Sediment-Driven Downslope Flow in Submarine Canyons and Channels: Three-Dimensional Numerical Experiments

Abstract

The role of submarine canyons and channels in sediment-driven downslope flow (sediment plumes) is examined, using a three-dimensional, rotational numerical model that couples the hydrodynamics and sediment transport. The model domain consists of a bottom ocean layer of constant height coupled with an essentially inert upper ocean. The model equations are cast in a rotated, bottom-following coordinate system in which vertical grid spacing is independent of the ocean depth and bathymetry can be resolved accurately. This allows for tracing bottom-attached sediment plumes (?decameters in height) from shallow water into great depths of the ocean. The calculations reproduce morphologic features related to the occurrance of sediment plumes, such as the formations of 1) localized deposition areas of sediment off the mouth of submarine canyons and 2) levees at both sides of submarine channels. Furthermore, it is demonstrated that sediment plumes are not only important for the transport of littoral sediment to deeper water, but also trigger renewal of deep water, as being observed in a tropical ocean. Sediment plumes, predicted here, are short-lived, transient features with lifetimes of days and velocities of up to 90 cm s?1.