Flow dynamics and sedimentation in an active submarine channel: a process-product approach

Lead Research Organisation: University of Leeds
Department Name: School of Earth and Environment

Abstract

Submarine channels are spectacular features that can extend for thousands of kilometres across the seafloor, are often kilometres wide and up to hundreds of metres deep. They are formed by density currents; underwater flows of sand, mud and water that are denser than sea water and therefore flow along the seafloor. These channels are very important as they are the major transport pathway for moving sediments to the deep sea and form the largest sedimentary deposits on Earth. These deposits are significant hosts for gas and oil reserves and hold key information on past climate change and mountain building episodes. Such flows are difficult to study, typically being infrequent and highly destructive; they pose a major hazard to sea-floor engineering such as cables and pipelines, and have often destroyed scientific measurement equipment. Consequently, our knowledge of such flows comes mainly from laboratory experiments, and understanding of their deposits from studies of ancient examples now exposed on land. As a consequence there are no detailed studies of these flows in natural channels, and no studies that link flow measurements to the deposits that are produced. There is almost no other environment on Earth where we do not have any knowledge of how flow processes are linked to their sedimentary deposits, and this in the largest deposits on Earth! Consequently, there is an urgent need to improve our understanding of the interactions between flow, morphology and deposits within an active submarine channel. However, in addition to the technical problems associated with monitoring these density-driven flows, most submarine channels actually formed when sea-levels were much lower than today; present-day flows are typically much smaller than those that formed the channels/deposits, making study of interactions impossible. Furthermore, innovative techniques are required to measure detailed flow patterns within these channels. Around 6,000 years ago sea-level approached its present level, and dense salty fluid (10-15 m thick) from the Mediterranean started flowing through the Bosphorus Strait (past Istanbul) into the Black Sea, forming an almost constantly active sea-floor channel network. The first spectacular images of this system and its sedimentary deposits were only obtained in 2005. This provides a unique opportunity to study both flows and deposits in an active sea-floor channel for the very first time and to use this knowledge to formulate and test predictive models. We have assembled a world-leading group of UK and international scientists to tackle this challenge. We will use Autosub3 NERC's new state-of-the-art autonomous submarine (yellow, of course!) to 'fly' our measurement equipment just above the bottom, allowing us to map channel morphology and the three dimensional (3D) flows in unprecedented detail compared to what is possible from traditional ship-based methods. The flow data will be linked to measurements of sea-bed properties, smaller morphological features such as bedforms, and seismic data that images through sediment to reveal the internal structure of the deposits. These data will be used as input conditions for an innovative computer simulation model of flow and deposition in submarine channels. The numerical modelling and field-data will be combined to enable us to: i) assess bedforms in the channels with respect to the flows forming them, allowing reconstruction of past flows from preserved bedforms in older rocks for the very first time; ii) model bend flow to enable sediment patterns in the deposits to be predicted, and, iii) develop a new understanding of how flow and morphology is linked to long-term sediment deposition. These data will revolutionise our understanding of both flows and deposits in submarine environments, with key applications to: i) geohazard analysis, ii) design criteria for seafloor engineering, and, iii) prediction of sedimentary deposit types and distributions.

Publications

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Kostaschuk R (2018) On the Causes of Pulsing in Continuous Turbidity Currents in Journal of Geophysical Research: Earth Surface

 
Title Underwater river - Video Art 
Description Video art of underwater rivers - exhibited as part of the 14th Istanbul Biennial in 2015, at Istanbul Modern, Turkey's leading contemporary art gallery. An educational talk was given alongside this. 
Type Of Art Film/Video/Animation 
Year Produced 2015 
Impact The work was then picked up by Ikono TV - an Arts TV station as part of 'Art Speaks Out' - a 24 hr live streaming TV programme. This compilation has then gone onto Istanbul Modern (again) to be shown in the early part of 2016. 
URL http://14b.iksv.org/participants.asp?id=54
 
Description First evidence for reversed secondary circulation in submarine channels relative to that observed in river channels. Such circulation had been proposed based on experiments and theory but had been extremely controversial. Finding this in nature has changed the field, with recognition now widespread. This is a key component of the three-dimensional flow field which ultimately controls sediment deposition and channel evolution in these submarine channels.

