Inadequacy of treating turbidity currents as river analogues and implications for autosuspension criterion

Abstract “Consider the [turbidity] current as that of a river” R. A. Bagnold (1962);the foundation of contemporary deep marine sedimentology.Submarine sediment-laden buoyancy-driven flows, or turbidity currents, are critical as key vectors for material, nutrient, and pollutant dispersal in the world’s oceans. Extant models of turbidity currents assume that material transport is dynamically similar to open-channel flows. Here, 70 years of empirical research is integrated with new data, to show that material transport by turbidity currents is fundamentally different from fluvial systems. Although central to previous work, turbidity currents do not follow classic flow-power models for material transport; and are not “rivers on the seafloor” as previously postulated. Contrary to current theory, work done keeping sediment in suspension is shown to have a strongly non-linear dependence on available flow power. The observed relationship is attributed to an underestimation of turbulent kinetic energy (TKE) production. The energy budget has direct implications for the enigmatic autosuspension processes and ultra-long runout of turbidity currents, thus these insights are crucial for the understanding of these flows. The accurate prediction of autosuspension and runout is essential to the understanding of deep marine biogeochemical cycling and anthropogenic environmental impact.