Deep-sea transport of sediment and associated matter, such as organic carbon, nutrients and pollutants, is controlled by near-bed currents. On the continental slope, these currents include episodic down-slope gravity-driven turbidity currents and more sustained thermohaline-driven along-slope contour currents. Recent advancements in deep-sea monitoring have catalysed a step change in our understanding of turbidity currents and contour currents individually. However, these processes rarely operate in isolation and the near-bed current regime is still to be quantified in a mixed system. Such measurements are crucial for understanding deep-sea particulate transport, calibrating numerical models and reconstructing palaeoflow. Here we use 4 years of observations from 34 instrument moorings in a mixed system offshore of Mozambique to show that near-bed currents are highly dynamic. We observe spatial variability in velocity over tidal and seasonal timescales, including reversals in current direction, and a strong steering and funnelling influence by local seabed morphology. The observed near-bed currents are capable of mobilizing and distributing sediments across the seabed, therefore complicating deep-sea particulate transport and reconstruction of palaeoceanographic conditions.

沉积物和相关物质（例如有机碳、营养物和污染物）的深海输送受到近床流的控制。在大陆坡上，这些洋流包括间歇性的下坡重力驱动的浊流和更持续的温盐驱动的沿坡等高线流。深海监测的最新进展促使我们对浊流和等高线流的理解发生了巨大的变化。然而，这些过程很少单独运行，并且近床电流状态仍有待在混合系统中量化。这些测量对于了解深海颗粒输送、校准数值模型和重建古水流至关重要。在这里，我们使用莫桑比克近海混合系统中 34 个仪器系泊设备 4 年的观测结果来表明近床流是高度动态的。我们观察到潮汐和季节时间尺度上速度的空间变化，包括当前方向的逆转，以及当地海底形态的强烈转向和漏斗影响。观测到的近床流能够移动和分布整个海底的沉积物，因此使深海颗粒输送和古海洋条件的重建复杂化。