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  • 1
    Electronic Resource
    Electronic Resource
    Grußwort (1993)
    Springer
    Ocean dynamics 45 (1993), S. 13-14 
    Details
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02226369
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Langzeitige Änderung des Salzgehaltes in der Unterweser (1983)
    Springer
    Ocean dynamics 36 (1983), S. 61-77 
    Details
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Summary Ever since construction has altered the estuary of the Weser River to make it more navigable, regular water samples were collected at several stations along the river (Fig. 1). Salinities were determined in order to assess possible changes as a consequence of the engineering activities. For almost 100 years the sampling scheme remained unaltered. Today this unique data set (Fig. 3) is of more than local interest. Whereas drastic changes of tidal phenomena are obvious from tidal gauge measurements (Fig. 2), natural fluctuations of salinity hide respective changes of the salinity distribution. We have tried to separate the natural from the man-made fluctuation of salinity using two simple models to eliminate known causes of natural fluctuations. Difficulties encountered were the incompleteness of the data set and the absence of data averaged over cross sections. Nevertheless it was possible to eliminate, approximately, the influence of the catchment area and salinity variations of the adjacent sea. Salinity variations as a consequence of the engineering works depend on the quantity $$K = H^2 /(\bar A \cdot \zeta _0 )$$ , whereH is the depth of a cross-section with area $$\bar A$$ averaged over the tides, and 2 $$\zeta _0 $$ is the tidal elevation. Because of long-term changes of the tides in the North Sea, it was not possible to isolate the influence of the engineering works. Conclusions include consequences for modern sampling strategies to determine trends of water quality.
    Abstract: Résumé Des séries de mesures effectuées depuis une centaine d'années ont permis d'examiner les variations sur une longue période du taux de salinité du cours inférieur de la Weser et leurs causes possibles. Cette étude s'est efforcé de distinguer les effets naturels des effets anthropogènes sur le taux de salinité. Malgré les données incomplètes, l'influence du bassin de drainage et des variations de salinité des zones maritimes limitrophes a pratiquement pu être éliminée. En raison des modifications du régime des marées en Mer du Nord sur une longue période, il n'a pas été possible de formuler des commentaires précis quant à l'impact sur la salinité des travaux de construction entrepris ces 100 dernières années du cours inférieur de la Weser. Les résultats de nos études fournissent des indications utiles pour la mise en place de réseaux modernes de mesure destinés à déterminer la qualité de l'eau.
    Notes: Zusammenfassung Anhand hundertjähriger Meßreihen wurden langfristige Salzgehaltsänderungen in der Unterweser und ihre möglichen Ursachen untersucht. Dabei wurde angestrebt, die natürlichen und die anthropogenen Einflüsse auf den Salzgehalt zu trennen. Trotz des unvollständigen Datensatzes konnten der Einfluß des Einzugsgebietes und Salzgehaltsschwankungen des angrenzenden Meeresgebietes nahezu eliminiert werden. Wegen der langzeitigen Änderungen der Gezeiten in der Nordsee waren genaue Aussagen über die Auswirkung der in den letzten hundert Jahren in der Unterweser durchgeführten Baumaßnahmen auf den Salzgehalt nicht möglich. Unsere Ergebnisse geben Hinweise für moderne Meßnetze zur Bestimmung der Wasserqualität.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02313285
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  • 3
    Electronic Resource
    Electronic Resource
    Barotropic tides in the Northeast Atlantic inferred from moored current meter data (1985)
    Springer
    Ocean dynamics 38 (1985), S. 7-22 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02226433
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  • 4
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    Can the Weak Surface Currents of the Cape Verde Frontal Zone Be Measured With Altimetry? (1993)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 98 (C2). pp. 2485-2493.
    Details
    Publication Date: 2017-10-04
    Description: Three data types are compared in the low-current-velocity regime in the southeastern North Atlantic, between 12-degrees-N and 30-degrees-N, 29-degrees-W and 18-degrees-W: Geosat altimetric sea level and derived surface geostrophic velocities, shallow current meter velocities, and dynamic heights derived from hydrographic data from cruises 4, 6, and 9 of the research vessel Meteor. The four current meter daily time series, at depths around 200 m, were smoothed over 1 month; the altimetric geostrophic velocities were computed from sea surface slopes over 142 km every 17 days. The correlation coefficients between the current meter and altimetric geostrophic velocities range between 0.64 and 0.90 for the moorings near 29-degrees-N but between 0.32 and 0.71 for the two around 21-degrees-N; the associated rms discrepancies between the two measurement types range between 1.5 and 4.4 cm/s, which is 49% to 127% of the rms of the respective current meter time series. Dynamic heights relative to 1950 dbar for the months of November 1986 (d(M4)), November 1987 (d(M6)), and February 1989 (d(M9)) were computed from Meteor cruises 4, 6, and 9. Both dynamic heights and altimetric heights (h(M4), h(M6), h(M9)) were averaged over 1-degrees boxes for the duration of each cruise. Differences d(M4) - d(M6) and d(M9) - d(M6) were computed only at bins where at least one station from both cruises existed, Assuming that dynamic heights d in dynamic centimeters are equivalent to sea level h in centimeters, the standard deviation sigma of the differences ((h(M4) - h(M6)) - (d(M4) - d(M6))) and corresponding M9 - M6 values was 2.1 cm. This value (squared) is only 13% of the (5.8 cm)2 variance of the dynamic height differences and is indistinguishable from the 2.7- to 5.6-cm natural variability of sea level in the area expected between the times when the ship and the satellite sampled the ocean. The areally averaged discrepancy for M9 - M6 was only 0.7 cm, but the corresponding value for M4 - M6 was 5.2 cm. A systematic difference between the water vapor corrections used before and after July 1987 is responsible for the M4 - M6 difference. The average M4 - M6 discrepancy is only 0.1 cm using the Fleet Numerical Oceanography Center correction, with a standard deviation of 3.1 cm. In spite of the underlying differences in sampling and physics, including unknown barotropic components not included in our hydrographic dynamic heights, and in data errors, including water vapor, ionospheric, and orbital effects on the altimetry, consistent interannual changes of the mean sea level from the independently obtained altimetric and hydrographic data sets are obtained, and correlated seasonal changes in surface currents are observed with both altimetry and current meters.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/92JC02729
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  • 5
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    Barotropic tides in the Northeast Atlantic inferred from moored current meter data (1985)
    Springer
    In:  Deutsche Hydrographische Zeitschrift, 38 (1). pp. 7-22.