First direct measurements of hydraulic jumps in an active submarine density current, following over four decades of speculation that these are an important feature of submarine density currents invoked in a wide range of seafloor processes.

The recognition of a new type of subaqueous hydraulic jump, and the development of the first process model for channel-lobe transition zones.

First measurements of the three-dimensional velocity and density structures of an active submarine gravity current that provides insight into the controlling forces acting on the flow, thus enabling better future models of these flows.

Theoretical analysis demonstrating the importance of three-dimensional material transport as the primary control of secondary flow dynamics of meandering submarine gravity currents, following over half a century of two-dimensional models in subaerial and submarine meander systems.

Development of a 2.5D shallow water model, incorporating empirical stratification, of channelized gravity current dynamics. First validation of theoretical against real-world gravity current dynamics, highlighting the importance of vertical flow stratification in flow channelization.

Integrative models of how secondary flows in submarine channels develop spatially and temporally in submarine channels.

Understanding of how global (latitudinal) variations in submarine channels occur, driven by the Coriolis forcing, in turn affecting three-dimensional flow fields and sedimentation.

Development of new process-based intra-channel sedimentary architecture models for submarine channels.

Developed an entirely new model of gravity currents (published in Nature Communications) that shows that they have similarities with jet dynamics such as those seen on Jupiter. This radical new model finally explains how turbidity currents (mixtures of sediment and water) manage to travel hundreds or even thousands of miles across the seafloor.
Exploitation Route Submarine channels and their deposits are major archives of palaeoclimate. The understanding of these processes helps us understand these systems, and has implications for future drilling of submarine fans.

The hydrocarbon industry is drilling the deposits of these submarine channels, in particular, in deepwater, offshore settings. They have an urgent need for a much improved understanding and modelling of these deposits. The work of this project has identified a series of major changes in our understanding of these processes, and will drive future numerical modelling of these systems and their deposits. This research is already being used to assess submarine channels at outcrop. The work will drive future numerical modelling of submarine channel flow dynamics and channel evolution to incorporate three-dimensional flow, and lateral density gradients.
Sectors Energy,Environment

 
Description Key impacts to date include a PhD studentship with GDF Suez looking at the detailed morphometrics of submarine channels, and the impact of this on flow; in collabaration with the University of New Hampshire, in the USA. A second PhD studentship is working on commercial data in the Zaire Canyon with a view to understanding submarine channel flows for the planning of sub-sea cables and pipelines. A third PhD student started in September 2016 looking at high-latitude submarine channel systems and their deposits. Societal impact has included greatly extending knowledge of submarine channels amongst the general public and the broader scientific community through the public dissemination of science. This work has included a talk, associated video streaming and YouTube video in the Geological Society of London's flagship public lecture series; the publishing of a feature article on the work of this NERC grant in New Scientist, and a whole segment of Discovery Channel's Daily Planet show on submarine channel dynamics and the understanding of this gained from the Black Sea. The PI was invited to the 14th Istanbul Biennial in 2015 as part of the Education programme, to talk about the Black Sea flows to those living around the Bosphorus; with video output being displayed in Istanbul Modern art gallery, and on Art TV. Other press coverage of this NERC funded research on the Black Sea submarine channel includes: National press: Telegraph; Daily Mail online. International Press: Abril (Brazil), Times of India, The Hindu (India), Net Gazeti (Georgia). TV: Aajtak (India), Romanian TV, NTV (national Turkish news). Radio: Radio 5 Live. Online: Wikipedia, AOLNews.com, Softpedia, The Money Times, Keral.com, International Water Association, RoboticTrends.com, underwatertimes.com, UPI (global); Buenos Aires News.net (Argentina); NineMSN, Australia News.net (Australia); Bangkok New.net, Bruneinews.net, Malaysia Sun Online; The Asian Age (Asia); Xinhuanet.com (China); OneIndia, Yahoo India News, AndhraNews.net, Sindhtoday.net, taaza.com (India); Trouw.nl, Scientas.nl (Netherlands); informativostelecinco.com (Spain); Sabah. Com (Turkish); GreenFudge.org, BioScienceTechnology, Tonic, NewsVine (USA). This media coverage has also led to broader opportunities to discuss science including the BBC One Show and a BBC2 documentary 'Swallowed by the sea: ancient Egypt's greatest lost city'.
First Year Of Impact 2013
Sector Education,Environment,Culture, Heritage, Museums and Collections
Impact Types Cultural,Societal,Economic

