Suspended particulate matter in a submarine canyon (Whittard Canyon, Bay of Biscay, NE Atlantic Ocean): Assessment of commonly used instruments to record turbidity

Haalboom, Sabine; Stigter, Henko de; Duineveld, G.C.A.; Haren, Hans van; Reichart, Gert‐Jan; Mienis, Furu

doi:10.1016/j.margeo.2021.106439

Cited by 28 publications

(18 citation statements)

References 99 publications

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“…Note how turbidity currents 1, 2, and 5, coincide with enhanced velocity or backscatter at M2. Some peaks in echo intensity do not coincide with high velocity down-canyon flows and are thought instead to relate to sediment re-suspension by internal tides as shown in previous studies 47 , 48 . Turbidity currents 3 and 4 cannot be correlated between M1 and M2.…”

Section: Resultsmentioning

confidence: 69%

“…This characteristic velocity and acoustic backscatter is similar to previously recorded turbidity currents in land-attached canyons 17 , 19 . Internal tides have well-defined, known periods, and typically lower peak velocities, and may also be accompanied by elevations in acoustic backscatter indicating that they are also episodically capable of resuspending seafloor sediment 47 , 48 (Fig. 1b ).…”

Section: Methodsmentioning

confidence: 99%

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Challenging the highstand-dormant paradigm for land-detached submarine canyons

et al. 2022

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Sediment, nutrients, organic carbon and pollutants are funnelled down submarine canyons from continental shelves by sediment-laden flows called turbidity currents, which dominate particulate transfer to the deep sea. Post-glacial sea-level rise disconnected more than three quarters of the >9000 submarine canyons worldwide from their former river or long-shore drift sediment inputs. Existing models therefore assume that land-detached submarine canyons are dormant in the present-day; however, monitoring has focused on land-attached canyons and this paradigm remains untested. Here we present the most detailed field measurements yet of turbidity currents within a land-detached submarine canyon, documenting a remarkably similar frequency (6 yr−1) and speed (up to 5–8 ms−1) to those in large land-attached submarine canyons. Major triggers such as storms or earthquakes are not required; instead, seasonal variations in cross-shelf sediment transport explain temporal-clustering of flows, and why the storm season is surprisingly absent of turbidity currents. As >1000 other canyons have a similar configuration, we propose that contemporary deep-sea particulate transport via such land-detached canyons may have been dramatically under-estimated.

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Section: Resultsmentioning

confidence: 69%

Section: Methodsmentioning

confidence: 99%

Challenging the highstand-dormant paradigm for land-detached submarine canyons

et al. 2022

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“…Semidiurnal internal tides with amplitudes up to 80 m have been observed, with implications of 1°C temperature fluctuations and dissolved oxygen concentration changes of 12 mmol kg -1 along certain sections of the canyon's walls (Hall et al, 2017). Additionally, dissipation of the observed energetic internal tide is expected to drive enhanced turbulent mixing, which is associated with increased concentrations of resuspended particulate organic matter (POM) and nepheloid layer formation within the canyon (Wilson et al, 2015;Hall et al, 2017;Aslam et al, 2018;Haalboom et al, 2021). Resuspension by intensified near-bed currents (including internal tides) and local slope failures within the canyon source fine grained material (Reid and Hamilton, 1990;Amaro et al, 2015;Amaro et al, 2016;Hall et al, 2017) which is transported down-canyon via turbidity currents and mud-rich sediment gravity flows (Cunningham et al, 2005;Amaro et al, 2016;Carter et al, 2018).…”

Section: Study Areamentioning

confidence: 99%

Spatial and temporal environmental heterogeneity induced by internal tides influences faunal patterns on vertical walls within a submarine canyon

