Influence of the Solar Cycle on the North Atlantic Oscillation

We examine the influence of the solar cycle on the North Atlantic Oscillation (NAO) on its pathway from the upper stratosphere to the surface by applying lagged regression analyses to recent observations, historical observations covering 194 years, and an Earth system model simulation covering 165 years. The propagation of the solar signal can well be explained by a top-down mechanism, but one that was strongly affected by air-sea coupling. The solar signal first appears in the subtropical upper stratosphere as a temperature signal. The associated zonal wind signal then propagates downward to the surface in response to stratospheric variability known as the Polar-night Jet Oscillation. The NAO signal tends to appear in February during years of peak solar activity. The solar signal is further modulated such that positive NAO signals tend to appear earlier in winter with increasing years after peak solar activity associated with the appearance of the NAO-related SST signal. There are also 50-year scale fluctuations and amplitude modulations of the solar-NAO signal, but the tendency of increasing NAO amplitude with increasing NAO-related SST amplitude suggests a strong influence of decadal ocean dynamics on these modulations.

Automated summary

The influence of the solar cycle on the North Atlantic Oscillation (NAO) can be explained by a top-down mechanism, where the solar signal first appears in the subtropical upper stratosphere and propagates downward to the surface through zonal wind signal. The NAO signal tends to appear in February during years of peak solar activity, and the solar signal is modulated by the appearance of NAO-related sea surface temperature (SST) signal.