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  • Other Sources  (44)
  • Nature Publishing Group  (21)
  • Schweizerbart  (20)
  • American Meteorological Society
  • MDPI Publishing
  • 1995-1999  (44)
  • 1
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    Nature Publishing Group
    In:  Nature, 397 (6718). pp. 389-391.
    Publication Date: 2015-07-16
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  • 2
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    In:  Zentralblatt für Geologie und Paläontologie / Teil 1, 1998 (5-6). pp. 435-445.
    Publication Date: 2018-02-06
    Description: The global sediment mass-age distribution indicates large variations in the rates of carbonate sedimentation through time. The largest mass of carbonate deposited during the entire history of the earth was produced during the Cambrian, possibly following on an episode of phosphogenesis in the Late Precambrian. A second major episode occurred during the Late Devonian, probably reflecting the invasion of land by plants that altered the rock-weathering and soil-forming regimes. Other lesser pulses of carbonate deposition occurred in the Late Permian, Triassic, and Cretaceous. A shift in the locus of carbonate deposition from shallow waters to the deep sea occurred during the Cretaceous.
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  • 3
    Publication Date: 2017-06-22
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  • 4
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    Schweizerbart
    In:  Zeitschrift für Angewandte Geologie, 45 . pp. 164-169.
    Publication Date: 2016-06-16
    Type: Article , NonPeerReviewed
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  • 5
    Publication Date: 2019-08-08
    Description: At Aqaba in the Northern Gulf of Aqaba, Red Sea, the stable oxygen isotope record of a Por#es lutea coral colony was studied. From a vertical and a horizontal core two parts from the base of the colony (10 years of coral growth), and two parts from the living surface (12 years of coral growth) were analysed with a monthly sampling resolution. The results show that seasonality of sea surface temperatures (SST) in the northem GulfofAqaba has increased since the early 19th century, mainly due to higher summer temper- atures. 8~80-ratios indicate that SST increased by at least 1.3~ Horizontal and vertical cores display dif- ferent variations in the modern parts, probably caused by the very shallow water depth of the youngest part of the vertical core.
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  • 6
    Publication Date: 2021-02-25
    Description: The El Niño/Southern Oscillation (ENSO) phenomenon is the strongest natural interannual climate fluctuation1. ENSO originates in the tropical Pacific Ocean and has large effects on the ecology of the region, but it also influences the entire global climate system and affects the societies and economies of manycountries2. ENSO can be understood as an irregular low-frequency oscillation between a warm (El Niño) and a cold (La Niña) state. The strong El Niños of 1982/1983 and 1997/1998, along with the more frequent occurrences of El Niños during the past few decades, raise the question of whether human-induced 'greenhouse' warming affects, or will affect, ENSO3. Several global climate models have been applied to transient greenhouse-gas-induced warming simulations to address this question4, 6, but the results have been debated owing to the inability of the models to fully simulate ENSO (because of their coarse equatorial resolution)7. Here we present results from a global climate model with sufficient resolution in the tropics to adequately represent the narrow equatorial upwelling and low-frequency waves. When the model is forced by a realistic future scenario of increasing greenhouse-gas concentrations, more frequent El-Niño-like conditions and stronger cold events in the tropical Pacific Ocean result
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  • 7
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    In:  Archiv für Hydrobiologie, 146 . pp. 55-64.
    Publication Date: 2019-03-05
    Description: Repeatable species dominance patterns across nutrient ratio gradients are found both in culture competition experiments and in natural waters. However, the mechanisms behind these similar patterns need not to be identical. In chemostat experiments, such patterns are caused by the two-way competitive interactions between contemporaneously occurring organisms. Nutrient competition may be important in situ too, but there is an additional effect of early successional species influencing the nutrient environment for later successional species, without being influenced themselves by their successors.
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  • 8
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    Nature Publishing Group
    In:  Nature, 402 . pp. 366-367.
    Publication Date: 2017-02-28
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  • 9
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    Nature Publishing Group
    In:  Nature, 397 . pp. 243-246.
