A combination of centrifugal and Coriolis forces drive the secondary circulation of turbidity currents in sinuous channels, and hence determine where erosion and deposition of sediment occur. Using laboratory experiments we show that when centrifugal forces dominate, the density interface shows a superelevation at the outside of a channel bend. However when Coriolis forces dominate, the interface is always deflected to the right (in the Northern Hemisphere) for both left and right turning bends. The relative importance of either centrifugal or Coriolis forces can be described in terms of a Rossby number defined as Ro = U/fR, where U is the mean downstream velocity, f the Coriolis parameter and R the radius of curvature of the channel bend. Channels with larger bends at high latitudes have ∣Ro∣ < 1 and are dominated by Coriolis forces, whereas smaller, tighter bends at low latitudes have ∣Ro∣ ≫ 1 and are dominated by centrifugal forces.

[1] Large-scale turbidity currents in submarine channels often show a significant asymmetry in the heights of their levee banks. In the Northern Hemisphere, there are many observations of the right-hand channel levee being noticeably higher than the left-hand levee, a phenomenon that is usually attributed to the effect of Coriolis forces upon turbidity currents. This article presents results from an analog model that documents the influence of Coriolis forces on the dynamics of gravity currents flowing in straight submarine channels. The observations of the transverse velocity structure, downstream velocity, and interface slope show good agreement with a theory that incorporates Ekman boundary layer dynamics. Coriolis forces will be important for most large-scale turbidity currents and need to be explicitly modeled when the Rossby number of these flows (defined as Ro = |U/Wf|, where U is the mean downstream velocity, W is the channel width, and f is the Coriolis parameter defined as f = 2W sin( ), with W being the Earth's rotation rate and being the latitude) is less than order 1. When Ro ( 1, the flow is substantially slower than a nonrotating flow with the same density contrast. The secondary flow field consists of frictionally induced Ekman transports across the channel in the benthic and interfacial boundary layers and a return flow in the interior. The cross-channel velocities are of the order of 10% of the along-channel velocities. The sediment transport associated with such transverse flow patterns should influence the evolution of submarine channel levee systems.Citation: Cossu, R., M. G. Wells, and A. K. Wåhlin (2010), Influence of the Coriolis force on the velocity structure of gravity currents in straight submarine channel systems,

Terra Nova, 25, 65–71, 2013 Abstract We present results from experimental gravity and turbidity currents to show that at high latitudes, the Coriolis effect strongly influences the internal flow structure in submarine channel systems. At high latitudes, Coriolis forces deflect the downstream velocity core, and consequently areas of deposition and erosion, to one side of the channel system. Over time, this supports the evolution of low‐sinuosity submarine channels. These findings help explain the recently found relation that channels at low latitudes often show strongly sinuous planform geometries, whereas channels at high latitudes tend to be much less sinuous. On the basis of our observations and an existing conceptual model for channel evolution, we propose a process model for sedimentation regimes in turbidity currents, which is applicable to all latitudinal settings.

Turbidity currents transport clastic sediments from the continental margin to deep ocean basins and along their pathways they erode large submarine channels. The driving mechanisms for submarine channel evolution are highly complex, reflected by recent debates about the formation and global distribution of sinuosity in turbidite channels. We present novel experiments on channelized gravity currents running over an erodible bed, where the magnitude of Coriolis forces is changed to reproduce conditions at low and high latitudes. We find a striking systematic change in deposition and erosion patterns as Coriolis forces become dominant at high latitudes so that erosion and deposition occur only on opposite sides of channels; in contrast, at low latitudes significant inner-bank intra-channel bars form on alternate sides of sinuous channels. Our observations show very good agreement with sedimentation patterns in Coriolis-dominated contourite drift systems and with deposits in modern and ancient turbidity current channels. We hypothesize that Coriolis forces are a key parameter for submarine channel evolution and sedimentary architecture at high latitudes but not at low latitudes; this proposal offers a new approach to interpret deep-sea architectural features at high latitudes.