Editorial Type:
Article
Article Type:
Research Article

Three-Dimensional Structure and Temporal Evolution of Submesoscale Thermohaline Intrusions in the North Pacific Subtropical Frontal Zone

A. Y. Shcherbina Applied Physics Laboratory, University of Washington, Seattle, Washington

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M. C. Gregg Applied Physics Laboratory, University of Washington, Seattle, Washington

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M. H. Alford Applied Physics Laboratory, University of Washington, Seattle, Washington

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R. R. Harcourt Applied Physics Laboratory, University of Washington, Seattle, Washington

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Print Publication:
01 Aug 2010
DOI:
https://doi.org/10.1175/2010JPO4373.1
Page(s):
1669–1689
Restricted access

Abstract

Four instances of persistent intrusive deformation of the North Pacific Subtropical Front were tagged individually by a Lagrangian float and tracked for several days. Each feature was mapped in three dimensions using repeat towed observations referenced to the float. Isohaline surface deformations in the frontal zone included sheetlike folds elongated in the alongfront direction and narrow tongues extending across the front. All deformations appeared as protrusions of relatively cold, and fresh, water across the front. No corresponding features of the opposite sign or isolated lenslike structures were observed. The sheets were O(10 m) thick, protruded about 10 km into the warm saline side of the front, and were coherent for 10–30 km along the front. Having about the same thickness and cross-frontal extent as the sheets, tongues extended less than 5 km along the front. All of the intrusions persisted as long as they were followed, several days to one week. Their structures evolved on both inertial (23 h) and subinertial (∼10 days) time scales in response to differential lateral advection. The water mass surrounding the intrusions participated in gradual anticyclonic rotation as a part of a mesoscale meander of the subtropical front. The intrusions may be interpreted as a manifestation of three-dimensional submesoscale turbulence of the frontal zone, driven by the mesoscale. Absence of large features of the opposite sign may be indicative of the asymmetry of the underlying dynamics.

Corresponding author address: A. Y. Shcherbina, APL-UW, 1013 NE 40th St., Seattle, WA 98105. Email: ashcherbina@apl.washington.edu

Abstract

Four instances of persistent intrusive deformation of the North Pacific Subtropical Front were tagged individually by a Lagrangian float and tracked for several days. Each feature was mapped in three dimensions using repeat towed observations referenced to the float. Isohaline surface deformations in the frontal zone included sheetlike folds elongated in the alongfront direction and narrow tongues extending across the front. All deformations appeared as protrusions of relatively cold, and fresh, water across the front. No corresponding features of the opposite sign or isolated lenslike structures were observed. The sheets were O(10 m) thick, protruded about 10 km into the warm saline side of the front, and were coherent for 10–30 km along the front. Having about the same thickness and cross-frontal extent as the sheets, tongues extended less than 5 km along the front. All of the intrusions persisted as long as they were followed, several days to one week. Their structures evolved on both inertial (23 h) and subinertial (∼10 days) time scales in response to differential lateral advection. The water mass surrounding the intrusions participated in gradual anticyclonic rotation as a part of a mesoscale meander of the subtropical front. The intrusions may be interpreted as a manifestation of three-dimensional submesoscale turbulence of the frontal zone, driven by the mesoscale. Absence of large features of the opposite sign may be indicative of the asymmetry of the underlying dynamics.

Corresponding author address: A. Y. Shcherbina, APL-UW, 1013 NE 40th St., Seattle, WA 98105. Email: ashcherbina@apl.washington.edu

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  • Alford, M. H., M. C. Gregg, and E. A. Asaro, 2005: Mixing, 3D mapping, and Lagrangian evolution of a thermohaline intrusion. J. Phys. Oceanogr., 35 , 1689–1711.

    • Search Google Scholar
    • Export Citation

  • Armi, L., D. Hebert, N. Oakey, J. F. Price, P. L. Richardson, H. T. Rossby, and B. Ruddick, 1989: Two years in the life of a Mediterranean salt lens. J. Phys. Oceanogr., 19 , 354–370.

    • Search Google Scholar
    • Export Citation

  • Boccaletti, G., R. Ferrari, and B. Fox-Kemper, 2007: Mixed layer instabilities and restratification. J. Phys. Oceanogr., 37 , 2228–2250.

    • Search Google Scholar
    • Export Citation

  • Capet, X., J. C. McWilliams, M. J. Molemaker, and A. F. Shchepetkin, 2008a: Mesoscale to submesoscale transition in the California Current system. Part II: Frontal processes. J. Phys. Oceanogr., 38 , 44–64.

