The impact of AMOC SST fingerprints on tropical storm risk along the U.S. East and Gulf coasts and Latin America

Abstract

Tropical cyclones (TCs) pose significant risk to coastal populations, including those throughout the Caribbean and along the Atlantic and Gulf coasts of North America. The impact of climate change on TCs is multifaceted, and patterns of sea surface temperature (SST) change may play a role in shaping future TC risk. While the SST fingerprints associated with changes in the Atlantic Meridional Overturning Circulation (AMOC) may be uncertain, the North Atlantic Warming Hole (NAWH) and enhanced SST warming near the Gulf Stream are robust features of both past and projected future climate change. Here we use the CESM2 global climate model to highlight the remote contributions of both of these potential SST fingerprints of AMOC decline to changes in TC genesis potential in the Atlantic basin, and thus to uncertainty in future coastal climate risk. Both the NAWH and enhanced warming near the Gulf Stream lead to significant changes in TC genesis potential, particularly in the western North Atlantic, the northeastern Gulf of Mexico and the Caribbean Sea, where changes are of the order ±10% over the Atlantic hurricane season, with considerably stronger responses in the two halves of the season. Diagnosis of the Genesis Potential Index (GPI) indicates that changes in mid-tropospheric humidity and vertical wind shear are the most important factors driving these responses. Simulated changes in GPI occur in regions of considerable historical TC genesis, highlighting the need to further understand historical and projected future patterns of SST change in the North Atlantic, including their relationship to potential AMOC decline.