From the Red River to the Gulf of Tonkin : dynamics and sediment transport along the estuary-coastal area continnum

• Main Author: Piton, Violaine
• Other Authors: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université Paul Sabatier - Toulouse III, Sylvain Ouillon, Marine Herrmann
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2019
• Subjects: Estuarine to regional circulation; Sediment transport; Variability; In-situ observations; regional ocean modelling; Estuary-coastal ocean continuum; Red River; Gulf of Tonkin; Circulation estuarienne à régionale; Transport sédimentaire; Variabilité; Modélisation océanique régionale; Continuum estuaire-océan côtier; Fleuve Rouge; Golfe du Tonkin; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Arctic; Le Plateau; Tonkin
• Online Access: https://tel.archives-ouvertes.fr/tel-02957680; https://tel.archives-ouvertes.fr/tel-02957680/document; https://tel.archives-ouvertes.fr/tel-02957680/file/2019TOU30235a.pdf

Deltas and coastal regions deliver the largest inputs of freshwater and sediments to the shelf and open ocean, understanding water and sediment dynamics and variability in those regions is therefore crucial. The spatio-temporal variability of estuarine and ocean dynamics under the influence of natural forcings and their impact on sediment transport and fate was assessed along the Red River estuary - coastal ocean - Gulf of Tonkin continuum. First, in-situ estuarine observations evidenced the seasonal and tidal variabilities of flow and suspended matter, and showed in particular the role of tidal pumping in the estuary siltation. Second, a 3D realistic hydrodynamic model was set up and calibrated with various observations and satellite data. Beforehand, a high-resolution model configuration was implemented and optimized with sensitivity tests of the Gulf of Tonkin's tidal components to bathymetry and various bottom friction parameterizations. Third, the resulting optimized configuration was used to study the large scale Gulf of Tonkin circulation at daily, seasonal and interannual scales, and to identify the drivers of their variabilities. Ekman transport variability due to monsoon winds reversal drives the seasonal circulation, which can be reversed in summer by episodic typhoon events and intensified in winter. ENSO, strong typhoon activity and Arctic Oscillation have been identified as drivers of the interannual circulation variability. Lastly, preliminary tests with a sediment transport module coupled with the hydrodynamics model revealed the importance of the seabed composition and of the parameterization of the erosion coefficients. Les deltas et les régions côtières constituent les sources les plus importantes d'eau douce et de matière en suspension vers le plateau continental puis le large, la compréhension de leur dynamique et de leur variabilité est donc cruciale. Cette thèse vise à mieux comprendre la variabilité spatio-temporelle de la dynamique estuarienne et océanique sous l'influence de forçages ...