First detailed synchronous sediment-concentration and velocity data for submarine turbidity currents

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Submarine sediment density flows ("turbidity currents") and rivers on land are volumetrically the most important processes for moving sediment across our planet. However, submarine flows are more episodic and are typically more violent (with speeds of up to 20m/s) than river floods. Moreover, a single submarine flow is capable of transporting ten times the annual sediment load from all of the world's rivers combined. Submarine flows are important because they produce many of the world's most extensive and voluminous sedimentary deposits, both on the modern sea floor and in the ancient rock record, but also because they can break seafloor cables that now carry over 95% of global data traffic (that underpin our daily lives through the internet and financial markets). Ancient submarine flows created subsurface rock sequences that contain many of our largest oil and gas reserves. Submarine flows carve canyons, which are deeper than the Grand Canyon, through processes that are still poorly understood, and flows within canyons play a key role in supplying organic carbon and nutrients to benthic ecosystem (that include important diversity hotspots) in the deep sea.The most remarkable aspect of submarine density flows is how difficult they are to monitor directly, and how few observations we presently have of such flows in action. This paucity of direct observation provides a stark contrast to the information available for other major sediment transport processes. Changes in the frontal speed of submarine flows have been measured in just five locations, mainly through indirect evidence provided by the timing of sequential underwater cable breaks. Their vertical velocity profile has only ever been measured in three locations and never with sampling rates more frequent than one per hour. No flow has been monitored along its full path, which is of key importance because flows evolve considerably in character along that path.To produce a fundamental step-change in our understanding of submarine flows we need to directly monitor active flows along their entire flow path. Until this is achieved, our understanding of the flow character and its spatial evolution will remain limited. This project will provide by far the most detailed monitoring data yet collected for submarine flows: be the first that places constraints on both dilute and dense near-bed flow components, be the first data set that spans the full flow path, and be the first data set to link measurements of flow processes and the resulting deposit character in such an environment. We aim to conduct a large-scale collaborative program to document and understand sediment transport processes occurring within Monterey Canyon offshore California during an 18-month period in 2014-16, in collaboration with the Monterey Bay Aquarium Research Institute (MBARI) and US Geological Survey (USGS). Such international collaboration is essential for spreading the cost of this ambitious work. MBARI are providing the project with access to a series of innovative tools for monitoring flows that MBARI have designed, built and field tested over the last decade; a contribution worth over $10 Million. This includes aBenthic Instrument Nodes for their Monterey Ocean Observing System that will provide the first high frequency (every 2 to 30 seconds rather than hourly) measurements of 3D velocity, temperature, salinity and density profiles from such flows. MBARI also provide access to the research vessels and ROVs necessary for equipment deployment and servicing during this 18 month period, as MBARI is located at the head of the canyon. MBARI and USGS will place further monitoring equipment in the canyon as part of the project that is worth a further $1.5 Million. Moreover, the MBARI and USGS bear the risk for the loss of all of their equipment. NERC bears a small fraction of the total cost and risk for this unique field experiment, which therefore represents exceptional value for money.