Multi-year variability in the Tasman sea and impacts on Southern Hemisphere climate in CMIP5 models

Abstract

aturally occurring multi-year to decadal variability is evident in rainfall, temperature, severe weather and flood frequency around the globe. It is therefore important that we understand the cause of this variability and the extent to which it can be predicted. Here we assess internally-generated decadal climate variability and its predictability potential in an ensemble of CMIP5 models. Global hotspots of subsurface ocean decadal variability are identified, revealing variability in the southern Tasman Sea that is coherent with variability in much of the Pacific Ocean and Southern Hemisphere. We find that subsurface temperature variability in the southern Tasman Sea primarily arises in response to preceding changes in southern hemisphere winds. This variability is multi-year to decadal in character and it is coherent with surface temperature in parts of the Southern Hemisphere up to several years later. This provides some degree of potential predictability to surface temperature in the south Tasman Sea and surrounding regions. A few models exhibit significant correlation between subsurface variability in the south Tasman Sea and zonally averaged precipitation south of 50°S, however the multi-model mean does not exhibit any significant correlation between subsurface variability and precipitation. Models which exhibit stronger subsurface variability in the southern Tasman Sea also have a stronger Interdecadal Pacific Oscillation signal in the Pacific.