Eddy heat diffusion and Subantarctic Mode Water formation

• Published in: Geophysical Research Letters
• Main Authors: Sallée, Jean-Baptiste, Morrow, R., Speer, K.
• Other Authors: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS), Department of Oceanography, Florida State University Tallahassee (FSU)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2008
• Subjects: Oceanography: Physical: Upper ocean and mixed layer processes; Oceanography: Physical: Eddies and mesoscale processes; Oceanography: Physical: Turbulence; diffusion; and mixing processes (4490); [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; Campbell Plateau; Indian; Pacific; Southern Ocean
• Online Access: https://hal.archives-ouvertes.fr/hal-00983745; https://doi.org/10.1029/2007GL032827

International audience Subantarctic mode waters (SAMW) form in the deep winter mixed layers occuring north of the Subantarctic Front (SAF). The recent increase of hydrographic and surface drifter data in the Southern Ocean allows a better spatial representation of the distinct regions of SAMW formation. This study focuses on the thermodynamical processes acting on the winter mixed layer heat budget. Eddy heat diffusion play a substantial role in the local heat balance, whereas its action vanishes with large-scale averaging. South of the western boundary currents and north of the SAF, the eddy heating plays an important role in specific regions, counterbalancing the cooling of the mixed layer by Ekman advection and air-sea fluxes. Specifically, the eddy diffusion term reduces the tendency for mixed layer destabilisation north of the SAF in the Western Indian Ocean downstream of the Agulhas Retroflection and in the Western Pacific downstream of Campbell Plateau. This role for mixed layer eddy fluxes emphasizes a large-scale control of mixed layer properties by topography and mesoscale processes in the Southern Ocean.