Sediment-driven downslope flow in submarine canyons and channels: Three-dimensional numerical experiments

The role of submarine canyons and channels in sediment-driven downslope how (sediment plumes) is examined,, using a three-dimensional, rotational nume rical model that couples the hydrodynamics and sediment transport. The mode l domain consists of a bottom ocean layer of constant height coupled with a n essentially Inert upper ocean. The model equations are cast in a rotated, bottom-following coordinate system in which vertical grid spacing is indep endent of the ocean depth and bathymetry can be resolved accurately. This a llows for tracing bottom-attached sediment plumes (similar to decameters in height) from shallow water into great depths of the ocean. The calculation s reproduce morphologic features related to the occurrance of sediment plum es, such as the formations of ii Localized deposition areas of sediment off the mouth of submarine canyons and 2) levees at both sides of submarine ch annels. Furthermore, it is demonstrated that sediment plumes are nor only i mportant for the transport of littoral sediment to deeper water, but also t rigger renewal of deep water, as being observed in a tropical ocean. Sedime nt plumes, predicted here, are short-lived, transient features with lifetim es of days and velocities of up to 90 cm s(-1).