 
Description EU High Performance in Infrastructure programme (EUHIT)
Amount € 7,000 (EUR)
Funding ID 312778 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 09/2016 
End 03/2017
 
Description Morphometrics of submarine channels 
Organisation GDF Suez
Country France 
Sector Private 
PI Contribution Unrivalled knowledge of submarine channel dynamics
Collaborator Contribution Financial and in time more specific input
Impact None yet
Start Year 2014
 
Description Prof James Gardner at the University of New Hampshire 
Organisation University of New Hampshire
Country United States 
Sector Academic/University 
PI Contribution Using our unequalled knowledge of submarine channel dynamics
Collaborator Contribution Access to the finest multibeam and CHIRP datasets on modern submarine channels available, along with extensive knowledge of these datasets and handling such datasets
Impact We started in October 2014
Start Year 2014
 
Description 14th Istanbul Biennial 
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 Video art installation as part of the 14th Istanbul Biennial arts festival, with accompanying educational talk on underwater rivers (submarine channels). The exhibition and piece were located at Istanbul Modern (Turkey's major contemporary art gallery) seen by over half a million people. The piece has then been used on Ikono TV - an arts based TV platform, and is once again back at Istanbul Modern for the early part of 2016.
Year(s) Of Engagement Activity 2015,2016
URL http://14b.iksv.org/participants.asp?id=54
 
Description EGU 2013 A million miles from rivers 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Poster was well received and led to some details discussions

Has influenced thinking on the nature and utility of modelling in terms of submarine channels
Year(s) Of Engagement Activity 2013
 
Description EGU talk - stratified flows 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Excellent feedback and discussion

Useful suggestions that were integrated into the paper that we published in 2014
Year(s) Of Engagement Activity 2013
 
Description Media - New Scientist 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact The New Scientist article (full multi-page article) led on the work of this NERC grant and the key results. Communicated this to a broad audience.
"Cryptic river: The torrents that flow on the seabed" March 2014

Further media work and interest in submarine channels - led onto Discovery Channel programme on Underwater Rivers
Year(s) Of Engagement Activity 2014
URL http://www.newscientist.com/article/mg22129570.700-cryptic-river-the-torrents-that-flow-on-the-seabe...
 
Description Public Lecture - Geological Society of London 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Generated online activity via video, Twitter and email, as well as discussion after each of the talks (lecture repeated in afternoon and evening due to demand).

Has had significant reach. This is the 4th highest viewed video on the Geological Society of London's YouTube site, and the highest non-fracking related video. Has led to other invites, e.g., New Scientist article, invite to the 14th Istanbul Biennial in 2015.
Year(s) Of Engagement Activity 2013
URL http://www.youtube.com/watch?v=1WILdCMqTJs&list=UUzhX_LOB1xUwIDmckTrPOqw
 
Description TV Programme - Discovery Channel Daily Planet 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact This 5 minute segment on Underwater Rivers was shown on Discovery Channel's Daily Planet in the US and Canada, this enabled research on submarine channels to reach a larger audience than any previous activity in the history of the research field.

Only aired recently, so plenty of time for further links to come through this.
Year(s) Of Engagement Activity 2014