North Atlantic Tropical Cyclone Response to Diverse El Niño Sea Surface Temperature Patterns Over the Past Millennium

Tropical cyclones (TCs) are destructive natural phenomena, but their future response to both natural and human-caused climate changes is still poorly understood. The El Niño-Southern Oscillation, which modulates tropical Pacific sea surface temperatures (SSTs), has been shown to affect TC genesis in previous work. Specifically, studies show that El Niño (warm) events suppress TCs in the North Atlantic Ocean, while La Niña (cool) events enhance TC activity. However, these studies are often based on only ~50 years of satellite observations. Furthermore, previous work has not accounted for how TCs respond to different types of El Niño sea surface temperature (SST) patterns in the tropical Pacific. Addressing this, here, we study how a large set of statistically/dynamically downscaled TCs respond to two key types of El Niño events, Central Pacific (CP) and Eastern Pacific (EP), over the last millennium. TCs are downscaled using climate conditions from a single full forcing simulation of CESM Last Millennium Ensemble. We identify differences in TC genesis, track density, frequency, and intensity during CP and EP El Niño years over the past millennium, extending the limited 20th-century data by hundreds of years to generate robust statistics surrounding TC characteristics. During both CP and EP events, North Atlantic TC frequency is suppressed compared to the climatology. During EP El Niños, North Atlantic TCs are more likely to form and track in the Southern Caribbean and West Atlantic Corridor. During CP events, on the other hand, TCs form and track more often in the Gulf of Mexico. Our findings provide critical insights into how interannual variability driven by ENSO affects Atlantic tropical cyclone activity; this information is critical for future projections of TCs. Given that climate models project more frequent CP El Niño events in our warming climate, we assert that the Gulf of Mexico may experience more frequent and more damaging TCs in the 21st century.