An obvious way to reduce the Rossby numbers is to consider much lower flow velocities. At 0.1 m/s, most channel bends of the NAMOC and Tanzania channels, and a significant proportion of the Danube data points, fall below the Ror 1⁄4 1 threshold (Fig. \ref{444764}); for the Amazon and Zaire data points, the centrifugal force is still about an order of magnitude larger than the Coriolis force. Although flows with such low velocities would not be able to transport most of the sediment that characterizes the active channel thalwegs in virtually all systems, current speeds of a few centimeters per second are probably common in the upper, more dilute, much finer-grained parts of the flows \citep{Andrieux_2013}. The below-unity Rossby numbers for the Danube and NAMOC channels are consistent with the observation that levees are strongly asymmetric in both systems \citep{Klaucke_1998,Popescu_2001}. The asymmetry of submarine levees at higher latitudes has long been recognized in other systems as well \citep{Komar_1969,Carter_1988}.
In summary, for the bottom-hugging parts of turbidity currents flowing in submarine channels that cover a wide range of latitudes and channel dimensions, the centrifugal force is at least an order of magnitude larger than the Coriolis force. Therefore, it is unlikely that the latter is responsible for the low sinuosity of some high-latitude channels.
Discussion
If we revisit Eq. 3, the expression of the Rossby number, we can see that the radius of curvature has a much larger impact on the value of \(Ro_r\) than latitude. Going from a latitude of 20º to the pole results in only a threefold decrease in the Rossby number, but radius of curvature in submarine channels can cover several orders of magnitude (from ~100 m to tens of kilometers), and \(Ro_r\) is a hundred times smaller in the case of a channel bend with \(R\ =\ 10\ km\) compared to one with \(R\ =\ 100\ m\).
In other words, for channels at high latitudes, the overall size of the channel is more important for determining the impact of the Coriolis force than the precise latitudinal position. As is the case for rivers, both radiuses of curvature and meander wavelengths of sinuous submarine channels correlate with channel widths \citep*{Pirmez_2003}; the average radius of curvature is a measure of the scale of the channel system and of the typical flows that have carved and built the channel. \citet{Peakall_2013} have suggested that ‘‘as bend sinuosity decreases with latitude, radius of curvature increases.’’ However, low sinuosity does not necessarily imply a large radius of curvature. To better understand the relationship between sinuosity development and changes in radius of curvature, we have used an implementation of the \citet*{Howard_1984} curvature-based centerline model and briefly discuss the results here.