• Agrawal, Y. C., and D. G. Aubrey, 1992: Velocity observations above a rippled bed using laser Doppler velocimetry. J. Geophys. Res., 97 , 2024920259.

    • Search Google Scholar
    • Export Citation
  • Anis, A., and J. N. Moum, 1994: Prescriptions for heat flux and entrainment rates in the upper ocean during convection. J. Phys. Oceanogr., 24 , 21422155.

    • Search Google Scholar
    • Export Citation
  • Batchelor, G. K., 1959: Small-scale variations of convected quantities like temperature in turbulent fluid: General discussion and the case of small conductivity. J. Fluid Mech., 5 , 113133.

    • Search Google Scholar
    • Export Citation
  • De Silva, I. P. D., and H. J. S. Fernando, 1992: Some aspects of mixing in a stratified turbulent patch. J. Fluid Mech., 240 , 601625.

    • Search Google Scholar
    • Export Citation
  • Dewey, R. K., P. H. Leblond, and W. R. Crawford, 1988: The turbulent bottom boundary layer and its influence on local dynamics over the continental shelf. Dyn. Atmos. Oceans, 12 , 143172.

    • 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 D. R. Caldwell, 1980: The Batchelor spectrum and dissipation in the upper ocean. J. Geophys. Res., 85 , 19101916.

  • Dillon, T. M., J. A. Barth, A. Yu. Erofeev, and G. H. May, 1998: Towed observations of scalar dissipation on the mid Atlantic shelf. Eos, Trans. Amer. Geophys. Union, 79 (1) OS. 101.

    • Search Google Scholar
    • Export Citation
  • Efron, B., 1982: The Jackknife, the Bootstrap and Other Resampling Plans. Society for Industrial and Applied Mathematics, 92 pp.

  • Gibson, C. H., 1980: Fossil temperature, salinity and vorticity turbulence in the ocean. Mar. Turbul., J. C. J. Nihoul, Ed., Elsevier, 221–257.

    • Search Google Scholar
    • Export Citation
  • Gibson, C. H., V. N. Nabatov, and R. V. Ozmidov, 1993: Measurements of turbulence and fossil turbulence near Ampere seamount. Dyn. Atmos. Oceans, 19 , 175204.

    • Search Google Scholar
    • Export Citation
  • Gregg, M. C., 1987: Diapycnal mixing in the thermocline. J. Geophys. Res, 92 , 52495286.

  • Gregg, M. C., and J. A. MacKinnon, 1998: Mixing on a continental shelf during CMO 97—Preliminary results. Eos, Trans. Amer. Geophys. Union, 79 (1) OS. 100.

    • Search Google Scholar
    • Export Citation
  • Ivey, G., and J. Imberger, 1991: On the nature of turbulence in a stratified fluid. Part 1: The energetics of mixing. J. Phys. Oceanogr., 21 , 650658.

    • Search Google Scholar
    • Export Citation
  • Kolmogorov, A. N., 1941: On log-normal distribution of the sizes of particle in the course of breakdown (in Russian). Doklady USSR Akad. Sci., 31 ((2),) 99101.

    • Search Google Scholar
    • Export Citation
  • Ledwell, J. R., A. J. Watson, and C. S. Law, 1993: Evidence for slow mixing across the pycnocline from an open-ocean tracer-released experiment. Nature, 364 , 701703.

    • Search Google Scholar
    • Export Citation
  • Lozovatsky, I. D., and R. V. Ozmidov, Eds.,. 1992: The Variability of the Hydrophysical Fields in the Coastal Zone during Autumn Cooling. Vol. 5, Data of Oceanography Study, Geophysical Commit., 212 pp.

    • Search Google Scholar
    • Export Citation
  • Lozovatsky, I. D., R. V. Ozmidov, and J. C. J. Nihoul, 1977: Bottom turbulence in stratified enclosed seas. Bottom Turbulence, J. C. J. Nihoul, Ed., Elsevier, 49–58.

    • Search Google Scholar
    • Export Citation
  • Lozovatsky, I. D., T. M. Dillon, A. Yu Erofeev, and V. N. Nabatov, 1999: Variations of thermohaline and turbulent structure on the shallow Black Sea shelf in the beginning of autumn cooling. J. Mar. Syst., 21 , 255282.

    • Search Google Scholar
    • Export Citation
  • MacKinnon, J. A., and M. C. Gregg, 1998: Mechanisms of mixing on the New England continental shelf during CMO 96. Eos, Trans. Amer. Geophys. Union, 79 (1) OS. 100.

    • Search Google Scholar
    • Export Citation
  • Miller, P. L., and P. E. Demotakis, 1996: Measurements of scalar power spectra in high Schmidt number turbulent jets. J. Fluid Mech., 308 , 129146.

    • Search Google Scholar
    • Export Citation
  • Munk, W. H., 1966: Abyssal recipes. Deep-Sea Res., 13 , 207230.

  • Oakey, N. S., 1982: Determination of the rate of dissipation of turbulent energy from simultaneous temperature and velocity shear microstructure measurements. J. Phys. Oceanogr., 12 , 256271.

    • Search Google Scholar
    • Export Citation
  • Osborn, T. R., and C. S. Cox, 1972: Oceanic fine structure. Geophys. Fluid Dyn., 3 , 321345.

  • Paka, V. T., V. N. Nabatov, I. D. Lozovatsky, and T. M. Dillon, 1999: Ocean microstructure measurements by BAKLAN and GRIF. J. Atmos. Oceanic Technol., 16 , 15191532.

