HR: 1340h
AN: OS53A-0982    [Abstracts]
TI: Iceberg scours offshore of South Carolina
AU: * Hill, J C
EM: jchill@coastal.edu
AF: Coastal Carolina University, Center for Marine and Wetland Studies, Conway, SC 29526, United States
AU: Gayes, P T
EM: ptgayes@coastal.edu
AF: Coastal Carolina University, Center for Marine and Wetland Studies, Conway, SC 29526, United States
AU: Driscoll, N W
EM: ndriscoll@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093,
AU: Johnstone, E A
EM: eajohnst@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093,
AU: Sedberry, G
EM: George.Sedberry@noaa.gov
AF: Gray's Reef National Marine Sanctuary, National Oceanic and Atmospheric Administration, Savannah, GA 31411, United States
AB: High resolution swath bathymetry data collected offshore of South Carolina as part of the NOAA Ocean Explorations program in 2006 and 2007 show evidence of extensive iceberg scouring along the upper slope (170-220 m water depth). Numerous furrows, 10-100 m wide and <10 m deep, are oriented WSW along regional bathymetric contours. Lateral berms along the length of the furrows record the plowing of iceberg keels along the seafloor. Video observations along these berms show evidence of large upturned blocks and boulders. Many of the furrows terminate in semicircular pits ringed by several meters high ridges. These are interpreted as terminal grounding pits, indicating icebergs have come to rest on the seafloor. The location and orientation of the keel marks suggests icebergs were entrained a southwestward flowing coastal current. Presently, warm waters of the rapid, northeastward flowing Gulf Stream bathe the upper slope across the region. An offshore shift in the Gulf Stream axis during sea level lowstand may have allowed glacially fed coastal currents to penetrate farther south, transporting icebergs to this portion of the margin. Subsequent reintroduction of the Gulf Stream appears to have enhanced the scour topography through bottom current erosion and reworking. This is the first evidence of iceberg transport to subtropical latitudes along the U.S. Atlantic margin. Additional high resolution surveys along the upper slope of the eastern United States will likely reveal further evidence of iceberg scouring along the margin.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3002 Continental shelf and slope processes (4219)
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 4926 Glacial
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting