Future extratropical cyclones with more moisture and fewer associated atmospheric rivers

Future changes in extratropical cyclones (ETCs), their moisture transport, and their connection to atmospheric rivers (ARs) remain uncertain. Here, using downscaled simulations from the Community Earth System Model version 2 under the high-emissions scenario SSP5-8.5, we show that moisture uptake associated with intense North Atlantic ETCs will increase by ~14.5%, or ~3.29% per Kelvin of global warming by the end of this century. Subregional analysis revealed greater increases during the most intense cyclone stages, with changes of 52.1% (11.8% K−1) in the eastern North Atlantic, 33.4% (7.6% K−1) in the western North Atlantic, and 29.1% (6.6% K−1) in the northern North Atlantic. Rather than a consistent increase within existing climatological source regions, the moisture origin exhibits a geographic shift, likely linked with changes in storm-track pathways and ocean circulation under warming. Using a novel method to couple ETC moisture sources with ARs, we demonstrate that while this coupling continues to be a defining characteristic at the basin scale, the strength of their association is projected to weaken. Historical differences between low- and fully associated ETCs, particularly in terms of moisture sources and proximity to the AR axis, diminish and lose significance in a warming climate.