A Canyon Conundrum: What controls contemporary sediment, carbon and pollutant transport in submarine canyons?

Dr Mike Clare, Dr Veerle Huvenne, Prof Stephen Darby, Assoc Prof Rob Hall, Dr Furu Mienis
Rationale: 

Submarine canyons occur along all the world’s submerged continental margins and host important sediment, nutrient, pollutant and biodiversity hotspots. These incised conduits are the dominant pathway for particulate transfer between continental shelves and the deep-sea1. How, where, and at what rate material is conveyed through submarine canyons is dictated by the nature, frequency and magnitude of seafloor currents that are steered by their often-complex topography2. However these aspects remain poorly constrained as, until recently, such information was inferred solely from seafloor deposits. Recent technological advances now enable direct measurements of powerful turbidity currents and internal tides in active submarine canyons1,3. This project takes advantage of new unusually-detailed and long-term monitoring datasets from four distinct, deep-sea systems, to develop a general model for contemporary particulate transport in submarine canyons. The project will answer for the first time: [1] How do internal tides and turbidity currents interact and can internal tides modulate or trigger turbidity currents? [2] What deposits do these processes leave behind and have past studies misdiagnosed transport mechanisms from deposits? [3] What is the relative role played by each process in sediment, carbon and pollutant transport and how does that vary between different canyon systems? 

Methodology: 

This project provides access to world-class monitoring datasets (that have already been acquired and will be extended during early stages of the project by NERC-funded projects) from four end-member systems: major river-fed Congo Canyon (W Africa), longshore drift-fed Monterey Canyon (California), carbonate-dominated Mozambique margin, and land-detached Whittard Canyon (NE Atlantic). Acoustic Doppler Current Profiler (ADCP) time-series at these sites include high-resolution velocity and acoustic backscatter (proxy for sediment concentration) measurements and are supplemented by seafloor sediment core and sediment trap samples held by NOC and NIOZ. The ADCP time series at the four sites record multiple turbidity currents with velocities of up to 8m/s and energetic internal tides with near bed velocities in excess of 1m/s. Analysis of ADCP data will identify turbidity current and internal tide events, and characterise their behaviour and interactions. Analysis of sediment cores and trap samples (using sedimentological and X-Ray logging) will link identified event types with their depositional signature3. Total organic carbon content and microplastic quantification will be performed on select samples following established protocols, while novel inversion of acoustic backscatter1 will quantify suspended particulate concentrations to determine the volumes transported by each event in the different systems.

 

Location: 
NOC, Southampton
Training: 

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at National Oceanography Centre. Specific training will include: geospatial analysis in GIS (QGIS/ArcGIS), processing and analysis of ADCP data using Matlab, sedimentological analysis at the British Ocean Sediment Core Research Facility (BOSCORF), microplastics extraction, identification and quantification, and organic carbon content determination. These skills will be equally valuable for an academic as well as industry careers e.g. survey, geotechnical engineering, geohazards assessment, telecommunications, renewables, oil and gas. There may be opportunities to join upcoming offshore research campaigns, including already NERC-funded campaigns to the deep-sea Congo Canyon (W Africa), Gaoping Canyon (Taiwan) or Whittard Canyon (NE Atlantic); hence offshore survival training will also be provided. 

Eligibility & Funding Details: 

Please see https://inspire-dtp.ac.uk/how-apply for details.

Background Reading: 

1. Azpiroz-Zabala, M., Cartigny, M.J., Talling, P.J., Parsons, D.R., Sumner, E.J., Clare, M.A., Simmons, S.M., Cooper, C. and Pope, E.L., 2017. Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons. Science advances3(10), p.e1700200.

 

2. Aslam, T., Hall, R.A. and Dye, S.R., 2018. Internal tides in a dendritic submarine canyon. Progress in Oceanography169, pp.20-32.

 

3. Maier, K.L., Rosenberger, K.J., Paull, C.K., Gwiazda, R., Gales, J., Lorenson, T., Barry, J.P., Talling, P.J., McGann, M., Xu, J. and Lundsten, E., 2019. Sediment and organic carbon transport and deposition driven by internal tides along Monterey Canyon, offshore California. Deep Sea Research Part I: Oceanographic Research Papers153, p.103108.

 

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