Multidecadal climate variability in the subtropics/mid-latitudes of the Southern Hemisphere oceans

Abstract

Observations of multidecadal variability in sea surface temperature (SST), surface air temperatureand winds over the Southern Hemisphere are presented and an ocean general circulationmodel applied towards investigating links between the SST variability and that of the overlyingatmosphere. The results suggest that the dynamical effect of the wind stress anomalies is significantmainly in the neighbourhood of the western boundary currents and their outflows acrossthe mid-latitudes of each Southern Hemisphere basin (more so in the South Indian and SouthAtlantic than in the South Pacific Ocean) and in the equatorial upwelling zones. Over most ofthe subtropics to mid-latitudes of the Southern Hemisphere oceans, changes in net surface heatflux (particularly in latent heat) appear to be more important for the SST variability thandynamical effects. Implications of these results for modelling and understanding low frequencyclimate variability in the Southern Hemisphere as well as possible links with mechanisms ofdecadal/interdecadal variability in the Northern Hemisphere are discussed.