    Publication Date: 2017-02-28
    Description: The overflow and descent of cold dense water from the Denmark Strait sill-a submarine passage between Greenland and Iceland-is a principal means by which the deep ocean is ventilated, and is an important element in the global thermohaline circulation. Previous investigations of its variability-in particular, direct current measurements(1,2) in the overflow core since 1986-have shown surprisingly little evidence of long-term changes in now speed. Here we report significant changes in the overflow characteristics during the winter of 1996-97, measured using two current-meter moorings and an inverted echo sounder located at different depths in the fastest part of the now. The overflow warmed to the highest monthly value yet recorded (2.4 degrees C), and showed a pronounced slowing and thinning at its lower margin. We believe that the extreme warmth of the overflow caused it to run higher on the continental slope off east Greenland, so that the lower current meters and the echo sounder were temporarily outside and deeper than the fast-flowing core; model simulations appear to confirm this interpretation, We suggest that the extreme warmth of the overflow is a lagged response to a warming upstream in the Fram Strait three years earlier (caused by an exceptional amplification of the winter North Atlantic Oscillation). If this is so, over-now characteristics may be predictable.
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  • 10
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    In:  Archiv für Hydrobiologie Spec. Iss. Advances in Limnology, 51 . pp. 41-62.
    Publication Date: 2017-12-01
    Description: Cyanobacteria are important constituents of most aquatic ecosystems on earth, and planktonic forms frequently show mass development in lakes and estuaries. Despite extensive scientific efforts directed towards research on cyanobacteria, a comprehensive theory explaining their success is lacking. Because cyanobacteria comprise a diverse group of organisms, it is concluded that any analysis of the conditions leading to cyanobacterial dominance in pelagic ecosystems should consider at least three different subgroups, classified based on presence or absence of (i) buoyancy regulation and (ii) the ability to fix molecular nitrogen. In this review, nine single-factor hypotheses regarding regulation of cyanobacterial development are examined against the background of physiological and ecological characteristics of these organisms. Special emphasis has been put on understanding differences in nitrogen metabolism between cyanobacteria and algae which directly relate to a hypothesis conceming inorganic nitrogen forms and cyanobacterial success previously presented by our research group. The review lends support to the theory that cyanobacteria have a low competitive ability for nitrate compared with algae and a high ability to compete for ammonium, particularly under nitrogen-limiting conditions. Finally it is concluded that to understand cyanobacterial devlopment and how high Standing Stocks in pelagic ecosystems are maintained requires parts o f all the single-factor hypotheses initially presented.
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  • 11
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    Schweizerbart
    In:  Zentralblatt für Geologie und Paläontologie / Teil 1, 1996 (11/12). pp. 1445-1454.
    Publication Date: 2018-02-06
    Description: The density of seawater is a complex function of temperature, salinity, and pressure. Because of the non-linearity of the equation of state of seawater, the densities of sea waters having the same temperature and the same salinity differences (with respect to the mean salinity of the ocean) will vary with the mean salinity of the ocean. Although this strange property of seawater is evident in a plot of the equation of state, it has never been considered in trying to reconstruct ancient ocean circulation. These differences in the density field may have caused the ocean to respond differently to atmospheric forcing in the past. The different response may hold the key to understanding "ocean anoxic events" and episodes of large-scale burial of organic carbon and production of petroleum source rocks.
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  • 12
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    In:  Zentralblatt für Geologie und Paläontologie / Teil 1, 1996 (11/12). pp. 1433-1444.
    Publication Date: 2018-02-06
    Description: The Late Cretaceous was much warmer than today. There was no significant ice at high latitudes, meridional thermal gradients were low, and continental interiors remained warm during winter. Late Cretaceous atmospheric C02 concentrations were about four times greater than today and an enhanced "greenhouse" effect contributed to the overall warmth of the Late Cretaceous. However , increases in atmospheric C02 tend to increase temperatures at all latitudes and do not explain the very low thermal gradients recognized in the geologic record. Increased poleward ocean heat transport has been cited as a mechanism for maintaining low meridional thermal gradients during the Cretaceous. However , ocean heat transport values larger than the present day are difficult to reconcile. In addition, low meridional thermal gradients suggest sluggish atmospheric circulation, implying that the advection of heat from the warm oceans into the continental interiors was limited. In general, paleoclimate simulations using Atmospheric General Circulations Models (AGCMs) have not been successful in simulating the low meridional thermal gradients and warm winter continental interiors of the Cretaceous, forcing the concept of "equability" to be questioned. Until recently, the physical effects of vegetation on pre-Quaternary climates have largely been ignored. Terrestrial ecosystems influence global climate by affecting the exchange of energy, water, and momentum between the land surface and the atmosphere. In a new approach to pre-Quaternary paleoclimate modeling, Campanian (80 Ma) climate and vegetation have been simulated using a global climate model (GENESIS Version 2.0), coupled to a predictive vegetation model (EVE), resulting in a realistic simulation of Late Cretaceous climate. The predicted distribution of Late Cretaceous vegetation played an important role in the maintenance of low meridional thermal gradients, polar warmth, and equable continental interiors. High latitude forests reduced albedo, especially during snowcovered months, and increased net surface radiation and latent heat flux.
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  • 13
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    Nature Publishing Group
    In:  Nature, 394 . pp. 266-269.
    Publication Date: 2019-02-27
    Description: In steady state, the export of photosynthetically fixed organic matter to the deep ocean has to be balanced by an upward flux of nutrients into the euphotic zone1. Indirect geochemical estimates2 of the nutrient supply to surface waters have been substantially higher than direct biological and physical measurements3, particularly in subtropical regions. A possible explanation for the apparent discrepancy is that the sampling strategy of the direct measurements has under-represented episodic nutrient injections forced by mesoscale eddy dynamics, whereas geochemical tracer budgets integrate fluxes over longer time and space scales. Here we investigate the eddy-induced nutrient supply by combining two methods potentially capable of delivering synoptic descriptions of the ocean's state on a basin scale. Remotely sensed sea-surface height data from the simultaneous TOPEX/Poseidon and ERS-1 satellite missions are assimilated into a numerical eddy-resolving coupled ecosystem–circulation model of the North Atlantic Ocean. Our results indicate that mesoscale eddy activity accounts for about one-third of the total flux of nitrate into the euphotic zone (taken to represent new production) in the subtropics and at mid-latitudes. This contribution is not sufficient to maintain the observed primary production in parts of the subtropical gyre, where alternative routes of nitrogen supply will have to be considered.
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  • 14
    Publication Date: 2017-02-27
    Description: The ability to monitor the heat content of oceans over long distances is becoming increasingly important for understanding the role of oceans in climate change, for determining the variability of the state of the oceans, for operational ocean observing systems, and for studying large-scale ocean processes such as water-mass formation. Although the properties of the upper layers of the ocean can be routinely measured on large scales by satellite remote sensing (providing altimetric and infrared data) and with expendable probes dropped from commercial vessels, the deep interior of the ocean is more difficult to monitor. Ocean acoustic tomography1 is a promising technique for such applications, as it has the potential to provide systematic, instantaneous and repeated measurements of the ocean interior over large parts of an ocean basin. Here we demonstrate the capability of this technique for measuring the heat content across an entire (albeit small) ocean basin—the western Mediterranean Sea.
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  • 15
    Publication Date: 2017-02-27
    Description: The ocean stores and transports vast quantities of heat, fresh water, carbon and other materials, and its circulation plays an important role in determining both the Earth's climate and fundamental processes in the biosphere. Understanding the development of climate and important biological cycles therefore requires detailed knowledge of ocean circulation and its transport properties. This cannot be achieved solely through modelling, but must involve accurate observations of the spatio-temporal evolution of the global oceanic flow field. Estimates of oceanic flow are currently made on the basis of space-borne measurements of the sea surface, and monitoring of the ocean interior. Satellite altimetry and acoustic tomography are complementary for this purpose1, as the former provides detailed horizontal coverage of the surface, and the latter the requisite vertical sampling of the interior. High-quality acoustic-tomographic2 and altimetric3 data are now available to test the combined power of these technologies for estimating oceanic flows. Here we demonstrate that, with the aid of state-of-the-art numerical models, it is possible to recover from these data a detailed spatio-temporal record of flow over basin-scale volumes of fluid. Our present results are restricted to the Mediterranean Sea, but the method described here provides a powerful tool for studying oceanic circulation worldwide.
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  • 16
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    Nature Publishing Group
    In:  Nature, 387 . pp. 31-32.
    Publication Date: 2017-02-28
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  • 17
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    American Meteorological Society
    In:  Monthly Weather Review, 125 (5). pp. 819-830.
    Publication Date: 2020-06-30
    Description: In this study, the impact of oceanic data assimilation on ENSO simulations and predictions is investigated. The authors’ main objective is to compare the impact of the assimilation of sea level observations and three-dimensional temperature measurements relative to each other. Three experiments were performed. In a control run the ocean model was forced with observed winds only, and in two assimilation runs three-dimensional temperatures and sea levels were assimilated one by one. The root-mean-square differences between the model solution and observations were computed and heat content anomalies of the upper 275 m compared to each other. Three ensembles of ENSO forecasts were performed additionally to investigate the impact of data assimilation on ENSO predictions. In a control ensemble a hybrid coupled ocean–atmosphere model was initialized with observed winds only, while either three-dimensional temperatures or sea level data were assimilated during the initialization phase in two additional forecast ensembles. The predicted sea surface temperature anomalies were averaged over the eastern equatorial Pacific and compared to observations. Two different objective skill measures were computed to evaluate the impact of data assimilation on ENSO forecasts. The authors’ experiments indicate that sea level observations contain useful information and that this information can be inserted successfully into an oceanic general circulation model. It is inferred from the forecast ensembles that the benefit of sea level and temperature assimilation is comparable. However, the positive impact of sea level assimilation could be shown more clearly when the forecasted temperature differences rather than the temperature anomalies themselves were compared with observations.
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  • 18
    Publication Date: 2017-01-04
    Description: This paper presents trace element and Sm-Nd isotope data on the Mönchalpgneiss in order to compare the geochemistry of the two polymetamorphic igneous suites that comprise over 30% of the Austroalpine Silvretta nappe. The first are the so-called "Younger Orthogneisses" of the "Fliielagranitic Association" and the second are the "Older Orthogneisses" including the Mönchalpgneisswhich are associated with metagabbros, metadiorites, metatonalites and metagranitoids. U-Pb zircon results from the Mönchalpgneiss are indicative of anatectic processes in late Cambrian to Ordovician times. A volcanic-arc (VA) tectonic environment during intrusion explains the direct association of gabbroic and metagranitoid rocks in the Engadine area. This model is in line with the distribution of major, trace and rare earth elements in these anatectic rocks. However, the significance of the geochemical results remains ambiguous, since the average continental crust and paragneisses of the Silvretta also show VA-type signatures in the respective diagrams. Nd model ages on four Mönchalpgneiss whole-rock samples from the type locality are closely grouped around 1.70 Ga, which is a commonly obtained value for European continental crust. This age is interpreted to be the result of a homogeneous mixture of different crustal components
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  • 19
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    Nature Publishing Group
    In:  Nature, 389 (6652). pp. 683-684.
    Publication Date: 2021-02-15
    Description: Recent captures of two female giant squid ( Architeuthis ) off southern Australia have provided the first record of a mated female specimen of these almost mythical deepsea creatures. We found sperm packages (spermatophores) embedded within the skin of both ventral arms of the larger of the two specimens. It seems that male giant squids may use their muscular elongate penis to ‘inject’ sperm packages under pressure directly into the arms of females.
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  • 20
    Publication Date: 2018-01-09
    Description: The nitrogen-isotope record preserved in Southern Ocean sediments, along with several geochemical tracers for the settling fluxes of biogenic matter, reveals patterns of past nutrient supply to phytoplankton and surface-water stratification in this oceanic region. Areal averaging of these spatial patterns indicates that reduction of the CO2 'leak' from ocean to atmosphere by increased surface-water stratification south of the Polar Front made a greater contribution to the lowering of atmospheric CO2 concentration during the Last Glacial Maximum than did the increased export of organic carbon from surface to deep waters occurring further north.
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  • 21
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    American Meteorological Society
    In:  Monthly Weather Review, 125 . pp. 703-720.
