC-11, CCl3F). In general, a nearly linear correlation between CH4 and CFC-11 concentrations was observed. Air-sea exchange is the major source of methane to this region, and the distribution of methane is controlled mainly by mixing between surface water and methane-poor Warm Deep Water. A significant influence of methane oxidation over the predominant two end-member mixing was only found in the Weddell Sea Bottom Water (WSBW) of the deep central Weddell Basin, where the turnover time of methane appears to be about 20 years. Mixing also controls most of the δ13C-CH4 distribution, but lighter than expected carbon isotopic ratios occur in the deep WSBW of the basin. From box model simulations, it appears that this “anomaly” is due to methane oxidation with a low kinetic isotope fractionation of about 1.004. The surface waters in the Weddell Sea and the Antarctic Circumpolar Current showed a general methane undersaturation of 6 to 25% with respect to the atmospheric mixing ratio. From this undersaturation and model-derived air-sea exchange rates, we estimate a net uptake of CH4 of roughly −0.5 μmol m−2 d−1 during austral autumn.
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  • 56
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    Evaluation of palagonite: crystallization, chemical changes and element budget (2002)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 2 (7).
    Details
    Publikationsdatum: 2018-01-30
    Beschreibung: [1] The structural and chemical evolution of palagonite was studied as a function of glass composition, alteration environment, and time by applying a range of analytical methods (electron microprobe, infrared photometry, atomic force microscopy, X-ray fluorescence, and X-ray diffraction). Palagonitization of volcanic glass is a continuous process of glass dissolution, palagonite formation, and palagonite evolution, which can be subdivided into two different reaction stages with changing element mobilities. The first stage is characterized by congruent dissolution of glass and contemporaneous precipitation of “fresh,” gel-like, amorphous, optically isotropic, mainly yellowish palagonite. This stage is accompanied by loss of Si, Al, Mg, Ca, Na, and K, active enrichment of H2O, and the passive enrichment of Ti and Fe. The second stage is an aging process during which the thermodynamically unstable palagonite reacts with the surrounding fluid and crystallizes to smectite. This stage is accompanied by uptake of Si, Al, Mg, and K from solution and the loss of Ti and H2O. Ca and Na are still showing losses, whereas Fe reacts less consistently, remaining either unchanged or showing losses. The degree and direction of element mobility during palagonitization was found to vary mainly with palagonite aging, as soon as the first precipitation of palagonite occurs. This is indicated by the contrasting major element signatures of palagonites of different aging steps, by the changes in the direction of element mobility with palagonite aging, and by the general decrease of element loss with increasing formation of crystalline substances in the palagonite. Considering the overall element budget of a water-rock system, the conversion of glass to palagonite is accompanied by much larger element losses than the overall alteration process, which includes the formation of secondary phases and palagonite aging. The least evolved palagonitized mafic glass studied has undergone as much as 65 wt% loss of elements during palagonite formation, compared to ∼28 wt% element loss during bulk alteration. ABout 33 wt% element loss was calculated for one of the more evolved, in terms of the aging degree, rocks studied, compared to almost no loss for bulk alteration.
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  • 57
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    Amphibious Seismic Survey Images Plate Interface at 1960 Chile Earthquake (2003)
    AGU (American Geophysical Union)
    In:  Eos, Transactions American Geophysical Union, 84 (32). 301,304-305.
    Details
    Publikationsdatum: 2017-02-14
    Beschreibung: The southern central Chilean margin at the site of the largest historically recorded earthquake in the Valdivia region, in 1960 (Mw = 9.5), is part of the 5000-km-long active subduction system whose geodynamic evolution is controversially debated and poorly understood. Covering the area between 36° and 40°S, the oceanic crust is segmented by prominent fracture zones. The offshore forearc and its onshore continuation show a complex image with segments of varying geophysical character, and several fault systems active during the past 24 m.y. In autumn 2001, the project SPOC was organized to study the Subduction Processes Off Chile, with a focus on the seismogenic coupling zone and the forearc. The acquired seismic data crossing the Chilean subduction system were gathered in a combined offshore-onshore survey and provide new insights into the lithospheric structure and evolution of active margins with insignificant frontal accretion.
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  • 58
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    Effects of attached data loggers on the activity budgets of captive Humboldt Penguins (2002)
    Wiley
    In:  Zoo Biology, 21 (4). pp. 365-373.
    Details
    Publikationsdatum: 2017-12-05
    Beschreibung: Although they can provide valuable information on at-sea ecology, data-loggers may adversely affect energetics, diving performance, and breeding success of equipped birds. With the aim of determining the effects of leg-attached data-loggers on the activity budgets of Humboldt penguins (Spheniscus humboldti) while on land, we equipped birds kept at the Landau Zoo, Landau, Germany, with such devices. We followed them during sample periods and recorded the occurrence and length of behaviors. Birds quickly habituated to the devices within 1 day of deployment, and mean rates of device-pecking were low (0.7–1.7 pecks/hr), with device-induced behaviors accounting for 〈1% of the mean daily activity budget. The method of device attachment appears behaviorally less stressful than the traditional tape-based system in which devices are normally attached to the penguin's back. By facilitating the testing of newly developed data-loggers on captive birds, or the development of methods for device attachment, zoos and aquaria may strengthen their role in animal conservation by helping research on free-ranging animals.
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  • 59
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    Tide at the eastern section of the Strait of Gibraltar (2000)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 105 (C6). pp. 14197-14213.
    Details
    Publikationsdatum: 2018-04-17
    Beschreibung: From October 1995 to April 1996, three mooring lines were deployed at the eastern entrance of the Strait of Gibraltar. The spatial coverage of the mooring array allows for a good description of the tides. They exhibit a dominant semidiurnal nature and a noticeable baroclinic structure that matches the one of the mean exchange. Tidal currents in the upper layer are irregular and usually too weak to reverse the mean upper layer how that keeps on flowing east. Lower layer flow reverses with semidiurnal periodicity because of the smallness of the mean flow and the appreciable amplitude of the regular semidiurnal oscillation of tidal currents in this layer. Tidal transports can be satisfactorily compared with previous estimates of Bryden et al. [1994] if we allow for strong internal divergences associated with the internal tide. No significant eddy flux of water transport (tidal rectification) is observed at the eastern section, contrary to the almost 50% of the total layer transport found by Bryden et al. [1994] in Camarinal Sill section. Time-dependent hydraulic theory provides a good scenario for interpreting these two independent sets of observations despite the fact that the composite Froude number does not reach the critical values predicted in the hydraulic models most of the time.
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  • 60
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    Seasonal sea level variability in the North Atlantic (2000)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 105 (C3). pp. 6307-6326.
