Lateral circulation and sediment transport driven by axial winds in an idealized, partially mixed estuary

American Geophysical Union (AGU) - Tập 114 Số C12 - 2009
Shih‐Nan Chen1,2, Lawrence P. Sanford3, David K. Ralston4
1Now at Applied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA.
2University of Maryland Center for Environmental Science, Horn Point Laboratory, Cambridge, Maryland, USA
3Horn Point Laboratory University of Maryland Center for Environmental Science Cambridge Maryland USA
4Applied Ocean Physics and Engineering Department Woods Hole Oceanographic Institution Woods Hole Massachusetts USA

Tóm tắt

A 3D hydrodynamic model (ROMS) is used to investigate lateral circulation in a partially mixed estuary driven by axial wind events and to explore the associated transport of sediments. The channel is straight with a triangular cross section. The model results suggest that driving mechanisms for lateral circulation during axial wind events are different between stratified and unstratified conditions. When the water column is largely unstratified, rotational effects do not drive significant lateral circulation. Instead, differential advection of the axial salinity gradient by wind‐driven axial flow is responsible for regulating the lateral salinity gradients that in turn drive bottom‐divergent/convergent lateral circulation during down/up‐estuary winds. From the subtidal lateral salt balance, it is found that the development of lateral salinity gradient by wind‐induced differential advection is largely counterbalanced by the advection of salt by lateral circulation itself. When the water column is stratified, the lateral flow and salinity structures below the halocline closely resemble those driven by boundary mixing, and rotational effects are important. Lateral sediment flux and the event‐integrated sediment transport are from channel to shoals during down‐estuary winds but reversed for up‐estuary winds. Potential impacts of wind‐generated waves on lateral sediment transport are evaluated with two cases representing event conditions typical of upper Chesapeake Bay. Accounting for wind wave effects results in an order of magnitude increase in lateral sediment fluxes because of greater bottom stresses and sediment resuspension.

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American Geophysical Union (AGU)

Tập 114 Số C12

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