    Publication Date: 2020-06-30
    Description: In this paper the performance of the global coupled general circulation model (CGCM) ECHO-2, which was integrated for 10 years without the application of flux correction, is described. Although the integration is rather short, strong and weak points of this CGCM can be clearly identified, especially in view of the model's performance of the annual cycle in the tropical Pacific. The latter is simulated with more success relative to the earlier version, ECHO-I. A better representation of the low-level stratus clouds in the atmosphere model associated with a reduction in the shortwave radiative flux at the air-sea interface improved the coupled model's performance in the southeastern tropical oceans, with a strongly reduced warm bias in these regions. Modifications in the atmospheric convection scheme also eliminated the AGCM's tendency to simulate a double ITCZ, and this behavior is maintained in the CGCM simulation. Finally, a new numerical scheme for active tracer advection in the ocean model strongly reduced the numerical mixing, which seems to enhance considerably the level of interannual variability in the equatorial Pacific. One weak point is an overall cold bias in the Tropics and midlatitudes, which typically amounts to 1°C in open ocean regions. Another weak point is the still too strong equatorial cold tongue, which penetrates too far into the western equatorial Pacific. Although this model deficiency is not as pronounced as in ECHO-1, the too strong cold tongue reduces the level of interannual rainfall variability in the western and central equatorial Pacific. Finally, the interannual fluctuations in equatorial Pacific sea surface temperatures (SSTs) are too equatorially trapped, a problem that is also found in ocean-only simulations. Overall, however, the authors believe that the ECHO-2 CGCM has been considerably improved relative to ECHO-1.
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  • 22
    Publication Date: 2020-07-31
    Description: Abstract The famous association of metagabbros, eclogites, glaucophanites, jadeite rocks and ultramafics from the island of Syros forms a distinct lithostratigraphic or tectonic unit. It is interpreted as a high-pressure metamorphic ophiolite suite. This paper provides geochemical and Sr-isotope constraints on the geotectonic setting in which the magmatic protoliths of the Syros metabasites were formed. A compositional gap exists between the metagabbros with Mg-numbers [Mg# = Mg/(0.85Fetot + Mg) atomic ratio] of 0.75-0.88 on the one hand and eclogites and garnet-glaucophanites on the other hand with Mg# of 0.35-0.62, and maximum total iron contents of up to 18 wt.% FeOtot. Metagabbros from various localities and glaucophanites collected around Manna form geochemically coherent groups with smooth correlations between compatible as well as immobile incompatible elements and Mg#. By contrast, the behaviour of immobile incompatible elements, and to some extent also of compatible elements, is highly unsystematic in the eclogites and garnet-glaucophanites. Also, the more mobile elements display a wide scatter in all rocks. This, in conjunction with the unsystematic variation of Sr-isotopes, is thought to be due to secondary alteration. From the strong correlation of Ni and Cr with Mg# and the flat REE patterns lacking Eu-anomalies, a cumulus nature is inferred for olivine, clinopyroxene, and spinel, associated with intercumulus formation of plagioclase in the magmatic protoliths of the metagabbros. There is no direct genetic link between these rocks and the precursors of the Manna-type glaucophanites with REE characteristics typical of N- to T-type MORB. The extremely high geochemical diversity of the eclogites and garnet-glaucophanites from Syros favours individual evolution of their protoliths in small magma bodies as suggested for superferric eclogites from the Western and Ligurian Alps, as well as the ferrogabbros from the ophiolites of the Northern Apennines. From the geochemistry of the Syros metabasites along with the initial 87Sr/86Sr ratios of the metagabbros between 0.7031 and 0.7033, as well as an eNd value of 7.7 from a garnet glaucophanite, the magmatic protoliths are inferred to have formed in a back-arc setting. By analogy to the association of gabbros and ferrogabbros adjacent to the Atlantis II fracture zone of the SW Indian Ridge, we further suggest an origin at a spreading ridge in proximity to a transform fault.
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  • 23
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    Schweizerbart
    In:  Neues Jahrbuch Für Mineralogie - Monatshefte, 1996 (2). pp. 57-72.
    Publication Date: 2017-03-20
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  • 24
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    Schweizerbart
    In:  Zentralblatt für Geologie und Paläontologie / Teil 1, 1995 (1/2). pp. 271-286.
    Publication Date: 2017-06-23
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  • 25
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    Schweizerbart
    In:  Senckenbergiana Maritima, 27 (1/2). pp. 33-48.
    Publication Date: 2019-08-08
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  • 26
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    Nature Publishing Group
    In:  Nature, 382 (6589). pp. 344-346.