    • Search Google Scholar
    • Export Citation

  • Capet, X., J. C. McWilliams, M. J. Molemaker, and A. F. Shchepetkin, 2008b: Mesoscale to submesoscale transition in the California Current system. Part I: Flow structure, eddy flux, and observational tests. J. Phys. Oceanogr., 38 , 29–43.

    • Search Google Scholar
    • Export Citation

  • Cevher, V., R. Velmurugan, and J. H. McClellan, 2006: A range-only multiple target particle filter tracker. Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, doi:10.1109/ICASSP.2006.1661116.

    • Search Google Scholar
    • Export Citation

  • D’Asaro, E. A., 2003: Performance of autonomous Lagrangian floats. J. Atmos. Oceanic Technol., 20 , 896–911.

  • Fedorov, K. N., 1978: The Thermohaline Finestructure of the Ocean. Pergamon Press, 170 pp.

  • Garrett, C. J. R., and J. W. Loder, 1981: Dynamical aspects of shallow sea fronts. Philos. Trans. Roy. Soc. London, 302 , 563–581.

  • Gregg, M. C., 1980: The three-dimensional mapping of a small thermohaline intrusion. J. Phys. Oceanogr., 10 , 1468–1492.

  • Gregg, M. C., and C. S. Cox, 1972: The vertical microstructure of temperature and salinity. Deep-Sea Res., 19 , 355–376.

  • Gregg, M. C., and J. H. McKenzie, 1979: Thermohaline intrusions lie across isopycnals. Nature, 280 , 310–311.

  • Hansen, P. C., 1998: Rank-Deficient and Discrete Ill-Posed Problems: Numerical Aspects of Linear Inversion. Society for Industrial and Applied Mathematics, 247 pp.

    • Search Google Scholar
    • Export Citation

  • Hitchcock, G. L., T. Rossby, J. L. Lillibridge, E. J. Lessard, E. R. Levine, D. N. Connors, K. Y. Børsheim, and M. Mork, 1994: Signatures of stirring and mixing near the Gulf Stream front. J. Mar. Res., 52 , 797–836.

    • Search Google Scholar
    • Export Citation

  • Hosegood, P., M. C. Gregg, and M. H. Alford, 2006: Submesoscale lateral density structure in the oceanic surface mixed layer. Geophys. Res. Lett., 33 , L22604. doi:10.1029/2006GL026797.

    • Search Google Scholar
    • Export Citation

  • Joyce, T. M., 1977: A note on the lateral mixing of water masses. J. Phys. Oceanogr., 7 , 626–629.

  • Klein, P., A. M. Treguier, and B. L. Hua, 1998: Three-dimensional stirring of thermohaline fronts. J. Mar. Res., 56 , 589–612.

  • Klymak, J. M., and M. C. Gregg, 2001: The three-dimensional nature of flow near a sill. J. Geophys. Res., 106C , 22295–22311.

  • Kunze, E., and T. B. Sanford, 1984: Observations of near-inertial waves in a front. J. Phys. Oceanogr., 14 , 566–581.

  • Mahadevan, A., and A. Tandon, 2006: An analysis of mechanisms for submesoscale vertical motion at ocean fronts. Ocean Modell., 14 , 241–256.

    • Search Google Scholar
    • Export Citation

  • Mahadevan, A., L. N. Thomas, and A. Tandon, 2008: Comment on “Eddy/Wind interactions stimulate extraordinary mid-ocean plankton blooms”. Science, 320 , 448b.

    • Search Google Scholar
    • Export Citation

  • McIntyre, M. E., 1970: Diffusive destabilization of the baroclinic circular vortex. Geophys. Fluid Dyn., 1 , 19–57.

  • McWilliams, J. C., M. J. Molemaker, and I. Yavneh, 2001: From stirring to mixing of momentum: Cascades from balanced flows to dissipation in the oceanic interior. Proc. ’Aha Huliko’a Hawaiian Winter Workshop, Honolulu, HI, University of Hawaii at Manoa, 59–66.

    • Search Google Scholar
    • Export Citation

  • Molemaker, M. J., J. C. McWilliams, and I. Yavneh, 2005: Baroclinic instability and loss of balance. J. Phys. Oceanogr., 35 , 1505–1517.

    • Search Google Scholar
    • Export Citation

  • Perona, P., and J. Malik, 1990: Scale-space and edge detection using anisotropic diffusion. IEEE Trans. Pattern Anal. Mach. Intel., 12 , 629–639.

