• Bosart, L. F., 2003: Topopause folding, upper-level frontogenesis, and beyond. A Half-Century of Progress in Meteorology: A Tribute to Richard Reed, R. H. Johnson and R. A. Houze, Eds., Amer. Met. Soc., 13–47.

    • Crossref
    • Export Citation
  • Bower, A., 1989: Potential vorticity balances and horizontal divergence along particle trajectories in Gulf Stream meanders east of Cape Hatteras. J. Phys. Oceanogr., 19, 16691681, https://doi.org/10.1175/1520-0485(1989)019<1669:PVBAHD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bower, A., 1991: A simple kinematic mechanism for mixing fluid parcels across a meandering jet. J. Phys. Oceanogr., 21, 173180, https://doi.org/10.1175/1520-0485(1991)021<0173:ASKMFM>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Callies, J., R. Ferrari, J. M. Klymak, and J. Gula, 2015: Seasonality in submesoscale turbulence. Nat. Commun., 6, 68626870, https://doi.org/10.1038/ncomms7862.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Chekroun, M. D., H. Liu, and J. C. McWilliams, 2017: The emergence of fast oscillations in a reduced primitive equation model and its implications for closure theories. Comput. Fluids, 151, 322, https://doi.org/10.1016/j.compfluid.2016.07.005.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Davies, H. C., and A. M. Rossa, 1998: PV frontogenesis and upper-tropospheric fronts. Mon. Wea. Rev., 126, 15281539, https://doi.org/10.1175/1520-0493(1998)126<1528:PFAUTF>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ducet, N., P.-Y. Le Traon, and G. Reverdin, 2000: Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and-2. J. Geophys. Res., 105, 19 47719 498, https://doi.org/10.1029/2000JC900063.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fox-Kemper, B., R. Ferrari, and R. W. Hallberg, 2008: Parameterization of mixed layer eddies. Part I: Theory and diagnosis. J. Phys. Oceanogr., 38, 11451165, https://doi.org/10.1175/2007JPO3792.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gula, J., M. J. Molemaker, and J. C. McWilliams, 2014: Submesoscale cold filaments in the Gulf Stream. J. Phys. Oceanogr., 44, 26172643, https://doi.org/10.1175/JPO-D-14-0029.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gula, J., M. J. Molemaker, and J. C. McWilliams, 2015: Gulf Stream dynamics and frontal eddies along the southeastern U.S. seaboard. J. Phys. Oceanogr., 45, 690715, https://doi.org/10.1175/JPO-D-14-0154.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., and F. P. Bretherton, 1972: Atmospheric frontogenesis models: Mathematical formulation and solution. J. Atmos. Sci., 29, 1137, https://doi.org/10.1175/1520-0469(1972)029<0011:AFMMFA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Keyser, D., 1999: On the representation and diagnosis of frontal circulations in two and three dimensions. The Life Cycles of Extratropical Cyclones, C. Newton and S. Gronas, Eds., Amer. Met. Soc., 239–264.

    • Crossref
    • Export Citation
  • Keyser, D., and M. Shapiro, 1986: A review of the structure and dynamics of upper-level frontal zones. Mon. Wea. Rev., 114, 452499, https://doi.org/10.1175/1520-0493(1986)114<0452:AROTSA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Klymak, J., and Coauthors, 2016: Submesoscale streamers exchange water on the North Wall of the Gulf Stream. Geophys. Res. Lett., 43, 12261233, https://doi.org/10.1002/2015GL067152.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lindstrom, S., X. Qian, and D. Watts, 1997: Vertical motion in the Gulf Stream and its relation to meanders. J. Geophys. Res., 102, 84858503, https://doi.org/10.1029/96JC03498.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lorenz, E., 1960: Energy and numerical weather prediction. Tellus, 12, 364373, https://doi.org/10.3402/tellusa.v12i4.9420.

  • McWilliams, J. C., 2017: Submesoscale surface fronts and filaments: Secondary circulation, buoyancy flux, and frontogenesis. J. Fluid Mech., 823, 391432, https://doi.org/10.1017/jfm.2017.294.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McWilliams, J. C., 2018: Surface wave effects on submesoscale fronts and filaments. J. Fluid Mech., 843, 479817, https://doi.org/10.1017/jfm.2018.158.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McWilliams, J. C., and P. R. Gent, 1980: Intermediate models of planetary circulations in the atmosphere and ocean. J. Atmos. Sci., 37, 16571678, https://doi.org/10.1175/1520-0469(1980)037<1657:IMOPCI>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McWilliams, J. C., I. Yavneh, M. J. P. Cullen, and P. R. Gent, 1998: The breakdown of large-scale flows in rotating, stratified fluids. Phys. Fluids, 10, 31783184, https://doi.org/10.1063/1.869844.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McWilliams, J. C., L. P. Graves, and M. T. Montgomery, 2003: A formal theory for vortex Rossby waves and vortex evolution. Geophys. Astrophys. Fluid Dyn., 97, 275309, https://doi.org/10.1080/0309192031000108698.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nagai, T., A. Tandon, H. Yamazaki, and M. Doubell, 2009: Evidence of enhanced turbulent dissipation in the frontogenetic Kuroshio Front thermocline. Geophys. Res. Lett., 36, L12609, https://doi.org/10.1029/2009GL038832.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rotunno, R., C. Snyder, and W. Skamarock, 1994: An analysis of frontogenesis in numerical simulations of baroclinic waves. J. Atmos. Sci., 51, 33733398, https://doi.org/10.1175/1520-0469(1994)051<3373:AAOFIN>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schubert, R., A. Biastoch, M. Cronin, and R. Greatbatch, 2018: Instability-driven benthic storms below the separated Gulf Stream and the North Atlantic Current in a high-resolution ocean model. J. Phys. Oceanogr., 48, 22832303, https://doi.org/10.1175/JPO-D-17-0261.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Shapiro, M. A., 1981: Frontogenesis and geostrophically forced secondary circulations in the vicinity of jet stream-frontal zone systems. J. Atmos. Sci., 38, 954972, https://doi.org/10.1175/1520-0469(1981)038<0954:FAGFSC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Shapiro, M. A., and D. Keyser, 1990: Fronts, jet streams, and the tropopause. Extratropical Cyclones: The Erik Palmén Memorial Volume, C. Newton and E. O. Holopainen, Eds., Amer. Met. Soc., 167–189.

