lnterannual variability and analysis of geostroph¡c turbulence in the Bay of Biscay from simulations

• Main Author: Assassi, Charefeddine
• Other Authors: Laboratoire de physique hydrodynamique et sédimentaire (DYNECO/PHYSED), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Université de Bretagne occidentale - Brest, Yves Morel, Frédéric Vandermeirsch
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2015
• Subjects: Bay of Biscay; Numerical simulation; Temperature; Salinity; Iberian poleward Current; Navidad; Upwelling; Slope Water Oceanic Eddies; Subsurface vortices; Geostrophic turbulence; Turbulent kinetic energy; Energy spectrum; Golfe de Gascogne; Simulations numériques; Salinité; Slope Water Oceanic eDDlES; Tourbillons de subsurface; Turbulence géostrophique; Énergie cinétique turbulente; Spectre d'énergie; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Tourbillons; North East Atlantic
• Online Access: https://tel.archives-ouvertes.fr/tel-01316340; https://tel.archives-ouvertes.fr/tel-01316340v2/document; https://tel.archives-ouvertes.fr/tel-01316340v2/file/These-2015-EDSM-Oceanographie_physique-ASSASSI_Charefeddine.pdf

The Bay of Biscay (BoB), an environment rich in physical processes has been studied from numerical simulations. Thestudy is built around scales from the size of BoB until sub mesoscale.ln the first part, we examined the interannual variability of the sea surface temperature and saliniÇ over a period of 53years: we were able to describe two trends related to the North-East Atlantic. Cooling and freshening until 1976 thatcould be related to the Great Salinity Anomaly and current salinification related to the atmospheric increase of CO2.The Bay of Biscay is characterized by a slope current, the lberian Poleward Current (lPC): its variability is linked to theSouth West wind strengthens the IPC by a geostrophic current in the lberian Basin. One of the interesting results foundin simulations and confirmed by observations is the appearance of cold anomalies related to upwellings and alternatingwith warm anomalies 'La Navidad'. These upwellings could be linked to the north wind in the lberian Basin but to the West current along the northern Spanish coast.ln the second part, we are committed to the meso and sub mesoscale eddies through a method of detection and throughthe variability of energy spectra. An index based on the ratio of surface density anomaly and sea level anomaly allowsdetecting subsurface vortices and distinguishing them from the surface ones. The application of this index from thesatellite data confirms the detection potential of Slope Water Oceanic Eddies (subsurface vortices of BoB).The description of the Eddy Kinetic Energy (EKE) in the BoB. shows a spatial variability with maximum along the Spanishnorth coast linked to the lPC. The slopes of the spectra (k-4.2 for SSH, k-2.4 for SST and k-2.4 for the kinetic energy) are different from satellite observations, but comparable with previous studies. These spectral slopes have a seasonalvariability with a maximum in winter and minimum in summe¡ related to the seasonal cycle of EKE. Le golfe de Gascogne (GdG), un milieu riche en processus physiques a été ...