    • Search Google Scholar
    • Export Citation

  • Roden, G. I., 1964: Shallow temperature inversions in the Pacific Ocean. J. Geophys. Res., 69 , 2899–2914.

  • Rubino, A., P. Brandt, and K. Hessner, 1998: Analytical solutions for circular eddies of the reduced-gravity, shallow-water equations. J. Phys. Oceanogr., 28 , 999–1002.

    • Search Google Scholar
    • Export Citation

  • Ruddick, B., and O. Kerr, 2003: Oceanic thermohaline intrusions: Theory. Prog. Oceanogr., 56 , 483–497.

  • Ruddick, B., and K. Richards, 2003: Oceanic thermohaline intrusions: Observations. Prog. Oceanogr., 56 , 499–527.

  • Rudnick, D. L., and J. R. Luyten, 1996: Intensive surveys of the Azores Front 1. Tracers and dynamics. J. Geophys. Res., 101C , 923–939.

    • Search Google Scholar
    • Export Citation

  • Schmitt, R. W., R. G. Lueck, and T. M. Joyce, 1986: Fine- and microstructure at the edge of a warm-core ring. Deep-Sea Res., 33 , 1665–1689.

    • Search Google Scholar
    • Export Citation

  • Shcherbina, A. Y., M. C. Gregg, M. H. Alford, and R. R. Harcourt, 2009: Characterizing thermohaline intrusions in the North Pacific subtropical frontal zone. J. Phys. Oceanogr., 39 , 2735–2756.

    • Search Google Scholar
    • Export Citation

  • Smith, K. S., and R. Ferrari, 2009: The production and dissipation of compensated thermohaline variance by mesoscale stirring. J. Phys. Oceanogr., 39 , 2477–2501.

    • Search Google Scholar
    • Export Citation

  • Smith, R. S., and M. D. O’Connell, 2005: Interpolation and gridding of aliased geophysical data using constrained anisotropic diffusion to enhance trends. Geophysics, 70 , V121–V127.

    • Search Google Scholar
    • Export Citation

  • Sokolov, S., and S. R. Rintoul, 1999: Some remarks on interpolation of nonstationary oceanographic fields. J. Atmos. Oceanic Technol., 16 , 1434–1449.

    • Search Google Scholar
    • Export Citation

  • Spilhaus, A. F., 1940: A detailed study of the surface layers of the ocean in the neighborhood of the Gulf Stream with the aid of rapid measuring hydrographic instruments. J. Mar. Res., 3 , 51–75.

    • Search Google Scholar
    • Export Citation

  • St. Laurent, L., and R. W. Schmitt, 1999: The contribution of salt fingers to vertical mixing in the North Atlantic Tracer Release Experiment. J. Phys. Oceanogr., 29 , 1404–1424.

    • Search Google Scholar
    • Export Citation

  • Stommel, H., and K. N. Fedorov, 1967: Small-scale structure in temperature and salinity near Timor and Mindanoa. Tellus, 19 , 76–81.

  • Stull, R. B., and E. B. Kraus, 1987: The transilient model of the upper ocean. J. Geophys. Res., 92C , 10745–10755.

  • Tang, C. L., A. S. Bennett, and D. J. Lawrence, 1985: Thermohaline intrusions in the frontal zones of a warm-core ring observed by batfish. J. Geophys. Res., 90C , 8928–8942.

    • 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 , 1086–1102.

  • Thomas, L. N., A. Tandon, and A. Mahadevan, 2008: Sub-mesoscale processes and dynamics. Ocean Modeling in an Eddying Regime, Geophys. Monogr., Vol. 177, Amer. Geophys. Union, 17–38.

    • Search Google Scholar
    • Export Citation

  • Thomas, L. N., C. M. Lee, and Y. Yoshikawa, 2010: The Subpolar Front of the Japan/East Sea. Part II: Inverse method for determining the frontal vertical circulation. J. Phys. Oceanogr., 40 , 3–25.

    • Search Google Scholar
    • Export Citation

  • Turner, J. S., and C. F. Chen, 1974: Two-dimensional effects in double-diffusive convection. J. Fluid Mech., 63 , 577–592.

  • Wahba, G., and J. Wendelberger, 1980: Some new mathematical methods for variational objective analysis using splines and cross validation. Mon. Wea. Rev., 108 , 1122–1143.

    • Search Google Scholar
    • Export Citation

  • Woods, J. D., R. Onken, and J. Fischer, 1986: Thermohaline intrusions created isopycnically at oceanic fronts are inclined to isopycnals. Nature, 322 , 446–449.

    • Search Google Scholar
    • Export Citation
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