This time series has been collected by the Italian Consiglio Nazionale delle Ricerche (CNR) in a station located at about 3500 m depth in the central Tyrrhenian Sea (39° 46.85 N, 011° 53.00 E) over the period 2003-2016. The dataset contains 21 hydrological profiles (Pressure (dbar), Temperature (ITS-90, °C) and Salinity) performed on average every six months, with a lack of data in the period 2007-2010. The dataset is highly homogeneous in technical characteristics and quality, since the instrument used to collect most of the data is the same CTD probe (SBE911plus) and data quality procedures have been performed. The calibration of the probe was performed at the NATO-CMRE Centre of La Spezia up to 2014, and by the manufacturer (SeaBird) or by the Oceanographic Calibration Center of OGS in Trieste thereafter. To verify the post calibration performance of the probe, redundant sensors were often used for both temperature and salinity measurements, and on board salinity analysis of the water samples was performed using a Guideline Autosal or a Portasal salinometer. Raw data are post-processed and averaged at 1 dbar. Until 2014, the data were collected by the Italian R/V URANIA, those of 2015 by the Italian R/V MINERVA UNO, and those of 2016 by the Spanish  R/V Angeles Alvarino. This is the longest time series (fourteen years) of temperature and salinity of thermohaline staircases due to double diffusion in the salt finger regime ever observed. Parameters included in the .csv data file: - Cruise name (Cruise) - Time as julian days (Time_julian day) - Latitude - Longitude - Pressure in dbar (Pressure_dbar) - Practical Salinity (Salinity) - Temperature ITS-90 in °C (Temperature_ITS-90_°C)