Key features of the lower atmosphere over sea ice include the top of the large-scale Arctic Inversion (AI), which separates the free troposphere from the atmosphere impacted by the presence of sea ice on the large scale, the surface-based and locally forced atmospheric boundary layer (ABL), which may be stable or well-mixed (then SML), and the cloud mixed layer (CML) penetrating downwards from the cloud tops and sometimes merging with a SML. Low-level jets (LLJs) are also features that enhance vertical mixing. The characteristics of these features (e.g., heights and thicknesses) are modulated by synoptic and mesoscale variability, especially with the many cyclones occurring during MOSAiC. For instance, with the approach of a warm front, the enhanced longwave surface radiation destabilizes the near-surface environment producing a shallow SML, while the same occurs with cold-air advection behind a cold. Deeper SMLs are often observed below LLJs, while the AI top seems to lower within the warm sector of a passing cyclone. Using primarily data from Met City, radiosondes, the Doppler lidars, and the cloud radar, this presentation will illustrate the physical processes producing the temporal variability in the characteristics and occurrences of these boundary-layer features during cyclone passages.