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  • 1
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    The response of drifting buoys to currents and wind (1989)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 94 (C3). pp. 3201-3210.
    Details
    Publication Date: 2020-10-20
    Description: Two buoy types have been tested with respect to their drift performance under drogued and undrogued conditions. Additionally, forces acting on the buoys were measured directly. Quadratic drag laws have been confirmed for the drag in water and the combined drag of wind and waves. Stokes drift contributes about one half to the wind factor of 0.023, which is obtained for undrogued buoys in the Atlantic. The forces on a windowshade drogue are given by a linear relation between force and water velocity for speeds exceeding 10 cm/s. They have been extrapolated to speeds of less than 10 cm/s by both a linear and a quadratic relationship. Correlations between drift and wind speed in the Atlantic suggest that the linear law is a better approximation under realistic conditions. According to these measurements in the Atlantic the described buoy-drogue system with a windowshade drogue in 100-m depth is a good current-measuring device. Slippage is negligible for wind speeds of less than 15 m/s and is less than 2 cm/s under gale conditions. Undrogued buoys are strongly affected by wind and cannot be used for the analysis of currents without correction, even under light winds.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/JC094iC03p03201
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Modelling CFC inventories and formation rates of Labrador Sea Water (2003)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 30 (2). p. 1050.
    Details
    Publication Date: 2018-02-20
    Description: A high-resolution model of the North Atlantic Ocean is used to examine the potential of chlorofluorocarbon (CFC) inventories for calculating the rate of Labrador Sea Water (LSW) formation. While the simulated CFC-11 inventory and its geographical distribution in 1997 is fairly similar to observations, the model indicates pronounced variations in the history of CFC uptake, reflecting pulsations in LSW renewal in response to changes in wintertime atmospheric conditions. The LSW formation rate based on the volume of newly homogenized water during a winter season varies between 0 Sv and 11 Sv, and it is correlated (with a lag of 1 year) with the North Atlantic Oscillation (NAO) Index. The CFC-based estimate of the mean LSW formation rate is 3.5–4.4 Sv, approximately representing the mean volumetric formation rate (4.3 Sv) for the period 1970–1997.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2002GL014855
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Lagrangian perspectives of deep water export from the subpolar North Atlantic (2006)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 33 (L21S08).
    Details
    Publication Date: 2018-02-19
    Description: Direct observations at the Grand Banks have raised a quandary concerning the pathways of the lower branch of the meridional overturning circulation: In contrast to moored current meters that depict an intense, narrow Deep Western Boundary Current (DWBC), observations using different float types failed to show this continuous export path. Here, this issue is addressed by a Lagrangian analysis of synthetic particles in an eddy-resolving circulation model. Due to intense eddy activity around the Grand Banks, about 40% of the deep water in the DWBC is diverted into the interior, spreading southward along the western flank of the Mid-Atlantic Ridge or with the eddying flow field in the basin interior. Imposing constraints on the vertical displacements of particles similar to those experienced by observational floats further reduces their adherence to the DWBC, particularly near the southern tip of the Grand Banks.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2006GL026470
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Decadal variability of subpolar gyre transport and its reveberation in the North Atlantic overturning. (2006)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 33 (L21S01).
    Details
    Publication Date: 2018-02-19
    Description: Analyses of sea surface height (SSH) records based on satellite altimeter data and hydrographic properties have suggested a considerable weakening of the North Atlantic subpolar gyre during the 1990s. Here we report hindcast simulations with high-resolution ocean circulation models that demonstrate a close correspondence of the SSH changes with the volume transport of the boundary current system in the Labrador Sea. The 1990s-decline, of about 15% of the long-term mean, appears as part of a decadal variability of the gyre transport driven by changes in both heat flux and wind stress associated with the North Atlantic Oscillation (NAO). The changes in the subpolar gyre, as manifested in the deep western boundary current off Labrador, reverberate in the strength of the meridional overturning circulation (MOC) in the subtropical North Atlantic, suggesting the potential of a subpolar transport index as an element of a MOC monitoring system.
    Type: Article , PeerReviewed
    DOI: 10.1029/2006GL026906
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Differences in drift behavior between drogued and undrogued satellite-tracked drifting buoys (1991)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 96 (C4). pp. 7249-7263.
    Details
    Publication Date: 2018-07-19
    Description: Drift behavior of drogued and undrogued Hermes‐type buoys is studied. After drogue loss, an increase in drift speed and acceleration is observed as well as improved correlations between drift and wind in both speed and direction. With these criteria, a method for the separation of large data sets into a drogued and an undrogued part has been developed. In most areas of the North Atlantic this works very well; problems arise in regions with strong surface currents and/or light winds. A statistical analysis is performed in a selected area to demonstrate the errors that can be caused by indiscriminate use of drogued and undrogued drifters. Mean and rms velocities as well as kinetic energies change significantly when undrogued buoys are considered. Therefore caution is essential when using surface drifters without drogues.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/90JC02667
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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