Raw physical oceanography data was acquired by a ship-based Seabird SBE911plus CTD-Rosette system onboard RV Polarstern during research cruise PS126. The CTD was equipped with duplicate sensors for temperature (SBE3plus), conductivity (SBE4) and oxygen (SBE43). Additional sensors such as a WET Labs C-Star transmissometer, a WET Labs ECO-AFL fluorometer (FLRTD) and an altimeter (Teledyne Benthos PSA-916) were mounted to the CTD. The data was recorded using pre-cruise calibration coefficients. No correction, post-cruise calibration or quality control was applied. All sensors performed generally fine, except during one cast (PS126_23-8) where the secondary oxygen sensor had issues below 4000m. For more details see cruise report linked below. A PDF with scans of the handwritten protocols is included in this publication. The processed dataset will be linked below upon completion.