    Publication Date: 2017-02-27
    Description: The conventional model whereby plume volcanism forms linear age-progressive volcanic chains, with the youngest activity occurring nearest a spreading axis (at a 'hotspot'), has been challenged for the Easter seamount chain1–4. Whereas early work suggested the existence of a linear melting anomaly (a 'hotline')1,2, more recent studies3,4 have proposed a hotspot near Salas y Gomez island, connected with the Easter microplate spreading system by an ~800-km-long, volcanically active plume channel. Here we use geochemical, geological and geochronological data to argue that the hotspot lies close to Easter Island. Moreover, new isotopic data for lavas from the seamount chain provide evidence for bidirectional flow between the spreading axis and the plume, thus supporting geophysical and fluid-dynamical models of mantle flow in a plume/spreading axis system5–7. Material balance and flux considerations show the Easter plume to be weak and cool compared with those beneath larger features such as Iceland, Hawaii and the Galápagos islands.
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  • 27
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    In:  Zentralblatt für Geologie und Paläontologie / Teil 1, 1994 (7/8). pp. 917-934.
    Publication Date: 2018-02-06
    Description: Evolution of the Caribbean Plate can be modeled by motions about six successive rotation poles. Opening of Cayman Trough has occurred since 49.5 Ma through westward motion of the Caribbean Plate, eastern Greater Antilles and Chortis Block. Before 49.5 Ma, the eastern Greater-Antilles were west of Cuba, and the southeastern margins of Yucatan and the Nicaragua Rise (Chortis) were aligned. From 67.5 to 49.5 Ma the Caribbean Plate rotated clockwise, opening the Yucatan Basin. From 100 Ma to 67.5 Ma, the Caribbean Plate, with Cuba attached, moved along the southeastern margin of Yucatan-Chortis. At 130 Ma it was attached to northwestern South America.
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  • 28
    Publication Date: 2017-02-27
    Description: A knowledge of past changes in the biological productivity of the oceans is important for understanding the interactions between carbon cycling and climate. Phytoplankton productivity in today's oceans can be estimated from the concentrations of chlorophyll in sea water1, but chlorophyll is not preserved in the sediments. Existing proxies for past algal productivity do not represent total productivity; for example, biogenic opal2 reflects the contribution of only part of the phytoplankton community, and the organic carbon record can be subject to contamination from terrestrial inputs2,3. Although chlorins, the pigment-transformation products of chlorophyll, are widespread in Quaternary marine sediments, their potential as proxy measures of past variations in primary productivity has not been convincingly demonstrated. Here we report a high-resolution molecular stratigraphic record of chlorin concentrations over the past 350,000 years in a sediment core from the subtropical Atlantic continental margin. Maxima in the chlorin accumulation rate coincide with significant peaks in the accumulation rates of biogenic opal (at the end of glacial terminations) and organic carbon (between terminations). These results suggest that chlorins, unlike other proxies, can serve as a measure of total primary productivity variations.
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  • 29
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    In:  Neues Jahrbuch für Geologie und Paläontologie - Monatshefte, 1996 (5). pp. 257-278.
    Publication Date: 2017-02-16
    Description: Microspectralphotometric examinations of various recent pollen point to a different sporopollenin chemistry of the different taxa which is distinguishable by the UV-VIS absorptionspectra. The measurement areas have a diameter of 6 micron, by which several measurements for the spectra control in one pollen grain are possible. Labaratory experiments with chemical treatments as used by palynological preparation, show a clear change in the sporopollenin chemistry whichcould be identified by the absorption spectra. Therefore a new preparation technique for fossil and recent palynomorphs has to be developed to avoid chemical changes. First investigations of recent and fossil Pinus pollen have been clone on material from various facies types and a sediment core. The variations in the absorption spectra of the pollen indicate the different chemical influence of different facies types which could be used for facies analyses. Furthermore, significant changes in the absorption spectra are useful to identify reworked pollen or pollen with a different burial history. Zusammenfassung: Vergleichende mikrospektralphotometrische Untersuchungen der UV-VIS Absorptionsspektren verschiedener rezenter Pollen-Taxa zeigen, daß die Zusammensetzung bzw. Struktur des Sporopollenins bei verschiedenen Taxa variiert und daß diese anhand der Absorptionsspektren klar unterschieden werden kann. Die gemessene Fläche auf den jeweiligen Pollen hat einen Durchmesser von 6 j.lm, so daß mehrere Kontrollmessungen an einem Pollen möglich sind. Laborversuche an rezenten Pollen zeigen, daß chemische Einflüsse (z. B. HN03, Acetolyse) deutlich meßbare Veränderungen in der Struktur des Sporopollenins verursachen. Um Veränderungen des Sporepollenins durch die chemische Probenaufbereitung auszuschließen, wurde eine neue Präparationsmethode für fossile und rezente Palynomorphen entwickelt.