    • Search Google Scholar
    • Export Citation
  • Peters, H. M., 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
  • Rehmann, C. R., and T. F. Duda, 2000: Diapycnal diffusivity inferred from scalar microstructure measurements near the New England shelf/slope front. J. Phys. Oceanogr., 30 , 13541371.

    • Search Google Scholar
    • Export Citation
  • Ruddick, B., D. Walsh, and N. Oakey, 1997: Variations in apparent mixing efficiency in the North Atlantic Central Water. J. Phys. Oceanogr., 27 , 25892605.

    • Search Google Scholar
    • Export Citation
  • Seim, H. E., and M. C. Gregg, 1994: Detailed observations of a naturally occurring shear instability. J. Geophys. Res., 99 , 1004910073.

    • Search Google Scholar
    • Export Citation
  • Simpson, J. H., W. R. Crawford, T. R. Rippeth, A. R. Campbel, and J. V. S. Cheok, 1996: The vertical structure of turbulent dissipation in shelf seas. J. Phys. Oceanogr., 26 , 15791590.

    • Search Google Scholar
    • Export Citation
  • Simpson, J. J., and J. R. Hunter, 1974: Fronts in the Irish Sea. Nature, 250 , 404406.

  • Stillinger, D. C., K. N. Helland, and C. W. Van Atta, 1983: Experiments on the transition of homogeneous turbulence to internal waves in a stratified fluid. J. Fluid Mech., 131 , 91122.

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

  • Washburn, L., T. F. Duda, and D. C. Jacobs, 1997: Interpreting conductivity microstructure: Estimating the temperature variance dissipation rate. J. Atmos. Oceanic Technol., 13 , 11661188.

    • Search Google Scholar
    • Export Citation
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Mixing on a Shallow Shelf of the Black Sea

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  • 1 Environmental Fluid Dynamics Program, Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, Arizona
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Abstract

Microstructure measurements were carried out on the shallow shelf of the Black Sea, from the sea surface to the bottom, using a free-falling BAKLAN-S profiler released from an anchored ship. A northeast to southwest transect consisting of eight measurement stations, with several casts made at each station, enabled the evaluation of microstructure statistics across the shelf. The eddy and scalar diffusivities as well as the mixing efficiencies were evaluated for distinct layers that were identified based on mean stratification and the “state” of turbulence. These include five main layers with persistent features (upper and bottom boundary layers, diurnal and main pycnoclines, and a stratified weakly turbulent inner layer) and several transient (patchy) features embedded within such layers (quasi-homogeneous, active turbulent, stratified dissipative, and microstructure displacement patches). The Thorpe displacement scale LTh measurements of this study, together with those reported in Dillon and Gibson et al. indicated that the normalized (by the patch thickness hp) Thorpe scale LTh/hp is a function of the mixing Reynolds number Rm and the patch Richardson number Rip, but approaches a constant value for high Rm. Layer-averaged diffusivities, which are of direct utility in computing vertical transports at various depths in shelf waters, were evaluated and from which the weighted column-averaged diffusivity 〈K〉 ≈ 10−4 m2 s−1 in the Black Sea shallow shelf waters under moderate winds in the beginning of the autumn transition season was estimated. This latter value, however, may be an underestimation given the neglect of near-surface (<3 m) turbulent mixing in the calculations.

Corresponding author address: Dr. I. D. Lozovatsky, Environmental Fluid Dynamics Program, Dept. of Mechanical and Aerospace Engineering, Arizona State University, Box 879809, Tempe, AZ 85287. Email: i.lozovatsky@asu.edu

Additional affiliation: P. P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

Abstract

Microstructure measurements were carried out on the shallow shelf of the Black Sea, from the sea surface to the bottom, using a free-falling BAKLAN-S profiler released from an anchored ship. A northeast to southwest transect consisting of eight measurement stations, with several casts made at each station, enabled the evaluation of microstructure statistics across the shelf. The eddy and scalar diffusivities as well as the mixing efficiencies were evaluated for distinct layers that were identified based on mean stratification and the “state” of turbulence. These include five main layers with persistent features (upper and bottom boundary layers, diurnal and main pycnoclines, and a stratified weakly turbulent inner layer) and several transient (patchy) features embedded within such layers (quasi-homogeneous, active turbulent, stratified dissipative, and microstructure displacement patches). The Thorpe displacement scale LTh measurements of this study, together with those reported in Dillon and Gibson et al. indicated that the normalized (by the patch thickness hp) Thorpe scale LTh/hp is a function of the mixing Reynolds number Rm and the patch Richardson number Rip, but approaches a constant value for high Rm. Layer-averaged diffusivities, which are of direct utility in computing vertical transports at various depths in shelf waters, were evaluated and from which the weighted column-averaged diffusivity 〈K〉 ≈ 10−4 m2 s−1 in the Black Sea shallow shelf waters under moderate winds in the beginning of the autumn transition season was estimated. This latter value, however, may be an underestimation given the neglect of near-surface (<3 m) turbulent mixing in the calculations.

Corresponding author address: Dr. I. D. Lozovatsky, Environmental Fluid Dynamics Program, Dept. of Mechanical and Aerospace Engineering, Arizona State University, Box 879809, Tempe, AZ 85287. Email: i.lozovatsky@asu.edu

Additional affiliation: P. P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

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