Across-Shelf Transport on a Continental Shelf: Do Across-Shelf Winds Matter?

Charles E. Tilburg Graduate College of Marine Studies, University of Delaware, Newark, Delaware

Search for other papers by Charles E. Tilburg in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Wind-forced across-shelf flow on a continental shelf is often described as a two-dimensional balance between flow within a surface boundary layer generated by alongshelf winds and a compensating subsurface flow. Typically, the effects of across-shelf winds are ignored because transport in the surface Ekman layer parallel to winds is assumed zero. Recent studies, however, have shown that the traditional view of across-shelf transport breaks down in shallow waters where friction is important. In this study, a series of two-dimensional simulations is used to show that across-shelf winds can result in across-shelf velocities in the upper few meters of the water column that are similar in magnitude to those generated by alongshelf winds. This circulation has important consequences for the transport of surface-dwelling material, such as blue crab larvae off of Delaware and Chesapeake Bays. The effects of both alongshelf and across-shelf winds on simulated surface dwelling tracer patches are examined. These studies show that across-shelf winds can account for a large amount of surface on- and offshore transport within the stratified outer shelf and, in fact, can be the primary mechanism for across-shelf transport within the friction-dominated inner shelf. Simple estimates of the parameters that describe this transport agree very well with output from the simulations.

Corresponding author address: Dr. Charles Tilburg, School of Marine Programs, Franklin College of Arts and Sciences, University of Georgia, Athens, GA 30602-3636. Email: tilburg@uga.edu

Abstract

Wind-forced across-shelf flow on a continental shelf is often described as a two-dimensional balance between flow within a surface boundary layer generated by alongshelf winds and a compensating subsurface flow. Typically, the effects of across-shelf winds are ignored because transport in the surface Ekman layer parallel to winds is assumed zero. Recent studies, however, have shown that the traditional view of across-shelf transport breaks down in shallow waters where friction is important. In this study, a series of two-dimensional simulations is used to show that across-shelf winds can result in across-shelf velocities in the upper few meters of the water column that are similar in magnitude to those generated by alongshelf winds. This circulation has important consequences for the transport of surface-dwelling material, such as blue crab larvae off of Delaware and Chesapeake Bays. The effects of both alongshelf and across-shelf winds on simulated surface dwelling tracer patches are examined. These studies show that across-shelf winds can account for a large amount of surface on- and offshore transport within the stratified outer shelf and, in fact, can be the primary mechanism for across-shelf transport within the friction-dominated inner shelf. Simple estimates of the parameters that describe this transport agree very well with output from the simulations.

Corresponding author address: Dr. Charles Tilburg, School of Marine Programs, Franklin College of Arts and Sciences, University of Georgia, Athens, GA 30602-3636. Email: tilburg@uga.edu

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

    • Search Google Scholar
    • Export Citation
  • Blumberg, A. F., and G. L. Mellor, 1987: A description of a three-dimensional coastal ocean circulation model. Three-Dimensional Coastal Ocean Models, N. Heaps, Ed., Amer. Geophys. Union, 1–16.

    • Search Google Scholar
    • Export Citation
  • Csanady, G. T., 1967: On resistance law of a turbulent Ekman layer. J. Atmos. Sci., 24 , 467471.

  • Csanady, G. T., 1978: Arrested topographic wave. J. Phys. Oceanogr., 8 , 4762.

  • Cushman-Roisin, B., 1994: Introduction to Geophysical Dynamics. Prentice Hall, 320 pp.

  • Ekman, V. W., 1905: On the influence of the earth's rotation on ocean currents. Ark. Mat. Astron. Fys., 2 , 153.

  • Epifanio, C. E., and R. W. Garvine, 2001: Larval transport on the Atlantic continental shelf of North America: A review. Estuarine Coastal Shelf Sci., 52 , 5177.

    • Search Google Scholar
    • Export Citation
  • Garvine, R. W., 1971: A simple model of coastal upwelling dynamics. J. Phys. Oceanogr., 1 , 169179.

  • Johnson, D. R., and B. S. Hester, 1989: Larval transport and its association with recruitment of blue crabs to Chesapeake Bay. Estuarine Coastal Shelf Sci., 28 , 459472.

    • Search Google Scholar
    • Export Citation
  • Jones, M. B., and C. E. Epifanio, 1995: Settlement of brachyuran megalopae in Delaware Bay: A time series analysis. Mar. Ecol. Prog. Series, 125 , 6776.

    • Search Google Scholar
    • Export Citation
  • Lentz, S. J., 1992: The surface boundary layer in coastal upwelling regions. J. Phys. Oceanogr., 22 , 15171539.

  • Lentz, S. J., 1995: Sensitivity of the inner-shelf circulation to the form of the eddy-viscosity profile. J. Phys. Oceanogr., 25 , 1928.

    • Search Google Scholar
    • Export Citation
  • Little, K. T., and C. E. Epifanio, 1991: Mechanisms for the re-invasion of an estuary by two species of brachyuran megalopae. Mar. Ecol. Prog. Series, 68 , 235242.

    • Search Google Scholar
    • Export Citation
  • Madsen, O. S., 1977: A realistic model of the wind-induced Ekman boundary layer. J. Phys. Oceanogr., 7 , 248255.

  • Olmi, E. J., 1995: Ingress of blue crab megalopae in the York River, Virginia, 1987–1989. Bull. Mar. Sci., 57 , 753780.

  • Pollard, R., P. B. Rhines, and R. O. R. Y. Thompson, 1973: The deepening of the wind-mixed layer. Geophys. Fluid Dyn., 3 , 381404.

  • Sandstrom, H., 1980: On the wind-induced sea level changes on the Scotian Shelf. J. Geophys. Res., 85 , 461468.

  • Smolarkiewicz, P. K., and W. W. Grabowski, 1990: The multidimensional positive definite advection transport algorithm. J. Comput. Phys., 86 , 355375.

    • Search Google Scholar
    • Export Citation
  • Trasviña, A., E. D. Barton, J. Brown, H. S. Velez, P. M. Kosro, and R. L. Smith, 1995: Offshore wind forcing in the Gulf of Tehuantepec, Mexico: The asymmetric circulation. J. Geophys. Res., 100 , 2064920664.

    • Search Google Scholar
    • Export Citation
  • Weatherly, G. L., and P. J. Martin, 1978: On the structure and dynamics of the oceanic bottom boundary layer. J. Phys. Oceanogr., 8 , 557570.

    • Search Google Scholar
    • Export Citation
  • Yankovsky, A. E., R. W. Garvine, and A. Münchow, 2000: Mesoscale currents on the inner New Jersey shelf driven by the interaction of buoyancy and wind forcing. J. Phys. Oceanogr., 30 , 22142230.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 1 1 0
Full Text Views 479 93 6
PDF Downloads 183 68 8