• 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, 1843–1866.

  • Beckman, A., and D. B. Haidvogel, 1993: Numerical simulation of flow around a tall seamount. Part I: Problem formulation and model accuracy. J. Phys. Oceanogr.,23, 1736–1753.

  • Blackburn, S. I., and G. R. Cresswell, 1993: A coccolithophorid bloom in Jervis Bay, Australia. Aust. J. Mar. Freshwater Res.,44, 253–260.

  • Blanton, J., 1971: Exchange of Gulf Stream Water with North Carolina shelf water in Onslow Bay during stratified conditions. Deep-Sea Res.,18, 167–178.

  • Blumberg, A. F., and G. L. Mellor, 1983: Diagnostic and prognostic numerical circulation studies of the South Atlantic Bight. J. Geophys. Res.,88, 4579–4592.

  • ——, and L. H. Kantha, 1985: Open boundary conditions for circulation models. J. Hydr. Eng.,111, 237–255.

  • ——, and G. L. Mellor, 1987: A description of a three-dimensional coastal ocean circulation model. Three-Dimensional Coastal Ocean Models, Vol. 4, N. Heaps, Ed., Amer. Geophys. Union, 1–16.

  • Boland, F. M., 1979: A time series of expendable bathythermograph sections across the East Australian Current. Aust. J. Mar. Freshwater Res.,30, 303–313.

  • Boucher, J., F. Ibanez, and L. Prieur, 1987: Daily and seasonal variations in the spatial distribution of zooplankton populations in relation to the physical structure in the Ligurian Sea Front. J. Mar. Res.,45, 133–173.

  • Church, J. A., and G. R. Cresswell, 1986: Oceanographic features of Southeast Australian Waters. CSIRO Marine Laboratories Internal Summary Rep. [Available from CSIRO Marine Research, GPO Box 1538, Hobart, Tasmania 7001, Australia.].

  • Cresswell, G. R., 1994: Nutrient enrichment of the Sydney continental shelf. Aust. J. Mar. Freshwater Res.,45, 677–691.

  • ——, C. Ellyett, R. Legeckis, A. F. Pearce, and R. Boyd, 1983: Nearshore features of the East Australian Current system. Aust. J. Mar. Freshwater Res.,34, 105–114.

  • Flather, R. A., 1976: A tidal model of the northwest European continental shelf. Mem. Soc. Roy. Sci. Leige, Ser. 6,10, 141–164.

  • Garret, C., P. MacCready, and P. Rhines, 1993: Boundary mixing and arrested Ekman layers: Rotating stratified flow near a sloping boundary. Annu. Rev. Fluid Mech.,25, 291–323.

  • Gibbs, M. T., J. H. Middleton, and P. Marchesiello, 1998: Baroclinic response of Sydney shelf waters to local wind and deep ocean forcing. J. Phys. Oceanogr.,28, 178–190.

  • Gill, A. E., and E. H. Schulmann, 1979: Topographically induced changes in the structure of an inertial coastal jet: Application to the Agulhas Current. J. Phys. Oceanogr.,9, 975–991.

  • Godfrey, J. S., G. R. Cresswell, and F. M. Boland, 1980a: Observations of low Richardson numbers and undercurrents near a front in the East Australian Current. J. Appl. Meteor.,10, 301–307.

  • ——, ——, T. J. Golding, and A. F. Pearce, 1980b: The separation of the East Australian Current. J. Phys. Oceanogr.,10, 430–440.

  • Hallegraeff, G. M., and S. W. Jeffrey, 1993: Annually recurrent diatom blooms in spring along the New South Wales coast of Australia. Aust. J. Mar. Freshwater Res.,44, 325–334.

  • Hitchcock, G. L., A. J. Mariano, and T. Rossby, 1993: Mesoscale pigment fields in the Gulf Stream: Observations in a meander crest and trough. J. Geophys. Res.,98, 8425–8445.

  • Hsueh, Y., and J. J. O’Brien, 1971: Steady coastal upwelling induced by an along-shore current. J. Phys. Oceanogr.,1, 180–186.

  • Hynd, J. S., 1969: Isotherm maps for tuna fisherman. Aust. Fish.,28(7), 13–22.

  • Levitus, S., 1982: Climatological Atlas of the World Ocean. NOAA Prof. Paper No. 13, U.S. Department of Commerce, National Oceanographic and Atmospheric Administration, 173 pp.

  • MacCready, P., and P. B. Rhines, 1993: Slippery bottom boundary layers on a slope. J. Phys. Oceanogr.,23, 5–22.

  • Mahadevan, A., J. Oliger, and R. Street, 1996: A nonhydrostatic mesoscale ocean model. Part I: Well-posedness and scaling. J. Phys. Oceanogr.,26, 1868–1880.

  • Mellor, G. L., and T. Yamada, 1982: Development of a turbulence closure model for geophysical fluid problems. Rev. Geophys. Space Phys.,20, 851–875.

  • ——, T. Ezer, and L.-Y. Oey, 1994: The pressure gradient conundrum of sigma coordinate ocean models. J. Atmos. Oceanic Technol.,11, 1126–1134.

