Temperature and heating-induced temperature were measured along a chain of thermistors. Digital Thermistor Chain DTC55 is an autonomous instrument that was installed on drifting sea ice in the Arctic Ocean during the MOSAiC expedition on 26 August 2020. The thermistor chain was 5.12 m long and included sensors with a regular spacing of 2 cm. The initial ice thickness was 1.14 m, the snow thickness was 0.03 m, and the pond depth was 0.17 m. 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 between 26 August 2020 and 20 September 2020 in sample intervals of 6 hours. It also contains manually estimated positions of air-snow, snow-ice, and ice-water interfaces. The DTC was installed in the undeformed second/multiyear ice next to the Met City and the ice mass balance buoy 2020T84: doi:10.1594/PANGAEA.958397.

Temperature after the cooling cycle and temperature before the heating cycle both represent in situ temperature. The temperature before the heating cycle may contain errors in measurements and is provided for reference. It is recommended to use temperature after the cooling cycle and temperature difference after the heating cycle for further analysis.