• Arneborg, L., V. Fiekas, L. Umlauf, and H. Burchard, 2007: Gravity current dynamics and entrainment—A process study based on observations in the Arkona Basin. J. Phys. Oceanogr., 37, 20942113.

    • Search Google Scholar
    • Export Citation
  • Beaird, N., I. Fer, P. Rhines, and C. Eriksen, 2012: Dissipation of turbulent kinetic energy inferred from Seagliders: An application to the eastern Nordic Seas overflows. J. Phys. Oceanogr., 42, 22682282.

    • Search Google Scholar
    • Export Citation
  • Darelius, E., I. Fer, and D. Quadfasel, 2011: Faroe Bank Channel overflow: Mesoscale variability. J. Phys. Oceanogr., 41, 2137–2154.

  • Egbert, G. D., S. Y. Erofeeva, and R. D. Ray, 2010: Assimilation of altimetry data for nonlinear shallow-water tides: Quarter-diurnal tides of the Northwest European Shelf. Cont. Shelf Res.,30, 668–679, doi:10.1016/j.csr.2009.10.011.

  • Ezer, T., 2006: Topographic influence on overflow dynamics: Idealized numerical simulations and the Faroe Bank Channel overflow. J. Geophys. Res., 111, C02002, doi:10.1029/2005JC003195.

    • Search Google Scholar
    • Export Citation
  • Fer, I., 2009: Weak vertical diffusion allows maintenace of cold halocline in the central Arctic. Atmos. Oceanic Sci. Lett., 2, 148152.

    • Search Google Scholar
    • Export Citation
  • Fer, I., G. Voet, K. S. Seim, B. Rudels, and K. Latarius, 2010: Intense mixing of the Faroe Bank Channel overflow. Geophys. Res. Lett., 37, L02604, doi:10.1029/2009GL041924.

    • Search Google Scholar
    • Export Citation
  • GEBCO, cited 2012: General Bathymetric Chart of the Oceans (GEBCO). [Available online at www.gebco.net.]

  • Geyer, F., S. Østerhus, B. Hansen, and D. Quadfasel, 2006: Observations of highly regular oscillations in the overflow plume downstream of the Faroe Bank Channel. J. Geophys. Res., 111, C12020, doi:10.1029/2006JC003693.

    • Search Google Scholar
    • Export Citation
  • Hansen, B., and S. Østerhus, 2007: Faroe Bank Channel overflow 1995-2005. Prog. Oceanogr., 75, 817856.

  • Høyer, J. L., and D. Quadfasel, 2001: Detection of deep overflows with satellite altimetry. Geophys. Res. Lett., 28, 16111614.

  • Mauritzen, C., J. Price, T. Sanford, and D. Torres, 2005: Circulation and mixing in the Faroese Channels. Deep-Sea Res. I, 52, 883913.

    • Search Google Scholar
    • Export Citation
  • Pickart, R., 1995: Gulf stream-generated topographic Rossby waves. J. Phys. Oceanogr., 25, 574586.

  • Rhines, P., 1970: Edge, bottom, and Rossby waves in a rotating stratified fluid. J. Fluid Mech., 69, 273302.

  • Seim, K., I. Fer, and J. Berntsen, 2010: Regional simulations of the Faroe Bank Channel overflow using a sigma-coordinate ocean model. Ocean Modell., 35 (1–2), 3144.

    • Search Google Scholar
    • Export Citation
  • Sherwin, T. J., M. O. Williams, W. R. Turrell, S. L. Hughes, and P. I. Miller, 2006: A description and analysis of mesoscale variability in the Faroe-Shetland Channel. J. Geophys. Res., 111, C03003, doi:10.1029/2005JC002867.

    • Search Google Scholar
    • Export Citation
  • Voet, G., and D. Quadfasel, 2010: Entrainment in the Denmark Strait overflow plume by meso-scale eddies. Ocean Sci., 6, 301310.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 2 2 2
PDF Downloads 0 0 0

Observations of Barotropic Oscillations and Their Influence on Mixing in the Faroe Bank Channel Overflow Region

View More View Less
  • 1 Geophysical Institute, University of Bergen, Bergen, Norway
Restricted access

Abstract

Observations of hydrography, currents, and microstructure are presented together with sea surface height (SSH) patterns from concurrent satellite tracks to describe the subinertial oscillations in the region downstream of the Faroe Bank Channel overflow. Energetic oscillations with a dominant 3–5-day period have previously been observed in the dense bottom layer and found to be consistent with topographic Rossby waves. Here, the authors present evidence that the oscillations extend over the whole water column and are connected to a wave-like pattern in SSH along the continental slope. The waves are observed in two satellite tracks running parallel to the slope and indicate a wavelength of 50–75 km, an amplitude of about 5 cm, and a phase speed of 15–20 cm s−1. The pattern extends at least 450 km along the slope. Repeat occupations of a section through a 4-day period show a barotropic velocity anomaly that is associated with an increase in plume transport [from 0.5 to 2.5 Sv (1 Sv ≡ 106 m3 s−1)] and interface height (from 100 to 200 m) as well as changes in dissipation rates and mixing. Estimates of entrainment velocity wE vary with a factor of 102 over the oscillation period, and there is an inverse relation between wE and plume thickness, that is, mixing is most intense when the dense bottom layer is thin. High values of wE coincide with a large percentage of critical Richardson numbers in the interfacial layer. The rotational motion, or the horizontal “stirring,” is observed to bring water from the south, traceable because of its low oxygen concentrations, into the plume.

Corresponding author address: E. Darelius, Geophysical Institute, University of Bergen, Alleg. 70, 5007 Bergen, Norway. E-mail: darelius@gfi.uib.no

Abstract

Observations of hydrography, currents, and microstructure are presented together with sea surface height (SSH) patterns from concurrent satellite tracks to describe the subinertial oscillations in the region downstream of the Faroe Bank Channel overflow. Energetic oscillations with a dominant 3–5-day period have previously been observed in the dense bottom layer and found to be consistent with topographic Rossby waves. Here, the authors present evidence that the oscillations extend over the whole water column and are connected to a wave-like pattern in SSH along the continental slope. The waves are observed in two satellite tracks running parallel to the slope and indicate a wavelength of 50–75 km, an amplitude of about 5 cm, and a phase speed of 15–20 cm s−1. The pattern extends at least 450 km along the slope. Repeat occupations of a section through a 4-day period show a barotropic velocity anomaly that is associated with an increase in plume transport [from 0.5 to 2.5 Sv (1 Sv ≡ 106 m3 s−1)] and interface height (from 100 to 200 m) as well as changes in dissipation rates and mixing. Estimates of entrainment velocity wE vary with a factor of 102 over the oscillation period, and there is an inverse relation between wE and plume thickness, that is, mixing is most intense when the dense bottom layer is thin. High values of wE coincide with a large percentage of critical Richardson numbers in the interfacial layer. The rotational motion, or the horizontal “stirring,” is observed to bring water from the south, traceable because of its low oxygen concentrations, into the plume.

Corresponding author address: E. Darelius, Geophysical Institute, University of Bergen, Alleg. 70, 5007 Bergen, Norway. E-mail: darelius@gfi.uib.no
Save