First remote sensing of turbidity currents via seismic signals: how much can we learn about the longest sediment flows on Earth?

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Turbidity currents transport globally significant volumes of sediment and organic carbon into the deep-sea and pose a considerable hazard to sea floor infrastructure. Despite advances in technology, turbidity currents are notoriously difficult to monitor due to their relatively inaccessible location and often unpredictable occurrence. Most importantly, their powerful nature often damages instruments placed in their path. Pioneering work in the last 5 years has shown it was possible to monitor turbidity currents using moorings. Most recently, this included a flow that ran out for >1,200 km from the Congo River mouth in Jan. 2020; the longest sediment flow (of any type) yet measured on Earth. Mooring measurements, however, are expensive and logistically difficult. In addition, they are located within turbidity currents, and thus in harm’s way. These challenges mean that only a few field sites can ever be studied, yet we need to study turbidity currents at locations worldwide to understand their controls. We therefore need sensing systems for turbidity currents, which are located out of harm’s way. Excitingly, recently acquired ocean bottom seismometer (OBS) data from the Congo Canyon offshore West Africa suggest that turbidity currents emit distinctive seismic signals. These newly-recognised seismic signals now enable monitoring events across large areas via remote sensing systems located outside the event. To make a step change in understanding turbidity currents and their wider impacts, I propose to develop globally applicable methods to remotely monitor turbidity currents using OBS data from the Congo Canyon, where powerful turbidity currents are known to occur. To do this, the OBS results will be compared to independent information provided by adjacent moorings on the flows and their timing. This will help to understand what seismic signals can tell us about not only when turbidity currents occur, but also the internal flow structure and its evolution and even erosion rates. OBS surveys have a high potential of constituting an important pillar of sea floor hazard monitoring in the future. The results of this project will form the basis of the analyses of such future surveys.