Temperature and heating-induced temperature difference profiles were measured through the atmosphere, sea ice, and ocean using a SIMBA-type sea ice mass balance buoy equipped with a several meter long thermistor chain. The present dataset was recorded by SIMBA 2012T4 (original name Awi_31) installed on landfast sea ice in Atka Bay, Antarctica, during the expedition Neumayer AFIN in 2012. Data is available between 2012-11-22 17:01:00 and 2014-02-09 22:06:00. The thermistor chain was Variable 5 m long and included 240 sensors with a regular spacing of 2 cm. The resulting time series includes the evolution of temperature and temperature differences at 30 s and 120 s during a heating cycle of 120 s as a function of location, depth and time. The sampling intervals were usually between hourly and daily, but were most frequently configured to 6 hours for temperature, and 24 hours for temperature differences. In addition to temperatures and geographic location were measured. The present dataset was processed as follows: obvious inconsistencies (missing values) and unrealistic values of GPS position have been removed. This instrument was deployed as part of the project projects Antarctic Fast Ice Network (AFIN) and Sea Ice Physics @ AWI (AWI_SeaIce).