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Global and hemispheric climate variations affecting the Southern Ocean

Published online by Cambridge University Press:  30 November 2004

IAN SIMMONDS
Affiliation:
School of Earth Sciences, The University of Melbourne, VIC 3052, Australia
JOHN C. KING
Affiliation:
British Antarctic Survey, NERC, High Cross, Madingley Rd, Cambridge CB3 0ET, UK

Abstract

The hemispheric and regional atmospheric circulation influences the Southern Ocean in many and profound ways, including intense air-sea fluxes of momentum, energy, fresh water and dissolved gases. The Southern Ocean ventilates a large fraction of the world ocean and hence these influences are spread globally. We use the NCEP-2 reanalysis data set to diagnose aspects of the large-scale atmospheric structure and variability and explore how these impact on the Southern Ocean. We discuss how the ‘Southern Annular Mode’ and the ‘Pacific-South American’ pattern influence the Southern Ocean, particularly in the eastern Pacific. We review the importance of atmospheric eddies in Southern Ocean climate, and the role they play in the transport of mechanical energy into the ocean. The fluxes of fresh water across the air-sea boundary influence strongly the processes of water mass formation. It is shown that climatological precipitation exceeds evaporation over most of the Southern Ocean. When averaged over the ocean from 50°S to the Antarctic coast the annual mean excess is 0.80 mm day−1. The magnitude of the flux displays only a small measure of seasonality, and its largest value of 0.92 mm day−1 occurs in summer.

Type
Research Article
Copyright
© Antarctic Science Ltd 2004

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