    Details
    Publikationsdatum: 2017-06-06
    Beschreibung: We investigate the seasonal sea surface height (SSH) variability on large spatial scales in the North Atlantic by using both a numerical simulation and in situ data. First, an ocean general circulation model is run with daily forcing from the European Centre for Medium-Range Weather Forecasts reanalysis. We evaluate the different contributions to the seasonal SSH variability resulting from the surface heat fluxes, advection, salt content variability, deep ocean steric changes, and bottom pressure variability. These terms are compared with estimates from in situ data. North of 20°N, there is an approximate balance between hQ, the air-sea heat flux induced changes in steric height, and SSH variability. The next important component is the advection (its contribution to the annual amplitude is of the order of 1 cm except near the western boundary); other contributions are found to be smaller. Between 10°N and 10°S the advection variability induced by the seasonal wind stress cycle is the primary source of SSH variability. We then compare the sea surface height annual harmonic from TOPEX/Poseidon altimetry with the steric effect from the heat flux and with model and/or in situ estimates of the other terms. In many areas north of 20°N the balance between hQ and the altimetric SSH seasonal cycle is closed within the uncertainty limit of each of the terms of the SSH budget. However, hQ and the SSH do not balance each other in the eastern North Atlantic, and the results are sensitive to the choice of the heat flux product, suggesting that significant errors, typically 20–40 W m−2 for the seasonal cycle amplitude, are present in the meteorological model heat fluxes.
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  • 61
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    Decoupling of fluids and fluid-mobile elements during shallow subduction: Evidence from halogen-rich andesite melt inclusions from the Izu arc volcanic front (2003)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 4 (7).
    Details
    Publikationsdatum: 2018-01-31
    Beschreibung: [1] Very rare, halogen-rich andesite melt inclusions (HRA) in bytownitic plagioclase phenocrysts (An89–90) from tephra fallout of the Izu arc volcanic front (Izu VF) provide new insights into the processes of fluid release from slab trenchward to the volcanic front in a cool subduction zone. These HRA are markedly enriched in Cl, F and Li - by factors of up to 8 (Cl, F) and 1.5 (Li) - but indistinguishable with respect to the fluid-mobile large-ion lithophile elements (LILE; K, Sr, Rb, Cs, Ba, Pb, U), rare earths (REE) or high field strength elements (HFSE) from the low-K tholeiitic magmas of the Izu VF. We suggest that the chemical signature of the HRA reflects the presence of a fluid in the mantle source that originated from the serpentinized mantle peridotite above the metacrust. This “wedge serpentinite” presumably formed by fluid infiltration beneath the forearc and was subsequently down-dragged with the slab to arc front depths. The combined evidence from the Izu VF (∼110 km above slab) and the outer forearc serpentinite seamounts (∼25 to 30 km above slab) suggests that the slab flux of B and Cl is highest beneath the forearc, and decreases with increasing slab depths. In contrast, the slab flux of Li is minor beneath the forearc, but increases with depth. Fluorine may behave similarly to Li, whereas the fluid-mobile LILE appear to be largely retained in the slab trenchward from the Izu VF. Consequently, the chemical signatures of both Izu trench sediments and basaltic rocks appear preserved until arc front depths.
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  • 62
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    Seismic imaging of the downwelling Indian lithosphere beneath Central Tibet (2003)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 300 (5624). pp. 1424-1427.
    Details
    Publikationsdatum: 2016-09-09
    Beschreibung: A tomographic image of the upper mantle beneath central Tibet from INDEPTH data has revealed a subvertical high-velocity zone from ~ 100- to ~ 400- kilometers depth, located approximately south of the Bangong-Nujiang Suture. We interpret this zone to be downwelling Indian mantle lithosphere. This additional lithosphere would account for the total amount of shortening in the Himalayas and Tibet. A consequence of this downwelling would be a deficit of asthenosphere, which should be balanced by an upwelling counterflow, and thus could explain the presence of warm mantle beneath north-central Tibet.
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    Deep and bottom water export from the Southern Ocean to the Pacific Ocean over the past 38 million years (2004)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 19 . PA1020.
    Details
    Publikationsdatum: 2017-01-26
    Beschreibung: The application of radiogenic isotopes to the study of Cenozoic circulation patterns in the South Pacific Ocean has been hampered by the fact that records from only equatorial Pacific deep water have been available. We present new Pb and Nd isotope time series for two ferromanganese crusts that grew from equatorial Pacific bottom water (D137-01, “Nova,” 7219 m water depth) and southwest Pacific deep water (63KD, “Tasman,” 1700 m water depth). The crusts were dated using 10Be/9Be ratios combined with constant Co-flux dating and yield time series for the past 38 and 23 Myr, respectively. The surface Nd and Pb isotope distributions are consistent with the present-day circulation pattern, and therefore the new records are considered suitable to reconstruct Eocene through Miocene paleoceanography for the South Pacific. The isotope time series of crusts Nova and Tasman suggest that equatorial Pacific deep water and waters from the Southern Ocean supplied the dissolved trace metals to both sites over the past 38 Myr. Changes in the isotopic composition of crust Nova are interpreted to reflect development of the Antarctic Circumpolar Current and changes in Pacific deep water circulation caused by the build up of the East Antarctic Ice Sheet. The Nd isotopic composition of the shallower water site in the southwest Pacific appears to have been more sensitive to circulation changes resulting from closure of the Indonesian seaway.
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    Oceanic bromoform sources for the tropical atmosphere (2004)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 31 (23). L23S05.
    Details
    Publikationsdatum: 2018-02-27
    Beschreibung: Oceanic bromoform (CHBr3) is the major source of organic Br to the atmosphere and may be significant for ozone depletion through the contribution of reactive bromine to the upper troposphere and lower stratosphere of the midlatitudes and tropics. We report the first analyses of boundary layer air, surface and deep ocean waters from the tropical Atlantic. The data provide evidence of a source of CHBr3 throughout the tropical open ocean associated with the deep chlorophyll maximum within the tropical thermocline. Equatorial upwelling carries the CHBr3 to the surface, adding to increased concentrations in the equatorial mixed layer and driving oceanic emissions that support locally elevated atmospheric concentrations. In air masses that had crossed the coastal upwelling region off NW Africa even higher atmospheric mixing ratios were measured. The observations suggest a link between climate, wind-driven upwelling, and the supply of Br to the upper atmosphere of the tropics.
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  • 65
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    Stage-specific mortality of Baltic cod (Gadus morhua L.) eggs (2000)
    Wiley
    In:  Journal of Applied Ichthyology, 16 . pp. 266-272.
    Details
    Publikationsdatum: 2017-06-23
    Beschreibung: A study on cod egg mortality was carried out in the Bornholm Basin (southern central Baltic Sea) toward the end of July 1996. An initial egg aggregation marked by a satellite-tracked drifter buoy was sampled repeatedly over an 11-day period; profiles of temperature, salinity and dissolved oxygen were concurrently recorded. Three replicate estimates of mortality were obtained for each pair of subsequent developmental stages from newly spawned eggs to early larvae. A consistent pattern of stage-specific mortality coincided well with previous experimental observations. Average daily mortality rates were 7.2% (eggs IA/IB), 38.7% (eggs (IB/II), 25.6% (eggs II/III), 40.0% (eggs III/IV), and 42.3% (eggs IV/early larvae). The cumulative mortality until hatch amounted to 99.9%. Results from hydrodynamic modelling, however, indicated that the drifter's trajectory was influenced by wind stress. Hence, the mortality rates might be biased despite the short sampling intervals; a modification of the sampling design is recommended for future studies.
