• Allen, J., , and P. Newberger, 1996: Downwelling circulation on the Oregon continental shelf. Part I: Response to idealized forcing. J. Phys. Oceanogr., 26, 20112035.

    • Search Google Scholar
    • Export Citation
  • Austin, J. A., , and S. Lentz, 2002: The inner shelf response to wind-driven upwelling and downwelling. J. Phys. Oceanogr., 32, 21712193.

    • Search Google Scholar
    • Export Citation
  • Avicola, G., , and P. Huq, 2003: The characteristics of the recirculating bulge region in coastal buoyant outflows. J. Mar. Res., 61, 435463, doi:10.1357/002224003322384889.

    • Search Google Scholar
    • Export Citation
  • Chao, S., , and W. Boicourt, 1986: Onset of estuarine plumes. J. Phys. Oceanogr., 16, 21372149.

  • Chapman, D., , and S. Lentz, 1994: Trapping of a coastal density front by the bottom boundary layer. J. Phys. Oceanogr., 24, 14641479.

  • Chapman, D., , and S. Lentz, 1997: Adjustment of stratified flow over a sloping bottom. J. Phys. Oceanogr., 27, 340356.

  • Fong, D., , and W. Geyer, 2001: Response of a river plume during an upwelling favorable wind event. J. Geophys. Res., 106 (C1), 10671084.

    • Search Google Scholar
    • Export Citation
  • Garvine, R., 2001: The impact of model configuration in studies of buoyant coastal discharge. J. Mar. Res., 59, 193225.

  • Geyer, W. R., , P. Hill, , T. Milligan, , and P. Traykovski, 2000: The structure of the Eel River plume during floods. Cont. Shelf Res., 20, 20672093, doi:10.1016/S0278-4343(00)00063-7.

    • Search Google Scholar
    • Export Citation
  • Gill, A., 1976: Adjustment under gravity in a rotating channel. J. Fluid Mech., 77, 603621, doi:10.1017/S0022112076002280.

  • Hickey, B., , S. Geier, , N. Kachel, , and A. MacFadyen, 2005: A bi-directional river plume: The Columbia in summer. Cont. Shelf Res., 25, 16311656, doi:10.1016/j.csr.2005.04.010.

    • Search Google Scholar
    • Export Citation
  • Hickey, B., and Coauthors, 2010: River influences on shelf ecosystems: Introduction and synthesis. J. Geophys. Res., 115, C00B17, doi:10.1029/2009JC005452.

    • Search Google Scholar
    • Export Citation
  • Horner-Devine, A. R., 2009: The bulge circulation in the Columbia River plume. Cont. Shelf Res., 29, 234251, doi:10.1016/j.csr.2007.12.012.

    • Search Google Scholar
    • Export Citation
  • Horner-Devine, A. R., , D. A. Jay, , P. M. Orton, , and E. Y. Spahn, 2009: A conceptual model of the strongly tidal Columbia River plume. J. Mar. Syst., 78, 460475, doi:10.1016/j.jmarsys.2008.11.025.

    • Search Google Scholar
    • Export Citation
  • Kourafalou, V., , L. Oey, , J. Wang, , and T. Lee, 1996: The fate of river discharge on the continental shelf 1. Modeling the river plume and the inner shelf coastal current. J. Geophys. Res., 101 (C2), 34153434.

    • Search Google Scholar
    • Export Citation
  • Kudela, R. M., and Coauthors, 2008: New insights into the controls and mechanisms of plankton productivity in coastal upwelling waters of the Northern California current system. Oceanography, 21, 4659.

    • Search Google Scholar
    • Export Citation
  • Lentz, S., 2004: The response of buoyant coastal plumes to upwelling-favorable winds. J. Phys. Oceanogr., 34, 24582469.

  • Lentz, S., , and K. R. Helfrich, 2002: Buoyant gravity currents along a sloping bottom in a rotating fluid. J. Fluid Mech., 464, 251278, doi:10.1017/S0022112002008868.

    • Search Google Scholar
    • Export Citation
  • Lentz, S., , and J. Largier, 2006: The influence of wind forcing on the Chesapeake Bay buoyant coastal current. J. Phys. Oceanogr., 36, 13051316.

    • Search Google Scholar
    • Export Citation
  • Lentz, S., , R. Guza, , S. Elgar, , F. Feddersen, , and T. Herbers, 1999: Momentum balances on the North Carolina inner shelf. J. Geophys. Res., 104 (C8), 205226.

    • Search Google Scholar
    • Export Citation
  • McWilliams, J. C., , E. Huckle, , and A. F. Shchepetkin, 2009: Buoyancy effects in a stratified Ekman layer. J. Phys. Oceanogr., 39, 25812599.

    • Search Google Scholar
    • Export Citation
  • Mellor, G., , and T. Yamada, 1982: Development of a turbulence closure model for geophysical fluid problems. Rev. Geophys., 20, 851875.

    • Search Google Scholar
    • Export Citation
  • Moffat, C., , R. C. Beardsley, , W. B. Owens, , and N. van Lipzig, 2008: A first description of the Antarctic Peninsula Coastal Current. Deep-Sea Res. II, 55 (3–4), 277293, doi:10.1016/j.dsr2.2007.10.003.

