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  • 1
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    PANGAEA
    In:  Supplement to: Yesson, Chris; Clark, M R; Taylor, M; Rogers, A D (2011): The global distribution of seamounts based on 30-second bathymetry data. Deep Sea Research Part I: Oceanographic Research Papers, 58(4), 442-453, https://doi.org/10.1016/j.dsr.2011.02.004
    Publikationsdatum: 2024-02-17
    Beschreibung: Seamounts and knolls are 'undersea mountains', the former rising more than 1000 m from the sea floor. These features provide important habitats for aquatic predators, demersal deep-sea fish and benthic invertebrates. However most seamounts have not been surveyed and their numbers and locations are not well known. Previous efforts to locate and quantify seamounts have used relatively coarse bathymetry grids. Here we use global bathymetric data at 30 arc-second resolution to identify seamounts and knolls. We identify 33,452 seamounts and 138,412 knolls, representing the largest global set of identified seamounts and knolls to date. We compare estimated seamount numbers, locations, and depths with validation sets of seamount data from New Zealand and Azores. This comparison indicates the method we apply finds 94% of seamounts, but may overestimate seamount numbers along ridges and in areas where faulting and seafloor spreading creates highly complex topography. The seamounts and knolls identified herein are significantly geographically biased towards areas surveyed with ship-based soundings. As only 6.5% of the ocean floor has been surveyed with soundings it is likely that new seamounts will be uncovered as surveying improves. Seamount habitats constitute approximately 4.7% of the ocean floor, whilst knolls cover 16.3%. Regional distribution of these features is examined, and we find a disproportionate number of productive knolls, with a summit depth of 〈1.5 km, located in the Southern Ocean. Less than 2% of seamounts are within marine protected areas and the majority of these are located within exclusive economic zones with few on the High Seas. The database of seamounts and knolls resulting from this study will be a useful resource for researchers and conservation planners.
    Schlagwort(e): CoralFISH; Ecosystem based management of corals, fish and fisheries in the deep waters of Europe and beyond
    Materialart: Dataset
    Format: application/zip, 3 datasets
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2024-02-17
    Schlagwort(e): Area; CoralFISH; Ecosystem based management of corals, fish and fisheries in the deep waters of Europe and beyond; ELEVATION; Filter; Height; Identification; LATITUDE; LONGITUDE
    Materialart: Dataset
    Format: text/tab-separated-values, 133808 data points
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2024-02-17
    Schlagwort(e): CoralFISH; Description; Ecosystem based management of corals, fish and fisheries in the deep waters of Europe and beyond; Feature; Uniform resource locator/link to file
    Materialart: Dataset
    Format: text/tab-separated-values, 18 data points
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2024-02-17
    Schlagwort(e): Area; CoralFISH; Ecosystem based management of corals, fish and fisheries in the deep waters of Europe and beyond; ELEVATION; Filter; Height; Identification; LATITUDE; LONGITUDE
    Materialart: Dataset
    Format: text/tab-separated-values, 553648 data points
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2015-06-19
    Beschreibung: Low-frequency, wide field-of-view (FoV) radio telescopes such as the Murchison Widefield Array (MWA) enable the ionosphere to be sampled at high spatial completeness. We present the results of the first power spectrum analysis of ionospheric fluctuations in MWA data, where we examined the position offsets of radio sources appearing in two datasets. The refractive shifts in the positions of celestial sources are proportional to spatial gradients in the electron column density transverse to the lineof sight. These can be used to probe plasma structures and waves in the ionosphere. The regional (10–100 km) scales probed by the MWA, determined by the size of its FoV and the spatial density of radio sources (typically thousands in a single FoV), complement the global (100–1000 km) scales of GPS studies and local (0.01–1 km) scales of radar scattering measurements. Our data exhibit a range of complex structures and waves. Some fluctuations have the characteristics of travelling ionospheric disturbances (TIDs), while others take the form of narrow, slowly-drifting bands aligned along the Earth's magnetic field.
    Print ISSN: 0048-6604
    Digitale ISSN: 1944-799X
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2019
    Beschreibung: Abstract Martian magmas were likely enriched in S and Cl with respect to H2O. Exsolution of a vapor phase from these magmas and ascent of the gas bubbles through the magma plumbing system would have given rise to shallow magmas that were gas‐charged. Release and cooling of this gas from lava flows during eruption may have resulted in the addition of a significant amount of vapor‐deposited phases to the fines of the surface. Experiments were conducted to simulate degassing of gas‐charged lava flows and shallow intrusions in order to determine the nature of vapor‐deposited phases that may form through this process. The results indicate that magmatic gas may have contributed a large amount of Fe, S, and Cl to the Martian surface through the deposition of iron oxides (magnetite, maghemite, and hematite), chlorides (molysite, halite, and sylvite), sulfur, and sulfides (pyrrhotite and pyrite). Primary magmatic vapor‐deposited minerals may react during cooling to form a variety of secondary products, including iron oxychloride (FeOCl), akaganéite (Fe3+O (OH,Cl)), and jarosite (KFe3+3(OH)6(SO4)2). Vapor‐deposition does not transport significant amounts of Ca, Al, or Mg from the magma and hence, this process does not directly deposit Ca‐ or Mg‐sulfates.
