This dataset comprises measurements from thermistor (SBE56) mounted on the Mooring Dirigibile Italia (MDI), which is managed by the Institute of Polar Sciences of the National Research Council (CNR). The mooring is placed in the Kongsfjorden, Svalbard Island, since September 2010 and the thermistor at the nominal depths of 92 and 97 m was operative from June 2017 to August 2020. This dataset is also part of the SIOS-Svalbard Integrated Arctic Earth Observing System, developed to observe the impacts of climate change, including the rapid loss of sea ice cover, the retreat of local glaciers, and the Atlantification of Arctic seas. Measured properties are: sea-water temperature.