Temperature and heating-induced temperature were measured along a chain of thermistors. Digital Thermistor Chains (DTCs) are autonomous instruments that were installed on drifting sea ice in the Arctic Ocean from November 5, 2019, to September 5, 2020, during the MOSAiC expedition. The thermistor chains had various lengths of 2.56 m, 4.16 m, 5.12 m, 7.36 m and included sensors with a regular spacing of 2 cm. The resulting time series describes the evolution of temperature during the heating cycle of 20 s and after the heating cycle during the following 40 s as a function of geographic position (GPS), depth, and time in sample intervals of 6 hours. The DTCs were installed in various ice types including undeformed and deformed first- and second year ice and pressure ridges. The dataset also includes positions of air-snow, snow-ice, and ice-water interfaces, estimated from temperature data with and without heating. A total of 23 DTCs were processed. The dataset includes time and temperature after 20 s of heating and 40 s of cooling. Snow surface and bottom interfaces were estimated from the vertical temperature gradient, ice bottom interface was estimated from the difference between in situ temperature and temperature after the heating cycle. The main sites include Fort Ridge (co-located with SIMBA buoy), remote sensing sites (RS1, RS2, RS4), FYI and SYI dark sites (co-located with SIMBA buoys), Transect North, and leg 5 Central Observatory (CO3). For the MOSAiC Central Observatory 1 and 2 (CO1–2) and DTC08–44, we used a local coordinated system based on the location of two buoys: 2020T66 (FYI coring site, doi:10.1594/PANGAEA.938134) and 2020T61 (Alli's Ridge; doi:10.1594/PANGAEA.926580). Five separate GPS trackers T61, 2020R10 (doi:10.1594/PANGAEA.949124 ), S97 (doi:10.1594/PANGAEA.935675), T79 (doi:10.1594/PANGAEA.940712), 2020P227 (Figure 1) were installed at CO1. Each DTC is attached to the local CS linked to one of these 5 trackers. We divided CO1 into 5 parts, attached to 5 separated GPS trackers T61, R10, S97, T79, and P227 to account for the relative movement of those buoys and nearby DTCs relative to CO1 and CO2, fixed to T66 and T61 buoys. For the MOSAiC Central Observatory 3 (CO3) and DTC51–56, we also used a local coordinated system based on the location of two buoys: 2020T78 (doi:10.1594/PANGAEA.958438) and ASFS50 (doi:10.18739/A2445HD46).