Summertime modification of surface fronts in the North Atlantic subpolar gyre

• Published in: Journal of Geophysical Research
• Main Authors: Desprès, Agnès, Reverdin, Gilles, d'Ovidio, Francesco
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Échanges dans la couche de surface : des pôles aux tropiques (SURF), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Couplage physique-biogéochimie-carbone (PHYBIOCAR), INSU grants (OVIDE, SURATLANT), ANR-09-BLAN-0365,redhots,Reconstruction de la Dynamique Haute résolution Océanique Tridimensionnelle des couches Supérieures(2009)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDE.MCG]Environmental Sciences/Global Changes; North Atlantic; Orca
• Online Access: https://hal.science/hal-00753868; https://hal.science/hal-00753868/document; https://hal.science/hal-00753868/file/2011JC006950.pdf; https://doi.org/10.1029/2011JC006950

International audience A 12-yearlong thermosalinograph data set from ships of opportunity was used to make an extensive study of meso-scale surface fronts in the western part of the North Atlantic subpolar gyre from 1997 to 2009. Fronts are identified on a sea-surface-salinity/sea surface temperature gradient criterion with a typical width of 20 to 60 km. The seasonal hydrographic properties of fronts are investigated. We find that, whereas salinity jumps across fronts are close to the larger scale variations, the temperature jumps across fronts are often smaller than the larger scale variations, in particular in summer-time. We also find in June vertical profiles that the relative weight of temperature over salinity in the density jump across fronts is smaller at the surface than at depth. A Lagrangian model based on altimetry data and in situ vertical hydrographic profiles indicates that surface stirring is able to create fronts, but not the contrast between temperature and salinity gradients. We suggest that air-sea fluxes, mostly heat fluxes, but possibly also differential vertical stirring, are responsible for damping the meso-scale horizontal surface temperature gradient. This is supported by an eddy-permitting numerical simulation of this region (DRAKKAR simulation ORCA-025-G70) which includes some heat flux feedbacks.