Diagnosing the 11‐year solar cycle's influence on the East Atlantic pattern

Abstract The North Atlantic sector has been identified as a region where the 11‐year solar cycle has small but potentially non‐negligible impacts on winter climate, but a debate persists about the robustness of such impacts. This work explores the signatures of the 11‐year solar cycle over the North Atlantic in the ERA5 and 20th Century Reanalysis datasets. The results confirm previous studies with a robust positive boreal winter response in mean‐sea‐level pressure (mslp) in the region of the Azores at lags of three years after solar maximum. The spatial evolution of the response is examined in detail by first decomposing the mslp time series into the dominant modes of North Atlantic winter mslp variability, including the North Atlantic Oscillation (NAO), the East Atlantic (EA) and the Scandinavian patterns, before performing a multilinear regression analysis. We find that the maximum 11‐year solar response in the December–January–February (DJF) average does not project directly onto the NAO. However, when the early/late‐winter responses are examined separately, a statistically significant NAO response is seen in late winter (January–February) at lag 0–1 years and a statistically significant NAO response is also seen at lag +3 years in early winter (November–December). These results are consistent with predicted responses from previously proposed top‐down influences from the stratosphere in late winter followed by the re‐emergence of a signal from underlying sea surface temperatures in early winter. However, the NAO response is not the primary contributor to the total DJF response at lag +3 years. A previously unidentified solar‐cycle response in the EA pattern is found in late winter at lag +3 years with larger amplitude than the NAO response. The evolution of the DJF mslp response over the Azores region can thus be understood as a summation of the NAO and EA patterns at lag +3 years.