Global (latitudinal) variation in submarine channel sinuosity: REPLY

Peakall, Jeff; Wells, Mathew G.; Cossu, Remo; Kane, Ian A.; Masson, D.G.; Keevil, Gareth M.; McCaffrey, William D.; Corney, Ransome K. T.

doi:10.1130/g34319y.1

Cited by 15 publications

(14 citation statements)

References 8 publications

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“…1 can be rewritten as:

\frac{d h}{d y} = {Fr}^{2} (\frac{italicfh}{U_{d}} + \frac{h}{R_{normalc}}), where {Fr}^{2} = \frac{U^{2}}{g^{'} h^{'}}

this, in turn, can be rewritten in terms of the Rossby number, Ro:

\frac{d h}{d y} = {Fr}^{2} \frac{h}{R_{c}} \frac{1}{Ro + 1}

where Ro = U/fR c . Small Rossby numbers indicate the increasing influence of Coriolis force, with Rossby numbers less than ca 1 to 9 indicative that the Coriolis force is important in influencing current movement (Cossu & Wells, , ; Cossu et al ., ; Peakall et al ., ). At low latitudes, much higher Rossby numbers are typically found [for example, 30 to 130 for the Amazon channel (cf.…”

Section: Discussionmentioning

confidence: 97%

“…The frequency of conditions under which Coriolis forces will dominate is poorly known, although recent analysis by Peakall et al . () suggests that high‐latitude channels with relatively straight planforms will be heavily influenced by Coriolis forces. Whilst much remains to be discovered about the ranges under which Coriolis force influences flows, the morphodynamics and sedimentary deposits of submarine channels can be expected to vary dramatically as a function of latitude and flow parameters.…”

Section: Discussionmentioning

confidence: 99%

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Three‐dimensional gravity‐current flow within a subaqueous bend: Spatial evolution and force balance variations

et al. 2013

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The nature of three-dimensional flow in submarine channel bends is poorly understood, largely due to the absence of detailed data from natural channels. Herein, data from density-driven flows in a large reservoir on the Huanghe (Yellow) River are presented showing the spatio-temporal variation of flow around a subaqueous bend. The data demonstrate for the first time that reversed helical flow, relative to that found in river channel bends, can occur from the centrifugal forcing of flow, even when the Coriolis force acts in the opposite direction. The data also suggest that reversed helical flow fields in submarine channels may be more frequent than currently estimated, notably for bends where Coriolis and centrifugal forces combine in the same direction. In addition, this study provides the first field evidence suggesting that sinuous submarine channels can exhibit an asymmetry in helical flow orientation between left and right-turning bends, which will have major implications for the morphodynamics of submarine channels, their resultant patterns of sedimentation and, ultimately, the distribution of depositional units across submarine fan systems.

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“…1 can be rewritten as:

\frac{d h}{d y} = {Fr}^{2} (\frac{italicfh}{U_{d}} + \frac{h}{R_{normalc}}), where {Fr}^{2} = \frac{U^{2}}{g^{'} h^{'}}

this, in turn, can be rewritten in terms of the Rossby number, Ro:

\frac{d h}{d y} = {Fr}^{2} \frac{h}{R_{c}} \frac{1}{Ro + 1}

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Three‐dimensional gravity‐current flow within a subaqueous bend: Spatial evolution and force balance variations

et al. 2013

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“…The role of these factors has been further discussed in Peakall et al [4,51] and Sylvester et al [52]. Slope shows only a weak influence on global changes in channel meandering in comparison with Coriolis forces [51] and should not be neglected.…”

Section: Discussionmentioning

confidence: 99%

The possible role of Coriolis forces in structuring large-scale sinuous patterns of submarine channel–levee systems

Wells

Cossu

2013

Phil. Trans. R. Soc. A.

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Submarine channel–levee systems are among the largest sedimentary structures on the ocean floor. These channels have a sinuous pattern and are the main conduits for turbidity currents to transport sediment to the deep ocean. Recent observations have shown that their sinuosity decreases strongly with latitude, with high-latitude channels being much straighter than similar channels near the Equator. One possible explanation is that Coriolis forces laterally deflect turbidity currents so that at high Northern latitudes both the density interface and the downstream velocity maximum are deflected to the right-hand side of the channel (looking downstream). The shift in the velocity field can change the locations of erosion and deposition and introduce an asymmetry between left- and right-turning bends. The importance of Coriolis forces is defined by two Rossby numbers, Ro W = U / Wf and Ro R = U / Rf , where U is the mean downstream velocity, W is the width of the channel, R is the radius of curvature and f is the Coriolis parameter. In a bending channel, the density interface is flat when Ro R ∼−1, and Coriolis forces start to shift the velocity maximum when | Ro W |<5. We review recent experimental and field observations and describe how Coriolis forces could lead to straighter channels at high latitudes.

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“…Equation gives the Rossby number as the ratio of inertial to Coriolis force; the sign of the Rossby number is therefore a function of latitude and of the rotational direction of the flow, with clockwise flow negative and anticlockwise flow positive (Figure ). Minimal values of the Rossby number, of order 0.1, may occur in large bends located at high latitudes [ Peakall et al ., ], and maximal values of the Rossby number will occur near the equator as f → 0. Furthermore, the densimetric Froude number, Fr d , denotes the ratio of inertial to gravitational forces

F r_{d} = {\overset{u}{true}}_{θ} / \sqrt{g \bar{ϕ} h}

.…”

Section: Physical Model For Secondary Flow Within a Subaerial Or Submmentioning

confidence: 99%

Superelevation and overspill control secondary flow dynamics in submarine channels

et al. 2013

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In subaerial and submarine meander bends, fluid flow travels downstream in a helical spiral, the structure of which is determined by centrifugal, hydrostatic, baroclinic, and Coriolis forces that together balance frictional stresses generated by the flow. The sense of rotation of this helical flow, and in particular, whether the near bed flow is directed toward the inner bank, e.g., “river‐normal,” or outer bank, e.g., “river‐reversed,” is crucial to the morphodynamic evolution of the channel. However, in recent years, there has been a debate over the river‐normal or river‐reversed nature of submarine flows. Herein, we develop a novel three‐dimensional closure of secondary flow dynamics, incorporating downstream convective material transport, to cast new light on this debate. Specifically, we show that the presence of net radial material transport, arising from flow superelevation and overspill, exerts a key control on the near bed orientation of secondary flow in submarine meanders. Our analysis implies that river‐reversed flows are likely to be much more prevalent throughout submarine‐canyon fan systems than prior studies have indicated.

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Global (latitudinal) variation in submarine channel sinuosity: REPLY

Cited by 15 publications

References 8 publications

Three‐dimensional gravity‐current flow within a subaqueous bend: Spatial evolution and force balance variations

Three‐dimensional gravity‐current flow within a subaqueous bend: Spatial evolution and force balance variations

The possible role of Coriolis forces in structuring large-scale sinuous patterns of submarine channel–levee systems

Superelevation and overspill control secondary flow dynamics in submarine channels

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