Southern Ocean Intrinsic and Forced Modes of Low Frequency

• Main Authors: O'Kane, TJ, Matear, R, Chamberlain, MA, Risbey, JS, Sloyan, BM, Horenko, I
• Format: Conference Object
• Language: English
• Published: Australasian Fluid Mechanics Society 2012
• Subjects: Earth Sciences; Oceanography; Physical Oceanography; Antarctic; Southern Ocean; The Antarctic; Pacific; Antarc*; Sea ice
• Online Access: http://afms.org.au/proceedings.html; http://ecite.utas.edu.au/119774

A coupled Ocean-Sea ice General Circulation Model (OGCM)is used to identify a Southern Ocean southeast Pacific intrinsicmode of low frequency variability. This mode is co-locatedwith a major region of Sub-Antarctic Mode Water (SAMW)and Antarctic Intermediate Water (AAIW) formation. UsingCORE data a comprehensive suite of experiments were carriedout to elucidate excitation and amplification mechanismsof this intrinsic mode by low frequency forcing (ENSO, SAM)and stochastic forcing due to high frequency winds. Subsurfacethermocline anomalies were found to teleconnect the Pacificand Atlantic regions of the Antarctic Circumpolar Current(ACC). The Pacific region of the ACC is characterised by intrinsicbaroclinic disturbances that respond to both SAM andENSO, while the Atlantic sector of the ACC is sensitive tohigher frequency winds that act to amplify thermocline anomaliespropagating downstream from the Pacific resonant witheastward travelling Rossby waves. This simulation study identifiesplausible mechanisms that determine the predictability ofthe Southern Ocean climate on multi-decadal timescales.