Mid- to Late Holocene Contraction of the Intertropical Convergence Zone Over Northeastern South America

Modern precipitation over northeastern (NE) South America is strongly controlled by the seasonal meridional migration of the Intertropical Convergence Zone (ITCZ). Ample evidence from the Northern Hemisphere suggests a mid- to late Holocene southward migration of the ITCZ. Such a shift would be expected to increase precipitation over semi-arid northern NE Brazil (Southern Hemisphere). However, the most robust precipitation record from northern NE Brazil shows a drying trend throughout the Holocene. Here, we address this issue presenting a high-temporal resolution reconstruction of precipitation over northern NE Brazil based on data from a marine sediment core, together with analyses of mid- and late Holocene simulations performed with the fully coupled climate model FGOALS-s2. Both, our data and the climate model simulations show a decrease in precipitation over northern NE Brazil from the mid- to the late Holocene. The model outputs further indicate a latitudinal contraction of the seasonal migration range of the ITCZ that, together with an intensification of the regional Walker circulation, were responsible for the mid- to late Holocene changes in precipitation over NE South America. Our results reconcile apparently conflicting precipitation records and climate mechanisms used to explain changes in precipitation over NE South America.

Automated summary

Research indicates that precipitation over northeastern South America has been strongly influenced by the seasonal migration of the Intertropical Convergence Zone (ITCZ) in the past few thousand years. During the mid-to late Holocene, the migration range of the ITCZ contracted, leading to a decrease in precipitation over northern NE Brazil.