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  • 30
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    In:  Senckenbergiana Maritima, 27 . pp. 145-150.
    Publication Date: 2019-08-08
    Description: ana marit., 27 (3/6): 145-150, 2 figs.; Frankfurt a. M.] According to the (neo-)Darwinian theory of evolution the appearance of "design" and optimization of biological properties are the results of natural selection and not of teleology. An opti· mization by selection is only possible for entities which are able to reproduce ("units of selection"). The "unit-of-selection"-problem will be discussed in relation to the atomism-holism-continuum of ecological and evolutionary concepts which range from Dawkins' "selfish gene" to LoveJock's "Gaia". Special emphasis will be given to the discussion of the group-selection problem which seems to be the critical breakpoint along this continuum. It will be shown that optimization through natural selection is only possible for units which can multiply and preserve their identity to a sufficient degree through multiplications. Such units are called replicators. Associations, communities, ecosystems and the biosphere do not qualify as replicators.
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  • 31
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    Nature Publishing Group
    In:  Nature, 382 . pp. 802-805.
    Publication Date: 2017-02-27
    Description: A fundamental issue in marine science is the identification of the factors controlling biological uptake of CO2, in high-nitrate, low-chlorophyll regions. A recent in situ iron fertilization experiment demonstrated that iron limitation is responsible for low phytoplankton stocks in the equatorial Pacific4. Here we show that flavodoxin, a biochemical marker of iron limitation, can be used to map the degree of iron stress in natural populations. Flavodoxin assays along a 900-km east-west transect in the northeastern subarctic Pacific revealed a pronounced increase in iron stress in the region west of the 135° W meridian. Addition of dissolved iron alleviated this stress. Immunostaining of single cells from the most western station showed that flavodoxin is present specifically within the chloroplasts of diatoms. Our approach provides a rapid means of defining the extent of iron stress in the ocean5 and supports the hypothesis that diatoms are iron stressed in the northeast Pacific.
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  • 32
    Publication Date: 2020-07-30
    Description: In Sedimenten aus flachen Bohrungen in der Nordsee wurden gasförmige Kohlenwasserstoffe gefunden. Kohlenstoff- (Methan bis Propan) und Wasserstoff-Isotopanwerte lassen auf eine Mischung von Gasen bakterieller und thermischer Entstehung schließen. Die thermischen Gase sind in größerer Tiefe aus überwiegend mariner organischer Substanz entstanden und in die oberflächennahen Sedimente migriert. [Methane through pentane have been found in sediments from shallow North Sea boreholes. Carbon (methane through propane) and hydrogen (methane) isotope ratlos indicate both bacterial and thermal origins. The gases of thermal origin are interpreted as having been generated at considerable depth from predominantly marine source rocks and then to have migrated into the overlying sediments.]
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  • 33
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    Nature Publishing Group
    In:  Nature, 384 (6608). p. 421.
    Publication Date: 2021-08-20
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  • 34
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    Nature Publishing Group
    In:  Nature, 377 (6545). p. 107.
    Publication Date: 2017-07-04
    Type: Article , PeerReviewed
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  • 35
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    Nature Publishing Group
    In:  Nature, 374 (6520). p. 314.
    Publication Date: 2017-07-06
    Type: Article , PeerReviewed
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  • 36
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    Schweizerbart
    In:  Zentralblatt für Geologie und Paläontologie / Teil 1, 1994 (1/2). pp. 83-95.
    Publication Date: 2016-04-22
    Description: The chemical composition of sediments from the Reykjanes Ridge is controlled by allochthonous and autochthonous processes. The surface sediments are characterized by relatively high contents of calciumoxide and strontium. Calcium and strontium dominate in the carbonate phase due to the high content of biogenic carbonate. A high percentage of iron and manganese are bound to oxides and hydroxides. An indication of hydrothermal activity was not observed. A considerable portion of adsorbed barium is transported in clay minerals. The higher amounts of aluminium in glacial sequences indicate an enhanced input of terrigenous material; the increase of stable bonding elemen~s points toward the large influence of detrital minerals. The distinct differences in the bonding characteristics of elements in these marine sediments in comparison to fluvial and coastal - deposits could be due to the different environmental conditions.
