• Allen, J. S., and P. A. 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
  • Allen, J. S., P. A. Newberger, and J. Federiuk, 1995: Upwelling circulation on the Oregon continental shelf. Part I: Response to idealized forcing. J. Phys. Oceanogr., 25 , 18431866.

    • Search Google Scholar
    • Export Citation
  • Arthur, R. S., 1965: On the calculation of vertical motion in eastern boundary currents from determinations of horizontal motion. J. Geophys. Res., 70 , 27992803.

    • Search Google Scholar
    • Export Citation
  • Barth, J. A., S. D. Pierce, and R. L. Smith, 2000: A separating coastal upwelling jet at Cape Blanco, Oregon and its connection to the California Current System. Deep-Sea Res. II, 47 , 783810.

    • Search Google Scholar
    • Export Citation
  • Barth, J. A., S. D. Pierce, and R. M. Castelao, 2005: Time-dependent, wind-driven flow over a shallow midshelf submarine bank. J. Geophys. Res., 110 , C10S05. doi:10.1029/2004JC002761.

    • Search Google Scholar
    • Export Citation
  • Bormans, M., and C. Garrett, 1989: A simple criterion for gyre formation by the surface outflow from a strait, with application to the Alboran Sea. J. Geophys. Res., 94 , 1263712644.

    • Search Google Scholar
    • Export Citation
  • Castelao, R. M., and J. A. Barth, 2006: The relative importance of wind strength and alongshelf bathymetric variations on the separation of a coastal upwelling jet. J. Phys. Oceanogr., 36 , 412425.

    • Search Google Scholar
    • Export Citation
  • Dale, A. C., and J. A. Barth, 2001: The hydraulics of an evolving upwelling jet flowing around a cape. J. Phys. Oceanogr., 31 , 226243.

    • Search Google Scholar
    • Export Citation
  • Durski, S. M., and J. S. Allen, 2005: Finite amplitude evolution of instabilities associated with the coastal upwelling front. J. Phys. Oceanogr., 35 , 16061628.

    • Search Google Scholar
    • Export Citation
  • Figueroa, D., and C. Moffat, 2000: On the influence of topography in the induction of coastal upwelling along the Chilean coast. Geophys. Res. Lett., 27 , 39053908.

    • Search Google Scholar
    • Export Citation
  • Gan, J., and J. S. Allen, 2005: Modeling upwelling circulation off the Oregon coast. J. Geophys. Res., 110 , C10S07. doi:10.1029/2004JC002692.

    • Search Google Scholar
    • Export Citation
  • Haidvogel, D. B., H. G. Arango, K. Hedstrom, A. Beckmann, P. Malanotte-Rizzoli, and A. F. Shchepetkin, 2000: Model evaluation experiments in the North Atlantic Basin: Simulations in nonlinear terrain-following coordinates. Dyn. Atmos. Oceans, 32 , 239281.

    • Search Google Scholar
    • Export Citation
  • Hill, R. B., and J. A. Johnson, 1974: A theory of upwelling over the shelf break. J. Phys. Oceanogr., 4 , 1926.

  • Holton, J. R., 1992: An Introduction to Dynamic Meteorology. Academic Press, 507 pp.

  • Jiang, X., 1995: Flow separation by interfacial upwelling in the coastal ocean. M.S. thesis, School of Earth and Ocean Sciences, University of Victoria, 55 pp.

  • Johnson, D. R., T. Fonseca, and H. Sievers, 1980: Upwelling in the Humboldt coastal current near Valparaiso, Chile. J. Mar. Res., 38 , 116.

    • Search Google Scholar
    • Export Citation
  • Kelly, K. A., 1985: The influence of winds and topography on the sea surface temperature patterns over the northern California slope. J. Geophys. Res., 90 , 1178311798.

    • Search Google Scholar
    • Export Citation
  • Klinger, B. A., 1994: Inviscid current separation from rounded capes. J. Phys. Oceanogr., 24 , 18051811.

  • Kosro, P. M., 2005: On the spatial structure of coastal circulation off Newport, Oregon, during spring and summer 2001 in a region of varying shelf width. J. Geophys. Res., 110 , C10S06. doi:10.1029/2004JC002769.

