Temperature and heating-induced temperature differences were measured along a chain of thermistors. SIMBA 2019T69 (a.k.a. FMI6-02) is an autonomous instrument that was installed on drifting sea ice in the Arctic Ocean during the 1st leg of MOSAiC in October 2019. The thermistor chain was 5 m long and included 241 sensors with a regular spacing of 2cm. The resulting time series describes the evolution of temperature and temperature differences after two heating cycles of 30 and 120 s as a function of place, depth and time between 11 October 2019 and 30 September 2020 in sample intervals of 6 hours for temperature and 24 hours for temperature differences. In addition to temperature, geographic position, barometric pressure, air temperature measured 1m over the ice level, tilt and compass were measured.