Gravitational circulation as driver of upstream migration of estuarine sand dunes
van der Sande, W.M.; Roos, P.C.; Gerkema, T.; Hulscher, S.J.M.H. (2021). Gravitational circulation as driver of upstream migration of estuarine sand dunes. Geophys. Res. Lett. 48(14): e2021GL093337. https://dx.doi.org/10.1029/2021gl093337 In: Geophysical Research Letters. American Geophysical Union: Washington. ISSN 0094-8276; e-ISSN 1944-8007, more |   |
| Authors | | Top | - van der Sande, W.M.
- Roos, P.C.
- Gerkema, T., more
- Hulscher, S.J.M.H.
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| Abstract | Sand dunes are large-scale rhythmic bed patterns commonly occurring in sandy shelf seas, estuaries and rivers. Field observations of sand dunes in the Gironde estuary (France) have suggested that the gravitational circulation may cause seasonal reversal of asymmetry, which is linked to migration direction. In this paper, we aim to unravel the influence of gravitational circulation on the migration of estuarine sand dunes. To this end, we present an idealised process-based sand dune model with tide and river forcing, and the addition of a longitudinal salinity gradient (imposed diagnostically) that induces gravitational circulation. Linear stability analysis shows the emergence of dunes from a flat bed and confirms that reversal of dune migration may occur, provided the gravitational circulation is sufficiently strong compared to the river flow velocity. Lastly, we show that the migration direction of estuarine sand dunes is not necessarily the same as the direction of net sediment transport. |
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