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  • AGU (American Geophysical Union)  (14)
  • Elsevier  (13)
  • Academic Press  (2)
  • Hamburg : Leitstelle Meteor, Inst. für Meereskunde der Univ. Hamburg  (2)
  • Marine Technology Society  (2)
  • 11
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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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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 12
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    First resolution of flow through the Hunter Channel in the South Atlantic (1992)
    Elsevier
    In:  Earth and Planetary Science Letters, 113 (1-2). pp. 287-292.
    Details
    Publication Date: 2018-03-02
    Description: Dense Antarctic Bottom Water formed around the continent of Antarctica spreads northward in the Atlantic underneath North Atlantic Deep Water, gradually mixing and upwelling into it. This Antarctic Water forms a significant element of the meridional circulation in both directions: northward as bottom water and southward as deep water. It is important to determine the strength of each component to assess its role in ocean circulation. Such measurements are useful when made in constricted pathways because any flow is more clearly defined. A new set of fine-resolution hydrograhic measurements in the Hunter Channel of the South Atlantic Ocean has been obtained, which allow the geostrophic bottom flow there to be estimated for the first time. The northward flow through the Hunter Channel of water cooler than 2-degrees-C is thus estimated to be 0.7 X 10(6) m3 s-1.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0012-821X(92)90226-L
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 13
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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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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 14
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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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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 15
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    Barotropic and Baroclinic Tidal Currents in the Eastern Basins of the North Atlantic (1991)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 96 (C12). pp. 22259-22271.
    Details
    Publication Date: 2017-09-26
    Description: Data from a large-scale moored array in the Iberian and Canary basins are used to determine the energies of barotropic and baroclinic M2 and S2 tides. An analysis of time-varying dynamical modes is performed. The results for barotropic modes confirm the global surface tide model results of Schwiderski (1980) for this region. The barotropic modes dominate in the deep basins, but increased baroclinic contributions are usually found over rough topography. At three locations near the continental slope in the southern Canary Basin the baroclinic modes dominate the barotropic mode. Results from an array of three moorings at the northern part of the Cape Verde Rise show an inverse behavior of barotropic and baroclinic energies, such that the baroclinic energy is steadily enhanced while the barotropic energy is reduced towards the continental margin. The increase in baroclinic energy is consistent with a generation of internal tides close to the shelf by surface tidal forcing over topography. Further evidence for this process is provided by the 2-week periodicity of the first-order baroclinic mode at the slope, corresponding to the spring-neap cycle of the barotropic tide.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/91JC02319
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 16
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    Walter Zenk: a distinguished ocean observer (2005)
    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 52 (3-4). pp. 375-381.
    Details
    Publication Date: 2020-08-05
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.dsr2.2004.12.002
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 17
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    Energy conversion in the Cape Verde Frontal Zone (1998)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 103 (C10). 21,469-21,479.
    Details
    Publication Date: 2018-04-30
    Description: Mechanical energy terms are calculated from moored current meter data in the Cape Verde Frontal Zone (about 20°N, 25°W) and compared with those derived from a mesoscale model of this frontal region. The model is of the Bleck and Boudra [1981] type with isopycnal coordinates. An initially zonal jet, representing the Canary Current, is allowed to develop under the influence of baroclinic and barotropic instability processes. We find reasonable agreement in magnitudes, somewhat smaller in the model, and similar distributions in the vertical. This leads to the conclusion that the energy transfer terms from the model can be expected to be sufficiently close to reality. Determination of the transfer terms confirms that the energy transfer in the zone is dominated by baroclinic instability processes while barotropic instability is of minor importance. Average baroclinic instability energy transfer terms reach values of 2–3 μW m−3 in the pycnocline. Peak layer mean values are of the order 10 μW m−3. It is shown that the spatial distribution of active transfer regions is closely related to the structure of the transient eddy field in the frontal zone and that strong instability processes are restricted to the pycnocline.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/98JC01887
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 18
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    Mooring systems used in the Eastern Atlantic (1967)
    Marine Technology Society
    In:  Transactions of the International Buoy Technology Symposium, 1967 . pp. 77-83.
    Details
    Publication Date: 2017-06-26
    Type: Article , NonPeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - without review
  • 19
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    Consistency Relations for Internal Waves (1976)
    Elsevier
    In:  Deep Sea Research and Oceanographic Abstracts, 23 (7). pp. 613-628.
    Details
    Publication Date: 2018-03-08
    Description: A complete set of linearly independent relationships among the different cross spectral components obtained from pairs of moored instruments is derived which can be utilized to test whether or not the observed fluctuations within the internal wave frequency band represent a field of propagating internal waves. A further complete set of relationships is derived which enables to test whether or not the internal wave field is horizontally isotropic and (or) vertically symmetric. These relations are compared with corresponding relations for alternative models (standing internal wave modes, three-dimensional isotropic turbulence) and their capability to discriminate between the various models is investigated. The tests are applied to a set of data for which it is found that the observed fluctuations are consistent with both propagating and standing internal waves whereas isotropic turbulence must be rejected for the most part of the internal wave frequency band.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0011-7471(76)90004-8,
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 20
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    Path of the North Atlantic Deep Water in the Brazil Basin (1998)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 103 (C3). pp. 5419-5428.
    Details
    Publication Date: 2018-04-30
    Description: Recent hydrographic sections and high-quality historical data sets are used to determine geostrophic currents at subtropical latitudes in the western basin of the South Atlantic. Levels of no motion are determined from water mass information and a mass balance constraint to obtain the transport field of North Atlantic Deep Water (NADW) in this region. The incoming NADW transport of about 20 Sv from the north at 19 degrees S appears to be balanced by only one third of this transport leaving in the south and two thirds leaving to the east or northeast at the Mid-Atlantic Ridge. A simple model is proposed to determine the cause of the NADW branching. It is shown that potential vorticity preservation in the presence of topographic changes leads to a similar flow pattern as observed, with branching near the Vitoria-Trindade-Ridge and also an eastward turning of the southward western boundary current at about 28 degrees S, the latitude where a balance of planetary vorticity change and stretching can be expected.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/97JC03287
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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