Abstract
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 ocean dynamics. 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, which we think to be an oceanic effect. The
fluctuations and amplitude modulation of the solar–NAO relationship on
a 50-year time scale also suggest that there will be nonlinear
interactions between solar forcing and ocean dynamics.