• Allen, J. T., and D. A. Smeed, 1996: Potential vorticity and vertical velocity at the Iceland–Faeroes front. J. Phys. Oceanogr., 26 , 26112634.

    • Search Google Scholar
    • Export Citation
  • Barth, J. A., T. J. Cowles, and S. D. Pierce, 2001: Mesoscale physical and bio-optical structure of the Antarctic Polar Front near 170°W during austral spring. J. Geophys. Res., 106 , 1387913902.

    • Search Google Scholar
    • Export Citation
  • D’Asaro, E. A., C. C. Eriksen, M. D. Levine, P. Niiler, C. A. Paulson, and P. V. Meurs, 1995: Upper-ocean inertial currents forced by a strong storm. Part I: Data and comparisons with linear theory. J. Phys. Oceanogr., 25 , 29092936.

    • Search Google Scholar
    • Export Citation
  • Dobrindt, U., and J. Schröter, 2003: An adjoint ocean model using finite elements: An application to the South Atlantic. J. Atmos. Oceanic Technol., 20 , 392407.

    • Search Google Scholar
    • Export Citation
  • Eliassen, A., 1951: Slow thermally or frictionally controlled meridional circulation in a circular vortex. Astrophys. Norv., 5 , 1960.

    • Search Google Scholar
    • Export Citation
  • Fedorov, K. N., 1983: The Physical Nature and Structure of Oceanic Fronts. Springer-Verlag, 333 pp.

  • Garrett, C. J. R., and J. W. Loder, 1981: Dynamical aspects of shallow sea fronts. Philos. Trans. Roy. Soc. London, 302A , 563581.

  • Giordani, H., L. Prieur, and G. Caniaux, 2006: Advanced insights into sources of vertical velocity in the ocean. Ocean Dyn., 56 , 513524.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., 1974: The role of potential vorticity in symmetric stability and instability. Quart. J. Roy. Meteor. Soc., 100 , 480482.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., and I. Draghici, 1977: The forcing of ageostrophic motion according to the semi-geostrophic equations and in an isentropic coordinate model. J. Atmos. Sci., 34 , 18591867.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., I. Draghici, and H. C. Davies, 1978: A new look at the ω-equation. Quart. J. Roy. Meteor. Soc., 104 , 3138.

  • Hua, B., D. W. Moore, and S. L. Gentil, 1997: Inertial nonlinear equilibration of equatorial flows. J. Fluid Mech., 331 , 345371.

  • Kunze, E., 1985: Near-inertial wave propagation in geostrophic shear. J. Phys. Oceanogr., 15 , 544565.

  • Leaman, K. D., and T. B. Sanford, 1975: Vertical energy propagation of internal waves: A vector spectral analysis of velocity profiles. J. Geophys. Res., 80 , 19751978.

    • Search Google Scholar
    • Export Citation
  • Lee, D. K., and P. P. Niiler, 1998: The inertial chimney: The near-inertial energy drainage from the ocean surface to the deep layer. J. Geophys. Res., 103 , 75797591.

    • Search Google Scholar
    • Export Citation
  • Le Traon, P. Y., 1990: A method for optimal analysis of fields with spatially variable mean. J. Geophys. Res., 95 , (C8). 1354313547.

  • Nagai, T., A. Tandon, and D. L. Rudnick, 2006: Two-dimensional ageostrophic secondary circulation at ocean fronts due to vertical mixing and large-scale deformation. J. Geophys. Res., 111 , C09038. doi:10.1029/2005JC002964.

    • Search Google Scholar
    • Export Citation
  • Naveira Garabato, A. C., J. T. Allen, H. Leach, V. H. Strass, and R. T. Pollard, 2001: Mesoscale subduction at the Antarctic Polar Front driven by baroclinic instability. J. Phys. Oceanogr., 31 , 20872107.

    • Search Google Scholar
    • Export Citation
  • Niiler, P., 1969: On the Ekman divergence in an oceanic jet. J. Geophys. Res., 74 , 70487052.

  • Ou, H., 1984: Geostrophic adjustment: A mechanism for frontogenesis? J. Phys. Oceanogr., 14 , 9941000.

  • Pallàs Sanz, E., and A. Viúdez, 2005: Diagnosing mesoscale vertical motion from horizontal velocity and density data. J. Phys. Oceanogr., 35 , 17441762.

    • Search Google Scholar
    • Export Citation
  • Pollard, R. T., and L. A. Regier, 1992: Vorticity and vertical circulation at an ocean front. J. Phys. Oceanogr., 22 , 609625.

  • Press, W. H., B. P. Flannery, S. K. Teukolsky, and W. T. Vetterling, 1993: Numerical Recipes in C. Cambridge University Press, 994 pp.

  • Rudnick, D. L., 1996: Intensive surveys of the Azores Front. 2. Inferring the geostrophic and vertical velocity fields. J. Geophys. Res., 101 , (C7). 1629116303.

    • Search Google Scholar
    • Export Citation
  • Rudnick, D. L., and J. R. Luyten, 1996: Intensive surveys of the Azores Front. 1. Tracers and dynamics. J. Geophys. Res., 101 , (C1). 923939.

    • Search Google Scholar
    • Export Citation
  • Shcherbina, A. Y., L. D. Talley, E. Firing, and P. Hacker, 2003: Near-surface frontal zone trapping and deep upward propagation of internal wave energy in the Japan/East Sea. J. Phys. Oceanogr., 33 , 900912.

    • Search Google Scholar
    • Export Citation
  • Shearman, R. K., J. A. Barth, and P. M. Kosro, 1999: Diagnosis of the three-dimensional circulation associated with mesoscale motion in the California Current. J. Phys. Oceanogr., 29 , 651670.

