Temperature and heating-induced temperature differences were measured along a chain of thermistors. SIMBA 2020T81 (a.k.a. FMI_06_08, IRIDIUM number 300234068708320) is an autonomous instrument that was installed on drifting sea ice in the Arctic Ocean during the 5th leg of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) in August 2020. The buoy was deployed over the open melt pond at the CO3 of MOSAiC. The thermistor chain was 5 m long and included 241 sensors with a regular spacing of 2cm. The 33rd sensor from the top was set at the pond water surface. 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 depth and time between 30 August 2020 and 11 February 2021 in sample intervals of 6 hours for temperature and 24 hours for temperature differences. The near-surface air temperature was measured at 1 m over the ice surface. In addition to temperature, geographic position, barometric pressure, tilt and compass were measured.

The data set has been processed and contains quality flags for different kinds for erroneous data. Flag values are the sum of individual error codes. The value of 0 refers to no error. Quality flag, position: The geographic position is flagged +1 if the drift velocity, as derived from the GPS longitude and latitude, exceeds a threshold of 10 deg latitude or 50 deg longitude per time step; +2 if the position exceeds extreme values, such as longitude > 360 deg; +4 if the position is exactly 0.0.