    • Search Google Scholar
    • Export Citation
  • Kurapov, A. L., J. S. Allen, G. D. Egbert, and R. N. Miller, 2005: Modeling bottom mixed layer variability on the mid-Oregon shelf during summer upwelling. J. Phys. Oceanogr., 35 , 16291649.

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

    • Search Google Scholar
    • Export Citation
  • O’Brien, J. J., and H. E. Hurlburt, 1972: A numerical model of coastal upwelling. J. Phys. Oceanogr., 2 , 1426.

  • Oke, P. R., and J. H. Middleton, 2000: Topographically induced upwelling off eastern Australia. J. Phys. Oceanogr., 30 , 512531.

  • Oke, P. R., J. S. Allen, R. N. Miller, and G. D. Egbert, 2002: A modeling study of the three-dimensional continental shelf circulation off Oregon. Part II: Dynamical analysis. J. Phys. Oceanogr., 32 , 13831403.

    • Search Google Scholar
    • Export Citation
  • Pedlosky, J., 1987: Geophysical Fluid Dynamics. Springer-Verlag, 710 pp.

  • Peffley, M. B., and J. J. O’Brien, 1976: A three-dimensional simulation of coastal upwelling off Oregon. J. Phys. Oceanogr., 6 , 164180.

    • Search Google Scholar
    • Export Citation
  • Rodrigues, R. R., and J. A. Lorenzzetti, 2001: A numerical study of the effects of bottom topography and coastline geometry on the southeast Brazilian coastal upwelling. Cont. Shelf Res., 21 , 371394.

    • Search Google Scholar
    • Export Citation
  • Shchepetkin, A. F., and J. C. McWilliams, 1998: Quasi-monotone advection schemes based on explicit locally adaptive dissipation. Mon. Wea. Rev., 126 , 15411580.

    • Search Google Scholar
    • Export Citation
  • Shchepetkin, A. F., and J. C. McWilliams, 2003: A method for computing horizontal pressure-gradient force in an oceanic model with a nonaligned vertical coordinate. J. Geophys. Res., 108 , 3090. doi:10.1029/2001JC001047.

    • 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.

    • Search Google Scholar
    • Export Citation
  • Song, Y. T., and D. B. Haidvogel, 1994: A semi-implicit ocean circulation model using a generalized topography-following coordinate system. J. Comput. Phys., 115 , 228244.

    • Search Google Scholar
    • Export Citation
  • Song, Y. T., D. B. Haidvogel, and S. M. Glenn, 2001: Effects of topographic variability on the formation of upwelling centers off New Jersey: A theoretical model. J. Geophys. Res., 106 , 92239240.

    • Search Google Scholar
    • Export Citation
  • Trowbridge, J. H., and S. J. Lentz, 1991: Asymmetric behavior of an oceanic boundary layer above a sloping bottom. J. Phys. Oceanogr., 21 , 11711185.

    • Search Google Scholar
    • Export Citation
  • Weisberg, R. H., B. D. Black, and Z. Li, 2000: An upwelling case study on Florida’s west coast. J. Geophys. Res., 105 , 1145911469.

  • Whitney, M. M., and J. S. Allen, 2009: Coastal wind-driven circulation in the vicinity of a bank. Part II: Modeling flow over the Heceta Bank Complex on the Oregon Coast. J. Phys. Oceanogr., 39 , 12981316.

    • Search Google Scholar
    • Export Citation
  • Zaytsev, O., R. Cervantes-Duarte, O. Montante, and A. Gallegos-Garcia, 2003: Coastal upwelling activity on the Pacific shelf of the Baja California Peninsula. J. Oceanogr., 59 , 489502.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 3 3 3
PDF Downloads 5 5 5

Coastal Wind-Driven Circulation in the Vicinity of a Bank. Part I: Modeling Flow over Idealized Symmetric Banks

View More View Less
  • 1 Department of Marine Sciences, University of Connecticut, Groton, Connecticut
  • | 2 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon
Restricted access

