Atlantic ocean circulation slowdown intensifies tropical cyclones in the North Atlantic

Abstract

The slowdown of the Atlantic Meridional Overturning Circulation (AMOC) is ubiquitous in climate projections, representing a major risk of global warming with far-reaching climatic impacts. Here, we investigate how the future AMOC slowdown can affect the activity tropical cyclones (TCs). To that end, we compare two sets of global warming simulations: one that exhibits AMOC weakening and another in which AMOC intensity is fixed. Using these experiments, we compute Genesis Potential Indices (GPI), to assess large-scale ocean-atmosphere conditions for TC formation, and conduct downscaling TC simulations for the two scenarios. Our analysis shows strongly enhanced tropical cyclogenesis in the North Atlantic, especially along the U.S. eastern seaboard and in the Gulf of Mexico, in a warm climate with a weakened AMOC. The AMOC slowdown causes roughly 60% of the estimated seasonal increase of 12 storms in the Atlantic with warming. Higher TC potential intensity (PI) in the North Atlantic due to greater air-sea thermodynamic disequilibrium and, to a lesser extent, reduced vertical windshear explain these findings, which highlight the important role of AMOC slowdown in 21st -century TCs.