• Bracco, A., and J. Pedlosky, 2003: Vortex generation by topography in locally unstable baroclinic flows. J. Phys. Oceanogr., 33 , 207219.

    • Search Google Scholar
    • Export Citation
  • Bracco, A., A. Provenzale, E. A. Spiegel, and P. A. Jecko, 1999: Spotted disks. Theory of Black Hole Accretion Disks, M. Abramowicz, G. Björnsson, and J. Pringle, Eds., Cambridge University Press, 293 pp.

    • Search Google Scholar
    • Export Citation
  • Brandt, P., F. A. Schott, A. Funk, and C. S. Martins, 2004: Seasonal to interannual variability of the eddy field in the Labrador Sea from satellite altimetry. J. Geophys. Res., 109 .C02028, doi:10.1029/2002JC001551.

    • Search Google Scholar
    • Export Citation
  • Buch, E., S. A. Pedersen, and M. H. Ribergaard, 2004: Ecosystem variability in West Greenland waters. J. Northwest Atlantic Fish. Sci., 34 , 1328.

    • Search Google Scholar
    • Export Citation
  • Carnevale, G. F., G. K. Vallis, R. Purini, and M. Briscolini, 1988: Propagation of barotropic modons over topography. Geophys. Astrophys. Fluid Dyn., 41 , 45101.

    • Search Google Scholar
    • Export Citation
  • Carnevale, G. F., R. C. Kloosterziel, and G. J. F. van Heijst, 1991: Propagation of barotropic vortices over topography in a rotating tank. J. Fluid Mech., 233 , 119139.

    • Search Google Scholar
    • Export Citation
  • Carnevale, G. F., O. U. Velasco Fuentes, and P. Orlandi, 1997: Inviscid dipole-vortex rebound from a wall or coast. J. Fluid Mech., 351 , 75103.

    • Search Google Scholar
    • Export Citation
  • Carnevale, G. F., S. G. Llewellyn Smith, F. Crisciani, R. Purini, and R. Serravalle, 1999: Bifurcation of a coastal current at an escarpment. J. Phys. Oceanogr., 29 , 969985.

    • Search Google Scholar
    • Export Citation
  • Cuny, J., P. B. Rhines, P. P. Niiler, and S. Bacon, 2002: Labrador Sea boundary currents and the fate of the Irminger Sea Water. J. Phys. Oceanogr., 32 , 627647.

    • Search Google Scholar
    • Export Citation
  • Czeschel, L., 2005: The role of eddies for the deep water formation in the Labrador Sea. Ph.D. thesis, Mathematisch-Naturwissenschaftliche Fakultat, Christian-Albrechts-Universitat zu Kiel, 101 pp.

  • Dengler, M., J. Fisher, F. A. Schott, and R. Zantopp, 2006: Deep Labrador Current and its variability in 1996–2005. Geophys. Res. Lett., 33 .L21S06, doi:101029:2006GL026702.

    • Search Google Scholar
    • Export Citation
  • Dewar, W. K., and C. Gailliard, 1994: The dynamics of barotropically dominated rings. J. Phys. Oceanogr., 24 , 529.

  • Eden, C., and C. Böning, 2002: Sources of eddy kinetic energy in the Labrador Sea. J. Phys. Oceanogr., 32 , 33463363.

  • Hátún, H., A. B. Sandø, H. Drange, B. Hansen, and H. Valdimarsson, 2005: Influence of the Atlantic subpolar gyre on the thermocline circulation. Science, 309 , 18411844.

    • Search Google Scholar
    • Export Citation
  • Hátún, H., C. Eriksen, P. B. Rhines, and J. Lilly, 2007: Buoyant eddies entering the Labrador Sea observed with gliders and altimetry. J. Phys. Oceanogr., 37 , 28382854.

    • Search Google Scholar
    • Export Citation
  • Heywood, K. J., E. L. McDonagh, and M. A. White, 1994: Eddy kinetic energy of the North Atlantic subpolar gyre from satellite altimetry. J. Geophys. Res., 99 , 2252522539.

    • Search Google Scholar
    • Export Citation
  • Jacob, J. P., E. P. Chassignet, and W. K. Dewar, 2002: Influence of topography on the propagation of isolated eddies. J. Phys. Oceanogr., 32 , 28482869.

    • Search Google Scholar
    • Export Citation
  • Katsman, C. A., M. A. Spall, and R. S. Pickart, 2004: Boundary current eddies and their role in the restratification of the Labrador Sea. J. Phys. Oceanogr., 34 , 19671983.

    • Search Google Scholar
    • Export Citation
  • LaCasce, J. H., 1998: A geostrophic vortex on a slope. J. Phys. Oceanogr., 28 , 23622381.

  • Lilly, J. M., P. B. Rhines, F. Schott, K. Lavender, J. Lazier, U. Send, and E. D’Asaro, 2003: Observations of the Labrador Sea eddy field. Prog. Oceanogr., 59 , 75176.