    • Crossref
    • Export Citation
  • Shchepetkin, A. F., and J. C. McWilliams, 2005: The Regional Oceanic Modeling System (ROMS): A split-explicit, free-surface, topography-following-coordinate oceanic model. Ocean Modell., 9, 347404, https://doi.org/10.1016/j.ocemod.2004.08.002.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thomas, L. N., and T. Joyce, 2010: Subduction on the northern and southern flanks of the Gulf Stream. J. Phys. Oceanogr., 40, 429438, https://doi.org/10.1175/2009JPO4187.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thomas, L. N., J. R. Taylor, R. Ferrari, and T. Joyce, 2013: Symmetric instability in the Gulf Stream. Deep-Sea Res. II, 91, 96110, https://doi.org/10.1016/j.dsr2.2013.02.025.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thomas, L. N., J. R. Taylor, E. A. D’Asaro, C. M. Lee, J. M. Klymak, and A. Shcherbina, 2016: Symmetric instability, inertial oscillations, and turbulence at the Gulf Stream front. J. Phys. Oceanogr., 46, 197217, https://doi.org/10.1175/JPO-D-15-0008.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Todd, R., and B. Owens, 2016: Gliders in the Gulf Stream. Scripps Institution of Oceanography, Instrument Development Group, https://doi.org/10.21238/s8SPRAY2675.

    • Crossref
    • Export Citation
  • Todd, R. E., W. B. Owens, and D. L. Rudnick, 2016: Potential vorticity structure in the North Atlantic western boundary current from underwater glider observations. J. Phys. Oceanogr., 46, 327348, https://doi.org/10.1175/JPO-D-15-0112.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yavneh, I., A. F. Shchepetkin, J. C. McWilliams, and L. P. Graves, 1997: Multigrid solution of rotating, stably stratified flows: The balance equations and their turbulent dynamics. J. Comput. Phys., 136, 245262, https://doi.org/10.1006/jcph.1997.5775.

    • Crossref
    • Search Google Scholar
    • Export Citation
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The Gulf Stream North Wall: Ageostrophic Circulation and Frontogenesis

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  • 1 Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, California
  • | 2 Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d’Océanographie Physique et Spatiale, IUEM, Brest, France
  • | 3 Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, California
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Abstract

Eastward zonal jets are common in the ocean and atmosphere, for example, the Gulf Stream and jet stream. They are characterized by atypically strong horizontal velocity, baroclinic vertical structure with an upward flow intensification, large change in the density stratification meridionally across the jet, large-scale meanders around a central latitude, narrow troughs and broad crests, and a sharp and vertically sloping northern (poleward) “wall” defined by horizontal maxima in the lateral gradients of both velocity and density. Measurements and realistic oceanic simulations show these features in the Gulf Stream downstream from its western boundary separation point. A diagnostic theory based on the conservative balance equations is developed to calculate the 3D velocity field associated with the dynamic height field. When applied to an idealized representation of a meandering jet, it explains the spatial structure of the associated ageostrophic secondary circulation around the jet and the positive frontogenetic tendency along the northern wall in the meander sector located upstream from the trough. This provides a basis for understanding why submesoscale instabilities and cross-wall intrusion and streamer events are more prevalent along the sector downstream from the trough and at the crest where there is not such a frontogenetic tendency. An important attribute for this frontogenesis pattern is the 3D shape of the jet, whose idealization is summarized above.

© 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: James C. McWilliams, jcm@atmos.ucla.edu

Abstract

Eastward zonal jets are common in the ocean and atmosphere, for example, the Gulf Stream and jet stream. They are characterized by atypically strong horizontal velocity, baroclinic vertical structure with an upward flow intensification, large change in the density stratification meridionally across the jet, large-scale meanders around a central latitude, narrow troughs and broad crests, and a sharp and vertically sloping northern (poleward) “wall” defined by horizontal maxima in the lateral gradients of both velocity and density. Measurements and realistic oceanic simulations show these features in the Gulf Stream downstream from its western boundary separation point. A diagnostic theory based on the conservative balance equations is developed to calculate the 3D velocity field associated with the dynamic height field. When applied to an idealized representation of a meandering jet, it explains the spatial structure of the associated ageostrophic secondary circulation around the jet and the positive frontogenetic tendency along the northern wall in the meander sector located upstream from the trough. This provides a basis for understanding why submesoscale instabilities and cross-wall intrusion and streamer events are more prevalent along the sector downstream from the trough and at the crest where there is not such a frontogenetic tendency. An important attribute for this frontogenesis pattern is the 3D shape of the jet, whose idealization is summarized above.

© 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: James C. McWilliams, jcm@atmos.ucla.edu
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