    • Search Google Scholar
    • Export Citation
  • Shearman, R. K., J. A. Barth, J. S. Allen, and R. L. Haney, 2000: Diagnosis of the three-dimensional circulation in mesoscale features with large Rossby number. J. Phys. Oceanogr., 30 , 26872709.

    • Search Google Scholar
    • Export Citation
  • Stern, M. E., 1965: Interaction of a uniform wind stress with a geostrophic vortex. Deep-Sea Res., 12 , 355367.

  • Takematsu, M., Z. Nagano, A. G. Ostrovski, K. Kim, and Y. Volkov, 1999: Direct measurements of deep currents in the northern Japan Sea. J. Oceanogr., 55 , 207216.

    • Search Google Scholar
    • Export Citation
  • Tandon, A., and C. Garrett, 1994: Mixed layer restratification due to a horizontal density gradient. J. Phys. Oceanogr., 24 , 14191424.

    • Search Google Scholar
    • Export Citation
  • Thomas, L. N., and C. M. Lee, 2005: Intensification of ocean fronts by down-front winds. J. Phys. Oceanogr., 35 , 10861102.

  • Thomas, L. N., A. Tandon, and A. Mahadevan, 2008: Submesoscale processes and dynamics. Ocean Modeling in an Eddying Regime, Geophys. Monogr., Vol. 126, Amer. Geophys. Union, 17–38.

    • Search Google Scholar
    • Export Citation
  • Thompson, L., 2000: Ekman layers and two-dimensional frontogenesis in the upper ocean. J. Geophys. Res., 105 , (C3). 64376451.

  • Viúdez, A., and D. G. Dritschel, 2004: Potential vorticity and the quasigeostrophic and semigeostrophic mesoscale vertical velocity. J. Phys. Oceanogr., 34 , 865887.

    • Search Google Scholar
    • Export Citation
  • Viúdez, A., J. Tintoré, and R. L. Haney, 1996: Circulation in the Alboran Sea as determined by quasi-synoptic hydrographic observations. Part I: Three-dimensional structure of the two anticyclonic gyres. J. Phys. Oceanogr., 26 , 684705.

    • Search Google Scholar
    • Export Citation
  • Wimbush, M., and W. Munk, 1970: The benthic boundary layer. New Concepts of Sea Floor Evolution, Part I: General Observations, A. E. Maxwell, E. Bullard, and J. L. Worzel, Eds., The Sea, Vol. 4A, John Wiley and Sons, 731–758.

    • Search Google Scholar
    • Export Citation
  • Wunsch, C., 1996: The Ocean Circulation Inverse Problem. Cambridge University Press, 442 pp.

  • Zhai, X., R. J. Greatbatch, and C. Eden, 2007: Spreading of near-inertial energy in a 1/12° model of the North Atlantic Ocean. Geophys. Res. Lett., 34 , L10609. doi:10.1029/2007GL029895.

    • Search Google Scholar
    • Export Citation
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The Subpolar Front of the Japan/East Sea. Part II: Inverse Method for Determining the Frontal Vertical Circulation

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  • 1 Department of Environmental Earth System Science, Stanford University, Stanford, California
  • | 2 Applied Physics Laboratory, University of Washington, Seattle, Washington
  • | 3 Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka, Japan
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Abstract

An inverse method for inferring vertical velocities from high-resolution hydrographic/velocity surveys is formulated and applied to observations collected at the subpolar front of the Japan/East Sea (JES) taken during several cold-air outbreaks. The method is distinct from vertical velocity inferences based on the omega equation in that the driving mechanism for the ageostrophic flow is inferred rather than assumed and hence is particularly appropriate for application to wind- or buoyancy-forced upper-ocean currents where friction, mixing, inertial/superinertial motions, or higher-order effects can contribute along with shear/strain of the geostrophic flow to force vertical motions.

The inferred vertical circulation at the subpolar front of the JES has amplitudes O(100 m day−1) compared to the ∼20 m day−1 vertical velocities predicted by the omega equation. Time-dependent, near-inertial motions driven by the winds and modified by the vertical vorticity of the frontal jet appear to be the primary cause of the strong vertical motions. The strongest vertical motions are associated with submesoscale, O(5 km), frontal downdrafts that tend to align with the slanted isopycnal surfaces of the front and advect water with low salinity and high chlorophyll fluorescence down the dense side of the front.

Corresponding author address: Leif N. Thomas, 473 Via Ortega, Y2E2 Bldg., Stanford University, Stanford, CA 94305-4215. Email: leift@stanford.edu

Abstract

An inverse method for inferring vertical velocities from high-resolution hydrographic/velocity surveys is formulated and applied to observations collected at the subpolar front of the Japan/East Sea (JES) taken during several cold-air outbreaks. The method is distinct from vertical velocity inferences based on the omega equation in that the driving mechanism for the ageostrophic flow is inferred rather than assumed and hence is particularly appropriate for application to wind- or buoyancy-forced upper-ocean currents where friction, mixing, inertial/superinertial motions, or higher-order effects can contribute along with shear/strain of the geostrophic flow to force vertical motions.

The inferred vertical circulation at the subpolar front of the JES has amplitudes O(100 m day−1) compared to the ∼20 m day−1 vertical velocities predicted by the omega equation. Time-dependent, near-inertial motions driven by the winds and modified by the vertical vorticity of the frontal jet appear to be the primary cause of the strong vertical motions. The strongest vertical motions are associated with submesoscale, O(5 km), frontal downdrafts that tend to align with the slanted isopycnal surfaces of the front and advect water with low salinity and high chlorophyll fluorescence down the dense side of the front.

Corresponding author address: Leif N. Thomas, 473 Via Ortega, Y2E2 Bldg., Stanford University, Stanford, CA 94305-4215. Email: leift@stanford.edu

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