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Direct monitoring of deep-sea turbidity currents to quantify their interaction with the seafloor and impacts on critical subsea infrastructure

Clare, Michael. 2019 Direct monitoring of deep-sea turbidity currents to quantify their interaction with the seafloor and impacts on critical subsea infrastructure. In: Scour and Erosion IX - Proceedings of the 9th International Conference on Scour and Erosion, ICSE 2018, Taipei; Taiwan, 5-8 November 2018. CRC Press, 9-10.

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Abstract/Summary

Avalanches of sediment in the ocean, known as turbidity currents, are among the volumetrically most important sediment transport processes globally. They can travel across vast tracts of seafloor at speeds (up to 20 m/s) that break important infrastructure and are major agents for seafloor erosion. Turbidity currents locally scour the seafloor, drive bedform migration, and sculpt submarine channels that extend into the deep sea. Despite their importance, there is still much we do not know about them. Unlike their onshore equivalents – rivers—only a handful of direct measurements exist for turbidity currents; hence, we have largely had to rely on the deposits that they left behind and scaled-down laboratory models to understand them. New developments in technology now enable detailed and direct measurements of turbidity currents at field scale. Repeat seafloor surveys reveal a range of bedforms that are created by these flows, as well as the processes that trigger them. In some very active settings such as fjord-head deltas, flows can trigger significant erosion (up to 40 m vertically in one season), forming features similar to knickpoints in bedrock rivers. Acoustic Doppler Current Profilers and water column imaging indicate that turbidity currents may be driven by a dense (>10% volume by concentration) near-bed layer – behaving more like a two-layer snow avalanche than the fully turbulent flows suggested by many laboratory experiments. Here, we present recent measurements from a range of fjord and deep-marine settings worldwide that provide new insights into flow behaviour, enable quantification of their seafloor interaction, provide key inputs for impact assessments for seafloor infrastructure, and challenge many existing preconceptions about turbidity currents.

Item Type: Publication - Conference Item (Paper)
Date made live: 15 Jan 2019 15:54 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/522035

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