This dataset comprises measurements from S1 Mooring, which is managed by the Institute of Polar Sciences of the National Research Council (CNR) and National Institute of Oceanography and Applied Geophysics (OGS). The data was gathered on the Fram Strait south of the Spitsbergen in an open-sea area strongly influenced by both the interaction between Atlantic (northward-moving) and Arctic (southward-moving) waters as well as by the presence and winter formation of sea ice and atmospheric forcing. To understand these dynamics, a deep-water oceanographic S1 Mooring was anchored at about 1040 meters depth, since June 2014 and is 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. The CTD sensor mounted at 820 m measures sea-water temperature and salinity. 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.