HR: 0800h
AN: OS11A-0479    [Abstracts]
TI: Circulation on the Inner-Shelf of Long Bay, South Carolina: Vertical Current Variability and Evidence for Cross-Shelf Variation in Near-Bed Currents
AU: * Gutierrez, B T
EM: bgutierrez@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 700 Sumter St., EWS-617, Columbia, SC 29208 United States
AU: Voulgaris, G
EM: gvoulgaris@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 700 Sumter St., EWS-617, Columbia, SC 29208 United States
AU: Work, P A
EM: paul.work@gtsav.gatech.edu
AF: School of Civil and Environmental Engineering, Georgia Institute of Technology, 210 Technology Circle, Savannah, GA 31407 United States
AU: Seim, H
EM: harvey_seim@unc.edu
AF: Marine Sciences Department, University of North Carolina-Chapel Hill, CB# 3300,12-7 Venable Hall, Chapel Hill, NC 27599 United States
AU: Warner, J C
EM: jcwarner@usgs.gov
AF: U.S. Geological Survey, Woods Hole Science Center, 384 Woods Hole Rd., Woods Hole, MA 02543 United States
AB: Cross-shelf variations of near-bed currents and variations in vertical flow were investigated on the inner shelf of Long Bay, South Carolina during the spring and fall of 2001. Current meters sampled near-bed currents at six locations as well as vertical current profiles at three of the sites. The observations showed that the tides accounted for approximately 45-66% of the flow variability. The dominant tidal component, the semi-diurnal constituent M2, exhibited tidal ellipse orientations that are increasingly aligned with the coast closer to the shore. The largest M2 current magnitudes were identified closest to shore and over the top of a sand shoal located 5.5 km offshore of Myrtle Beach. The remaining flow variability was associated with sub-tidal flows which respond to the passage of low-pressure systems across the region. These weather systems were characterized by periods of southwesterly winds in advance of low-pressure centers followed by northeasterly winds as the systems passed over the study area. When strong southwesterly winds persisted, surface flow was oriented approximately in the direction of the wind. At the same time near-bottom flows were also directed to the northeast in the direction of the wind except during periods of stratification when vertical current profiles suggest near-bed onshore flow. The stratified flows were observed mainly during the spring deployment. For periods of strong northeasterly winds, currents were directed alongshore to the southwest and exhibited little variation throughout the water column. These observations are consistent with recent field and modeling studies for the inner-shelf. Comparison of the near-bed flow measurements during the fall deployment revealed a cross-shore gradient in alongshore flow during periods of strong northeasterly winds. During these episodes flows at the offshore measurement stations were oriented in the direction of the wind, while flows closest to shore occurred in the opposite direction. These observations reveal 1) conditions which contribute to cross-shore transport and 2) the presence of an alongshore flow gradient which may affect sediment transport patterns during certain meteorological conditions.
DE: 4512 Currents
DE: 4546 Nearshore processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting