Beschreibung: In the present paper a hydrostatic “reduced gravity” model, generally used to simulate transient bottom-arrested gravity plumes, was coupled with a sediment transport model. The coupled model considers the respective contribution of suspended sediment particles on the buoyancy of a plume and allows one to simulate autosuspension and size-differential deposition of sediments based on the local turbulence and settling velocities. Simulations using the coupled model reveal that sediment-enriched plumes are able to inject both entrained and original shelf water masses into intermediate and bottom layers of an adjacent ocean basin in an ageostrophic dynamical balance. Hence the mechanism described here is more rapid than classic, “seawater” plumes, which are solely driven by surplus density of the water masses. Results suggest that “turbidity” plumes may constitute an important process in the formation and renewal of deep waters in the Arctic Ocean. In case a turbidity plume reaches its level of equilibrium density, deposition of suspended particles causes the density of the interstitial fluid to be lower than the density of the ambient fluid. This initiates upward convection within the water column. The substantial difference between TS- and turbidity plumes is described by model experiments that utilize idealized slope and sediment distributions. A realistic simulation of a turbidity plume cascading down the continental slope of the western Barents Sea is presented. The computed distribution of deposited sediments agrees well with observations in an area of high accumulation of shelf-derived sediments. The frequency of occurrence of sediment-enriched gravity plumes originating from the Barents Sea shelf is estimated from the various geological variables (thickness of sediments at the bottom, grain size composition) measured from bottom sediments samples.

Beschreibung: A two-dimensional, high-resolution, non-linear, two-layer, free-surface, boundary-fitted co-ordinate, hydrostatic model was applied to study the time–space variability of hydraulic controls and the development of internal bores in the Strait of Gibraltar. The model predicts the occurrence of four averaged (over a tropical month) controls located to the west of the Spartel Sill, at the Spartel and Camarinal Sills and in the Tarifa Narrows. The last of these controls is apparent in the sense that it consists of discrete fragments alternating with subcritical flow regions. The only control which extends over the whole width of the strait is the control at the Camarinal Sill, but it breaks down during neap tide, too. This control exists concurrently with the control in the Tarifa Narrows for short periods, while for much of the tropical month there is either just one or neither of the controls. The model predicts the development of a hydraulic jump and a jump-drop pair near the Camarinal Sill; the appearance of bulges of Mediterranean water to the east and west of the sill; the large-amplitude and small-amplitude internal bores released from the Camarinal Sill, which travel, respectively, eastward and westward, and their transformation due to radial spreading and dissipative effects. Also presented here are the results illustrating the effects of earth's rotation on the internal bores in the Strait of Gibraltar.