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    The Galapagos Effect: Implications for the generation of the cold tongue and tropical instability waves (2004)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 31 . L15308.
    Details
    Publikationsdatum: 2018-03-21
    Beschreibung: The Galápagos Islands provide a topographic barrier for the Southern Equatorial Current (SEC) and the Equatorial Undercurrent (EUC). An island wake effect can be diagnosed from the difference of an ocean general circulation model simulation which includes the Galápagos Islands and one which ignores their presence. Cold thermocline water upwells on the western side of the islands, and only during boreal winter season these cold waters can linger around the Islands at a depth of about 80 m and affect the far eastern equatorial Pacific surface waters. This effect is partly offset by the westward transport of cold surface waters by the SEC which creates a wake on the western side of the Islands. It is furthermore shown that changes in horizontal current shear, induced by the presence of the Galápagos Islands modify the generation of tropical instability waves and lead to a basin scale SST anomaly pattern.
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    North Atlantic Deep Water export to the Southern Ocean over the past 14 Myr: Evidence from Nd and Pb isotopes in ferromanganese crusts (2002)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 17 (2). 12-1-12-9.
    Details
    Publikationsdatum: 2017-01-18
    Beschreibung: The intensity of North Atlantic Deep Water (NADW) production has been one of the most important parameters controlling the global thermohaline ocean circulation system and climate. Here we present a new approach to reconstruct the overall strength of NADW export from the North Atlantic to the Southern Ocean over the past 14 Myr applying the deep water Nd and Pb isotope composition as recorded by ferromanganese crusts and nodules. We present the first long-term Nd and Pb isotope time series for deep Southern Ocean water masses, which are compared with previously published time series for NADW from the NW Atlantic Ocean. These data suggest a continuous and strong export of NADW, or a precursor of it, into the Southern Ocean between 14 and 3 Ma. An increasing difference in Nd and Pb isotope compositions between the NW Atlantic and the Southern Ocean over the past 3 Myr gives evidence for a progressive overall reduction of NADW export since the onset of Northern Hemisphere glaciation (NHG). The Nd isotope data allow us to assess at least semiquantitatively that the amount of this reduction has been in the range between 14 and 37% depending on location.
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    Changes of ENSO Stability due to Greenhouse Warming (2001)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 28 . pp. 2064-2066.
    Details
    Publikationsdatum: 2018-02-14
    Beschreibung: Based on a Coupled General Circulation Model (CGCM) simulation we study the influence of anthropogenic greenhouse warming on the stability of the El Niño-Southern Oscillation phenomenon (ENSO). The linear stability of such a complex model cannot be assessed directly, hence we will derive empirical low order models for ENSO from the CGCM simulation under consideration. These models capture essential features of ENSO and are sensitive also to temporal changes in ENSO statistics. An eigenvalue analysis of these reduced models reveals that as greenhouse warming progresses a transition takes place from a stable oscillatory behavior to an unstable oscillation. This transition coincides with an abrupt change in simulated ENSO activity and can be explained in terms of changing ocean dynamics.
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    Deep Lenses of Circumpolar Water in the Argentine Basin (2002)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 107 (C1). 10.1029-10.1040.
    Details
    Publikationsdatum: 2018-04-18
    Beschreibung: Three deep anticyclonic eddies of a species only reported once before [ Gordon and Greengrove, 1986 ] were intersected by hydrographic lines of the World Ocean Circulation Experiment (WOCE) and South Atlantic Ventilation Experiment (SAVE) programs in the Argentine Basin. The vortices are centered near 3500 m depth at the interface between North Atlantic Deep Water and Bottom Water. They have ∼1500-m-thick cores containing Lower Circumpolar Deep Water and a dynamic influence that may span up to two thirds of the water column. As one eddy was observed just downstream of the western termination of the Falkland Escarpment, a destabilization of the deep boundary current by the sudden slope relaxation is suggested as a potential cause of eddy formation. Besides isopycnal interleaving at the eddy perimeters, strongly eroded core properties in the upper parts of the lenses, associated with low density ratios, hint at double diffusion at the top of the structures as another major decay mechanism. The presence of an eddy in the northern Argentine Basin shows the possibility for a northward drift of the vortices, in this basin at least. Deep events in recent current measurements from the Vema Channel are presented that raise the question of further equatorward motion to the Brazil Basin.
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    Consumer effects decline with prey diversity (2004)
    Wiley
    In:  Ecology Letters, 7 . pp. 192-201.
    Details
    Publikationsdatum: 2017-02-22
    Beschreibung: While consumer species diversity is known to influence the capture of limited resources, little is known about how prey diversity impacts the transfer of energy and matter among trophic levels. Here, we perform a meta-analysis of experiments that have examined the impact of grazers on the biomass of periphytic algae to test the hypothesis that the magnitude of consumer (grazer) effects on prey (algae) depends on the species diversity of the prey assemblage. The analysis reveals that consumer effects tend to decrease as the diversity of a prey assemblage increases. This trend is robust for several different, yet complementary indices of grazer effect size and algal diversity. The trend also remains significant after statistically controlling for a variety of factors that can covary with prey diversity among studies. We discuss several possible mechanisms for the documented pattern, such as diversity enhancing the probability of inedibility and of positive interactions.
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    Backstop geometry and accretionary mechanics of the Sunda margin (2003)
    AGU (American Geophysical Union)
    In:  Tectonics, 22 (6). p. 1072.
    Details
    Publikationsdatum: 2017-06-28
    Beschreibung: The convergent Sunda margin off Indonesia displays all geological features characteristic of an accretion-dominated subduction zone. A combined interpretation of prestack depth-migrated seismic reflection data and velocity information gained from refraction studies is supplemented by high-resolution bathymetric data and for the first time allows the exact mapping of backstop regimes. Initially, the outer high evolved as material was pushed against a static rigid arc framework backstop underlying a forearc basin. Increasing material strength of the outer high due to lithification formed a dynamic backstop, which controls accretion today. An out-of-sequence thrust marks the transition from the recent active frontal accretionary prism to the outer high and may be traced in the seismic and bathymetric data over the whole extent of the study area. The existence of a static as well as a dynamic backstop controls the forearc geometry and is associated with the segmentation of the forearc, which is observed in regimes of frontal as well as of oblique subduction. Mass balance calculations, which account for porosity changes and metamorphism, indicate a subduction history dominated by accretionary processes since the late Eocene. Accretion is associated with the low values of basal friction inferred for the Sunda margin. Structural investigations of conjugate fault planes indicate a very weak basal detachment. Effective stress analyses reveal that intrinsically weak material causes the high strength ratio of the detachment to the overlying sediments, whereas overpressuring within the frontal accretionary prism is negligible.
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    Cloud inhomogeneity and broadband solar fluxes (2003)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Atmospheres, 108 (D19). Art.No. 4599.
    Details
    Publikationsdatum: 2018-02-06
    Beschreibung: Simplified representations of spatially inhomogeneous (three-dimensional (3-D)) clouds in radiative transfer models provide systematic errors when calculating solar broadband radiative fluxes. An example is the neglect of horizontal photon transports as it is the case for the independent column approximation (ICA). The present work tries to quantify and interpret these errors on the basis of a large set of 3-D mixed phase cloud scenarios with 3-D varying extinction coefficients, scattering phase functions, and single-scattering albedos. The cloud cases result from a mesoscale atmospheric circulation model with detailed cloud microphysics. Domain-averaged cloud radiative fluxes are calculated by means of a Monte Carlo radiative transfer model. Depending on cloud type and solar zenith angle (SZA) the differences between 3-D and ICA results range from +20 W m−2 to −30 W m−2 for the upward reflected fluxes and from +10 W m−2 to −7 W m−2 for the absorbed fluxes. The mean (averaged over all cloud realizations) errors of the ICA-based upward fluxes vary between 5 W m−2 overestimation at 15°SZA and 6 W m−2 underestimation at 75°SZA. The ICA underestimates the absorbed flux by ∼1–2 W m−2 for most SZA except for 75°. It is found that neglecting the horizontal variability of the absorption and scattering properties of the cloud hydrometeors leads to a general underestimation of solar broadband absorption by as much as 15 W m−2 with average values between 4 W m−2 at small SZA and 1 W m−2 at large SZA.
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    Cascading predation effects of Daphnia and copepods on microbial food web components (2003)
    Wiley
    In:  Freshwater Biology, 48 (12). pp. 2174-2193.
    Details
    Publikationsdatum: 2017-01-16
    Beschreibung: 1. We performed a mesocosm experiment to investigate the structuring and cascading effects of two predominant crustacean mesozooplankton groups on microbial food web components. The natural summer plankton community of a mesotrophic lake was exposed to density gradients of Daphnia and copepods. Regression analysis was used to reveal top-down impacts of mesozooplankton on protists and bacteria after days 9 and 15. 2. Selective grazing by copepods caused a clear trophic cascade via ciliates to nanoplankton. Medium-sized (20-40 mum) ciliates (mainly Oligotrichida) were particularly negatively affected by copepods whereas nanociliates (mainly Prostomatida) became more abundant. Phototrophic and heterotrophic nanoflagellates increased significantly with increasing copepod biomass, which we interpret as an indirect response to reduced grazing pressure from the medium-sized ciliates. 3. In Daphnia-treatments, ciliates of all size classes as well as nanoflagellates were reduced directly but the overall predation effect became most strongly visible after 15 days at higher Daphnia biomass. 4. The response of bacterioplankton involved only modest changes in bacterial biomass and cell-size distribution along the zooplankton gradients. Increasing zooplankton biomass resulted either in a reduction (with Daphnia) or in an increase (with copepods) of bacterial biovolume, activity and production. Patterns of bacterial diversity, as measured by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), showed no distinct grouping after 9 days, whereas a clear treatment-coupled similarity clustering occurred after 15 days. 5. The experiment demonstrated that zooplankton-mediated predatory interactions cascade down to the bacterial level, but also revealed that changes occurred rather slowly in this summer plankton community and were most pronounced with respect to bacterial activity and composition.
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    The Labrador Sea Deep Convection Experiment data collection (2003)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 4 (10). p. 1091.
    Details
    Publikationsdatum: 2018-01-31
    Beschreibung: Between 1996 and 1998, a concerted effort was made to study the deep open ocean convection in the Labrador Sea. Both in situ observations and numerical models were employed with close collaboration between the researchers in the fields of physical oceanography, boundary layer meteorology, and climate. A multitude of different methods were used to observe the state of ocean and atmosphere and determine the exchange between them over the experiment's period. The Labrador Sea Deep Convection Experiment data collection aims to assemble the observational data sets in order to facilitate the exchange and collaboration between the various projects and new projects for an overall synthesis. A common file format and a browsable inventory have been used so as to simplify the access to the data.
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    On the dynamics of internal waves in a nonlinear, weakly nonhydrostatic three-layer ocean (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 . 26,899-26,916.
    Details
    Publikationsdatum: 2018-04-18
    Beschreibung: Aspects of the dynamics of internal solitary waves evolving in a three-layer ocean are investigated using a new numerical multilayer model that solves the nonlinear, weakly nonhydrostatic Boussinesq equations and uses high-resolution in situ data. The model applications refer to two different phenomena frequently observed in the real ocean, which can be described using a three-layer model rather than a two-layer model. In the first application the influence of the strength of a shallow seasonal thermocline superimposed on a two-layer permanent stratification on the structure of internal solitary waves is studied. It is found that while for small to medium wave amplitudes a decrease in the strength of the thermocline yields an increase in the simulated wavelengths, for large wave amplitudes this dependence is no longer monotonic. In particular, in the limiting case of a vanishing thermocline, first-mode internal solitary wave solutions of the three-layer numerical model tend to the analytical internal solitary wave solutions of the Miyata equations, a two-layer model, in which the full nonlinearity of the shallow-water theory up to first-order phase dispersion is retained. In the second application that refers particularly to high-resolution observations made north and south of the Strait of Messina in the Eurafrican Mediterranean basin the generation of internal solitary waves by the evolution of surface and subsurface water jets is investigated. The analysis of the in situ data shows in fact that from very energetic surface and subsurface jet-like disturbances subject to strong turbulent mixing internal solitary waves emerge as robust, quasi-nondissipative oceanic features. Idealized flow conditions aimed at approximating possible initial stages of the observed water jets are imposed to force our numerical model. In general, good agreement is found between characteristics of observed and simulated wave fields. Our investigation identifies the observed water jets as peculiar features of the complex ocean dynamics and suggests that layered numerical models can represent helpful tools in understanding fundamental processes inherent in their intricate dynamics.
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  • 76
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    Structure-activity relationships of oligoagar elicitors towards Gracilaria conferta (Rhodophyta) (2001)
    Wiley
    In:  Journal of Phycology, 37 (3). pp. 418-426.
    Details
    Publikationsdatum: 2018-04-26
    Beschreibung: Agar oligosaccharides in the neoagarobiose series were prepared by partial enzyme hydrolysis, separated on Biogel P2 and P4, and analyzed by high-performance anion exchange chromatography with pulsed amperometric detection, yielding neoagarosaccharide fractions with a disaccharide repetition degree ranging from 1 (neoagarobiose) to more than 8 (neoagarohexadecaose). These fractions were analyzed for their biological activity toward the marine red alga Gracilaria conferta (Schousboe ex Montagne) J. et G. Feldmann in terms of increase of oxygen consumption, release of hydrogen peroxide, elimination of epiphytic bacteria, and induction of thallus tip bleaching. The structure–activity and dose–response relationships of neoagarosaccharides were very similar in the respiratory and oxidative burst responses and in their bactericidal properties, with neoagarosaccharides consisting of 6 to 8 disaccharide repeating units being the most active. All these responses were competitively inhibited by the reduced form of neoagarohexaose, neoagarohexaitol. In contrast, the tip-bleaching response was light dependent, required much higher concentrations of neoagarosaccharides, and was not inhibited by neoagarohexaitol, suggesting that it is an unspecific oxidative stress reaction. Putative structural effects on the recognition of endogenous agar-oligosaccharide elicitors by G. conferta are discussed.
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    Enhanced marine CH4 emissions to atmosphere off Oregon caused by coastal upwelling (2002)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 16 (3). p. 1081.
    Details
    Publikationsdatum: 2018-03-15
    Beschreibung: Methane in surface waters and marine air off Oregon (44°24′N–44°54′N, 124°36′W–125°24′W) was continuously surveyed in July 1999. During a high-resolution survey after a period of steady winds from the north, CH4 concentrations were high in the northeastern region, near the shelf edge. The highest CH4 concentrations were 2.5 times higher than equilibrium with the atmospheric partial pressure. In contrast, concentrations were near equilibrium in the western part of the survey area, the Hydrate Ridge. The increase in CH4 from southwest to northeast correlates with a drop in sea surface temperature (SST), from 16.5°C to 〈13.5°C, toward the shelf edge. The observed SST pattern was caused by summer upwelling off Oregon. The results suggest that CH4 derived from bottom sources near the shelf/slope break and methane found in connection with shallow (100–300 m) turbidity layers is transported to the surface by coastal upwelling, which causes an enhanced net flux of CH4 to the atmosphere. Vertical profiles of the methane distribution on the shelf in October demonstrate the accumulation of methane introduced by shelf sources. Surface concentrations at these stations in October (during nonupwelling conditions) were lower than in July (during upwelling) and were only slightly oversaturated with respect to the atmosphere. An acoustic Doppler current profiler survey indicates that the observed trend cannot be attributed to a surface flow reversal in the area. The low-salinity waters in the core of the Columbia River plume (S 〈 31) showed no enhanced CH4 concentrations. The trend of higher CH4 concentrations at lower temperatures existed over the whole 17-day survey, but large spatial and temporal variations existed. The presence of methane sources in regions of coastal upwelling worldwide, such as shallow seeps, gas hydrates, and intermediate nepheloid layers, suggests that the enhancement of CH4 fluxes to the atmosphere by coastal upwelling occurs on a global scale.
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  • 78
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    Studying Past Deep-ocean Circulation and the Paleoclimate Record in the Gulf of Cadiz (2002)
    AGU (American Geophysical Union)
    In:  Eos, Transactions American Geophysical Union, 83 (43). pp. 481-488.
    Details
    Publikationsdatum: 2017-02-10
    Beschreibung: Deep marine currents are strongly influenced by climatic changes. They also deposit, rework, and sort sediment, and can generate kilometer-scale sedimentary bodies (drifts). These drifts are made of thoroughly bioturbated, stacked sedimentary sequences called contourites [Gonthier et al., 1984]. As a consequence, change in the direction or intensity of currents can be recorded in the sediments
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  • 79
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    What happens to the kype of male Atlantic salmon (Salmo salar) that survive spawning? (2004)
    Wiley
    In:  Journal of Morphology, 260 .
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    Publikationsdatum: 2018-04-03
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  • 80
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    Foraging interactions of wandering albatrosses Diomedea exulans breeding on Marion Island with longline fisheries in the southern Indian Ocean: Seasonal and gender effects (2002)
    Wiley
    In:  Ibis, 144 (3). E141-E154.
    Details
    Publikationsdatum: 2017-01-30
    Beschreibung: Wandering Albatrosses Diomedea exulans are frequently killed when they attempt to scavenge baited hooks deployed by long-line fishing vessels. We studied the foraging ecology of Wandering Albatrosses breeding on Marion Island in order to assess the scale of interactions with known long-line fishing fleets. During incubation and late chick-rearing, birds foraged further away from the island, in warmer waters, and showed high spatial overlap with areas of intense tuna Thunnus spp. long-line fishing. During early chick-rearing, birds made shorter foraging trips and showed higher spatial overlap with the local Patagonian Toothfish Dissostichus eleginoides long-line fishery. Tracks of birds returning with offal from the Toothfish fishery showed a strong association with positions at which Toothfish long-lines were set and most diet samples taken during this stage contained fishery-related items. Independent of these seasonal differences, females foraged further from the islands and in warmer waters than males. Consequently, female distribution overlapped more with tuna long-line fisheries, whereas males interacted more with the Toothfish long-line fishery. These factors could lead to differences in the survival probabilities of males and females. Non-breeding birds foraged in warmer waters and showed the highest spatial overlap with tuna long-line fishing areas. The foraging distribution of Marion Island birds showed most spatial overlap with birds from the neighbouring Crozet Islands during the late chick-rearing and non-breeding periods. These areas of foraging overlap also coincided with areas of intense tuna long-line fishing south of Africa. As the population trends of Wandering Albatrosses at these two localities are very similar, it is possible that incidental mortality during the periods when these two populations show the highest spatial overlap could be driving these trends.
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  • 81
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    Transport estimates in the Strait of Gibraltar with a tidal inverse model (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 (C12). 31,033-31,044.
    Details
    Publikationsdatum: 2018-04-18
    Beschreibung: To estimate the volume transport through the Strait of Gibraltar and to study the spatial structure of the time-variable flow, a varying number of current meter moorings were maintained at the eastern entrance of the strait between October 1994 and April 1998, and was complemented with intensive shipboard measurements during the European Union project Canary Island Azores Gibraltar Experiment (CANIGO). A tidal inverse model is used to merge these data sets in order to investigate the flow at the eastern entrance of the strait. The two-dimensional structure of the tidal flow was described by simple analytical functions. Harmonics with the seven most important tidal frequencies were used as temporal functions. With this model, the tidal currents can be predicted for any time and location at the eastern entrance of the strait, and more than 92% of the variance of the lower layer flow is explained. It was used to remove the tidal currents from the individual measurements and to calculate the mean flow through the strait from the residuals. Combined with a similar inverse model for determining the depth of the interface between Mediterranean and Atlantic water, the volume transport was estimated to be 0.81 ± 0.07 Sv for the upper layer and −0.76 ± 0.07 Sv for the lower layer. The correlation of the tidal currents and the fluctuations of the interface accounts for ∼7% of the transport at the eastern entrance.
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  • 82
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    A monitoring design for the Atlantic meridional overturning circulation (2003)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 30 (7). p. 1314.
