Eddy response to Southern Ocean climate modes

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Morrow, Rosemary, Ward, Marshall, Hogg, Andrew Mcc., Pasquet, S.
• Other Authors: Océan du Large et Variabilité Climatique (OLVAC), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS), Research School of Earth Sciences Canberra (RSES), Australian National University (ANU)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Southern Ocean; Pacific
• Online Access: https://hal.science/hal-00798759; https://hal.science/hal-00798759/document; https://hal.science/hal-00798759/file/jgrc11594.pdf; https://doi.org/10.1029/2009JC005894

International audience Interannual variations in Southern Ocean eddy kinetic energy (EKE) are investigated using 16 years of altimetric data. Circumpolar averages show a peak in EKE from 2000 to 2002, 2-3 years after the peak in the Southern Annular Mode (SAM) index. Although the SAM forcing is in phase around the circumpolar band, we find the EKE response varies regionally. The strongest EKE is in the Pacific, with energy peaks occurring progressively later toward the east. We suggest that this is due to the presence of two climate modes: SAM and ENSO. When strong positive SAM events coincide with La Niña periods, as in 1999, anomalous meridional wind forcing is enhanced in the South Pacific Ocean, contributing to the observed increase in EKE 2-3 years later. When positive SAM events coincide with El Niño periods, as in 1993, the climate modes are in opposition in the South Pacific, leading to a weak EKE response during the mid-1990s. Numerical modeling supports these observations. By applying different combinations of SAM and ENSO, we can reproduce both the elevated Pacific EKE response to SAM as well as an additional amplification/suppression of EKE during La Niña/El Niño. In general, we find that the EKE response depends on the interplay between wind forcing, topography, and mean flow and produces a strongly heterogeneous distribution in the Southern Ocean.