Abstract

This study examines how coastal banks influence wind-driven circulation along stratified continental shelves. Numerical experiments are conducted for idealized symmetric banks; the standard bank (200 km long and 50 km wide) has dimensions similar to the Heceta Bank complex along the Oregon shelf. Model runs are forced with 10 days of steady winds (0.1 Pa); upwelling and downwelling cases are compared. The bank introduces significant alongshelf variability in the currents and density fields. Upwelling-favorable winds create an upwelling front and a baroclinic jet (flowing opposite coastal-trapped wave propagation) that bend around the standard bank, approximately centered on the 90-m isobath. The upwelling jet is strongest over the upstream bank half, where it advects a tongue of dense water over the bank. There is a current reversal shoreward of the main jet at the bank center. Upwelling is most intense over the upstream part of the bank, while there is reduced upwelling and even downwelling over other bank sections. Downwelling-favorable winds create a near-bottom density front and a baroclinic jet (flowing in the direction of coastal-trapped wave propagation) that bend around the standard bank; the jet core moves from the 150-m isobath to the 100-m isobath and back over the bank. The downwelling jet is slowest and widest over the bank; there are no current reversals. Results over the bank are more similar to 2D results (that preclude alongshelf variability) than in the upwelling case. Downwelling is weakened over the bank. The density field evolution over the bank is fundamentally different from the upwelling case. Most model results for banks with different dimensions are qualitatively similar to the standard run. The exceptions are banks having a radius of curvature smaller than the inertial radius; the main jet remains detached from the coast far downstream from these banks. The lowest-order across-stream momentum balance indicates that the depth-averaged flow is geostrophic. Advection, ageostrophic pressure gradients, wind stress, and bottom stress are all important in the depth-averaged alongstream momentum balance over the bank. There is considerable variability in alongstream momentum balances over different bank sections. Across-shelf and alongshelf advection both change the density field over the bank. Barotropic potential vorticity is not conserved, but the tendency for relative vorticity changes and depth changes to partially counter each other results in differences between the upwelling and downwelling jet paths over the bank. Only certain areas of the bank have significant vertical velocities. In these areas of active upwelling and downwelling, vertical velocities at the top of the bottom boundary layer are due to either the jet crossing isobaths or bottom Ekman pumping.

Corresponding author address: Michael M. Whitney, Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, CT 06340-6097. Email: michael.whitney@uconn.edu

Abstract

This study examines how coastal banks influence wind-driven circulation along stratified continental shelves. Numerical experiments are conducted for idealized symmetric banks; the standard bank (200 km long and 50 km wide) has dimensions similar to the Heceta Bank complex along the Oregon shelf. Model runs are forced with 10 days of steady winds (0.1 Pa); upwelling and downwelling cases are compared. The bank introduces significant alongshelf variability in the currents and density fields. Upwelling-favorable winds create an upwelling front and a baroclinic jet (flowing opposite coastal-trapped wave propagation) that bend around the standard bank, approximately centered on the 90-m isobath. The upwelling jet is strongest over the upstream bank half, where it advects a tongue of dense water over the bank. There is a current reversal shoreward of the main jet at the bank center. Upwelling is most intense over the upstream part of the bank, while there is reduced upwelling and even downwelling over other bank sections. Downwelling-favorable winds create a near-bottom density front and a baroclinic jet (flowing in the direction of coastal-trapped wave propagation) that bend around the standard bank; the jet core moves from the 150-m isobath to the 100-m isobath and back over the bank. The downwelling jet is slowest and widest over the bank; there are no current reversals. Results over the bank are more similar to 2D results (that preclude alongshelf variability) than in the upwelling case. Downwelling is weakened over the bank. The density field evolution over the bank is fundamentally different from the upwelling case. Most model results for banks with different dimensions are qualitatively similar to the standard run. The exceptions are banks having a radius of curvature smaller than the inertial radius; the main jet remains detached from the coast far downstream from these banks. The lowest-order across-stream momentum balance indicates that the depth-averaged flow is geostrophic. Advection, ageostrophic pressure gradients, wind stress, and bottom stress are all important in the depth-averaged alongstream momentum balance over the bank. There is considerable variability in alongstream momentum balances over different bank sections. Across-shelf and alongshelf advection both change the density field over the bank. Barotropic potential vorticity is not conserved, but the tendency for relative vorticity changes and depth changes to partially counter each other results in differences between the upwelling and downwelling jet paths over the bank. Only certain areas of the bank have significant vertical velocities. In these areas of active upwelling and downwelling, vertical velocities at the top of the bottom boundary layer are due to either the jet crossing isobaths or bottom Ekman pumping.

Corresponding author address: Michael M. Whitney, Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, CT 06340-6097. Email: michael.whitney@uconn.edu

Save