Suspended Sediment Dynamics in the Macrotidal Seine Estuary (France) - Part 1: Numerical Modeling of Turbidity Maximum Dynamics
|Author(s)||Grasso Florent1, Verney Romaric1, Le Hir Pierre1, Thouvenin Benedicte1, Schulz Elisabeth1, 2, Kervella Youenn3, Fard I. Khojasteh Pour1, 4, Lemoine J. -P.5, Dumas Franck1, 6, Garnier Valerie7|
|Affiliation(s)||1 : IFREMER DYNECO DHYSED, Ctr Bretagne, Plouzane, France.
2 : Leibniz Inst Balt Sea Res Warnemunde IOW, Dept Phys Oceanog & Instrumentat, Warnemunde, Germany.
3 : OPEN OCEAN, Rech & Dev, Brest, France.
4 : Univ Isfahan, Esfahan, Iran.
5 : Grp Interet Publ Seine Aval, Pole Reg Savoirs, Rouen, France.
6 : Serv Hydrog & Oceanog Marine, Brest, France.
7 : Univ Brest, CNRS, IFREMER, IRD,Lab Oceanog Phys & Spatiale,IUEM, Plouzane, France.
|Source||Journal Of Geophysical Research-oceans (2169-9275) (Amer Geophysical Union), 2018-01 , Vol. 123 , N. 1 , P. 558-577|
|WOS© Times Cited||8|
|Keyword(s)||Estuary, mud, sand, hydrodynamics, turbidity maximum, waves, measurement, modeling|
Tidal pumping, baroclinic circulation and vertical mixing are known to be the main mechanisms responsible for the estuarine turbidity maximum (ETM) formation. However, the influence of hydro-meteorological conditions on ETM dynamics is still not properly grasped and requires further investigation to be quantified. Based on a realistic 3-dimensional numerical model of the macrotidal Seine Estuary (France) that accounts for mud and sand transport processes, the objective of this study is to quantify the influence of the main forcing (river flow, tides, waves) on the ETM location and mass changes. As expected, the ETM location is strongly modulated by semidiurnal tidal cycles and fortnightly timescales with a high sensitivity to river flow variations. The ETM mass is clearly driven by the tidal range, characteristic of the tidal pumping mechanism. However, it is not significantly affected by the river flow. Energetic wave conditions substantially influence the ETM mass by contributing up to 44% of the maximum mass observed during spring tides and by increasing the mass by a factor of three during mean tides compared to calm wave conditions. This means that neglecting wave forcing can result in significantly underestimating the ETM mass in estuarine environments. In addition, neap-to-spring phasing has a strong influence on ETM location and mass through a hysteresis response associated with the delay for tidal pumping and stratification to fully develop. Finally, simulations show that the uppermost limit of the Seine ETM location did not change notably during the last 35 years; however, the seaward limit migrated few kilometers upstream.