This dataset provides 37 CTD profiles measured on board of the German R/V Sonne (cruise SO269) in the northern South China Sea, under the project SOCLIS – South China Sea Natural Laboratory under Climatic and Anthropogenic Stress, in August and September 2019. The 37 profiles of temperature, salinity, dissolved oxygen, fluorescence, turbidity, surface irradiance (SPAR) and Photosynthetically active radiation (PAR), and sound velocity were measured using a CTD Sea-Bird SBE 911 plus, together with oxygen sensor (SBE 43), PAR sensor (Biospherical, QCP-2350 + QSR-2200), and a fluorometer (WET Labs ECO-FLNTU(RT)D). Additionally, dissolved oxygen, potential temperature and sigma-theta (with reference to the surface) were calculated. The 37 additional CTD files complement the physical oceanography dataset (Waniek et al., 2021).