Future Summer Marine Heatwaves in the Western South Atlantic

Abstract

AbstractMarine heatwaves (MHWs) are periods of abnormally high ocean temperatures and their impacts threaten physical, biological, and human systems. Here, we show through different scenarios of the Coupled Model Intercomparison Project Phase 6 (CMIP6) that significant positive trends in frequency, duration, and cumulative intensity are identified for the western South Atlantic, leading to an almost permanent state of MHW by the end of the 21st century considering a constant baseline. We also find that the main mechanism that causes MHWs in this region, atmospheric blocking, is likely to intensify in the future. Thus, the increase in occurrence of MHWs is not just due to the direct effect of long‐term warming. Moreover, the largest trends occur during 2021–2050, and not during 2071–2100. This has important implications for marine ecosystems and the ocean ability of absorbing heat and CO2, underlying the urgency for a global reduction in greenhouse gas emissions.