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Abstract This study examines the causes and impacts of the unusual warming of the tropical Atlantic from late 2023 to early 2024, focusing on the South Atlantic. Positive sea surface temperature anomalies persisted in the North Atlantic throughout 2023. However, the southern Tropical Atlantic underwent a rapid transition from abnormally cold surface waters in September‐October to unprecedented warm conditions in November‐December. This transition occurred through unusually weak cooling from latent heat flux, associated with weak surface winds. The anomalous atmospheric conditions over the South Atlantic were likely caused by an atmospheric Rossby wave train induced by El Niño and superimposed on a background of global warming. Meanwhile, in the equatorial Atlantic, the late 2023 warming was mainly caused by downwelling equatorial Kelvin wave activity generated by weaker surface wind. In early 2024, both thermodynamic and dynamic processes contributed to the equatorial warming. These distinct processes combined to produce basin‐wide warming. The resulting Atlantic warming, together with a Pacific El Niño created dry conditions over the Amazon basin and wet conditions over northeastern Brazil in early 2024. Simplified General Circulation Modeling experiments support the predominant role of South Atlantic warming in increasing precipitation over northeastern Brazil.
Hounsou‐Gbo et al. (Wed,) studied this question.