Coupling Between Long-Term Arctic Surface Variability and the Stratosphere–Mesosphere–Lower Thermosphere System

The Arctic stratospheric polar vortex (SPV) manifests itself in the form of planetary‐scale eastward winds that encircle the mid‐ to high‐latitude polar region during the Northern Hemisphere (NH) winter. The SPV strength is modulated by upward propagating tropospheric planetary waves (PWs). In this work, we investigate long-term trends in the SPV and its coupling to the mesosphere and lower thermosphere (MLT) using Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) reanalysis data and simulations from the Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere–ionosphere extension (SD-WACCM-X). Our results show that the Arctic SPV experienced a weakening trend from 1980 to the early 2000s, followed by a strengthening trend thereafter. This transition is primarily linked to changes in PW activity, particularly zonal wavenumber-1, which is strongly influenced by Arctic surface variability. Positive trends in sea surface temperature (SST) over the Barents–Kara (B–K) Sea region prior to the early 2000s, and over the Central North Pacific (CNP) region after the early 2000s, are identified as key drivers of the observed PW variability. Furthermore, changes in SPV strength significantly impact MLT dynamics, including zonal winds and the migrating solar semidiurnal tide (SW2). The SW2 tide exhibits a positive trend of approximately 13% per decade before the early 2000s and a negative trend of about 14% per decade afterward. These results provide evidence of the impact of Arctic surface variabilities, on the MLT dynamics, especially SW2 tide.