  • NOAA, 1988: NGDC data announcement 88-MG-02: Digital relief of the surface of the Earth. U.S. Department of Commerce, NOAA, NGDC, Boulder, CO.

  • Oke, P. R. and J. H. Middleton, 2000: Nutrient enrichment off Port Stephens: the Role of the East Australian Current. Contin. Shelf Res., in press.

  • Olsen, D. B., O. B. Brown, and S. R. Emmerson, 1983: Gulf Stream frontal statistics from Florida Straits to Cape Hatteras derived from satellite and historical data. J. Geophys. Res.,88, 4569–4577.

  • Palma, E. D., and R. P. Matano, 1998: On the implementation of passive open boundary conditions for the Princeton Ocean Model: The barotropic mode. J. Geophys. Res.,103, 1319–1341.

  • Ridgway, K. R., and J. S. Godfrey, 1997: Seasonal cycle of the East Australian Current. J. Geophys. Res.,102, 22 921–22 936.

  • Rochford, D. J., 1972: Nutrient enrichment of East Australian coastal waters. I. Evans Head upwelling. CSIRO Aust. Div. Fish. Oceanogr. Tech. Paper 33, 1-37. [Available from CSIRO Marine Research, GPO Box 1538, Hobart, Tasmania 7001, Australia.].

  • ——, 1975: Nutrient enrichment of East Australian coastal waters. II. Laurieton upwelling. Aust. J. Mar. Freshwater Res.,26, 233–243.

  • Smagorinsky, J., 1963: General circulation experiments with primitive equations, I. The basic experiment. Mon. Wea. Rev.,91, 99–164.

  • Stanton, B. R., 1976: An oceanic frontal jet near the Norfolk Ridge north-west of New Zealand. Deep-Sea Res.,23, 821–829.

  • Tranter, D. J., D. J. Carpenter, and G. S Leech, 1986: The coastal enrichment effects of the East Australian Current eddy field. Deep-Sea Res.,33, 1705–1728.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 336 129 12
PDF Downloads 173 97 10

Topographically Induced Upwelling off Eastern Australia

View More View Less
  • 1 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon
  • | 2 School of Mathematics, University of New South Wales, Sydney, Australia
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

A high-resolution, numerical study of an idealized western boundary current flow over variable topography is presented, with application to the East Australian Current (EAC). The results indicate that alongshelf topographic variations off Australia’s east coast cause the EAC to accelerate over the narrowing continental shelf near Cape Byron. This acceleration is sufficient to hinder the geostrophic adjustment in the bottom boundary layer (BBL), which would usually cause the EAC-driven BBL to shut down. Consequently, a region of persistent, high bottom stress was established off Cape Byron, which was responsible for driving an upwelling BBL. It is shown that the enhanced vertical mixing, associated with a low Richardson number flow beneath the EAC, reduced the local stratification. Consequently, the Burger number is decreased resulting in a long shutdown timescale of the BBL, which enables a nearshore thermal to be established and maintained. Such fronts are commonly observed in the region. As a part of the analysis the term balances of the model equations are presented, comparing the dynamical balances at locations along the domain that exhibit varying degrees of topographic variability. The results indicate that the BBL dynamics were not purely geostrophic, further explaining why BBL shutdown was not prevailing. Moreover, it is shown that the formation of the thermal front was dependent on the magnitude of the EAC’s southward transport, explaining why the occurrence of thermal fronts is greater during the spring and summer periods.

Corresponding author address: Dr. Peter R. Oke, COAS, Oregon State University, 104 Ocean Admin. Building, Corvallis, OR 97331.

Email: proke@oce.orst.edu

Abstract

A high-resolution, numerical study of an idealized western boundary current flow over variable topography is presented, with application to the East Australian Current (EAC). The results indicate that alongshelf topographic variations off Australia’s east coast cause the EAC to accelerate over the narrowing continental shelf near Cape Byron. This acceleration is sufficient to hinder the geostrophic adjustment in the bottom boundary layer (BBL), which would usually cause the EAC-driven BBL to shut down. Consequently, a region of persistent, high bottom stress was established off Cape Byron, which was responsible for driving an upwelling BBL. It is shown that the enhanced vertical mixing, associated with a low Richardson number flow beneath the EAC, reduced the local stratification. Consequently, the Burger number is decreased resulting in a long shutdown timescale of the BBL, which enables a nearshore thermal to be established and maintained. Such fronts are commonly observed in the region. As a part of the analysis the term balances of the model equations are presented, comparing the dynamical balances at locations along the domain that exhibit varying degrees of topographic variability. The results indicate that the BBL dynamics were not purely geostrophic, further explaining why BBL shutdown was not prevailing. Moreover, it is shown that the formation of the thermal front was dependent on the magnitude of the EAC’s southward transport, explaining why the occurrence of thermal fronts is greater during the spring and summer periods.

Corresponding author address: Dr. Peter R. Oke, COAS, Oregon State University, 104 Ocean Admin. Building, Corvallis, OR 97331.

Email: proke@oce.orst.edu

Save