From mesosphere to regional climate variability: Mechanism for downward coupling of polar mesospheric ozone loss

Solar driven energetic particle precipitation (EPP) is an important factor in polar atmospheric ozone balance throughout mesosphere and stratosphere. EPP has previously been linked to ground-level regional climate variability, but the linking mechanism has remained ambiguous. Reported observed and simulated ground-level changes start well before the processes from the main candidate, the so-called EPP-indirect effect, would start. Here, we show that initial reduction of polar mesospheric ozone and the resulting change in atmospheric heating rapidly couples to dynamics, transferring the signal downwards through the mesosphere and stratosphere, resulting in shifting the tropospheric jet polewards. This pathway is not constrained to the polar vortex, rather, a subtropical route plays a key role. Our results show that the signal propagates downwards in timescales consistent with observed tropospheric level climatic changes linked to EPP. This pathway, from mesospheric ozone to regional climate, is independent of the EPP-indirect effect, and solves the long-standing mechanism problem for EPP effects on climate.