This dataset comprises measurements from a moored thermistor, collected by the Krossfjord Italian Mooring (KIM), which is managed by the Institute of Polar Sciences of the National Research Council (CNR). The data was gathered in the Krossfjord, Svalbard Island, since September 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. Mesured properties: seawater temperature. The acquisition of this time series data is still ongoing and will continue, bolstered by the inclusion of this infrastructure within the framework of the Italian PNRR project ITINERIS. This ensures sustained data collection and further enhances our understanding of the observed environmental changes.