• Adkins, C., , Gerdt D. , , and Baruch M. , 1998: Single mode fiber optic evanescent wave refractometer. U.S. Patent No. 6480638.

  • Alford, M. H., , Gregg M. C. , , and D’Asaro E. , 2005: Mixing, 3D mapping, and Lagrangian evolution of a thermohaline intrusion. J. Phys. Oceanogr., 35 , 16891711.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dillon, T. M., , and Caldwell D. R. , 1980: The Batchelor spectrum and dissipation in the upper ocean. J. Geophys. Res., 85 , 19101916.

  • Gargett, A. E., , and Holloway G. , 1992: Sensitivity of the GFDL ocean model to different diffusivities for heat and salt. J. Phys. Oceanogr., 22 , 11581177.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gerdt, D., , and Herr J. , 1996: Fiber optic evanescent wave sensor for immunoassay. U.S. Patent No. 5494798.

  • Gibson, C. H., , and Schwarz W. H. , 1963: The universal equilibrium spectra of turbulent velocity and scalar fields. J. Fluid Mech., 16 , 365384.

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

  • Gregg, M., 1998: Estimation and geography of diapycnal mixing in the stratified ocean. Physical Processes in Lakes and Oceans, J. Imberger, Ed., Vol. 54, Amer. Geophys. Union, 305–338.

    • Search Google Scholar
    • Export Citation
  • Gregg, M., , and Meagher T. , 1980: The dynamic response of glass rod thermistors. J. Geophys. Res., 85 , 27792786.

  • Gregg, M., , Winkel D. , , and Sanford T. , 1993: Varieties of fully resolved spectra of vertical shear. J. Phys. Oceanogr., 23 , 124141.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Head, M. J., 1983: The use of miniature four-electrode conductivity probes for high resolution measurement of turbulent density or temperature variations in salt-stratified water flows. Ph.D. thesis, University of California, San Diego, 211 pp.

  • Hinze, J. O., 1975: Turbulence. 2d ed. McGraw Hill, 790 pp.

  • Kraichnan, R., 1968: Small-scale structure of a scalar field convected by turbulence. Phys. Fluids, 11 , 945953.

  • Lacroix, S., , Gonthier F. , , and Bures J. , 1994: Modeling of symmetric 2 × 2 fused-fiber couplers. Appl. Opt., 33 , 83618369.

  • Lueck, R. G., , Hertzman O. , , and Osborn T. R. , 1977: The spectral response of thermistors. Deep-Sea Res., 24 , 951970.

  • Nash, J., , and Moum J. , 1999: Estimating salinity variance dissipation rate from conductivity microstructure measurements. J. Atmos. Oceanic Technol., 16 , 263274.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nash, J. D., , and Moum J. N. , 2002: Microstructure estimates of turbulent salinity flux and the dissipation spectrum of salinity. J. Phys. Oceanogr., 32 , 23122334.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 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.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Quan, X., , and Fry E. S. , 1995: Empirical equation for the index of refraction of seawater. Appl. Opt., 34 , 34773480.

  • Seaver, G., 1987: The optical determination of T, P, S, and density in physical oceanography. Mar. Technol. Soc. J., 21 , 6979.

  • Seaver, G., 1997: Laboratory calibration in distilled water and seawater of an oceanographic multichannel interferometer–refractometer. J. Atmos. Oceanic Technol., 14 , 267277.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Tennekes, H., , and Lumley J. L. , 1972: A First Course in Turbulence. MIT Press, 300 pp.

  • Washburn, L., , Duda T. , , and Jacobs D. , 1996: Interpreting conductivity microstructure: Estimating the temperature variance dissipation rate. J. Atmos. Oceanic Technol., 16 , 11661188.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 34 34 2
PDF Downloads 18 18 4

An Ocean Refractometer: Resolving Millimeter-Scale Turbulent Density Fluctuations via the Refractive Index

View More View Less
  • 1 Applied Physics Laboratory and School of Oceanography, University of Washington, Seattle, Washington
  • | 2 Empirical Technologies Corporation, Charlottesville, Virginia
© Get Permissions
Restricted access

Abstract

A fiberoptic sensor has been constructed to measure oceanic density fluctuations via their refractive index signature. The resolution (Δz = 1 mm, Δt = 0.2 ms) and precision (Δn < 10−8, Δρ = 3.4 × 10−5 kg m−3) of the device are far better than other methods and are sufficient to resolve the entire turbulent spectrum. Spectra show the salinity Batchelor rolloff at levels undetectable via conductivity measurements. However, the low-wavenumber portion of the spectrum occupied by the turbulent inertial subrange (≈1 m–1 cm scales) is marred by noise resulting from fiber motion in response to turbulent velocity fluctuations. The technique is described, and the first ocean measurements are reported.

Corresponding author address: M. Alford, Applied Physics Laboratory, 1013 E. 40th St., Seattle, WA 98105. Email: malford@apl.washington.edu

Abstract

A fiberoptic sensor has been constructed to measure oceanic density fluctuations via their refractive index signature. The resolution (Δz = 1 mm, Δt = 0.2 ms) and precision (Δn < 10−8, Δρ = 3.4 × 10−5 kg m−3) of the device are far better than other methods and are sufficient to resolve the entire turbulent spectrum. Spectra show the salinity Batchelor rolloff at levels undetectable via conductivity measurements. However, the low-wavenumber portion of the spectrum occupied by the turbulent inertial subrange (≈1 m–1 cm scales) is marred by noise resulting from fiber motion in response to turbulent velocity fluctuations. The technique is described, and the first ocean measurements are reported.

Corresponding author address: M. Alford, Applied Physics Laboratory, 1013 E. 40th St., Seattle, WA 98105. Email: malford@apl.washington.edu

Save