Characterization of the circulation around, above and across (through fracture zones) the Reykjanes Ridge

• Main Author: Petit, Tillys
• 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), Université de Bretagne occidentale - Brest, Herlé Mercier, Virginie Thierry
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2018
• Subjects: North-Atlantic; Subpolar gyre; Bathymetry; Water masses; Circulation; Observations; Gyre subpolaire Nord-Atlantique; Bathymétrie; Masses d’eau; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Bight Fracture Zone; Dorsale; Irminger Sea; La Dorsale; Reykjanes; Iceland; North Atlantic
• Online Access: https://theses.hal.science/tel-02117700; https://theses.hal.science/tel-02117700/document; https://theses.hal.science/tel-02117700/file/These-2018-SML-Oceanographie_physique_et_environnement-PETIT_Tillys.pdf

The Reykjanes Ridge is a major topographic feature of the North-Atlantic Ocean that extends from Iceland to the Charlie Gibbs Fracture Zone. Located between the Iceland Basin and the Irminger Sea, the Reykjanes Ridge strongly influences the subpolar gyre circulation and is a gate toward the deep convection areas. However, the circulation and distribution across the Reykjanes Ridge has never been directly quantified such that the characterization of the connection between the Iceland Basin and the Irminger Sea is still incomplete. As part of the Reykjanes Ridge Experiment project, we were able to analyze the circulation around, above and across the Reykjanes Ridge. Mainly based on hydrographic sections along and perpendicular to the ridge axis, the aim of this PhD thesis was thus to characterize the 3-D circulation and properties of the flow along and across the Reykjanes Ridge.We started by accurately quantifying geostrophic transports across the sections, which led to improvements in the treatment of S-ADCP data. Across the Reykjanes Ridge, the intensity of the wesward branch of the subpolar gyre was estimated at21.9 + 2.5 Sv in June – July 2015 with intensifications at the Bight Fracture Zone (BFZ) and at 59 – 62°N. At the BFZ, overflow waters are influenced by the bathymetry such as their hydrological properties evolve as they cross the Reykjanes Ridge. Finally, both the bathymetry and the cyclonic horizontal circulation of the Iceland Basin regulate the evoluton of the along-ridge flows by blocking water masses, and thus shaping the water mass distribution over the Reykjanes Ridge. In addition to waters from the crossridge flow, the Irminger Current incorporates waters from the center of the Irminger Sea. La dorsale de Reykjanes est une structure topographique majeure de l’océan Atlantique Nord qui s’étend de l’Islande à la zone de fracture de Charlie Gibbs. Située entre le bassin d’Islande et la mer d’Irminger, la dorsale de Reykjanes influence fortement la circulation du gyre subpolaire et est une porte ...