Speaker
Description
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-yr 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 3 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 multi-linear regression analysis. We find that the maximum 11-yr solar response in the December- January-February average does not project directly onto the NAO. 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. The observed responses in the North Atlantic region are then compared with large ensemble solar- forcing-only model simulations. We present that climate models struggle to simulate the observed solar cycle signals in the NAO and EA atmospheric modes.