• Beardsley, R. C., , and W. C. Boicourt, 1981: On estuarine and continental-shelf circulation in the Middle Atlantic Bight. Evolution of Physical Oceanography, A. Warren and C. Wuncsh, Eds., The MIT Press, 198–233.

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

    • Search Google Scholar
    • Export Citation
  • Codiga, D. L., 1993: Laboratory realizations of stratified seamount-trapped waves. J. Phys. Oceanogr., 23 , 20532071.

  • Codiga, D. L., , and A. E. Houk, 2002: Current profile timeseries from the FRONT moored array. Department of Marine Sciences Tech. Rep., University of Connecticut, 19 pp.

  • Codiga, D. L., , and L. V. Rear, 2004: Observed tidal currents outside Block Island Sound: Offshore decay and effects of estuarine outflow. J. Geophys. Res., 109 .C07S05, doi:10.1029/2003JC001804.

    • Search Google Scholar
    • Export Citation
  • Codiga, D. L., , J. A. Rice, , and P. A. Baxley, 2004: Networked acoustic modems for real-time data delivery from distributed moorings in the coastal ocean: Initial system development and performance. J. Atmos. Oceanic Technol., 21 , 331346.

    • Search Google Scholar
    • Export Citation
  • Codiga, D. L., , J. A. Rice, , P. A. Baxley, , and D. Hebert, 2005: Networked acoustic modems for real-time telemetry from distributed moorings in the coastal ocean: Application to an array of bottom-mounted ADCPs. J. Atmos. Oceanic Technol., in press.

    • Search Google Scholar
    • Export Citation
  • Dyer, K. R., 1997: Estuaries: A Physical Introduction. 2d ed. Wiley and Sons, 195 pp.

  • Edwards, C. A., , T. A. Fake, , and P. S. Bogden, 2004a: Spring–summer frontogenesis at the mouth of Block Island Sound. Part 1: A numerical investigation into tidal and buoyancy-forced motion. J. Geophys. Res., 109 .C12021, doi:10.1029/2003JC002132.

    • Search Google Scholar
    • Export Citation
  • Edwards, C. E., , T. A. Fake, , D. L. Codiga, , and P. S. Bogden, 2004b: Spring–summer frontogenesis at the mouth of Block Island Sound: Part 2: Combining acoustic Doppler current profiler records with a general circulation model to investigate the impact of subtidal forcing. J. Geophys. Res., 109 .C12022, doi:10.1029/2003JC002133.

    • Search Google Scholar
    • Export Citation
  • Garvine, R. W., 1995: A dynamical system for classifying buoyant coastal discharges. Cont. Shelf Res., 15 , 15851596.

  • Gay, P., , J. O’Donnell, , and C. A. Edwards, 2004: Exchange between Long Island Sound and adjacent waters. J. Geophys. Res., 109 .C06017, doi:10.1029/2004JC002319.

    • Search Google Scholar
    • Export Citation
  • Heaps, N. S., 1972: Estimation of density currents in the Liverpool Bay area of the Irish Sea. Geophys. J. Roy. Astron. Soc., 30 , 415432.

    • Search Google Scholar
    • Export Citation
  • Kincaid, C., , R. A. Pockalny, , and L. M. Huzzey, 2003: Spatial and temporal variability in flow at the mouth of Narragansett Bay. J. Geophys. Res., 108 .C73218, doi:10.1029/2002JC001395.

    • Search Google Scholar
    • Export Citation
  • Kirincich, A., 2003: Structure and variability of a coastal front. M.S. Thesis, Graduate School of Oceanography, University of Rhode Island, 124 pp.

  • Kirincich, A., , and D. Hebert, 2005: The structure of the coastal density front at the outflow of Long Island Sound during spring 2002. Cont. Shelf Res., 25 , 10971114.

    • Search Google Scholar
    • Export Citation
  • Large, W. G., , and S. Pond, 1981: Open ocean momentum flux measurements in moderate to strong winds. J. Phys. Oceanogr., 11 , 324336.

  • Lentz, S., , R. T. Guza, , S. Elgar, , F. Feddersen, , and T. H. C. Herbers, 1999: Momentum balances on the North Carolina inner shelf. J. Geophys. Res., 104 , C8,. 1820518226.

    • Search Google Scholar
    • Export Citation
  • Münchow, A., , and R. W. Garvine, 1993a: Dynamical properties of a buoyancy driven coastal current. J. Geophys. Res., 98 , 2006320078.

  • Münchow, A., , and R. W. Garvine, 1993b: Buoyancy and wind forcing of a coastal current. J. Mar. Res., 51 , 293322.

  • Münchow, A., , and R. J. Chant, 2000: Kinematics of inner shelf motions during the summer stratified season off New Jersey. J. Phys. Oceanogr., 30 , 247268.

    • Search Google Scholar
    • Export Citation
  • Sanders, T. M., , and R. W. Garvine, 2001: Fresh water delivery to the continental shelf and subsequent mixing: An observational study. J. Geophys. Res., 106 , (C11). 2708727101.

    • Search Google Scholar
    • Export Citation
  • Simpson, J. H., , and A. J. Souza, 1995: Semidiurnal switching of stratification in the region of freshwater influence of the Rhine. J. Geophys. Res., 100 , 70377044.

    • Search Google Scholar
    • Export Citation
  • Ullman, D. S., , and P. C. Cornillon, 1999: Satellite-derived sea surface temperature fronts on the continental shelf off the northeast U.S. coast. J. Geophys. Res., 104 , 2345923478.

    • Search Google Scholar
    • Export Citation
  • Ullman, D. S., , and D. L. Codiga, 2004: Seasonal variation of a coastal jet in the Long Island Sound outflow region based on HF radar and Doppler current observations. J. Geophys. Res., 109 .C07S06, doi:10.1029/2002JC001660.

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

    • Search Google Scholar
    • Export Citation
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Interplay of Wind Forcing and Buoyant Discharge off Montauk Point: Seasonal Changes to Velocity Structure and a Coastal Front

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  • 1 Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island
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Abstract

Seasonal-mean currents in fall, winter, and spring on the bathymetrically complex continental shelf 15–65 m deep off Montauk Point, outside Block Island Sound, are analyzed using moored profiling current-meter records from a 2.5-yr period. A sharp boundary, or coastal front, occurs where strong, shallow, generally southwestward flow that weakens nearly linearly with increasing depth meets deeper flow nearly opposite in direction (fall/winter) or markedly weaker (spring). Velocities veer clockwise (counterclockwise) with increasing depth inshore (offshore) of the front. Evidence is presented that thermal wind balance holds without major frictional modification: it accounts for the veering, and the seasonal-mean horizontal density gradients it implies are generally toward the southeast quadrant in agreement with limited hydrographic measurements. Substantial seasonal changes in flow and frontal attributes occur because of the interplay of annual cycles in wind forcing and buoyant discharge. In fall and winter, upwelling-favorable wind causes nearshore setdown of sea surface height and an inshore-directed barotropic pressure gradient: shallow down-coast (alongshore to the south and west) currents weaken, and deep currents are up-coast. In spring, buoyant discharge peaks and winds weaken: shallow down-coast flow strengthens and deep flow weakens. The front extends to the seafloor, with attachment depth shallowest in winter, deepest in spring, and intermediate in fall; its width is smaller in fall than in winter. Buoyant discharge theory based on bottom boundary layer density advection dynamics captures these seasonal shifts. Cross-shelf circulation includes offshore (onshore) shallow (deep) motion; deep onshore motion appears enhanced near a canyon and persistent through all three seasons, suggesting wind-driven upwelling is not solely responsible.

Corresponding author address: Dr. Daniel L. Codiga, Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882. Email: d.codiga@gso.uri.edu

Abstract

Seasonal-mean currents in fall, winter, and spring on the bathymetrically complex continental shelf 15–65 m deep off Montauk Point, outside Block Island Sound, are analyzed using moored profiling current-meter records from a 2.5-yr period. A sharp boundary, or coastal front, occurs where strong, shallow, generally southwestward flow that weakens nearly linearly with increasing depth meets deeper flow nearly opposite in direction (fall/winter) or markedly weaker (spring). Velocities veer clockwise (counterclockwise) with increasing depth inshore (offshore) of the front. Evidence is presented that thermal wind balance holds without major frictional modification: it accounts for the veering, and the seasonal-mean horizontal density gradients it implies are generally toward the southeast quadrant in agreement with limited hydrographic measurements. Substantial seasonal changes in flow and frontal attributes occur because of the interplay of annual cycles in wind forcing and buoyant discharge. In fall and winter, upwelling-favorable wind causes nearshore setdown of sea surface height and an inshore-directed barotropic pressure gradient: shallow down-coast (alongshore to the south and west) currents weaken, and deep currents are up-coast. In spring, buoyant discharge peaks and winds weaken: shallow down-coast flow strengthens and deep flow weakens. The front extends to the seafloor, with attachment depth shallowest in winter, deepest in spring, and intermediate in fall; its width is smaller in fall than in winter. Buoyant discharge theory based on bottom boundary layer density advection dynamics captures these seasonal shifts. Cross-shelf circulation includes offshore (onshore) shallow (deep) motion; deep onshore motion appears enhanced near a canyon and persistent through all three seasons, suggesting wind-driven upwelling is not solely responsible.

Corresponding author address: Dr. Daniel L. Codiga, Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882. Email: d.codiga@gso.uri.edu

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