    • Search Google Scholar
    • Export Citation
  • Ogston, A., , D. Cacchione, , R. Sternberg, , and G. Kineke, 2000: Observations of storm and river flood-driven sediment transport on the northern California continental shelf. Cont. Shelf Res., 20, 21412162, doi:10.1016/S0278-4343(00)00065-0.

    • Search Google Scholar
    • Export Citation
  • Pimenta, F. M., , A. D. Kirwan, , and P. Huq, 2011: On the transport of buoyant coastal plumes. J. Phys. Oceanogr., 41, 620640.

  • Pollard, R., , P. Rhines, , and R. Thompson, 1972: The deepening of the wind-mixed layer. Geophys. Astrophys. Fluid Dyn., 4, 381404.

  • Rennie, S., , S. Lentz, , and J. Largier, 1999: Observations of a pulsed buoyancy current downstream of Chesapeake Bay. J. Geophys. Res., 104 (C8), 18 22718 240.

    • Search Google Scholar
    • 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, doi:10.1016/j.ocemod.2004.08.002.

    • Search Google Scholar
    • Export Citation
  • Wang, B., 2006: Cultural eutrophication in the Changjiang (Yangtze River) plume: History and perspective. Estuarine Coastal Shelf Sci., 69 (3–4), 471477, doi:10.1016/j.ecss.2006.05.010.

    • Search Google Scholar
    • Export Citation
  • Warrick, J. A., and Coauthors, 2007: River plume patterns and dynamics within the Southern California Bight. Cont. Shelf Res., 27, 24272448, doi:10.1016/j.csr.2007.06.015.

    • Search Google Scholar
    • Export Citation
  • Whitney, M. M., , and R. W. Garvine, 2005: Wind influence on a coastal buoyant outflow. J. Geophys. Res., 110, C03014, doi:10.1029/2003JC002261.

    • Search Google Scholar
    • Export Citation
  • Wiseman, W. J., Jr., , and R. W. Garvine, 1995: Plumes and coastal currents near large river mouths. Estuaries, 18, 509517, doi:10.2307/1352368.

    • Search Google Scholar
    • Export Citation
  • Yankovsky, A., , and D. Chapman, 1997: A simple theory for the fate of buoyant coastal discharges. J. Phys. Oceanogr., 27, 13861401.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 30 30 3
PDF Downloads 29 29 1

On the Response of a Buoyant Plume to Downwelling-Favorable Wind Stress

View More View Less
  • 1 Departamento de Oceanografía, Universidad de Concepción, Concepción, Chile
  • | 2 Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
© Get Permissions
Restricted access

Abstract

Here, the response of a coastally trapped buoyant plume to downwelling-favorable wind forcing is explored using a simplified two-dimensional numerical model and a prognostic theory for the resulting width, depth, and density anomaly and along-shelf transport of the plume. Consistent with the numerical simulations, the analytical model shows that the wind causes mixing of the plume water and that the forced cross-shelf circulation can also generate significant deepening and surface narrowing, as well as increased along-shelf transport. The response is due to a combination of the purely advective process that leads to the steepening of the isopycnals and the entrainment of ambient water into the plume. The advective component depends on the initial plume geometry: plumes that have a large fraction of their total width in contact with the bottom (“bottom trapped”) suffer relatively small depth and width changes compared to plumes that have a large fraction of their total width detached from the bottom (“surface trapped”). Key theoretical parameters are Wγ/Wα, the ratio of the width of the plume detached from the bottom to the width of the plume in contact with it, and the ratio of the wind-generated mixed layer δe to the initial plume depth hp, which determines the amount of water initially entrained into the plume. The model results also show that the cross-shelf circulation can be strongly influenced by the wind-driven response in combination with the geostrophic shear of the plume. The continuous entrainment into the plume, as well as transient events, is also discussed.

Corresponding author address: Carlos Moffat, Departamento de Oceanografía, Universidad de Concepción, Concepción, Chile. E-mail: cmoffat@oceanografia.udec.cl

Abstract

Here, the response of a coastally trapped buoyant plume to downwelling-favorable wind forcing is explored using a simplified two-dimensional numerical model and a prognostic theory for the resulting width, depth, and density anomaly and along-shelf transport of the plume. Consistent with the numerical simulations, the analytical model shows that the wind causes mixing of the plume water and that the forced cross-shelf circulation can also generate significant deepening and surface narrowing, as well as increased along-shelf transport. The response is due to a combination of the purely advective process that leads to the steepening of the isopycnals and the entrainment of ambient water into the plume. The advective component depends on the initial plume geometry: plumes that have a large fraction of their total width in contact with the bottom (“bottom trapped”) suffer relatively small depth and width changes compared to plumes that have a large fraction of their total width detached from the bottom (“surface trapped”). Key theoretical parameters are Wγ/Wα, the ratio of the width of the plume detached from the bottom to the width of the plume in contact with it, and the ratio of the wind-generated mixed layer δe to the initial plume depth hp, which determines the amount of water initially entrained into the plume. The model results also show that the cross-shelf circulation can be strongly influenced by the wind-driven response in combination with the geostrophic shear of the plume. The continuous entrainment into the plume, as well as transient events, is also discussed.

Corresponding author address: Carlos Moffat, Departamento de Oceanografía, Universidad de Concepción, Concepción, Chile. E-mail: cmoffat@oceanografia.udec.cl
Save