A Holocene history of extreme rainfall events in Southern Brazil

Abstract Extreme rainfall events (ERE) are projected to increase in intensity and frequency worldwide. Southern Brazil, a densely populated region, is strongly affected by these events with severe socioeconomic impacts, such as the catastrophic flooding in Rio Grande do Sul State in April/May of 2024. Understanding the intensity and frequency of past ERE is fundamental for predicting future impacts in a global warming scenario. The lack of records of past ERE variability beyond the instrumental period hampers our ability to assess the relationship of ERE variability and large-scale climate drivers over longer timescales. Here we present the first ERE record from southern Brazil, based on the frequency of detrital layers within stalagmites from Malfazido cave, spanning the past 7500 years. Our results suggest a strong influence of Antarctic-tropical teleconnections on the long-term modulation of ERE and important contribution of strong/moderate El Niño events to the frequency of ERE in the last millennium. In the 20th century, ERE frequency is in the upper range of the variability of our record, suggesting an influence of anthropogenic forcing on ERE modulation.