    Details
    Publikationsdatum: 2018-02-20
    Beschreibung: Current hydrographic data can provide snapshots but no continuous timeseries of the meridional overturning circulation (MOC). Using output from two eddy-permitting numerical ocean models we test the feasibility of a monitoring system for the MOC in the North Atlantic. The results suggest that a relatively simple arrangement, using moorings placed across a longitude-depth section and the zonal wind stress, is able to capture most of the MOC strength and vertical structure as a function of time. Being closely related to the transport of energy to the North Atlantic, measuring the MOC would open the prospect of having continuous information about a key element of northern hemisphere climate.
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  • 83
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    Biotic contribution to air-sea fluces of CO〈sub〉2〈/sub〉 and O〈sub〉2〈/sub〉 and its relation to new production. Export production, and net community production (2004)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 18 (1). GB1015.
    Details
    Publikationsdatum: 2018-03-16
    Beschreibung: The contribution of the marine biota to air-sea fluxes of CO2 and O2 is often described in terms of biological production concepts, such as new production, export production, and net community production. We evaluate these three quantities using a basin-scale ecosystem-circulation model of the North Atlantic Ocean based on Redfield stoichiometry into which we introduce an artificial tracer which records the biotic contribution to air-sea exchange of gases like O2 and CO2. It is found that on average the biological production rates overestimate the biotically effected air-sea flux by some 20% and, in some regions, even predict the wrong direction. With primary production restricted to the euphotic zone, but respiration extending to farther below, the discrepancy can largely be attributed to the different integration depths used in the different concepts (euphotic zone, surface mixed layer), and on annual and longer timescales, all rates converge when using the base of the winter mixed layer rather than that of the euphotic zone as the reference depth. For the surface carbon budget, which ultimately controls air-sea exchange of CO2, it is irrelevant whether carbon atoms cross this boundary in organic or inorganic speciation. Hence the transports of biotically generated surpluses or deficits of dissolved inorganic matter must also be accounted for. While their contribution amounts to only a few percent on the basin scale, the subduction of newly remineralized inorganic matter can locally account for about half of the biotically effected air-sea flux, for example, in regions of mode-water formation.
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  • 84
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    Export of Weddell Sea Deep and Bottom Water (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 . pp. 9005-9017.
    Details
    Publikationsdatum: 2018-04-18
    Beschreibung: An extensive set of conductivity-temperature-depth (CTD)/lowered acoustic Doppler current profiler (LADCP) data obtained within the northwestern Weddell Sea in August 1997 characterizes the dense water outflow from the Weddell Sea and overflow into the Scotia Sea. Along the outer rim of the Weddell Gyre, there is a stream of relatively low salinity, high oxygen Weddell Sea Deep Water (defined as water between 0° and −0.7°C), constituting a more ventilated form of this water mass than that found farther within the gyre. Its enhanced ventilation is due to injection of relatively low salinity shelf water found near the northern extreme of Antarctic Peninsula's Weddell Sea shelf, shelf water too buoyant to descend to the deep-sea floor. The more ventilated form of Weddell Sea Deep Water flows northward along the eastern side of the South Orkney Plateau, passing into the Scotia Sea rather than continuing along an eastward path in the northern Weddell Sea. Weddell Sea Bottom Water also exhibits two forms: a low-salinity, better oxygenated component confined to the outer rim of the Weddell Gyre, and a more saline, less oxygenated component observed farther into the gyre. The more saline Weddell Sea Bottom Water is derived from the southwestern Weddell Sea, where high-salinity shelf water is abundant. The less saline Weddell Sea Bottom Water, like the more ventilated Weddell Sea Deep Water, is derived from lower-salinity shelf water at a point farther north along the Antarctic Peninsula. Transports of Weddell Sea Deep and Bottom Water masses crossing 44°W estimated from one LADCP survey are 25 × 106 and 5 × 106 m3 s−1, respectively. The low-salinity, better ventilated forms of Weddell Sea Deep and Bottom Water flowing along the outer rim of the Weddell Gyre have the position and depth range that would lead to overflow of the topographic confines of the Weddell Basin, whereas the more saline forms may be forced to recirculate within the Weddell Gyre.
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  • 85
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    Meta-analysis of cod-shrimp interactions reveals top-down control in oceanic food webs (2003)
    Wiley
    In:  Ecology, 84 (1). pp. 162-173.
    Details
    Publikationsdatum: 2017-02-21
    Beschreibung: Here we present a meta-analytic approach to analyzing population interactions across the North Atlantic Ocean. We assembled all available biomass time series for a well-documented predator–prey couple, Atlantic cod (Gadus morhua) and northern shrimp (Pandalus borealis), to test whether the temporal dynamics of these populations are consistent with the “top-down” or the “bottom-up” hypothesis. Eight out of nine regions showed inverse correlations of cod and shrimp biomass supporting the “top-down” view. Exceptions occurred only close to the southern range limits of both species. Random-effects meta-analysis showed that shrimp biomass was strongly negatively related to cod biomass, but not to ocean temperature in the North Atlantic Ocean. In contrast, cod biomass was positively related to ocean temperature. The strength of the cod–shrimp relationship, however, declined with increasing mean temperature. These results show that changes in predator populations can have strong effects on prey populations in oceanic food webs, and that the strength of these interactions may be sensitive to changes in mean ocean temperature. This means that the effects of overfishing in the ocean cascade down to lower trophic levels, as has been shown previously for lakes and coastal seas. In order to further investigate these processes, we establish a methodological framework to analyze species interactions from time series data.
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  • 86
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    Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica (2004)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 109 . B11403.
    Details
    Publikationsdatum: 2018-04-25
    Beschreibung: New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 ± 2 and 39 ± 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the rupture zone for future large earthquakes, at least over the short (∼1 year) observation period. We also estimate northwest motion of a coastal “sliver block” at 8 ± 3 mm/yr, probably related to oblique convergence. In the Osa region to the south, convergence is orthogonal to the trench. Cocos-Caribbean relative motion is partitioned here, with ∼8 cm/yr on the Cocos-Panama block boundary (including a component of permanent shortening across the Fila Costeña fold and thrust belt) and ∼1 cm/yr on the Panama block–Caribbean boundary. The GPS data suggest that the Cocos plate–Panama block boundary is completely locked from ∼10–50 km depth. This large locked zone, as well as associated forearc and back-arc deformation, may be related to subduction of the shallow Cocos Ridge and/or younger lithosphere compared to Nicoya, with consequent higher coupling and compressive stress in the direction of plate convergence.
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  • 87
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    Overview of Glacial Atlantic Ocean Mapping (GLAMAP 2000) (2003)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 18 (2). p. 1030.
