Large-scale climate drivers of extreme compound events in the Amazon from interannual to long-term timescales (1982–2024)

Abstract Over recent decades Amazonia has experienced a marked intensification of floods and droughts. The record-breaking 2023–2024 drought, characterized by exceptional heat and dryness, motivates a closer analysis of compound extremes and their large-scale drivers. This study documents that the leading interannual variability of Amazonian precipitation, air temperature, river levels, and terrestrial water storage is represented by a coherent compound hydroclimatic mode dominated by extreme events. To capture this variability, we introduce the Amazon Basin Compound Hydroclimatic Extremes Index (AB-CHEX), based on precipitation, air temperature, and river levels for 1982–2024. AB-CHEX identifies two dominant states, dry–hot and wet–cold, and reveals a contrasting seasonal evolution toward wetter–colder conditions in the wet season (November–April) and increasingly dry–hot in the dry season (June–September). While severe dry–hot events occurred in 1998 and 2016 during the wet season and in 2005, 2010, and 2023 during the dry season, the 2024 event stands out as unprecedented across both seasons. Spatially, 68% (76%) of the basin in the wet (dry) season exhibit variability characterized primarily by compound hydroclimatic conditions, linked to distinct seasonal ocean–atmosphere drivers. During the wet season, El Niño–Southern Oscillation (ENSO) dominates through large-scale circulation changes. In contrast, during the dry season, Caribbean–Tropical North Atlantic (TNA) sea surface temperature variability exerts the primary regional control, providing a background control with secondary ENSO influence. This configuration is associated with the most widespread and severe dry–hot conditions. The sustained warming of the Caribbean–TNA since mid-2000s suggests its role in intensifying dry–hot compounds, reinforcing land–atmosphere feedbacks, and amplifying hydroclimatic instability, alongside the overall warming and drying trend.