    Print ISSN: 2169-9097
    Digitale ISSN: 2169-9100
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 2013-04-26
    Beschreibung: [1]  Spectral and imaging data sets from Mars Reconnaissance Orbiter and Mars Odyssey, as well as spectral and topographic data from Mars Global Surveyor, are used to understand the origin of in-place rock units found in the intercrater plains and Hellas-circumferential graben floors of Noachis Terra, Mars. The rocky units are interpreted as effusive volcanic plains, on the basis of broad areal extent, structural competence, association with topographic lows, distinct mineralogy from regolith, and lack of sedimentary textures or minerals associated with aqueous processes. Some rocky expanses contain at least two compositionally distinct units. The relatively light-toned unit exhibits a higher plagioclase/pyroxene ratio than the lower, dark-toned unit. Both units exhibit ~10% olivine enrichment compared to surrounding regolith. These units are heavily degraded and exhibit crater model ages between ~3.80–4.0 Ga, making these some of the oldest preserved volcanic plains accessible by remote sensing. They are found in association with Hellas ring structures, where the westward extent of these rocky units is limited to the outermost ring structure. Fracturing associated with the Hellas impact may have enabled magmas to ascend from the base of the crust in the circum-Hellas region. Identification of these units as volcanic materials extends previous estimates for volume of outgassed volatiles. Though the estimated volcanic volume increase is minor, the local effects could have been significant. The role of multi-ring impact basins in providing a spatial control on Martian highlands volcanism and subsurface mineralization may have been underestimated in the past.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 2016-10-15
    Beschreibung: During Solar Proton Events (SPE), energetic protons ionize the polar mesosphere causing HF radiowave attenuation, more strongly on the dayside where the effective recombination coefficient, α eff , is low. Polar cap absorption (PCA) models predict the 30 MHz cosmic noise absorption, A , measured by riometers, based on real-time measurements of the integrated proton flux-energy spectrum, J . However, empirical models in common use cannot account for regional and day-to-day variations in the day- and nighttime profiles of α eff ( z ) or the related sensitivity parameter, . Large prediction errors occur during twilight when m changes rapidly, and due to errors locating the rigidity cutoff latitude. Modeling the twilight change in m as a linear or Gauss error-function transition over a range of solar-zenith angles ( χ l  〈  χ  〈  χ u ) provides a better fit to measurements than selecting day or night α eff profiles based on the Earth-shadow height. Optimal model parameters were determined for several polar cap riometers for large SPEs in 1998-2005. The optimal χ l parameter was found to be most variable, with smaller values (as low as 60°) post-sunrise compared with pre-sunset, and with positive correlation between riometers over a wide area. Day and night values of m exhibited higher correlation for closely spaced riometers. A nowcast simulation is presented in which rigidity boundary latitude and twilight model parameters are optimized by assimilating age-weighted measurements from 25 riometers. The technique reduces model bias, and root-mean-squared errors are reduced by up to 30% compared with a model employing no riometer data assimilation.
    Print ISSN: 1539-4964
    Digitale ISSN: 1542-7390
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 2013-08-01
    Beschreibung: Mangroves are species of halophytic intertidal trees and shrubs derived from tropical genera and are likely delimited in latitudinal range by varying sensitivity to cold. There is now sufficient evidence that mangrove species have proliferated at or near their poleward limits on at least five continents over the past half century, at the expense of salt marsh. Avicennia is the most cold-tolerant genus worldwide, and is the subject of most of the observed changes. Avicennia germinans has extended in range along the US Atlantic coast and expanded into salt marsh as a consequence of lower frost frequency and intensity in the southern USA. The genus has also expanded into salt marsh at its southern limit in Peru, and on the Pacific coast of Mexico. Mangroves of several species have expanded in extent and replaced salt marsh where protected within mangrove reserves in Guangdong Province. In south-eastern Australia, the expansion of Avicennia marina into salt marshes is now well documented, and Rhizophora stylosa has extended its range southward, while showing strong population growth within estuaries along its southern limits in northern New South Wales. Avicennia marina has extended its range southwards in South Africa. The changes are consistent with the pole-ward extension of temperature thresholds co-incident with sea-level rise, although the specific mechanism of range extension might be complicated by limitations on dispersal or other factors. The shift from salt marsh to mangrove dominance on subtropical and temperate shorelines has important implications for ecological structure, function, and global change adaptation. This article is protected by copyright. All rights reserved.
    Print ISSN: 1354-1013
    Digitale ISSN: 1365-2486
    Thema: Biologie , Energietechnik , Geographie
    Publiziert von Wiley
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Publikationsdatum: 1974-11-15
    Print ISSN: 0014-5793
    Digitale ISSN: 1873-3468
    Thema: Biologie , Chemie und Pharmazie
    Standort Signatur Erwartet Verfügbarkeit
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