    Details
    Publikationsdatum: 2017-05-10
    Beschreibung: GLAMAP 2000 presents new reconstructions of the Atlantic's sea surface temperatures (SST) at the Last Glacial Maximum (LGM), defined at both 21,500–18,000 years B.P. (“Last Isotope Maximum”) and 23,000–19,000 years B.P. (maximum glacial sea level low stand and orbital minimum of solar insolation; EPILOG working group; see Mix et al. [2001]). These reconstructions use 275 sediment cores between the North Pole and 60°S with carefully defined chronostratigraphies. Four categories of core quality are distinguished. More than 100 core sections provide a glacial record with subcentennial- to multicentennial-scale resolution. SST estimates are based on a new set of almost 1000 reference samples of modern planktic foraminifera and on improved transfer-function techniques to deduce SST from census counts of microfossils, including radiolarians and diatoms. New proxies also serve to deduce sea ice boundaries. The GLAMAP 2000 SST patterns differ significantly in crucial regions from the CLIMAP [1981] reconstruction and thus are important in providing updated boundary conditions to initiate and validate computational models for climate prediction.
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  • 88
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    Midlatitude shelf seas in the Cenomanian-Turonian greenhouse world: Temperature evolution and North Atlantic circulation (2004)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 19 (PA4020).
    Details
    Publikationsdatum: 2017-05-10
    Beschreibung: An 8 million year record of subtropical and midlatitude shelf-sea temperatures, derived from oxygen isotopes of well-preserved brachiopods from a variety of European sections, demonstrates a long-term Cenomanian temperature rise (16–20°C, midlatitudes) that reached its maximum early in the late Turonian (23°C, midlatitudes). Superimposed on the long-term trend, shelf-sea temperatures vary at shorter timescales in relation to global carbon cycle perturbations. In the mid-Cenomanian and the late Turonian, two minor shelf-sea cooling events (2–3°C) coincide with carbon cycle perturbations and times of high-amplitude sea level falls. Although this evidence supports the hypothesis of potential glacioeustatic effects on Cretaceous sea level, the occurrence of minimum shelf-sea temperatures within transgressive beds argues for regional changes in shelf-sea circulation as the most plausible mechanism. The major carbon cycle event in the latest Cenomanian (oceanic anoxic event 2) is accompanied by a substantial increase in shelf-sea temperatures (4–5°C) that occurred ∼150 kyr after the commencement of the δ13C excursion and is related to the spread of oceanic conditions in western European shelf-sea basins. Our oxygen isotope record and published δ18O data of pristinely preserved foraminifera allow the consideration of North Atlantic surface water properties in the Cenomanian along a transect from the tropics to the midlatitudes. On the basis of fossil-derived δ18O, estimated δw ranges, and modeled salinities, temperature-salinity-density ranges were estimated for tropical, subtropical, and midlatitude surface waters. Accordingly, the Cenomanian temperate shelf-seas waters have potentially the highest surface water density and could have contributed to North Atlantic intermediate to deep waters in the preopening stage of the equatorial Atlantic gateway.
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  • 89
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    Intra-annual variations in the stable oxygen and carbon and trace element composition of scelerosponges (2002)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 17 (3). p. 1045.
    Details
    Publikationsdatum: 2017-05-10
    Beschreibung: This paper presents data to support the presence of (1) intra-annual signals in the chemical composition (δ18O and Sr/Ca) of the skeletons of sclerosponges from the Bahamas and (2) variable rates of skeletal accretion. These conclusions are based on data obtained by using a microsampling method for the stable oxygen and carbon isotopes in which material was extracted at a resolution of one sample every 34 μm and a laser microprobe which obtained trace element data every 20 μm (Sr, Mg, and Pb). An age model was established using a combination of changes in the concentration of Pb, the change in the δ13C of the skeleton of the sclerosponges, and U/Th isotopic measurements. These methods yield a mean growth rate of 220 μm/yr but suggest that the growth rate in this particular sclerosponge was not constant. The calculated growth rate is within error identical to that determined by U/Th methods. The variable growth rate was confirmed through spectral analysis of the δ18O and Sr/Ca data that showed peaks corresponding to the annual cycle in these parameters as well as peaks corresponding to growth rates of approximately 128, 212, 270, and 400 μm/yr. The presence of these additional frequencies suggests a growth rate between approximately 100 and 300 μm/yr. These conclusions were supported by modeling of oxygen isotopic data measured on a scleractinian coral as well as model isotope data generated on synthetic time series. These findings have important implications for the use of sclerosponges as proxies of paleoclimate because they emphasize the need for a precise yearly chronology in order that proxy data can be compared with climatic variables.
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  • 90
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    Compatibility analysis of precipitation and runoff trends over the large Siberian watersheds (2004)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 31 (21). L21502.
    Details
    Publikationsdatum: 2015-01-26
    Beschreibung: The consistency of long-term yearly precipitation and runoff trends over the largest Arctic watersheds (Ob, Yenisei and Lena Rivers) is examined. Three gridded precipitation datasets (Climatic Research Unit, University of Delaware, NCEP) are used for comparative analyses with runoff data collected at basin outlets. The results generally demonstrate inconsistency in long-term changes of basin precipitation and runoff. The Yenisei River runoff increases significantly, while precipitation data show mostly negative trends. The Ob River does not show any significant trend either in precipitation or runoff. Positive trend in the Lena River runoff is accompanied by a weak precipitation increase; however, the precipitation increase is not strong enough to support the observed runoff change. The inconsistency identified in basin precipitation and runoff trends suggests uncertainty in both the quality of basin precipitation and runoff datasets, as well as the perceived hydrologic factors impacting runoff change.
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  • 91
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    Sediment dynamics on the Northwest African continental margin (1982)
    Wiley
    In:  In: The Ocean Floor : Bruce Heezen Commemorative Volume. , ed. by Scrutton, R. A. and Talwani, M. Wiley, Chicago, Ill., USA, pp. 148-163. ISBN 0-471-10091-9
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    Publikationsdatum: 2015-12-10
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  • 92
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    Arctic Ocean variability derived from historical observations (2003)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 30 (6). GRL-1298.
    Details
    Publikationsdatum: 2015-03-06
    Beschreibung: This study has been motivated by reports of extraordinary change in the Arctic Ocean observed in recent decades. Most of these observations are based on synoptic measurements, while evaluation of anomalies requires an understanding of the underlying long-term variability. Historical climatologies give reference means, and while these datasets are a reliable source of the mean Atlantic Layer temperature, they significantly underestimate variability. Using historical data, we calculated statistical parameters for selected Arctic Ocean regions. They demonstrate a high level of Atlantic Layer temperature variability in the Nansen Basin and sea-surface salinity fluctuations on the Siberian shelf and the Amundsen Basin. These estimates suggest strong limitations on our ability to define amplitudes of anomalies by comparing recent synoptic measurements with climatologies, especially for regions characterized by strong variability.
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  • 93
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    Laptev Sea System discussed at Russian-German workshop (2000)
    AGU (American Geophysical Union)
    In:  Eos, Transactions American Geophysical Union, 81 (32). 361, 366-367.
