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

Lead Research Organisation: National Oceanography Centre
Department Name: Science and Technology

Abstract

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.

Planned Impact

Networks of sea floor cables have considerable strategic importance because they now carry of 95% of global data traffic, including the internet and financial markets. It is important to understand submarine flow dynamics and triggers because such flows can break multiple cables. This is one of the few ways to seriously disrupt internet connections to large areas, as multiple breaks prevent mitigation by rerouting traffic on adjacent cables. Submarine pipelines and sea floor infrastructure used to recover oil and gas reserves in locations worldwide are worth many millions of dollars. Talling will disseminate results through presentations at the annual plenary session of the International Cable Protection Committee that is already funded by his Royal Society Industry Fellowship.

Submarine flows deposited layers of sandstone that hold strategically important subsurface petroleum reserves, both in the UK North Sea and worldwide. It is essential to understand submarine flows in order to predict the location, shape and extent of the sandstone layers more accurately; in order to recover the oil and gas reserves most effectively. Talling leads the UK Turbidite Architecture and Processes (UK-TAPS) industry consortium that has involved many of the major oil and gas companies since 2002. Project results will be disseminated to this audience through invited presentations and by presentations at the AAPG annual conference in 2016 (which will be paid for by industry through UK-TAPS).
Submarine flows in canyons also play a key role in the distribution of benthic habitats and ecosystem dynamics, through transport of organic carbon and nutrients, and their episodic erosion of the sea floor. These flows may also play a key role in transport and eventual burial of organic carbon in the deep ocean. For instance, terrestrial organic carbon burial on the Bengal Fan may exceed CO2 draw down due to silicate weathering in the Himalayas. Our work will be of interest to biologists and organic geochemists. Special sessions at AGU and EGU will disseminate project results to benthic ecologists and those interested in the export of organic carbon.

We will develop a web site aimed at a general audience outlining state of the art understanding of submarine flows, illustrated by project results. This website will be linked to relevant project updated Wikipedia entries. We will maintain a twitter feed on the project and collect video diaries which will be formatted for schools. Links will be exploited in Hull at The Deep (~250,000 visitors a year) where a large University of Hull hydrodynamics flume facility is based. A proposal for an exhibition on deep sea canyons and turbidity currents ('under water mud avalanches') will be organised and led by Parsons. Project results will also feature in future displays at the Monterey Bay Aquarium (1.8 Million annual visitors) in California

Publications

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Paull CK (2018) Powerful turbidity currents driven by dense basal layers. in Nature communications

Related Projects

Project Reference Relationship Related To Start End Award Value
NE/K011480/1 09/05/2014 30/06/2016 £347,799
NE/K011480/2 Transfer NE/K011480/1 01/09/2016 01/12/2018 £157,401
 
Description Turbidity currents are arguably the most important process for moving sediment across our planet. These often powerful flows break seafloor telecommunications cables, which now carry over 95% of global data (including the internet). We have provided the first detailed and direct measurements of velocity and sediment concentration in turbidity currents using novel technology. This project placed over 50 sensors in 9 moorings in Monterey Canyon, and the whole array recorded the most powerful turbidity currents yet. The final set of moorings and data were recovered in April 2017. This work recently featured on BBC 5 live, BBC world service and will form the basis for a display at the Natural History Museum.
Exploitation Route We are working with seafloor cable companies to use project results to understand how these flows interact with cables, how flows are triggered and their frequency, and how long cables will need to withstand high velocities.

The project has thus fed into a briefing note requested by the Cabinet Office for the UK Govt Chief Scientist on risks to strategic cable networks.
Sectors Environment,Security and Diplomacy

 
Description Our findings have underpinned a recent briefing document on hazards to sea floor cable networks that now carry over 95% of global data traffic. This briefing document was requested by the Cabinet Office for the UK Government's Chief Scientist, and it is part of ongoing discussions concerning whether this hazard should now be added to the UK National Risk Register.
First Year Of Impact 2015
Sector Environment,Security and Diplomacy
Impact Types Societal

 
Description Briefing document to UK Government Chief Scientist on Hazards to Seafloor Cable Networks
Geographic Reach National 
Policy Influence Type Gave evidence to a government review
 
Description Evidence to Government Review of Threats to Seafloor Cables
Geographic Reach Multiple continents/international 
Policy Influence Type Gave evidence to a government review
Impact I gave written evidence to the Department for Digital, Culture, Media and Sport a review by their Telecoms Security Team on seafloor cables that carry > 95% of global data traffic. This aimed to understand what a significant loss of transAtlantic cables would have on the UK, and the implications for the national security risk assessment
 
Description Developing a Global Listening Network for Turbidity Currents and Seafloor Processes
Amount £846,000 (GBP)
Funding ID NE/S009965/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 04/2019 
End 03/2024
 
Description How do deep-ocean turbidity currents behave that form the largest sediment accumulations on Earth?
Amount £509,950 (GBP)
Funding ID NE/R001952/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 04/2019 
End 03/2023
 
Description Monterey Bay Aquarium Research Institute 
Organisation Monterey Bay Aquarium Research Institute
Country United States 
Sector Charity/Non Profit 
PI Contribution Monterey Bay Aquarium Research Institute provided and managed 34 separate cruises, using their state of the art RPOVs and AUVs. This contribution was several times that of the NERC Grant. It resulted in by far the most ambitious monitoring of a submarine canyon anywhere in the world.
Collaborator Contribution Monterey Bay Aquarium Research Institute provided and managed 34 separate cruises, using their state of the art RPOVs and AUVs.
Impact Monterey Bay Aquarium Research Institute provided and managed 34 separate cruises, using their state of the art RPOVs and AUVs. It involved marine geology and geohazards, and development of cutting edge offshore technology.
Start Year 2016
 
Description Sensor loaned to Science Museum in London 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact There has been considerable interest in these powerful and enigmatic underwater flow. Our past monitoring work in Monterey Canyon was a lead article on the BBC Science website, and featured on BBC 5 live, Inside Science and World Update. We also loaned one of our 'smart boulders' (sensors that record their motion when moved by underwater avalanches to the Science Museum, who displayed it in London.
Year(s) Of Engagement Activity 2018