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  • 11
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: Online-Ressource (97 Seiten = 17 MB) , Graphen, Karten
    Language: German
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  • 12
    Type of Medium: Book
    Pages: 77 S. , graph. Darst., Kt. , 30 cm
    Series Statement: Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel 184
    Language: German
    Note: Literaturverz. S. 76 - 77
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Ocean dynamics 38 (1985), S. 7-22 
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Strömungsdaten von 7 Verankerungen, die im nordöstlichen Atlantik über mehrere Jahre ausgelegt waren, wurden im Hinblick auf halbtägige barotrope und barokline sowie eintägige barotrope Gezeiten analysiert. Bei den halbtägigen Tiden M2 und S2 dominiert normalerweise die Energie der barotropen Eigenfunktion, nur in wenigen Fällen enthält die barokline Welle 1. Ordnung höhere Energie. Die Ellipsenorientierungen für die barotropen Komponenten entsprechen früheren Ergebnissen von Tiefseepegeln in diesem Gebiet. Es gibt jedoch signifikante Abweichungen bei den Amplituden. Die Gezeiten in diesem Gebiet sind fast ausschließlich fortschreitende Wellen, in einigen wenigen Fällen jedoch vom gemischten Typ. Die räumliche Änderung der Strömungsellipsen entspricht weitgehend den Ergebnissen, die Cartwright, Edden, Spencer et al. [1980] indirekt aus Pegelbeobachtungen erhielten.
    Abstract: Résumé Les mesures de courants provenant de 7 mouillages sur plusieurs années en Atlantique Nord-Est ont été analysées en ce qui concerne les marées semi-diurnes barotropes et baroclines et les marées diurnes barotropes. Pour les marées semi-diurnes M2 et S2 la répartition de l'énergie est généralement dominée par le mode barotrope; dans peu de cas seulement, le mode barocline de premier ordre renferme la plus haute énergie. Les orientations de l'ellipse relevant de la marée barotrope sont en accord avec les résultats d'observations marégraphiques antérieures dans cette région. Des écarts significatifs apparaissent toutefois en amplitude. Les résultats concernant la composante Ki sont également présentés. A quelques exceptions près, les marées, dans cette région, se sont trouvées être des ondes progressives. Le type d'ellipse des courants est semblable aux résultats obtenus indirectement par Cartwright, Edden, Spencer et al. [1980] à partir des observations marégraphiques.
    Notes: Summary Current data obtained from 7 moorings in the Northeast Atlantic in the course of many years are analysed with respect to semi-diurnal barotropic and baroclinic tides and diurnal barotropic tides. For semi-diurnal tides M2 and S2 the energy distribution is usually dominated by the barotropic mode; only in a few cases does the first-order baroclinic mode contain higher energy. Barotropic tidal ellipse orientations are found to be consistent with results from earlier tide gauge observations in this area. Significant deviations occur, however, in amplitudes. Results for the diurnal component K1 are also presented. With few exceptions, tides are found to be progressive waves in this area. The current ellipse pattern is similar to results obtained indirectly by Cartwright, Edden, Spencer et al. [1980] from tide gauge observations.
    Type of Medium: Electronic Resource
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  • 14
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    Elsevier
    In:  Estuarine, Coastal and Shelf Science, 28 (6). pp. 615-638.
    Publication Date: 2017-01-04
    Description: Measurements in the mixing zone of the Elbe estuary were performed during three consecutive tidal cycles with three types of instruments—a moored tripod with velocity and temperature/conductivity/light attenuation sensors, a profiling sonde with similar sensors lowered from an anchored vessel, and instrumented moorings. Acoustic-travel-time sensors were used for velocity measurements. Spectral analysis of 12·8 min pieces of the obtained time series gives results that are consistent with isotropic turbulence for part of the frequency space. Temporal changes of turbulent kinetic energy are correlated with tidal current velocity. A retardation is found between changes in tidal current and turbulent energy. Not all shear stress terms are in similar phase with tidal flow. Mean gradients, Reynolds stress terms, and turbulent salt flux terms are combined to determine eddy viscosity and eddy diffusion coefficients.
