• Baringer, M. O., , and J. F. Price, 1997a: Mixing and spreading of the Mediterranean outflow. J. Phys. Oceanogr., 27 , 16541677.

  • Baringer, M. O., , and J. F. Price, 1997b: Momentum and energy balance of the Mediterranean outflow. J. Phys. Oceanogr., 27 , 16781692.

  • Batchelor, G. K., 1959: Small-scale variation of convected quantities like temperature in a turbulent fluid. I. General discussion and the case of small conductivity. J. Fluid Mech., 5 , 113133.

    • Search Google Scholar
    • Export Citation
  • Baumert, H., , and H. Peters, 2000: Second moment closures and length scales for stratified turbulent shear flows. J. Geophys. Res., 105 , 64536468.

    • Search Google Scholar
    • Export Citation
  • Bell, T. H., 1978: Radiation damping of inertial oscillations in the upper ocean. J. Fluid Mech., 88 , 289308.

  • Bower, A. S., , H. D. Hunt, , and J. F. Price, 2000: Character and dynamics of the Red Sea and Persian Gulf outflows. J. Geophys. Res., 105 , 63876414.

    • Search Google Scholar
    • Export Citation
  • Busch, N. E., 1977: Fluxes in the surface boundary layer over the sea. Modelling and Prediction of the Upper Layers of the Ocean, E. B. Kraus, Ed., Pergamon, 72–91.

  • Chave, A. D., , D. J. Thomson, , and M. E. Ander, 1987: On the robust estimation of power spectra, coherences, and transfer functions. J. Geophys. Res., 92 , 633648.

    • Search Google Scholar
    • Export Citation
  • Crawford, W. R., 1986: A comparison of length scales and decay times of turbulence in stratified flows. J. Phys. Oceanogr., 16 , 18471854.

    • Search Google Scholar
    • Export Citation
  • Dillon, T. M., 1982: Vertical overturns: A comparison of Thorpe and Ozmidov length scales. J. Geophys. Res., 87 , 96019613.

  • Dillon, T. M., , and M. M. Park, 1987: The available potential energy of overturns as an indicator of mixing in the seasonal thermocline. J. Geophys. Res., 92 , 53455353.

    • Search Google Scholar
    • Export Citation
  • Ellison, T. H., , and J. S. Turner, 1959: Turbulent entrainment in stratified flows. J. Fluid Mech., 6 , 423448.

  • Ferron, B., , H. Mercier, , K. Speer, , A. Gargett, , and K. Polzin, 1998: Mixing in the Romanche Fracture Zone. J. Phys. Oceanogr., 28 , 19291945.

    • Search Google Scholar
    • Export Citation
  • Firing, E., , and R. Gordon, 1990: Deep ocean acoustic Doppler current profiling. Proc. IEEE Fourth Working Conf. on Current Measurements, Clinton, MD, IEEE, 192–201.

  • Fischer, J., , and M. Visbeck, 1993: Deep velocity profiling with self-contained ADCPs. J. Atmos. Oceanic Technol., 10 , 764773.

  • Galbraith, P. S., , and D. E. Kelley, 1996: Identifying overturns in CTD profiles. J. Atmos. Oceanic Technol., 13 , 688702.

  • Gregg, M. C., 1987: Diapycnal mixing in the thermocline: A review. J. Geophys. Res., 92 , 52495286.

  • Gregg, M. C., , and W. C. Hess, 1985: Dynamic response calibration of Sea-Bird temperature and conductivity probes. J. Atmos. Oceanic Technol., 2 , 304313.

    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., , R. G. Lueck, , and T. B. Sanford, 1994a: Stress on the Mediterranean outflow plume: Part II. Turbulent dissipation and shear measurements. J. Phys. Oceanogr., 24 , 20842092.

    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., , T. B. Sanford, , and M. O. Baringer, 1994b: Stress on the Mediterranean outflow plume: Part I. Velocity and water property measurements. J. Phys. Oceanogr., 24 , 20722083.

    • Search Google Scholar
    • Export Citation
  • Lhermitte, R. M., 1968: Turbulent air motion as observed by Doppler radar. Proc. 13th Radar Meteorology Conf., Montreal, QC, Canada, Amer. Meteor. Soc., 498–503.

  • Lohrmann, A., , B. Hackett, , and L. D. Roed, 1990: High resolution measurements of turbulence, velocity, and stress using a pulse-to-pulse coherent sonar. J. Atmos. Oceanic Technol., 7 , 1937.

    • Search Google Scholar
    • Export Citation
  • Lu, Y., , and R. G. Lueck, 1999: Using a broadband ADCP in a tidal channel. Part II: Turbulence. J. Atmos. Oceanic Technol., 16 , 15681579.

    • Search Google Scholar
    • Export Citation
  • Munk, W., 1981: Internal waves and small-scale processes. Evolution of Physical Oceanography, B. A. Warren and C. Wunsch, Eds., MIT Press, 264–291.

  • Murray, S. P., , and W. E. Johns, 1997: Direct observations of seasonal exchange through the Bab el Mandeb Strait. Geophys. Res. Lett., 24 , 25572560.

    • Search Google Scholar
    • Export Citation
  • Osborn, T. R., 1980: Estimates of the local rate of vertical diffusion from dissipation measurements. J. Phys. Oceanogr., 10 , 8389.

  • Peters, H., 1997: Observations of stratified turbulent mixing in an estuary. Neap-to-spring variations during high river flow. Estuarine Coastal Shelf Sci., 45 , 6988.

    • Search Google Scholar
    • Export Citation
  • Peters, H., 1999: Spatial and temporal variability of turbulent mixing in an estuary. J. Mar. Res., 57 , 805845.

  • Peters, H., , and R. Bokhorst, 2001: Microstructure observations of turbulent mixing in a partially mixed estuary. Part II: Salt flux and stress. J. Phys. Oceanogr., 31 , 11051119.

    • Search Google Scholar
    • Export Citation
  • Peters, H., , M. C. Gregg, , and J. M. Toole, 1988: On the parameterization of equatorial turbulence. J. Geophys. Res., 93 , 11991218.

  • Peters, H., , M. C. Gregg, , and T. B. Sanford, 1995: Detail and scaling of turbulent overturns in the Pacific Equatorial Undercurrent. J. Geophys. Res., 100 , 1834918368.

    • Search Google Scholar
    • Export Citation
  • Peters, H., , W. E. Johns, , A. S. Bower, , and D. M. Fratantoni, 2005: Mixing and entrainment in the Red Sea outflow plume. Part I: Plume structure. J. Phys. Oceanogr., 35 , 569583.

    • Search Google Scholar
    • Export Citation
  • Phillips, O. M., 1977: The Dynamics of the Upper Ocean. 2d ed. Cambridge University Press, 336 pp.

  • Piera, J., , E. Roget, , and J. Catalan, 2002: Turbulent patch identification in microstructure profiles: A method based on wavelet denoising and Thorpe displacement analysis. J. Atmos. Oceanic Technol., 19 , 13901402.

    • Search Google Scholar
    • Export Citation
  • Polzin, K. L., , K. G. Speer, , J. M. Toole, , and R. W. Schmitt, 1996: Intense mixing of Antarctic Bottom Water in the Equatorial Atlantic Ocean. Nature, 380 , 5457.

    • Search Google Scholar
    • Export Citation
  • Polzin, K. L., , J. M. Toole, , J. R. Ledwell, , and R. W. Schmitt, 1997: Spatial variability of turbulent mixing in the abyssal ocean. Science, 276 , 9396.

    • Search Google Scholar
    • Export Citation
  • Polzin, K., , E. Kunze, , J. Hummon, , and E. Firing, 2002: The finescale response of lowered ADCP velocity profiles. J. Atmos. Oceanic Technol., 19 , 205224.

    • Search Google Scholar
    • Export Citation
  • Price, J. F., , and M. O. Baringer, 1994: Outflows and deep water production by marginal seas. Progress in Oceanography, Vol. 33, Pergamon, 161–200.

    • Search Google Scholar
    • Export Citation
  • Rippeth, T. P., , J. H. Simpson, , E. Williams, , and M. E. Inall, 2003: Measurement of the rates of production and dissipation of turbulent kinetic energy in an energetic tidal flow: Red Wharf Bay revisited. J. Phys. Oceanogr., 33 , 18891901.

    • Search Google Scholar
    • Export Citation
  • Schumann, U., , and T. Gerz, 1995: Turbulent mixing in stably stratified shear flows. J. Appl. Meteor., 34 , 3348.

  • SCOR Working Group 51, Ed.,. 1988: The Acquisition, Calibration and Analysis of CTD Data. Vol. 54, Unesco Technical Papers in Marine Science, Unesco, 94 pp.

    • Search Google Scholar
    • Export Citation
  • Stacey, M. T., , S. G. Monismith, , and J. R. Burau, 1999a: Measurements of Reynolds stress profiles in unstratified tidal flow. J. Geophys. Res., 104 , 1093310949.

    • Search Google Scholar
    • Export Citation
  • Stacey, M. T., , S. G. Monismith, , and J. R. Burau, 1999b: Observations of turbulence in a partially stratified estuary. J. Phys. Oceanogr., 29 , 19501970.