    Details
    Publikationsdatum: 2019-09-23
    Beschreibung: The fifth Laptev Sea System Project Workshop was held November 25-29,1999, at the State Research Center-Arctic and Antarctic Research Institute in St. Petersburg, Russia.The abstracts of the workshop have been published in Terra Nostra,Vol. 99 (11) by the Alfred Wegener Foundation, Cologne, Germany.
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  • 94
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    Prokaryotic Chromosomes and Disease (2003)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 301 (5634). pp. 790-793.
    Details
    Publikationsdatum: 2015-08-27
    Beschreibung: Recent insights into bacterial genome organization and function have improved our understanding of the nature of pathogenic bacteria and their ability to cause disease. It is becoming increasingly clear that the bacterial chromosome constantly undergoes structural changes due to gene acquisition and loss, recombination, and mutational events that have an impact on the pathogenic potential of the bacterium. Even though the bacterial genome includes additional genetic elements, the chromosome represents the most important entity in this context. Here, we will show that various processes of genomic instability have an influence on the many manifestations of infectious disease
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  • 95
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    Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis (2003)
    AGU (American Geophysical Union)
    In:  In: Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis. AGU (American Geophysical Union), Washington, DC, pp. 1-9. ISBN 0-87590-296-0
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    Publikationsdatum: 2015-09-09
    Materialart: Book chapter , NonPeerReviewed
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  • 96
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    Sea-surface temperatures of the southwest Pacific Ocean during the Last Glacial Maximum (2000)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 15 (1). pp. 95-109.
    Details
    Publikationsdatum: 2017-01-18
    Beschreibung: The southwest Pacific Ocean covers a broad range of surface-water conditions ranging from warm, salty water in the subtropical East Australian Current to fresher, cold water in the Circumpolar Current. Using a new database of planktonic foraminifera assemblages (AUSMAT-F2), we demonstrate that the modern analog technique can be used to accurately reconstruct the magnitude of sea-surfacetemperature (SST) in this region. We apply this technique to data from 29 deep-sea cores along a meridional transect of the southwest Pacific Ocean to estimate the magnitude of SST cooling during the Last Glacial Maximum. We find minimal cooling in the tropics (0°–2°C), moderate cooling in the subtropical midlatitudes (2°–6°C), and maximum cooling to the southeast of New Zealand (6°–10°C). The magnitude of cooling at the sea surface from the tropics to the temperate latitudes is found to generally be less than cooling at the surface of adjacent land masses.
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  • 97
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    Reconstruction of ice complex remnants on the eastern Siberian arctic shelf (2003)
    Wiley
    In:  Permafrost and Periglacial Processes, 14 (2). pp. 187-198.
    Details
    Publikationsdatum: 2015-01-29
    Beschreibung: Based on the analysis of seafloor topography together with historical, geological and palaeogeographical data obtained from published and archived sources, the position of former Ice Complex (IC) islands has been reconstructed. Within the Laptev Sea shelf and in the western part of the East Siberian Sea shelf, most of these islands have been destroyed by coastal thermal erosion and thermal abrasion during the last thousand years or so. The IC islands were the remnants of the ice-rich syncryogenic freshwater terrestrial deposits (so called IC), which covered most of the arctic coastal plains and the emerged arctic shelf during the Late Pleistocene. At the present time, sandbanks exist at the places of former IC islands. These sandbanks are the subject of intense seafloor thermal abrasion. The approximate rates of seafloor thermal abrasion and the time of complete disappearance of these islands during the last thousand years have been estimated. The rate is different for different islands and for different time intervals. The most common values are between 0.02 and 0.3 m/year. Schematic maps of the former IC islands within the Laptev Sea and western part of the East Siberian Sea shelves have been compiled.
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  • 98
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    Big Effects from Small Changes: Possible Ways to Explore Nature's Chemical Diversity (2002)
    Wiley
    In:  ChemBioChem, 3 (7). pp. 619-627.
    Details
    Publikationsdatum: 2016-02-19
    Beschreibung: Fungi or bacteria that produce secondary metabolites often have the potential to bring up various compounds from a single strain. The molecular basis for this well-known observation was confirmed in the last few years by several sequencing projects of different microorganisms. Besides well-known examples about induction of a selected biosynthesis (for example, by high- or low-phosphate cultivation media), no overview about the potential in this field for finding natural products was given. We have investigated the systematic alteration of easily accessible cultivation parameters (for example, media composition, aeration, culture vessel, addition of enzyme inhibitors) in order to increase the number of secondary metabolites available from one microbial source. We termed this way of revealing nature's chemical diversity the 'OSMAC (One Strain-Many Compounds) approach' and by using it we were able to isolate up to 20 different metabolites in yields up to 2.6 g L(-1) from a single organism. These compounds cover nearly all major natural product families, and in some cases the high production titer opens new possibilities for semisynthetic methods to enhance even more the chemical diversity of selected compounds. The OSMAC approach offers a good alternative to industrial high-throughput screening that focuses on the active principle in a distinct bioassay. In consequence, the detection of additional compounds that might be of interest as lead structures in further bioassays is impossible and clearly demonstrates the deficiency of the industrial procedure. Furthermore, our approach seems to be a useful tool to detect those metabolites that are postulated to be the final products of an amazing number of typical secondary metabolite gene clusters identified in several microorganisms. If one assumes a (more or less) defined reservoir of genetic possibilities for several biosynthetic pathways in one strain that is used for a highly flexible production of secondary metabolites depending on the environment, the OSMAC approach might give more insight into the role of secondary metabolism in the microbial community or during the evolution of life itself.
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  • 99
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    Natural Products from Marine Microorganisms (2002)
    Chemistry Europe | Wiley
    In:  ChemBioChem, 3 (11). pp. 1151-1154.
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    Publikationsdatum: 2020-07-27
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  • 100
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    Temporal variation of the microbial community associated with the mediterranean sponge Aplysina aerophoba (2001)
    Wiley
    In:  FEMS Microbiology Ecology, 38 (2-3). pp. 105-115.
    Details
    Publikationsdatum: 2015-08-27
    Beschreibung: Sponges of the Aplysinidae family contain large amounts of bacteria that are embedded within the sponge tissue matrix. In order to determine the stability and specificity of the Aplysina–microbe association, sponges were maintained in recirculating seawater aquariums for 11 days. One aquarium was left untreated, a second one contained 0.45 μm filtered seawater (starvation conditions) and the third one contained 0.45 μm filtered seawater plus antibiotics (antibiotics exposure). Changes in the microbial community were monitored using group-specific, 16S rRNA targeted oligonucleotide probes, by denaturing gradient gel electrophoresis and by electron microscopic observations. Furthermore, the changes in the natural product profile were monitored using high-performance liquid chromatography. The measured parameters showed that a large fraction of the sponge-associated microbial community could not be cleared under the given experimental conditions. Based on these cumulative results we postulate that a large fraction of sponge-associated bacteria resides permanently in the Aplysina aerophoba mesohyl pointing to a highly integrated interaction between the host sponge and associated microorganisms.
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