et al. 2023

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Vertical walls of submarine canyons represent features of high conservation value that can provide natural areas of protection for vulnerable marine ecosystems under increasing anthropogenic pressure from deep-sea trawling. Wall assemblages are spatially heterogeneous, attributed to the high environmental heterogeneity over short spatial scales that is a typical feature of canyons. Effective management and conservation of these assemblages requires a deeper understanding of the processes that affect faunal distribution patterns. Canyons are recognised as sites of intensified hydrodynamic regimes, with focused internal tides enhancing near-bed currents, turbulent mixing and nepheloid layer production, which influence faunal distribution patterns. Faunal patterns also respond to broad-scale hydrodynamics and gradients in water mass properties (e.g. temperature, salinity, dissolved oxygen concentration). Oscillating internal tidal currents can advect such gradients, both vertically and horizontally along a canyon's walls. Here we take an interdisciplinary approach using biological, hydrodynamic and bathymetry-derived datasets to undertake a high-resolution analysis of a subset of wall assemblages within Whittard Canyon, North-East Atlantic. We investigate if, and to what extent, patterns in diversity and epibenthic assemblages on deep-sea canyon walls can be explained by spatial and temporal variability induced by internal tides. Vertical displacement of water mass properties by the internal tide was calculated from autonomous ocean glider and shipboard CTD observations. Spatial patterns in faunal assemblage structure were determined by cluster analysis and non-metric Multi-Dimensional Scaling plots. Canonical Redundancy Analysis and Generalised Linear Models were then used to explore relationships between faunal diversity and assemblage structure and a variety of environmental variables. Our results support the hypothesis that internal tides influence spatial heterogeneity in wall faunal diversity and assemblages by generating both spatial and temporal gradients in hydrodynamic properties and consequently likely food supply.

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“…Direct measurements of water columns within similar canyons often reveal higher‐than‐normal concentrations of suspended sediment (nepheloid layers), and that phenomenon occurs for several reasons: storms; tide‐generated currents; retention of particulates from the entrained layers of turbidity currents; agitation of the substrate by shoaling internal waves and down‐canyon cascading of dense shelf water (e.g. Inman et al ., 1976; Shepard et al ., 1979; Xu et al ., 2002; Xu, 2011; Puig et al ., 2013a,b; Wilson et al ., 2015; Maier et al ., 2019; Sequeiros et al ., 2019; Haalboom et al ., 2021). Confirmation of such occurrences requires direct measurements and sampling, but it is logical to expect the same phenomena in Māhia Canyon, the Cook Strait canyons and Kaikōura Canyon.…”

Section: Discussionmentioning

confidence: 99%

Composition of fine‐grained sediment in the Hikurangi Trough: Evidence for intermingling among axial gravity flows, transverse gravity flows and margin‐parallel ocean currents

Underwood

2023

Sedimentology

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The International Ocean Discovery Program cored five sites during Expeditions 372 and 375 to investigate the Hikurangi margin, offshore Poverty Bay, North Island, New Zealand. Trench‐wedge deposits were recovered at Site U1520, and the frontal accretionary prism was cored at Site U1518. Based on X‐ray diffraction analyses of the clay‐sized fraction, illite and smectite are the dominant clay minerals. Compositional scatter is unusually large, and a well‐defined mixing trend is evident between illite‐rich and smectite‐rich end members. The proportion of smectite ranges from 9 to 59 wt.% at Site U1518 and from 12 to 62 wt.% at Site U1520. Nearby slope deposits at Sites U1517 and U1519 are more homogeneous, with consistently higher proportions of smectite. The East Cape Current is probably responsible for transporting smectite‐rich suspensions towards the south‐west from sources that include the Taupo Volcanic Zone. Illite‐rich muds require different sources and different routing paths to the trench. Some suspended sediment probably originated in the Waipaoa watershed on the North Island, entering the trench via Māhia Canyon. Other gravity flows probably started in Kaikōura Canyon or Cook Strait and moved towards the north‐east, down the trench's axial channel. The influence of turbidity currents on clay composition changes with water depth, as do the effects of reworking by contour currents and the role of passive hemipelagic settling. The broad continuum of clay compositions in the trench is enhanced by variable amounts of mixing among multiple ocean currents and fluctuating durations of suspension within a bottom nepheloid layer. That complexity deviates from the paradigm of turbidite‐dominated trench wedges. The margin's compositional diversity also complicates the goal of predicting or modelling three‐dimensional variations in frictional, geotechnical and hydrogeological properties. Those lithological properties are important because they affect slope stability along strike and changes in fault‐slip behaviour along the subduction interface.

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Suspended particulate matter in a submarine canyon (Whittard Canyon, Bay of Biscay, NE Atlantic Ocean): Assessment of commonly used instruments to record turbidity

Cited by 28 publications

References 99 publications

Challenging the highstand-dormant paradigm for land-detached submarine canyons

Challenging the highstand-dormant paradigm for land-detached submarine canyons

Spatial and temporal environmental heterogeneity induced by internal tides influences faunal patterns on vertical walls within a submarine canyon

Composition of fine‐grained sediment in the Hikurangi Trough: Evidence for intermingling among axial gravity flows, transverse gravity flows and margin‐parallel ocean currents

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