A standard Sea-Bird Electronics Inc SBE911+ CTD system with single temperature and conductivity sensors was used to measure temperature, conductivity and pressure at 73 stations during an expedition to the Laptev and East Siberian Seas in September-October 2019 aboard the research vessel Professor Multanovskiy. To measure chlorophyll content in the water, a pumped WETLabs WETStar fluorometer was connected to the SBE911+ system. Additionally, a Seabird 19plus V CTD with a pumped fluorescence sensor (WETStar) was mounted in the rosette frame to measure the fluorescence of dissolved organic matter (fDOM). Salinity and temperature data from the SBE 19plus V2 CTD are also part of the data set.We followed the manufacturer's recommendation to calculate salinity using Seabird processing software. Salinity is reported as practical salinity (PSU). Data were averaged at depth intervals of 1 m. Data are from the 2019 Transarktika Expedition (Leg 4/2 from Murmansk to Vladivostok), an initiative of the Russian Antarctic and Arctic Research Institute (AARI), carried out in collaboration with the Russian-German CATS project and funded by Minobrnauki (CATS RFMEFI61619X0108) and BMBF (CATS 03F0831B).