Twentieth century correlations between extratropical SST variability and ITCZ shifts

Abstract

The Intertropical Convergence Zone (ITCZ) is a global-scale band of tropical precipitation lying, in the annual mean, just north of the equator. Its position can be tied to the atmosphere's energy balance: the Northern Hemisphere is heated more strongly than the Southern Hemisphere, biasing the atmosphere's circulation and ITCZ north of the equator. In the context of this energy balance framework, we examine multidecadal connections between variations in the position of the global ITCZ and indices of extratropical sea surface temperature (SST) variability over the twentieth century. We find that the ITCZ and atmospheric circulation are shifted farther to the north during periods when North Atlantic and North Pacific SSTs are anomalously warm. Additionally, a warmer North Atlantic is correlated with a relatively warm Northern Hemisphere atmosphere. Our results suggest an important role for the ocean circulation in modulating ITCZ migrations on decade-and-longer timescales.