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  • OceanRep  (11)
  • AMS (American Meteorological Society)  (8)
  • Elsevier  (3)
  • 1995-1999  (5)
  • 1985-1989  (5)
  • 1975-1979  (1)
  • 1
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    The Namib Col Current (1995)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 42 (11-12). pp. 1933-1950.
    Details
    Publication Date: 2018-03-08
    Description: Recent measurements indicate the transatlantic extent of the Namib Col Current at depths of 1300-3000 m near Lat. 22 degrees S in the South Atlantic Ocean. This current forms a continuous circulation structure from the Namib Col on the Walvis Ridge to the western trough, though its characteristic change as deepwater with varying properties enters and leaves the current owing to a meridional flow component. Transport estimates from hydrographic sections on the Walvis Ridge and at 15 degrees W near the crest of the Mid-Atlantic Ridge indicate a strength of about 3 x 10(6) m(3) s(-1) The current is part of a larger-scale eastward Row at Lon. 25 degrees W; transport estimates across the salinity maximum core there show a similar strength. Associated with this high-salinity high-oxygen current is a basin-wide front in these properties of varying intensity (weaker in the east) marking the transition to deep water whose North Atlantic characteristics have been partly erased by mixing with Circumpolar Deep Water in the southwest South Atlantic. The water which finally crosses the Walvis Ridge is supplied both by the eastward flow of this (diluted) North Atlantic Deep Water and by a general southeastward interior flow from the northern Angola Basin. Evidence suggests that this deep water continues south in the eastern Cape Basin, leaving the South Atlantic near the African continent.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0967-0637(95)00088-7
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Turbulent momentum and salt transport in the mixing zone of the Elbe estuary (1989)
    Elsevier
    In:  Estuarine, Coastal and Shelf Science, 28 (6). pp. 615-638.
    Details
    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
    DOI: 10.1016/0272-7714(89)90050-4
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    The Volunteer Observing Ship and Future Ocean Monitoring (1995)
    AMS (American Meteorological Society)
    In:  Bulletin of the American Meteorological Society, 76 (1). pp. 5-11.
    Details
    Publication Date: 2019-01-21
    Description: Widespread and sustained in situ ocean measurements are essential to an improved understanding of the state of the ocean and its role in global change. Merchant marine vessels can play a major role in ocean monitoring, yet apart from routine weather observations and upper-ocean temperature measurements, they constitute a vastly underutilized resource due to lack of suitable instrumentation. Examples of ways in which vessels can assist include profiling techniques of physical properties, chemical sampling via automated water samplers, optical techniques to measure various biological parameters, and ground truth measurements for remote sensing from orbiting and geostationary satellites. Further, ships can act as relays between subsurface instrumentation and satellite communication services. To take advantage of the opportunities that the maritime industry can provide, two steps must be taken. The first is to initiate an instrumentation development program with emphasis on techniques optimized for highly automated use onboard ships at 15-20-kt speeds. The second is to forge partnerships or links between academic and government laboratories and the maritime industry for the institution and maintenance of such monitoring programs. No doubt significant resources will be required, but in the long run the improved ability to monitor the state of ocean in situ will make the effort more than worthwhile.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0477(1995)076〈0005:TVOSAF〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Drag Coefficients of Oceanographic Mooring Components (1986)
    AMS (American Meteorological Society)
    In:  Journal of Atmospheric and Oceanic Technology, 3 (2). pp. 255-264.
    Details
    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
    DOI: 10.1175/1520-0426(1986)003〈0255:DCOOMC〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Baroclinic Flow and Transient-Tracer Fields in the Canary–Cape Verde Basin (1986)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 16 (5). pp. 814-826.
    Details
    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
    DOI: 10.1175/1520-0485(1986)016〈0814:BFATTF〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    The Madeira Mode Water (1987)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 17 (10). pp. 1561-1570.
    Details
    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
    DOI: 10.1175/1520-0485(1987)017〈1561:TMMW〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Isopycnal and Diapycnal Mixing at the Cape Verde Frontal Zone (1995)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 25 (8). pp. 1771-1787.
    Details
    Publication Date: 2018-04-05
    Description: The Cape Verde Frontal Zone separates the North and the South Atlantic Central Waters in the eastern North Atlantic. It also represents the boundary between the ventilated subtropical gyre and the quasi-stagnant shadow zone in the southeast. The thermohaline front is nearly compensated with respect to density, and density parameters RP, suggest the existence of double-diffusive processes. Datasets from three cruises to the region, approximately one year apart each, are used to determine the effects of double-diffusive diapycnal versus isopycnal mixing. For this purpose results from the usual temperature-salinity analysis assuming isopycnal mixing are compared to results from a multiparameter analysis where nutrient and oxygen data are also used. Significant diapycnal fluxes are found in the frontal zone between 200 and 300 m, with water mass contents being changed by more than 20% through diapycnal mixing. The associated buoyancy fluxes have a similar magnitude as surface fluxes in the area and thus represent an important contribution to the vertical balances of heat and salt.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0485(1995)025〈1771:IADMAT〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Antarctic Bottom Water Flow through the Hunter Channel (1999)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 29 (11). pp. 2785-2801.
    Details
    Publication Date: 2020-08-04
    Description: The Rio Grande Rise acts as a natural barrier for the equatorward flow of Antarctic Bottom Water in the subtropical South Atlantic. In addition to the Vema Channel, the Hunter Channel cuts through this obstacle and offers a separate route for bottom-water import into the southern Brazil Basin. On the occasion of the Deep Basin Experiment, a component of the World Ocean Circulation Experiment (WOCE), the expected deep flow through the Hunter Channel was directly observed for the first time by an array of moored current meters and thermistor chains from December 1992 to May 1994. Main results are (i) the Hunter Channel is, in fact, a conduit for bottom-water flow into the Brazil Basin. Our new mean transport from moored current meters [2.92 (±1.24) × 106 m3 s−1] is significantly higher than earlier estimates that were based on geostrophic calculations. (ii) During the WOCE observational period a tendency toward increased bottom-water temperatures was observed. This observation from the Hunter Channel is consistent with findings from the Vema Channel. (iii) The overflow through the Hunter Channel is highly variable and puts in perspective earlier synoptic geostrophic transport estimates
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0485(1999)029〈2785:ABWFTT〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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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
  • 10
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    Strong Current Events Related to a Subtropical Front in the Northeast Atlantic (1985)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 15 (7). pp. 885-897.
    Details
    Publication Date: 2020-08-04
    Description: Long-term temperature and current-meter records from moorings in the northern Canary Basin display strong current events with time scales between one and three months and large vertical scales of several thousand meters. The data are compared to hydrographic surveys in the area that show a meandering subtropical front. The strong current events are found to be related to the passage of the front through the mooring positions. An analysis of composite time series, for selected depths, indicates cases of westward and of eastward propagation of frontal meanders. The frontal pattern is also found in geopotential anomalies inferred from historical XBT data sets, suggesting that the front is a persistent feature of the density field. In two cases strong current events appear to be related to a Mediterranean Water lens.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0485(1985)015〈0885:SCERTA〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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