    Type: Article , PeerReviewed
    Format: text
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  • 15
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    AMS (American Meteorological Society)
    In:  Journal of Atmospheric and Oceanic Technology, 3 (2). pp. 255-264.
    Publication Date: 2020-08-04
    Description: The inclination of oceanographic mooring lines due to current drag causes errors in time series observations of currents and temperatures. The prediction of this effect requires knowledge of the drag coefficients for the mooring components. Drag coefficients, known for simple geometric shapes such as spheres or cylinders, are commonly used for mooring response computations. Selected mooring components (buoyancy elements and instruments) were tested in a tow tank to determine their actual drag coefficients. Over the Reynolds Number range, typical of oceanic conditions, deviations of the drag coefficient up to 50% are found when compared with the appropriate simple geometric shape coefficients. A set of model moorings and model current profiles is used to determine the resulting changes in component depth level and displacement. The changes in horizontal displacement of the upper part of the mooring are on the order of 10% in extreme cases and 1% under typical conditions. Their effects on current measurements will usually be negligible. However, the related vertical displacements are on the order 100 to 10 m. Such vertical displacements may carry instruments to depth levels where currents and particularly thermocline temperatures are sufficiently different from the intended level to cause errors in the time series observations.
    Type: Article , PeerReviewed
    Format: text
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  • 16
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 16 (5). pp. 814-826.
    Publication Date: 2018-04-04
    Description: Simulated transient-tracer distributions (tritium, 3H3, freons) on the isopycnal horizons σ0=26.5 and 26.8 kg m−3 are presented for the East Atlantic, 10° −40°N. Tracer transport is modeled by employing a baroclinic flow field based on empirical data in a kinematic isopycnal advection-diffusion numerical model, in which winter convection is taken as the mechanism of communication with the ocean surface layer, and the isopycnal diffusivity is a free parameter. Diapucnic transport is ignored. The simulations employ time-dependent tracer boundary conditions, which are constructed on the basis of available observations. Simulations are compared to data obtained on a meridional section in 1981 (F/S Meteor, cruise 56/5). Best simulations were obtained by means of a subjective optimization procedure. On both levels, the observed distributions and the best simulated distributions agree well. The fact that the surface boundary conditions and interior distributions of the tracers are distinctly different leads us to the conclusion that our model provides a consistent description of upper main-thermocline ventilation and interior transport Surface-water densities in February are found to represent adequately the winter outcrop boundaries with an uncertainty of about ±300 km across. The required isopycnal diffusivity south of 29°N is 1700 m2 s−1, and 2900 m2 s−1 further north (+70/−40%). Interior transport is found to be predominantly advective. Advective ventilation across 30.5°N east of 33°W amounts to only 12% and 40% for the 26.5 and 26.8 horizons of the total ventilation rates reported by Sarmiento. The North Atlantic/South Atlantic Central Water boundary near 15°N is found to be predominantly determined by advection.
    Type: Article , PeerReviewed
    Format: text
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  • 17
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 17 (10). pp. 1561-1570.
    Publication Date: 2020-08-04
    Description: Quasi-homogeneous layers in vertical profiles of temperature and salinity in the eastern North Atlantic near Madeira indicate the existence of a subtropical Mode Water in the Eastern Basin. Temperature sections show a maximum horizontal extent of at least 500 km. The frequency distribution analysis of homogeneous layers in a historical XBT dataset shows a Mode Water formation region near and to the north of Madeira. This Mode Water is found at increasing depths and displaced to the west and southwest during the course of the year after its formation by wintertime convection. It disappears almost completely, due to mixing, before the next winter. Volume estimates suggest that this Madeira Mode Water in the eastern Atlantic accounts for 15–20% of the total Central Water formation in the corresponding density range as obtained from tracer studies in the North Atlantic gyre.
    Type: Article , PeerReviewed
    Format: text
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  • 18
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    Pergamon Press
    In:  Deep Sea Research Part A: Oceanographic Research Papers, 35 (5). pp. 811-837.
