Low‐frequency variability in the Southern Ocean region in a simplified coupled model

• Published in: Journal of Geophysical Research
• Main Authors: Maze, G., d'Andrea, F., Colin de Verdiere, Alain
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL), Laboratoire de physique des océans (LPO), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2006
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: https://hal.science/hal-00497986; https://hal.science/hal-00497986/document; https://hal.science/hal-00497986/file/Journal%20of%20Geophysical%20Research%20Oceans%20-%202006%20-%20Maze%20-%20Low%25u2010frequency%20variability%20in%20the%20Southern%20Ocean%20region%20in%20a.pdf; https://doi.org/10.1029/2005JC003181

International audience Patterns of interannual variability of the ocean‐atmosphere coupled system in the Southern Hemisphere extratropics are studied with a simple dynamical model in order to determine the basic physical processes of interaction independently of tropical forcing. The model used is an atmospheric quasi‐geostrophic model coupled to a “slab” oceanic mixed layer, which includes mean geostrophic advection by the Antarctic Circumpolar Current (ACC). The ocean‐atmosphere coupling occurs through surface heat fluxes and Ekman current heat advection. In a fully coupled simulation, the atmospheric part of the model, which includes high‐frequency transient eddies at midlatitudes, exhibits a strong Southern Annular Mode (SAM) as the first mode of variability at interannual timescales. The SAM‐related wind anomalies induce Ekman currents in the mixed layer which produce sea surface temperature anomalies. These are then advected along by the ACC. A forced mechanism where the ocean role is reduced to advect the sea surface temperature (SST) appears sufficient to reproduce the main features of the variability. Nevertheless, a positive feedback of the ocean was also found. It operates through anomalous Ekman currents heat advection and contributes to the maintenance of the SST anomaly.