Seawater temperature and salinity 2-m beneath landfast ice in Prydz Bay, East Antarctica, recorded from a cable–type CTD from April to November 2021

The data recorded field observations of seawater temperature and salinity outside Zhongshan Station in Prize Bay, East Antarctica. From April 16 to November 7, 2021, an observation station was established by the wintering team at the coastal landfast ice site, about 1 km off Zhongshan Station (69°22′ S, 76°22′ E). A cable–type CTD (model: ALEC ACTD–DF, produced by Japanese JFE Advantech Co., Ltd.) was deployed at 2 m beneath the ice surface and 30 m off the shoreline. CTD measured the ocean conductivity, temperature, and depth at a frequency of 30 s and the accuracy was ±0.02 mS cm-1 (±0.03 psu) for conductivity (salinity) and ±0.02℃ for temperature. To mitigate the error of high-frequency observations, data were sampled with the sliding mean to a 2-minute interval. The CTD recorded 194 days of high-frequency temperature records at the 2-minute interval, from 16 April to 6 November 2021. Due to the insufficient power of the instrument, there was a temporary data loss in the data recording from July 6 to July 16. The ocean temperature experienced a rapid increase during 16–23 April, from -1.62℃ to -1.30℃, then gradually decreased to -1.75℃ in the middle of May. In the following months, the ocean temperature remained around -1.79℃ and showed a small standard deviation of 0.01℃ until the end of observations. Seawater salinity experienced a quick increase, from 33.34 psu in April to 34.08 psu in May, and from then on seawater salinity maintained largely with a small daily and seasonal deviation, around 34.13±0.02 psu. The results showed that the CTD recorded data has good quality and can be used as a basic data set for sea ice thermodynamic analysis and remote sensing verification.The data is recorded in text format (.txt). The fields include time, seawater salinity, and seawater temperature.