Abstract The seasonal evolution of the ice and snow thickness is critical for modulating interactions in the atmosphere-sea ice-ocean system, among other physical properties that evolve in concert under temporally and spatially variable conditions for ice growth and melt. Here, we utilize data from about 70 sea ice mass balance buoys (SIMBA type) to investigate seasonal effects in the long-term variability of ice and snow thicknesses along the Transpolar Drift between 2012 and 2023, with a special emphasis on characteristics of the MOSAiC period in 2019/2020. We apply a newly developed uniform processing scheme to all buoys that is intended to reduce prior methodological ambiguities in the derivation of snow-ice-ocean interfaces and hence to improve the interannual comparability. The new data set provides thicknesses, interface positions and interface temperatures. We find tendencies towards an earlier melt onset and a slightly later start of the growth period, in line with other large-scale studies. However, ice growth rates in November and December during MOSAiC were larger than in most other years, mainly due to relatively thin ice at the deployment sites. Snow depth generally shows a high interannual variability, with MOSAiC not particularly standing out despite rather early snow melt from mid-May onwards.