Increasing frequency and intensity of compound droughts in the Amazon region

The Amazon rainforest, a critical global ecosystem, is increasingly threatened by climate change and extreme weather events. Over recent decades, the region has experienced record-high temperatures and unprecedented droughts. Compound drought and heatwave events (CDHWs), characterized by simultaneous dry and hot conditions, along with soil moisture (SM) deficits and high vapor pressure deficits (VPD), exacerbate ecosystem stress and intensify drought severity. This study investigates the climatology of CDHWs and compound low-SM/high-VPD events in the Amazon from 1981 to 2024 using the ERA5 dataset. Most compound events occurred during well-known drought years, including 1983, 1997/1998, 2010, 2015/2016, and 2023/2024. While compound events rarely impacted more than 20% of the region before 2010, subsequent years saw widespread effects, with the 2023/2024 drought ranking as the most extreme on record. During the austral summer of 2023/2024, CDHWs affected 70% of the Amazon's area, compared to 40% in 2015/2016. Similarly, low-SM/high-VPD conditions impacted 30% of the region in 2015/2016 and an unprecedented 60% in 2023/2024. Our results suggest an increase in the frequency, extent, and duration of compound extremes in the Amazon region, particularly over the last two decades, which could have critical implications for ecosystem resilience and climate adaptation strategies. The previous record compound event of 2015/2016 was particularly significant due to its ecological impacts, including tree mortality, biomass growth decline, and reductions in net primary productivity (NPP), gross primary productivity (GPP), and carbon uptake. Therefore, the ongoing record-breaking CDHW and low-SM/VPD conditions in 2023/2024 are expected to have even more severe impacts on the Amazon rainforest.