Ocean Bottom Seismometers Provide Direct Measurements of Pulsed‐Structure and Turbulence of Turbidity Currents Overspilling From a Submarine Channel

Abstract Turbidity currents transport vast amounts of sediment, carbon, and heat along submarine channels, yet their overspill onto channel‐levees and abyssal mixing remain poorly constrained due to lack of direct observations. Ocean‐bottom seismometers (OBS) deployed on the Congo Canyon–Channel levees captured the structure and turbulence of overspill during an exceptionally large canyon‐flushing event in 2020. Overspill persisted for 3 weeks and comprised numerous short (20‐min to 2‐hr) pulses focused at outer bends. Spectra during overspill show well‐resolved turbulence inertial subranges, yielding event‐average dissipation rates of 10 −6 –10 −5 m 2 s −3 , comparable to energetic internal‐tide breaking. Abyssal overspill can therefore be long‐lasting and highly pulsed, providing an episodic but locally important source of deep‐ocean mixing. This new view of levee overspill has important implications for building levees and the interpretation of ancient turbidites. Individual levee deposits may be formed incrementally by many pulses of dilute and fine‐grained flow from a single turbidity current.