Temperature and heating-induced temperature were measured along a chain of thermistors. Digital Thermistor Chain DTC25 is an autonomous instrument that was installed on drifting sea ice in the Arctic Ocean during the MOSAiC expedition on 8 January 2020. The thermistor chain was 5.12 m long 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 between 8 January 2020 and 23 March 2020 in sample intervals of 6 hours. It also contains manually estimated position of air-snow, snow-ice, and ice-water interfaces. The DTC was installed in Fort Ridge towards the level first-year ice. Ice mass balance SIMBA 2020T60 was installed at the Fort Ridge: doi:10.1594/PANGAEA.924269.

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.