    Details
    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
    DOI: 10.1007/BF02226433
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  • 6
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    Seasonal Changes in the North Atlantic Subtropical Gyre (1988)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 93 (C7). pp. 8111-8118.
    Details
    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
    Format: text
    DOI: 10.1029/JC093iC07p08111
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  • 7
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    Untersuchungen über die Bedeutung bestimmter Tonfrequenzbänder für die Verständlichkeit synthetischer Sprache und über Änderungen der Sprachverständlichkeit bei Kanalvertauschungen (1961)
    Springer
    In:  Zeitschrift für Angewandte Physik, 13 (6). pp. 275-283.
    Details
    Publication Date: 2019-01-21
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Seasonal Changes in the Tropical Atlantic Circulation: Observation and Simulation of the Guinea Dome (1992)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 97 (C1). pp. 703-715.
    Details
    Publication Date: 2017-09-26
    Description: The Guinea Dome is a permanent, quasi-stationary feature on the eastern side of the thermal ridge extending zonally across the tropical North Atlantic. The dome is a part of the large-scale near-surface flow fields associated with the North Equatorial Current, the North Equatorial Countercurrent and the North Equatorial Undercurrent. In the present study, historical and recently obtained hydrographic data are combined to investigate the thermohaline structure and geostrophic flow field in the vicinity of the dome. It is shown that the Guinea Dome exists throughout the year both in subthermocline and thermocline layers, that it has a corresponding cyclonic geostrophic flow, and that seasonal changes occur with respect to its vertical structure, horizontal extent, and position. The observational results are then compared with simulations from a general circulation model of the tropical Atlantic. A seven-year simulation forced by observed monthly winds is run to compute a monthly climatology. The model adequately simulates the Guinea Dome with respect to its structure, flow field, and seasonal variability.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/91JC02501
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  • 9
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    Long-Period Transport Changes in the Eastern North Atlantic and Their Simulation by Propagating Waves (1993)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 98 (C2). pp. 2393-2406.
    Details
    Publication Date: 2017-09-26
    Description: An analysis is presented of geostrophic volume transport across a zonal line along 28-degrees-N in the eastern Atlantic. The data are from an array of five moorings with 200-km spacing carrying temperature sensors and one current meter each for 1 or 2 years. Transport changes in the main thermocline relative to a fixed depth level are obtained by the use of temperature-salinity relationships. The transport variability is simulated by two propagating waves with first-order baroclinic mode structure. Solutions exist with annual and semi-annual periods and zonal wavelengths of 100-200 km and 300 km, respectively. Assuming quasi-geostrophic dynamics and using results on the Reynolds stress, the dominating waves of annual and semi-annual period are found to propagate to the southwest, with 45-degrees-60-degrees and 25-degrees to the south off the westward direction, respectively. Wave solutions with a 90-day period and a zonal wavelength of about 300 km are interpreted as an effect of barotropic waves arising due to horizontal temperature inhomogeneity. The propagation is about +/-25-degrees off the westward direction. In general, good approximations are obtained with the propagating wave simulations in the western and central part of the array, while large differences occur between observation and simulation close to the Canary archipelago. Possible causes for these differences are discussed.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/92JC02122
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  • 10
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    On the Origin of the Azores Current (1989)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 94 (C5). pp. 6159-6168.
    Details
    Publication Date: 2017-09-26
    Description: The Azores Current, south of the Azores Archipelago, is part of the subtropical North Atlantic gyre. Using an international hydrographic data set, we analyze mean and seasonal geostrophic transport fields in the upper 800 m of the ocean in order to determine the origin of the Azores Current in the western basin and seasonal changes in the related flow. Geostrophic currents are obtained by using the method applied by Stramma (1984) in the eastern basin. The Azores Current is found to originate in the area of the Southwest Newfoundland Rise (Figure 10). In winter an almost uniform current connects this region of origin with the Azores Current, while a branching into two current bands is observed in summer, with the southern band forming a marked cyclonic loop. Within the upper 800 m, all of the transport in the northern band and about 70% of the transport in the southern band recirculates in the eastern basin. Additionally, expendable bathythermograph data from the Azores Current region indicate an increase of eddy potential energy from winter to summer.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/JC094iC05p06159
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