Moisture exchange between South America and the Atlantic Ocean: implications for aridity

Abstract

Aridity patterns across South America arise from complex land-atmosphere interactions modulated by large-scale cir-culation and oceanic forcings. In particular, the transport of energy and moisture from the Atlantic Ocean plays a keycontrol in shaping the continental hydroclimate. Using ERA5 reanalysis for 1980–2020, this study examines the interan-nual variability of the vertically integrated water vapor fluxes across five Atlantic-South America boundaries and theircoupling with large-scale atmospheric and oceanic anomalies. Land hydroclimatic impacts are assessed using the Budykoaridity index. Enhanced Atlantic inflows are consistently associated with reduced aridity in southeastern South America,while northeastern regions experience drying linked to anomalous subsidence and suppressed precipitation, revealing asoutheastern-northeastern aridity dipole. Tropical inflows respond to Pacific and Atlantic variability, whereas southernboundaries are also modulated by extratropical wavetrains. Interactions between dynamic and thermodynamic effects oftencompensate, shaping the net moisture balance. These results demonstrate that South American aridity emerges from thecombined influence of circulation dynamics and ocean-atmosphere-land feedbacks.