The physical oceanography of a broad, mid-latitude fjord : observations, seasonality and wind response of Fortune Bay (Newfoundland, Canada)

• Main Author: Donnet, Sébastien
• Other Authors: Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Northwest Atlantic Fisheries Centre (NWAFC), Fisheries and Oceans Canada (DFO), Université de Bretagne occidentale - Brest, Pascal Lazure
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2022
• Subjects: Broad fjord; Sub-arctic climate; Wind; Downwelling & upwelling; Internal Kelvin wave; Mooring; Fjord; Climat sub-arctique; Vent; Onde interne de Kelvin; Mouillage; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; Arctic; Canada; Arctique*; Newfoundland; Terre-Neuve
• Online Access: https://theses.hal.science/tel-04212424; https://theses.hal.science/tel-04212424/document; https://theses.hal.science/tel-04212424/file/These-2022-SML-Oceanographie_physique_et_environnement-DONNET_Sebastien.pdf

This thesis is concerned with the physical environment of Fortune Bay, a mid-latitude broad fjordlocated in Newfoundland, Canada. It presents the results of 2-years of continuous observations as well as of the analysis of historical records and numerical model simulations. Newly collected observations reveal the presence of coherent downwelling and upwelling signals, associated with vigorous alongshore currents,propagating cyclonically around the fjord. Along with the historical data, they also allow the determination of the seasonal climate of the water structure and some of its main forcing (wind, tides and freshwater runoff) as well as some measures of inter-annual variability. The implementation of a fully non-linear, 3-dimensional, numerical model allows the identification of the main process responsible for those dominant signals as well as their origin and some of their propagation characteristics.It is shown that Fortune Bay is seasonally and strongly stratified; influenced by local freshwater runoff, wind forcing and shelf input and that it is warmer than the shelf both at the surface and at intermediary depth due to saline stratification for the former and warm deep water renewal for the latter. Deep water renewal occurs bi-annually from two distinct water masses, one cold and fresh during the summer, the other warm and salty during the winter. Mean circulation is rather weak and so is the tidal influence. Currents are dominated by the weather band and are highly variable. The stratified season is dynamically dominated by transient baroclinic current pulses associated with downwelling and upwelling events. Those events are predominantly expressed as long internal Kelvin waves which are generated both locally and remotely. The generation of local and remote signals result in rather complex interactions which can enhance or diminish the amplitude of the response within the fjord. The effect of bay’ shape and dimension on the signals is suspected but was not clearly determined. Cette thèse porte sur ...