Abstract <p>The use of the Fluidity-ICOM (the Imperial College Ocean Model) in a nonhydrostatic formulation allows correctly studying the influence of the bottom heterogeneities on the shelf and continental slope on small-scale dynamics and stability of density currents in a mesoscale development. The occurrence of extreme cascading on a slope in the presence of an open polynya is simulated. Embedded model bottom heterogeneities are geometrically similar to detected field ones. The spread of dense water across the shelf is largely governed by submesoscale bottom heterogeneities: elevations and depressions. When flowing over the shelf edge, meander-eddies are captured by troughs, regardless of the ratio of their scales. The most stable capture occurs when the scales are close. Cascading along troughs occurs faster than that along a smooth slope and is characterized by relative stability without an obvious eddy formation. The presence of local elevations on the slope is a natural cause for hydrodynamic instability of bottom density currents. Eddies periodically form above them, and a self-oscillatory mechanism for the formation and descent of eddies arises. The presence of any bottom heterogeneities on the slope potentially increases the intensity of intermediate water ventilation. The obtained direct estimates of dense water flows on the slope during cascading development suggest that the emerging extreme cascading reaches a quasistationary development within the polynya lifetime.</p>