This data set contains the hydrographic profile data collected with the ship based CTD rosette during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). The CTD is an SBE911plus with 24 bottles, 12 liters each, operated with a winch and crane on the side of Polarstern. The data set contains calibrated and quality-controlled parameters (temperature, conductivity, oxygen and their derived variables) as well as only pre-cruise calibrated parameters where no post-cruise calibration or quality control was applied (all other). CDOM fluorescence data are the exception. Quality control was performed but data have to be handled with care, as the sensor seems to have broken down during leg 3 such that no post-cruise calibration could be applied. The data are provided as text file (all cruise legs in one file) as well as in netCDF format (one file per cruise leg). The accuracy for salinity and conductivity is 0.004 while the accuracy for temperature is 0.002. Additional information on the sensor used for the final data set, the water depth as well as the availability of profile or bottle data is given in a separate info-text-file. Contact: Sandra.Tippenhauer@awi.de. Quality flags are given based on paragraph 6. "Quality flags" from https://www.seadatanet.org/content/download/596/file/SeaDataNet_QC_procedures_V2_%28May_2010%29.pdf. QC flag meanings: 0 = unknown, 1 = good_data, 2 = probably good_data, 3 = probably bad data, 4 = bad data set to nan.This work was carried out and data was produced as part of the international Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) with the tag MOSAiC20192020. We thank all persons involved in the expedition of the Research Vessel Polarstern during MOSAiC in 2019-2020 (AWI_PS122_00) as listed in Nixdorf et al. (2021).