Observing the Local Emergence of the Southern Ocean Residual-Mean Circulation

• Published in: Geophysical Research Letters
• Main Authors: Sevellec, F., Naveira Garabato, A., Vic, C., Ducousso, N.
• 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), Ocean and Earth Science Southampton, University of Southampton-National Oceanography Centre (NOC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Antarctic; Drake Passage; Southern Ocean; Antarc*
• Online Access: https://hal.science/hal-02136451; https://hal.science/hal-02136451/document; https://hal.science/hal-02136451/file/manuscript.pdf; https://doi.org/10.1029/2018GL081382

International audience The role of mesoscale turbulence in maintaining the mean buoyancy structure and overturning circulation of the Southern Ocean is investigated through a 2‐year‐long, single‐mooring record of measurements in Drake Passage. The buoyancy budget of the area is successively assessed within the Eulerian and the Temporal‐Residual‐Mean frameworks. We find that a regime change occurs on time scales of 1 to 100 days, characteristic of mesoscale dynamics, whereby the eddy‐induced turbulent horizontal advection balances the vertical buoyancy advection by the mean flow. We use these diagnostics to reconstruct the region's overturning circulation, which is found to entail an equatorward downwelling of Antarctic Intermediate and Bottom Waters and a poleward upwelling of Circumpolar Deep Water. The estimated eddy‐induced flow can be accurately parameterized via the Gent‐McWilliams closure by adopting a diffusivity of ∼2,000 m2 s−1 with a middepth increase to 2,500 m2 s−1 at 2,100 m, immediately underneath the maximum interior stratification.