    Publication Date: 2020-08-04
    Description: The spatial distribution of the subtropical salinity maximum is identified using historical and recent data from the eastern North Atlantic. In the regions with high frequency of occurrence of the salinity maximum, the relative contributions of advection, eddy diffusion and double diffusion to the salt balance below the maximum salinity layer are determined. McDougall's (1984, Journal of Physical Oceanography, 14, 1577–1589) salt balance equation for neutral surfaces is used in this analysis. The data base consists of two meridional CTD sections along 33° and 27°W between 10° and 35°N, mean temperature-salinity profiles in 5° × 5° squares presented by Emery and Dewar (1982), and mean velocity profiles in 3° × 3° squares evaluated by Stramma (1984, Journal of Marine Research, 42, 537–558). The tropical salinity maximum tongue is found to be quite persistent in its salinity value and its geographic distribution, but less clearly in its vertical or isopycnal position. Double diffusion due to salt-fingering appears to be an important process for the salt balance below the salinity maximum layer. An approximate estimate of the double-diffusive salt flux is obtained. Near the subtropical source region, the double-diffusive salt flux is balanced primarily by isopycnal advection; further to the south it is also balanced by isopycnal eddy diffusion. Maximum double-diffusive fluxes correspond in magnitude to the mean salt flux caused by the excess in evaporation at the surface in the central subtropics. The resulting isopycnal and diapycnal eddy-mixing coefficients derived by a linear inversion technique have the reasonable values of Ki = (11 ± 5) × 102 m2 s−1 and Kd = (4 ± 2) × 10−5 m2 s−1. Considering the intermittency of the double-diffusive process, limiting values for the mean eddy-mixing coefficients are determined by neglecting the contribution of the double-diffusive salt fluxes. This leads to Ki = (5 ± 2) × 102 m2 s−1 and Kd = (5 ± 1) × 10−5 m2 s−1 for the isopycnal and diapycnal mixing coefficients, respectively.
    Type: Article , PeerReviewed
    Format: text
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  • 19
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    Springer
    In:  Deutsche Hydrographische Zeitschrift, 38 (1). pp. 7-22.
    Publication Date: 2016-11-02
    Description: Current data obtained from 7 moorings in the Northeast Atlantic in the course of many years are analysed with respect to semi-diurnal barotropic and baroclinic tides and diurnal barotropic tides. For semi-diurnal tides M2 and S2 the energy distribution is usually dominated by the barotropic mode; only in a few cases does the first-order baroclinic mode contain higher energy. Barotropic tidal ellipse orientations are found to be consistent with results from earlier tide gauge observations in this area. Significant deviations occur, however, in amplitudes. Results for the diurnal component K1 are also presented. With few exceptions, tides are found to be progressive waves in this area. The current ellipse pattern is similar to results obtained indirectly by Cartwright, Edden, Spencer et al. [1980] from tide gauge observations.
    Type: Article , PeerReviewed
    Format: text
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  • 20
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    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 93 (C7). pp. 8111-8118.
    Publication Date: 2017-09-26
    Description: The eastern part of the North Atlantic subtropical gyre is found in the region between the Azores and the Cape Verde Islands. A study of the gyre structure in the area east of 35°W between 8°N and 41°N is presented. The geostrophic flow field determined from historical temperature-salinity data sets by objective analysis indicates seasonal variations in shape but no significant changes in the magnitude of volume transports. The eastern part of the gyre has a larger east-west and smaller north-south extension in summer compared with the winter season. The center shifts by about 2° latitude to the south from winter to summer. Long-term temperature time series (6.5 years) from a mooring near the Azores are consistent with these results, showing always a consistent temperature increase at the beginning of the year which is apparently due to the displacement of the northeastern part of the gyre. A comparison between the mean flow fields and fields obtained from individual zonal sections indicates large deviations north and south of the gyre but small deviations within the gyre.
    Type: Article , PeerReviewed
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