Observed Atlantic major hurricane frequency has exhibited pronounced multidecadal variability since the 1940s. However, the cause of this variability is debated. Using observations and a coupled earth system model (GFDL-ESM2G), here we show that the decline of the Atlantic major hurricane frequency during 2005–2015 is associated with a weakening of the Atlantic Meridional Overturning Circulation (AMOC) inferred from ocean observations. Directly observed North Atlantic sulfate aerosol optical depth has not increased (but shows a modest decline) over this period, suggesting the decline of the Atlantic major hurricane frequency during 2005–2015 is not likely due to recent changes in anthropogenic sulfate aerosols. Instead, we find coherent multidecadal variations involving the inferred AMOC and Atlantic major hurricane frequency, along with indices of Atlantic Multidecadal Variability and inverted vertical wind shear. Our results provide evidence for an important role of the AMOC in the recent decline of Atlantic major hurricane frequency.
Ocean to Climate 
This new paper used both observations and models to suggest that the observed AMOC slowdown since 2005 is the main cause of the rapid downward swing of the AMO index and thus the declining Atlantic hurricane activity. The AMOC reconstruction (i.e., fingerprint) and the 4-year backward shift to represent the AMOC propagation to the mid-latitude are very interesting. However, it is bit unclear whether the tropical Pacific has any influence on the results.
The following study also pointed out the relationship between the AMOC and Atlantic hurricane activity in the future climate. Lee et al. (2011) showed that the projected AMOC slowdown in the future could also slow down the warming in the North Atlantic and thus stabilize the atmosphere and increase the vertical wind shear aloft, ultimately reducing hurricane activity in the future.
Lee, S.-K., D. B. Enfield and C. Wang, 2011: Future impact of differential inter-basin ocean warming on Atlantic hurricanes. J. Climate, 24, 1264-1275.
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