HR: 1340h
AN: OS13A-0518    [Abstracts]
TI: Downwelling dynamics of the western Adriatic Coastal Current
AU: * Geyer, W R
EM: rgeyer@whoi.edu
AF: Applied Ocean Physics and Engineering, Woods Hole Oceanographic Inst, Woods Hole, MA 02543 United States
AU: Mullenbach, B L
AF: Department of Oceanography, Texas A&M, College Station, TX 77840 United States
AU: Kineke, G C
AF: Department of Geology and Geophysics, Boston College, Chestnut Hill, MA 02467 United States
AU: Sherwood, C R
AF: US Geological Survey, Woods Hole Road, Woods Hole, MA 02540 United States
AU: Signell, R P
AF: US Geological Survey, Woods Hole Road, Woods Hole, MA 02540 United States
AU: Ogston, A S
AF: School of Oceanography, University of Washington, Seattle, WA 98195 United States
AU: Puig, P
AF: Institut de Ciencies, del Mar, Barcelona, 08003 Spain
AU: Traykovski, P
AF: Applied Ocean Physics and Engineering, Woods Hole Oceanographic Inst, Woods Hole, MA 02543 United States
AB: The western Adriatic coastal current (WACC) flows for hundreds of kilometers along the east coast of Italy at speeds of 20 to 100 cm/s. It is fed by the buoyancy input from the Po River and other rivers of the northern Adriatic Sea, with typical freshwater discharge rates of 2000 m**3/s. The Bora winds provide the dominant forcing agent of the WACC during the winter months, resulting in peak southeastward flows reaching 100 cm/s. The energy input of the Bora is principally in the northern Adriatic, and the coastal current response is due mainly to the set up of the pressure field, although there is sometimes an accompanying local component of down-coast winds that further augments the coastal current. Downwelling conditions occur during Bora, with or without local wind-forcing, because the bottom Ekman transport occurs in either case. Downwelling results in destratification of the coastal current, due to both vertical mixing and straining of the cross-shore density gradient. The relative contributions of mixing and straining depends on the value of the Kelvin number K=Lf/(g_Oh)**1/2, where L is the width of the coastal current, f is the Coriolis parameter, g_O is reduced gravity, and h is the plume thickness. For a narrow coastal current (K$<$1), straining occurs more rapidly than vertical mixing. This is the case in the WACC during Bora events, with strain-induced destratification occurring in less than 24 hours. The straining process limits vertical mixing of the coastal current with the ambient Adriatic water, because once the isopycnals become vertical, no more mixing can occur. This limitation of mixing may explain the persistence of the density anomaly of the coastal current in the presence of high stresses. The straining process also has important implications for sediment transport: destratification allows sediment to be distributed throughout the water column during Bora events, resulting in enhanced down-coast fluxes. The influence of the downwelling dynamics on cross-shore sediment transport is still under examination.
DE: 4219 Continental shelf processes
DE: 4243 Marginal and semienclosed seas
DE: 4558 Sediment transport
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting