HR: 09:15h
AN: OS11D-06    [Abstracts]
TI: Fine Sediment Distribution in the Western Adriatic Coastal Current
AU: * Kineke, G C
EM: kinekeg@bc.edu
AF: Dept. of Geology & Geophysics Boston College, 140 Commonwealth Ave, Chestnut Hill, MA 02467
AU: Sherwood, C R
EM: csherwood@usgs.gov
AF: U.S. Geological Survey, 384 Woods Hole Road, Woods Hole, MA 02543
AU: Geyer, W R
EM: rgeyer@whoi.edu
AF: Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
AU: Mullenbach, B L
EM: bmullenbach@ocean.tamu.edu
AF: Dept. of Oceanography, Texas A&M University, College Station, TX 77840-3146
AB: A study of water properties and suspended sediments on the Apennine margin was conducted as part of the Po and Apennine Sediment Transport and Accumulation (PASTA) component of the EuroSTRATAFORM project. Repeated hydrographic transects encompassing a Bora wind event during February 2003 documented variability of the cross-shelf extent of the coastal current, significant changes in the width of the front, vertical stratification, and suspended sediment inventory over periods of a few days. During calm conditions, suspended sediment concentrations (SSCs) off the Apennine margin were generally low, 10 mg/l or less in water depths of < 10 m, with the maximum close to shore. During Bora conditions, the coastal current deepens and destratifies as the result of downwelling. The SSC maximum increases and moves seaward to approximately 15 m depth in the vicinity of the sand-mud transition (SMT), bounded on the seaward side by the cross-shelf density front. The maximum in SSC is likely the result of interrelated factors: a) the mix of grain sizes at the SMT are more easily resuspended than coarser sediments closer to shore and more cohesive sediments seaward; b) depth of resuspension due to waves; c) adjustment of the coastal current during Bora events and subsequent relaxation. The latter could be important with respect to moving sediment offshore, as well as governing the location of the sand-mud transition. Fine sediments from the Apennine Rivers initially deposited in shallow water are easily resuspended and transported along shore (most of the flux) within the coastal current. With wave resuspension and downwelling, sediments are distributed throughout the water column extending to greater depths, but are confined by the density front. With relaxation of the Bora event, stratification is re-established and sediments in the vicinity of the front are deposited in deeper water, resulting in net transport offshore. Comparison with realistic simulations from a 3-dimensional numerical model support the key features of the interpretation including change in width and depth of the coastal current, location of the SSC maximum, and a boundary shear stress minimum at the front.
DE: 3022 Marine sediments--processes and transport
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting