The Southern Ocean western boundary currents: Comparison of fine resolution Antarctic model results with Geosat altimeter data

Abstract

Variability in the major western boundary current systems of the Southern Ocean is studied by comparing results from the United Kingdom fine resolution Antarctic model (FRAM) to 3 years of Geosat altimeter data. Several analysis techniques (harmonic analysis, principal component, and principal oscillating pattern analysis) are applied to both model results and the “real ocean” altimeter data. The analysis results from the very complex altimeter observations were verified, and the interpretation of Geosat data in the three Southern Ocean western boundary systems was improved. This could be achieved by testing a basic hypothesis underlying the analysis of the partially known sea surface topographies from Geosat with the completely known FRAM model results. The hypothesis that ring formations can be catalogued and studied from variations in the decorrelation time of successive sea level anomaly fields (Feron et al.5 1992) is confirmed by FRAM. Applying the technique to altimeter data of the Agulhas, Brazil/Malvinas, and East Australian Currents showed that quasi‐periodic ring formations take place, roughly every 100, 150, and 130 days, respectively. The FRAM model.only generated periodic ring formations in the Agulhas and East Australian Currents, both with a very regular 125 to 130 day period. This period is clearly a model‐favored harmonic (1/3 year) which is, however, close to the observations.