    • Search Google Scholar
    • Export Citation
  • Thorpe, S. A., 1977: Turbulence and mixing in a Scottish loch. Philos. Trans. Roy. Soc. London, A286 , 125181.

  • Tropea, C., 1983: A note concerning the use of a one-component lda to measure stress terms. Exp. Fluids I, 10 , 209210.

  • Turner, J. S., 1986: Turbulent entrainment: The development of the entrainment assumption, and its applications to geophysical flows. J. Fluid Mech., 173 , 431471.

    • Search Google Scholar
    • Export Citation
  • Visbeck, M., 2002: Deep velocity profiling using lowered acoustic Doppler current profilers: Bottom track and inverse solutions. J. Atmos. Oceanic Technol., 19 , 794807.

    • Search Google Scholar
    • Export Citation
  • Wesson, J. C., , and M. C. Gregg, 1994: Mixing at Camarinal Sill in the Strait of Gibraltar. J. Geophys. Res., 99 , 98479878.

  • Wijesekera, H. W., , and T. M. Dillon, 1997: Shannon entropy as an indicator of age for turbulent overturns in the oceanic thermocline. J. Geophys. Res., 102 , 32793291.

    • Search Google Scholar
    • Export Citation
  • Wilson, W., 1994: Deep ocean current profiling with a broadband acoustic Doppler current profiler. Proc. Oceans ’94, Brest, France, IEEE, 660–665.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 79 79 11
PDF Downloads 59 59 7

Mixing and Entrainment in the Red Sea Outflow Plume. Part II: Turbulence Characteristics

View More View Less
  • 1 Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

South of the Strait of Bab el Mandeb, saline Red Sea Water flows downslope into the Gulf of Aden mainly along the narrow 130-km-long “Northern Channel” (NC) and the shorter and wider “Southern Channel” (SC). In the NC, the Red Sea plume simultaneously exhibited weak entrainment into a 35–120-m-thick, weakly stratified bottom layer while a 35–285-m-thick interfacial layer above showed signs of vigorous mixing, overturns up to 30 m thick, and extensive zones of gradient Richardson numbers below 1/4. Turbulent overturning scales, or Thorpe scales, are extracted from regular CTD profiles and equated to Ozmidov scales. On this basis, interfacial mixing is quantified in terms of estimated turbulent dissipation rates, vertical turbulent salt flux, and interfacial stress. Even though these estimates are subject to significant uncertainty, they demonstrate the intensity of mixing during strong winter outflow in terms of eddy diffusivities Kρ on the order of 10−2 m2 s−1. The large Kρ occur in strong stratification such that vertical turbulent salt fluxes are also large. Along the NC, relative maxima of Kρ correspond to maxima in the bulk Froude number. Direct short-term measurements of the Reynolds stress just above the seafloor at two locations, one in the NC and one in the SC, allow comparisons of the bottom stress τb with the interfacial turbulent stress τi. The ratio τi/τb shows large scatter in a small sample, with maximum values on the order of 1. An outlines procedures of making and reducing lowered acoustic Doppler current profiler measurements optimized for observing descending plumes.

Corresponding author address: H. Peters, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149. Email: hpeters@rsmas.miami.edu

Abstract

South of the Strait of Bab el Mandeb, saline Red Sea Water flows downslope into the Gulf of Aden mainly along the narrow 130-km-long “Northern Channel” (NC) and the shorter and wider “Southern Channel” (SC). In the NC, the Red Sea plume simultaneously exhibited weak entrainment into a 35–120-m-thick, weakly stratified bottom layer while a 35–285-m-thick interfacial layer above showed signs of vigorous mixing, overturns up to 30 m thick, and extensive zones of gradient Richardson numbers below 1/4. Turbulent overturning scales, or Thorpe scales, are extracted from regular CTD profiles and equated to Ozmidov scales. On this basis, interfacial mixing is quantified in terms of estimated turbulent dissipation rates, vertical turbulent salt flux, and interfacial stress. Even though these estimates are subject to significant uncertainty, they demonstrate the intensity of mixing during strong winter outflow in terms of eddy diffusivities Kρ on the order of 10−2 m2 s−1. The large Kρ occur in strong stratification such that vertical turbulent salt fluxes are also large. Along the NC, relative maxima of Kρ correspond to maxima in the bulk Froude number. Direct short-term measurements of the Reynolds stress just above the seafloor at two locations, one in the NC and one in the SC, allow comparisons of the bottom stress τb with the interfacial turbulent stress τi. The ratio τi/τb shows large scatter in a small sample, with maximum values on the order of 1. An outlines procedures of making and reducing lowered acoustic Doppler current profiler measurements optimized for observing descending plumes.

Corresponding author address: H. Peters, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149. Email: hpeters@rsmas.miami.edu

Save