First direct measurements of hydraulic jumps in an active submarine density current

Sumner, Esther J.; Peakall, Jeff; Parsons, Daniel R.; Wynn, Russell B.; Darby, Stephen E.; Dorrell, R. M.; McPhail, S.D.; Perrett, James; Webb, A.; White, David

doi:10.1002/2013gl057862

Cited by 49 publications

(56 citation statements)

References 18 publications

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“…7 and 8), with mean paleoflow toward the northeast. Lenticular erosive features in the Baviaans area may represent either: shallow scours, often associated with channel-lobe transition zones (e.g., Wynn et al, 2002;Macdonald et al, 2011aMacdonald et al, , 2011bHofstra et al, 2015;Pemberton et al, 2016;Brooks et al, 2018b) formed by hydraulic jumps where flows transition from super-to subcritical due to a reduction in slope gradient and/or flow confinement (Mutti andNormark, 1987, 1991;Weirich, 1989;Kostic and Parker, 2006;Sumner et al, 2013;Dorrell et al, 2016); or weakly confined distributive channels eroding into proximal lobes, with distributive patterns likely due to the reduction of slope gradient (e.g., van der Werff and . These characteristics indicate deposition in a base-of-slope area.…”

Section: Discussionmentioning

confidence: 99%

Disconnected submarine lobes as a record of stepped slope evolution over multiple sea-level cycles

et al. 2018

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The effects of abrupt changes in slope angle and orientation on turbidity current behavior have been investigated in numerous physical and numerical experiments and examined in outcrop, subsurface, and modern systems. However, the long-term impact of subtle and evolving seabed topography on the stratigraphic architecture of deep-water systems requires fine-scale observations and extensive 3-D constraints. This study focuses on the Permian Laingsburg and Fort Brown formations, where multiple large sand-rich systems (Units A-F) have been mapped from entrenched slope valleys, through channel-levee systems, to basin-floor lobe complexes over a 2500 km 2 area. Here, we investigate three thinner (typically <5 m in thickness) and less extensive sand-rich packages, Units A/B, B/C, and D/E, between the large-scale systems. Typically, these sand-rich units are sharp-based and topped, and contain scours and mudstone clast conglomerates that indicate deposition from high-energy turbidity currents. The mapped thickness and facies distribution suggest a lobate form. These distinctive units were deposited in similar spatial positions within the basin-fill and suggest similar accommodation patterns on the slope and basin floor prior to the larger systems (B, C, and E). Stratigraphically, these thin units represent the first sand deposition following major periods of shut-down in sediment supply, and are interpreted as marking a partial re-establishment of sand delivery pathways creating "disconnected lobes" that are fed mainly by flows sourced from failures on the shelf and upper slope rather than major feeder channel-levee systems.Thickness and facies patterns throughout the deep-water stratigraphy suggest seabed topography was present early in the basin formation and maintained persistently in a similar area to ultimately form a stepped slope profile. The stepped slope profile evolved through three key stages of development: Phase 1, where sediment supply exceeds deformation rate (likely caused by differential subsidence); Phase 2, where sediment supply is on average equal to deformation rate; and Phase 3, where deformation rate outpaces sediment supply. This study demonstrates that smaller systems are a sensitive record of evolving seabed topography and they can consequently be used to recreate more accurate paleotopographic profiles.

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Section: Discussionmentioning

confidence: 99%

Disconnected submarine lobes as a record of stepped slope evolution over multiple sea-level cycles

et al. 2018

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“…This is part of collaborative work by Paull and others at the Monterey Bay Aquarium Research Institute (MBARI), who are developing new sensors embedded in moving near-bed layers that record their acceleration and sense of rotation, and techniques for recovering data from such sensors through gliders. New insights have also been gained from studies of saline density flows in the Black Sea (Flood et al 2009;Parsons et al 2011;Hiscott et al 2013;Sumner et al 2013aSumner et al , 2014. Together with work in other locations (e.g., Paull et al 2010aPaull et al , 2013Maier et al 2013), this highlights the potential of autonomous underwater vehicles (AUVs) for flow monitoring and mapping.…”

Section: Suggestions For Key Future Research Directionsmentioning

confidence: 93%

“…3A, B). Future coordinated efforts to monitor sinuous channels, perhaps based around test sites such as the Congo Canyon or Bute Inlet (Conway et al 2012), can extend ongoing work on channelized saline underflows in the Black Sea (Parsons et al 2011;Hiscott et al 2013;Sumner et al 2013aSumner et al , 2014. Measurements from overbank areas (Khripounoff et al 2003) can complement recent advances made by detailed studies of ancient outcrop and subsurface Kane and Hodgson 2011) and modern (Nakajima and Kneller 2013) levee deposits.…”

Section: (D) Submarine Channels: Flow Dynamics and Deposit Architecturementioning

confidence: 98%

“…Are trains of more widely spaced scours the result of cyclic steps ( Fig. 5; Fildani et al 2006;Armitage et al 2012;Covault et al 2014), or are they due to retrogressive head scarps or local erosion (Sumner et al 2013a? This topic of supercritical flow will see important theoretical and experimental progress in the next few years, and links between process and product will require technically difficult field observations to be made.…”

