Linking Long-Term Arctic Surface Variability and Changes in the Stratosphere, Mesosphere, and Lower Thermosphere

We present the long-term trends of the Arctic stratospheric polar vortex (SPV) using the Modern Era Retrospective Research analysis for Research and Application-2 (MERRA-2) reanalysis data, and assess its impact on the mesosphere and lower thermosphere (MLT) using Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (SD-WACCM-X) simulations. Our findings reveal that the SPV showed a weakening trend from 1980 until the early 2000s, but a strengthening trend after the 2000s. This change is attributed to the weakening of the planetary wave (PW) activities, particularly the wavenumber-1, which can be driven by long-term Arctic surface changes. A strong link has been found between the observed PWs activity and the increasing sea surface temperature (SST) over/nearby the Barents-Kara Sea before early 2000s and over the Central North Pacific region after the 2000s. Furthermore, we observe that the SPV trend influences the zonal mean zonal winds and migrating solar semidiurnal tide (SW2) in the MLT. The SW2 exhibits a ∼13%/decade positive trend from 1980 to the early 2000s and a ∼14%/decade negative trend after 2000s. These results provide evidence of the impact of Arctic surface variabilities, including sea-ice, on the MLT dynamics, especially SW2 tide.