    • Search Google Scholar
    • Export Citation
  • McWilliams, J. C., and G. R. Flierl, 1979: On the evolution of isolated, nonlinear vortices. J. Phys. Oceanogr., 9 , 11551182.

  • Pedlosky, J., 1987: Geophysical Fluid Dynamics. 2nd ed. Springer-Verlag, 710 pp.

  • Pickart, R. S., and M. A. Spall, 2007: Impact of Labrador Sea convection on the North Atlantic meridional overturning circulation. J. Phys. Oceanogr., 37 , 22072227.

    • Search Google Scholar
    • Export Citation
  • Prater, M. D., 2002: Eddies in the Labrador Sea as observed by profiling RAFOS floats and remote sensing. J. Phys. Oceanogr., 32 , 411427.

    • Search Google Scholar
    • Export Citation
  • Samelson, R. M., and J. Pedlosky, 1990: Local baroclinic instability of flow over variable topography. J. Fluid Mech., 221 , 411436.

  • Sathiyamoorthy, S., and G. W. K. Moore, 2002: Buoyancy flux at Ocean Weather Station Bravo. J. Phys. Oceanogr., 32 , 458474.

  • Spall, M. A., 2004: Boundary current and water mass transformation in marginal seas. J. Phys. Oceanogr., 34 , 11971213.

  • Whitehead, J. A., M. E. Stern, G. R. Flierl, and B. A. Klinger, 1990: Experimental observations of baroclinic eddies on a sloping bottom. J. Geophys. Res., 95 , 95859610.

    • Search Google Scholar
    • Export Citation
  • Wolfe, C. L., and C. Cenedese, 2006: Laboratory experiments of eddy generation by a buoyant coastal current flowing over variable bathymetry. J. Phys. Oceanogr., 36 , 395411.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 145 55 4
PDF Downloads 109 39 4

Eddy Formation near the West Coast of Greenland

Annalisa BraccoDepartment of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

Search for other papers by Annalisa Bracco in
Current site
Google Scholar
PubMed
Close
,
Joseph PedloskyDepartment of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

Search for other papers by Joseph Pedlosky in
Current site
Google Scholar
PubMed
Close
, and
Robert S. PickartDepartment of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

Search for other papers by Robert S. Pickart in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

This paper extends A. Bracco and J. Pedlosky’s investigation of the eddy-formation mechanism in the eastern Labrador Sea by including a more realistic depiction of the boundary current. The quasigeostrophic model consists of a meridional, coastally trapped current with three vertical layers. The current configuration and topographic domain are chosen to match, as closely as possible, the observations of the boundary current and the varying topographic slope along the West Greenland coast. The role played by the bottom-intensified component of the boundary current on the formation of the Labrador Sea Irminger Rings is explored. Consistent with the earlier study, a short, localized bottom-trapped wave is responsible for most of the perturbation energy growth. However, for the instability to occur in the three-layer model, the deepest component of the boundary current must be sufficiently strong, highlighting the importance of the near-bottom flow. The model is able to reproduce important features of the observed vortices in the eastern Labrador Sea, including the polarity, radius, rate of formation, and vertical structure. At the time of formation, the eddies have a surface signature as well as a strong circulation at depth, possibly allowing for the transport of both surface and near-bottom water from the boundary current into the interior basin. This work also supports the idea that changes in the current structure could be responsible for the observed interannual variability in the number of Irminger Rings formed.

Corresponding author address: Annalisa Bracco, School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, GA 30306. Email: abracco@gatech.edu

Abstract

This paper extends A. Bracco and J. Pedlosky’s investigation of the eddy-formation mechanism in the eastern Labrador Sea by including a more realistic depiction of the boundary current. The quasigeostrophic model consists of a meridional, coastally trapped current with three vertical layers. The current configuration and topographic domain are chosen to match, as closely as possible, the observations of the boundary current and the varying topographic slope along the West Greenland coast. The role played by the bottom-intensified component of the boundary current on the formation of the Labrador Sea Irminger Rings is explored. Consistent with the earlier study, a short, localized bottom-trapped wave is responsible for most of the perturbation energy growth. However, for the instability to occur in the three-layer model, the deepest component of the boundary current must be sufficiently strong, highlighting the importance of the near-bottom flow. The model is able to reproduce important features of the observed vortices in the eastern Labrador Sea, including the polarity, radius, rate of formation, and vertical structure. At the time of formation, the eddies have a surface signature as well as a strong circulation at depth, possibly allowing for the transport of both surface and near-bottom water from the boundary current into the interior basin. This work also supports the idea that changes in the current structure could be responsible for the observed interannual variability in the number of Irminger Rings formed.

Corresponding author address: Annalisa Bracco, School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, GA 30306. Email: abracco@gatech.edu

Save