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Decadal variability in an OGCM Southern Ocean: intrinsic modes, forced modes and metastable states

Citation

O'Kane, TJ and Matear, RJ and Chamberlain, MA and Risby, JS and Sloyan, BM and Horenko, I, Decadal variability in an OGCM Southern Ocean: intrinsic modes, forced modes and metastable states, Ocean Modelling, 69 pp. 1-21. ISSN 1463-5003 (2013) [Refereed Article]

Copyright Statement

Copyright 2013 Crown Copyright

DOI: doi:10.1016/j.ocemod.2013.04.009

Abstract

An ocean general circulation model (OGCM) is used to identify a Southern Ocean southeast Pacific intrinsic mode of low frequency variability. Using CORE data a comprehensive suite of experiments were carried out to elucidate excitation and amplification responses of this intrinsic mode to low frequency forcing (ENSO,SAM) and stochastic forcing due to high frequency winds. Subsurface anomalies were found to teleconnect the Pacific and Atlantic regions of the Antarctic Circumpolar Current (ACC) thermocline. The Pacific region of the ACC is characterised by intrinsic baroclinic disturbances that respond to both SAM and ENSO, while the Atlantic sector of the ACC is sensitive to higher frequency winds that act to amplify thermocline anomalies propagating downstream from the Pacific. Non-stationary cluster analysis was used to identify the systemís dynamical regimes and characterise meta-stability, persistence and transitions between the respective states. This analysis reveals significant trends, indicating fundamental changes to the meta-stability of the ocean dynamics in response to changes in atmospheric forcing. Intrinsic variability in sea-ice concentration was found to be coupled to thermocline processes. Seaice variability localised in the Atlantic was most closely associated with high frequency weather forcing. The SAM was associated with a circumpolar sea-ice response whereas ENSO was found to be a major driver of sea-ice variability only in the Pacific. This simulation study identifies plausible mechanisms that determine the predictability of the Southern Ocean climate on multi-decadal timescales.

Item Details

Item Type:Refereed Article
Keywords:Southern Ocean, decadal variability, cluster analysis
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical Oceanography
Objective Division:Environment
Objective Group:Other Environment
Objective Field:Antarctic and Sub-Antarctic Oceanography
Author:O'Kane, TJ (Dr Terry O'Kane)
Author:Matear, RJ (Dr Richard Matear)
Author:Sloyan, BM (Dr Bernadette Sloyan)
ID Code:119350
Year Published:2013
Web of Science® Times Cited:30
Deposited By:Centre for Oceans and Cryosphere
Deposited On:2017-07-31
Last Modified:2017-08-29
Downloads:0

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