Modelling multidecadal variability in the South Indian Ocean region: localforcing or a near-global mode?

Evidence for decadal to multidecadal climate variability has been found for many Southern Hemisphere regions, including the South Indian Ocean. Here w e apply atmospheric and ocean general circulation models (GCM) to investiga te the mechanisms potentially associated with a mode of multidecadal climat e variability over the South Indian Ocean region. This mode is characterize d by a strengthening and weakening of the South Indian Ocean anticyclone an d basin-scale sea-surface temperature (SST) anomalies that reverse sign bet ween the southern midlatitudes and the subtropics. It is suggested that the SST variability most likely results from forcing by local atmospheric chan ges, whereas the latter may arise as the manifestation over the Indian Ocea n of a near-global multidecadal mode.