Recent significant drying in Central Congo Basin linked to weakened Walker circulation and warmer Atlantic

The Congo River Basin (CRB), hosting the second-largest tropical forest on Earth, is of global significance for the water and carbon cycles. Its population and ecosystems are also strongly dependent on freshwater availability, which is increasingly threatened by current climate change and deforestation. Persistent drought conditions in CRB have been reported, but their drivers and impacts on the basin's hydrology remain unknown. Here, we analyze 42 years (1981–2022) of atmospheric and hydrological variability to show that the drying trend in Central Congo is linked to reduced atmospheric moisture convergence and precipitation, primarily during the rainiest period. This trend correlates with a weakening of the Walker circulation and an increase in Sea Surface Temperature in the Central Eastern Tropical Atlantic Ocean which influences moisture convergence over the Central Congo with a ~3-month lag. Our findings emphasize the need for integrative atmospheric and hydrological approaches to address CRB's freshwater and forest vulnerability to climate change.