The physical oceanography of Fortune Bay, an overview

• Published in: Regional Studies in Marine Science
• Main Authors: Donnet, Sebastien, Lazure, Pascal, Ratsimandresy, Andry, Han, Guoqi
• 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)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU]Sciences of the Universe [physics]; Canada; Newfoundland; Sea ice
• Online Access: https://hal.science/hal-04203907; https://hal.science/hal-04203907/document; https://hal.science/hal-04203907/file/1-s2.0-S2352485522002936-main.pdf; https://doi.org/10.1016/j.rsma.2022.102698

International audience This paper describes the physical oceanography of Fortune Bay, a broad, mid-latitude fjord located in Newfoundland (Canada). Fortune Bay is subject to a strong seasonal stratification (0–16 °C sea-surface temperature range with up to 1 °C/m vertical gradient) influenced by local freshwater runoff, wind forcing and shelf inputs. Sea-ice is seldom present in the bay and unlikely to be of importance on the seasonal stratification and mixing processes. Fortune Bay is warmer than its adjacent shelf both at the surface (by about 2 °C) and at intermediate depths (by about 1 °C from 50–150 m). While the former is likely due to local freshwater runoff stratification influence, the latter is probably related to the warm, deep water input occurring in winter below sill depth and subsequently mixed with the intermediate layer via the input of a colder water mass flowing in summer and which eventually reaches the bottom as well. Currents are dominated by the ‘weather band’ (2–20 d) and characterized by energetic pulses associated with downwelling and upwelling events. Mean circulation is rather weak and the seasonal pattern obtained her e did not reveal either the presence of a distinct estuarine circulation nor a strong influence of the main coastal current. Tidal currents are weak also and no inertial signal was observed. Estimates of water exchange between the inner and outer part of the bay were calculated using several methods and led to residence times of the order of a few to several months for the upper layers and of the order of a year for the bottom layer with a probable strong seasonal variability (larger residence time in summer for the upper layers). The “baroclinic pumping” processes, which include the downwelling/upwelling events, appear to be important players but more work is needed to better understand their nature and actual contribution.