Section: (B) Supercritical-flow Dynamics and Depositsmentioning

confidence: 99%

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Key Future Directions For Research On Turbidity Currents and Their Deposits

Talling

Allin

Armitage

et al. 2015

Journal of Sedimentary Research

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160

117

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Turbidity currents, and other types of submarine sediment density flow, redistribute more sediment across the surface of the Earth than any other sediment flow process, yet their sediment concentration has never been measured directly in the deep ocean. The deposits of these flows are of societal importance as imperfect records of past earthquakes and tsunamogenic landslides and as the reservoir rocks for many deep-water petroleum accumulations. Key future research directions on these flows and their deposits were identified at an informal workshop in September 2013. This contribution summarizes conclusions from that workshop, and engages the wider community in this debate. International efforts are needed for an initiative to monitor and understand a series of test sites where flows occur frequently, which needs coordination to optimize sharing of equipment and interpretation of data. Direct monitoring observations should be combined with cores and seismic data to link flow and deposit character, whilst experimental and numerical models play a key role in understanding field observations. Such an initiative may be timely and feasible, due to recent technological advances in monitoring sensors, moorings, and autonomous data recovery. This is illustrated here by recently collected data from the Squamish River delta, Monterey Canyon, Congo Canyon, and offshore SE Taiwan. A series of other key topics are then highlighted. Theoretical considerations suggest that supercritical flows may often occur on gradients of greater than , 0.6u. Trains of up-slope-migrating bedforms have recently been mapped in a wide range of marine and freshwater settings. They may result from repeated hydraulic jumps in supercritical flows, and dense (greater than approximately 10% volume) near-bed layers may need to be invoked to explain transport of heavy (25 to 1,000 kg) blocks. Future work needs to understand how sediment is transported in these bedforms, the internal structure and preservation potential of their deposits, and their use in facies prediction. Turbulence damping may be widespread and commonplace in submarine sediment density flows, particularly as flows decelerate, because it can occur at low (, 0.1%) volume concentrations. This could have important implications for flow evolution and deposit geometries. Better quantitative constraints are needed on what controls flow capacity and competence, together with improved constraints on bed erosion and sediment resuspension. Recent advances in understanding dilute or mainly saline flows in submarine channels should be extended to explore how flow behavior changes as sediment concentrations increase. The petroleum industry requires predictive models of longer-term channel system behavior and resulting deposit architecture, and for these purposes it is important to distinguish between geomorphic and stratigraphic surfaces

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“…Internal hydraulic jumps constitute an exemplary case of sharp, horizontal density and flow gradients and have been observed in stratified flows both in the atmosphere (e.g., Drobinski et al 2001;Armi and Mayr 2011) and oceans and estuaries (Partch and Smith 1978;Farmer and Smith 1980;Klymak and Gregg 2001;Nash and Moum 2001;Cummins et al 2006;Cummins and Armi 2010;Sumner et al 2013). Internal jumps are essentially arrested internal bores and are regions of rapidly varying flow that mark the transition from internally supercritical to subcritical conditions (e.g., Baines 1998).…”

Section: Introductionmentioning

confidence: 99%

Oblique Internal Hydraulic Jumps at a Stratified Estuary Mouth

Honegger

Haller

Geyer

et al. 2017

Journal of Physical Oceanography

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Observations and analyses of two tidally recurring, oblique, internal hydraulic jumps at a stratified estuary mouth (Columbia River, Oregon/Washington) are presented. These hydraulic features have not previously been studied due to the challenges of both horizontally resolving the sharp gradients and temporally resolving their evolution in numerical models and traditional observation platforms. The jumps, both of which recurred during ebb, formed adjacent to two engineered lateral channel constrictions and were identified in marine radar image time series. Jump occurrence was corroborated by (i) a collocated sharp gradient in the surface currents measured via airborne along-track interferometric synthetic aperture radar and (ii) the transition from supercritical to subcritical flow in the cross-jump direction via shipborne velocity and density measurements. Using a two-layer approximation, observed jump angles at both lateral constrictions are shown to lie within the theoretical bounds given by the critical internal long-wave (Froude) angle and the arrested maximum-amplitude internal bore angle, respectively. Also, intratidal and intertidal variability of the jump angles are shown to be consistent with that expected from the two-layer model, applied to varying stratification and current speed over a range of tidal and river discharge conditions. Intratidal variability of the upchannel jump angle is similar under all observed conditions, whereas the downchannel jump angle shows an additional association with stratification and ebb velocity during the low discharge periods. The observations additionally indicate that the upchannel jump achieves a stable position that is collocated with a similarly oblique bathymetric slope.

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First direct measurements of hydraulic jumps in an active submarine density current

Cited by 49 publications

References 18 publications

Disconnected submarine lobes as a record of stepped slope evolution over multiple sea-level cycles

Disconnected submarine lobes as a record of stepped slope evolution over multiple sea-level cycles

Key Future Directions For Research On Turbidity Currents and Their Deposits

Oblique Internal Hydraulic Jumps at a Stratified Estuary Mouth

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