Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons

Azpiroz-Zabala, María; Cartigny, Matthieu; Talling, Peter J.; Parsons, Daniel R.; Sumner, Esther J.; Clare, Michael; Simmons, S.; Cooper, Cortis; Pope, Ed

doi:10.1126/sciadv.1700200

Cited by 217 publications

(269 citation statements)

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“…For instance, continuous turbidity currents have been documented in Lake Luzzone (De Cesare et al, ) and Lake Lugano (De Cesare et al, ) in Switzerland, Lake Ohau in New Zealand (Cossu et al, ), Lillooet Lake in Canada (Best et al, ; Desloges & Gilbert, ; Gilbert, ; Gilbert et al, ; Menczel & Kostaschuk, ), and the Xiaolangdi Reservoir on the Huanghe (Yellow) River in China (Wei, ; Wei et al, ). Studies in the Congo Canyon in the Atlantic Ocean (Azpiroz‐Zabala et al, ) show that weeklong turbidity currents can develop, not directly from river flow but from an erosive front that feeds sediment to an expanding trailing body.…”

Section: Introductionmentioning

confidence: 99%

On the Causes of Pulsing in Continuous Turbidity Currents

et al. 2018

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Velocity pulsing has previously been observed in continuous turbidity currents in lakes and reservoirs, even though the input flow is steady. Several different mechanisms have been ascribed to the generation of these fluctuations, including Rayleigh‐Taylor (RT) instabilities that are related to surface lobes along the plunge line where the river enters the receiving water body and interfacial waves such as Kelvin‐Helmholtz instabilities. However, the understanding of velocity pulsing in turbidity currents remains limited. Herein we undertake a stability analysis for inclined flows and compare it against laboratory experiments, direct numerical simulations, and field data from Lillooet Lake, Canada, and Xiaolangdi Reservoir, China, thus enabling an improved understanding of the formative mechanisms for velocity pulsing. Both RT and Kelvin‐Helmholtz instabilities are shown to be prevalent in turbidity currents depending on initial conditions and topography, with plunge line lobes and higher bulk Richardson numbers favoring RT instabilities. Other interfacial wave instabilities (Holmboe and Taylor‐Caulfield) may also be present. While this is the most detailed analysis of velocity pulsing conducted to date, the differences in spatial scales between field, direct numerical simulations, and experiments and the potential complexity of multiple processes acting in field examples indicate that further work is required. In particular, there is a need for simultaneous field measurements at multiple locations within a given system to quantify the spatiotemporal evolution of such pulsing.

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Section: Introductionmentioning

confidence: 99%

On the Causes of Pulsing in Continuous Turbidity Currents

et al. 2018

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“…This dataset represents the first detailed direct measurements of turbidity currents in the deep ocean (Cooper et al, 2013;Azpiroz-Zabala et al, 2017). Ten flows were measured, with durations ranging from eight hours to over nine days.…”

Section: Methodsmentioning

confidence: 99%

“…Our data were recorded at 2,000 m water depth in the Congo Canyon (Cooper et al, 2013;Azpiroz-Zabala et al, 2017). The Congo Canyon is the proximal part of one of the largest submarine channel systems on Earth, which is fed directly by the Congo River (Heezen et al, 1964).…”

Section: Study Areamentioning

confidence: 99%

“…The Congo Canyon is a highly active system in the present day. Several turbidity currents occur each year in the upper canyon, based on cable breaks (Heezen et al, 1964) and direct flow measurements (Khripounoff et al, 2003;Cooper et al, 2013;2016;Azpiroz-Zabala et al, 2017).…”

Section: Study Areamentioning

confidence: 99%

“…There are few direct observations of deep-sea turbidity currents (Khripounoff et al, 2003;Vangriesheim et al, 2009;Talling et al, 2015;Cooper et al, 2016). Before collection of this dataset (Cooper et al, 2013, Azpiroz-Zabala et al, 2017, there were no detailed (sub-minute) measurements from within a meander bend in the deepsea. Instead, our understanding of meandering deep-sea channels was based on laboratoryscale experiments and numerical modelling, or on comparisons to rivers, estuaries and saline density flows.…”

Section: Introductionmentioning

confidence: 99%

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A general model for the helical structure of geophysical flows in channel bends

Azpiroz-Zabala¹,

Cartigny²,

Sumner³

et al. 2017

Preprint

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Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record.  First direct measurements of the helical flow structure of turbidity currents as they travel around a bend. Turbidity currents of different thicknesses and velocities exhibit the same helical flow structure. We reconcile current controversy with a new model that explains helical flow structure for a wide range of geophysical flows.© 2017 American Geophysical Union. All rights reserved. AbstractMeandering channels formed by geophysical flows (e.g. rivers and seafloor turbidity currents) include the most extensive sediment transport systems on Earth. Previous measurements from rivers show how helical flow at meander bends plays a key role in sediment transport and deposition. Turbidity currents differ from rivers in both density and velocity profiles. These differences, and the lack of field measurements from turbidity currents, have led to multiple models for their helical flow around bends. Here we present the first measurements of helical flow in submarine turbidity currents. These ten flows lasted for 1-to-10 days, were up to ~80-metres thick, and displayed a consistent helical structure. This structure comprised two vertically-stacked cells, with the bottom cell rotating with the opposite direction to helical flow in rivers. Furthermore, we propose a general model that predicts the range of helical flow structures observed in rivers, estuaries and turbidity currents based on their density stratification.

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Turbidity Currents With Equilibrium Basal Driving Layers: A Mechanism for Long Runout

Luchi

Balachandar

Seminara

et al. 2018

Geophysical Research Letters

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Turbidity currents run out over 100 km in lakes and reservoirs, and over 1,000 km in the ocean. They do so without dissipating themselves via excess entrainment of ambient water. Existing layer‐averaged formulations cannot capture this. We use a numerical model to describe the temporal evolution of a turbidity current toward steady state under condition of zero net sediment flux at the bed. The flow self‐partitions itself into two layers. The lower “driving layer” approaches an invariant flow thickness, velocity profile, and suspended sediment concentration profile that sequesters nearly all of the suspended sediment. This layer can continue indefinitely at steady state over a constant bed slope. The upper “driven layer” contains a small fraction of the suspended sediment. The devolution of the flow into these two layers likely allows the driving layer to run out long distances.

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Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons

Abstract: Runaway turbidity currents stretch into the deep ocean to form the largest sediment accumulations on Earth.

Cited by 217 publications

References 55 publications

On the Causes of Pulsing in Continuous Turbidity Currents

On the Causes of Pulsing in Continuous Turbidity Currents

A general model for the helical structure of geophysical flows in channel bends

Turbidity Currents With Equilibrium Basal Driving Layers: A Mechanism for Long Runout

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