Previous studies have largely focused on mean changes in tropical cyclone (TC) activity, despite the importance of seasonal extremes for societal impacts. We investigated future changes in active and inactive Atlantic hurricane seasons driven by combinations of the El Niño – Southern Oscillation (ENSO) and Atlantic Meridional Mode (AMM) by performing ensembles of E3SM simulations forced with sea-surface temperature patterns associated with ENSO and the AMM in historical and future climates. We found that future Atlantic TC frequency increases during both the active and inactive seasons, with greater increases during the active season.
The projected changes in both the active and inactive Atlantic hurricane seasons represent a potential worsening of Atlantic TC impacts in the future.
North Atlantic tropical cyclones (TCs) have considerable interannual variability, with La Niña and the positive phase of the Atlantic Meridional Mode (AMM) tending to drive active hurricane seasons, and El Niño and the negative AMM often driving inactive seasons. Here, we analyzed how active and inactive Atlantic hurricane seasons may change in the future using the high-resolution Energy Exascale Earth System Model (E3SM). We performed atmosphere-only simulations forced by sea-surface temperature patterns characteristic of La Niña and the positive AMM jointly, and by El Niño and the negative AMM jointly, in historical and future climates. Projected Atlantic TCs become more frequent in the future by approximately 34% during El Niño and negative AMM and by 66% during La Niña and positive AMM, with a significant increase in the proportion of intense TCs for both the active and inactive seasons. Increased potential intensity and relative humidity and decreased vertical wind shear support stronger and more frequent TCs in the future.