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  • 37
    Publication Date: 2020-06-30
    Description: The seasonal cycle over the tropical Pacific simulated by 11 coupled ocean–atmosphere general circulation models (GCMs) is examined. Each model consists of a high-resolution ocean GCM of either the tropical Pacific or near-global means coupled to a moderate- or high-resolution atmospheric GCM, without the use of flux correction. The seasonal behavior of sea surface temperature (SST) and eastern Pacific rainfall is presented for each model. The results show that current state-of-the-art coupled GCMs share important successes and troublesome systematic errors. All 11 models are able to simulate the mean zonal gradient in SST at the equator over the central Pacific. The simulated equatorial cold tongue generally tends to be too strong, too narrow, and extend too far west. SSTs are generally too warm in a broad region west of Peru and in a band near 10°S. This is accompanied in some models by a double intertropical convergence zone (ITCZ) straddling the equator over the eastern Pacific, and in others by an ITCZ that migrates across the equator with the seasons; neither behavior is realistic. There is considerable spread in the simulated seasonal cycles of equatorial SST in the eastern Pacific. Some simulations do capture the annual harmonic quite realistically, although the seasonal cold tongue tends to appear prematurely. Others overestimate the amplitude of the semiannual harmonic. Nonetheless, the results constitute a marked improvement over the simulations of only a few years ago when serious climate drift was still widespread and simulated zonal gradients of SST along the equator were often very weak.
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  • 38
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    Nature Publishing Group
    In:  Nature, 376 (6537). pp. 212-213.
    Publication Date: 2016-06-16
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  • 39
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    Nature Publishing Group
    In:  Nature, 373 . p. 28.
    Publication Date: 2017-02-27
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  • 40
    Publication Date: 2017-02-27
    Description: Seismic tomography and the isotope geochemistry of Cenozoic volcanic rocks suggest the existence of a large, sheet-like region of upwelling in the upper mantle which extends from the eastern Atlantic Ocean to central Europe and the western Mediterranean. A belt of extension and rifting in the latter two areas appears to lie above the intersection of the centre of the upwelling region with the base of the lithosphere. Lead, strontium and neodymium isotope data for all three regions converge on a restricted composition, inferred to be that of the upwelling mantle.
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  • 41
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    Schweizerbart
    In:  Neues Jahrbuch Für Mineralogie - Monatshefte, 1995 (4). pp. 146-160.
    Publication Date: 2020-09-28
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  • 42
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    Nature Publishing Group
    In:  Nature, 376 (6538). pp. 301-302.
    Publication Date: 2018-08-15
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  • 43
    Publication Date: 2017-02-27
    Description: THE hydrothermal circulation of sea water through permeable ocean crust results in rock–water interactions that lead to the formation of massive sulphide deposits. These are the modern analogues of many ancient ophiolite-hosted deposits1–4, such as those exposed in Cyprus. Here we report results obtained from drilling a series of holes into an actively forming sulphide deposit on the Mid-Atlantic Ridge. A complex assemblage of sulphide–anhydrite–silica breccias provides striking evidence that such hydrothermal mounds do not grow simply by the accumulation of sulphides on the sea floor. Indeed, the deposit grows largely as an in situ breccia pile, as successive episodes of hydrothermal activity each form new hydrothermal precipitates and cement earlier deposits. During inactive periods, the collapse of sulphide chimneys, dissolution of anhydrite, and disruption by faulting cause brecciation of the deposit. The abundance of anhydrite beneath the present region of focused hydrothermal venting reflects the high temperatures ( 〉 150 °C) currently maintained within the mound, and implies substantial entrainment of cold sea water into the interior of the deposit. These observations demonstrate the important role of anhydrite in the growth of massive sulphide deposits, despite its absence in those preserved on land.
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  • 44
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    Schweizerbart
    In:  Zentralblatt für Geologie und Paläontologie / Teil 1, 1994 (1/2). pp. 67-81.
    Publication Date: 2017-06-23
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