Time series data of physical oceanography (seawater conductivity, temperature, pressure, salinity) and ocean current velocities were obtained from mooring AK4 in the eastern Arctic Ocean north of Severnaya Zemlya (82.105 °N, 94.772 °W, water depth 1985 m) in 2015 - 2018. The mooring was deployed during Akademik Tryoshnikov expedition AT2015 as part of the NSF-funded NABOS (Nansen and Amundsen Basins Observational System) - program and recovered during AT2018, which was jointly organized between NABOS and the German BMBF-funded CATS (Changing Arctic Transpolar System)-project. The attached archive contains raw data files of Seabird SBE37 microcats, Seabird SBE26 bottom pressure recorders, RDI Acoustic Doppler Current profiler and Aanderaa point current meters. Auxiliary information such as sensor calibration sheets, mooring diagrams and schedule files are also provided, if applicable.

The file AK4.zip includes all available sensor raw data and the drawings from mooring AK4. The structure of the unzipped folders is mooring>sensor/sampler type->serial number->instrument files. All instruments were synched to UTC before deployment, and the offset after the recovery is supplied in the respective instrument folder, if available. The archive also contains the sensor calibration sheets/files and relevant sampler schedule files, if available. Finally, mooring schematics are also attached as pdfs in the root folder. The file Moorings_AK_2015-2018.xlsx includes the metadata of all moorings that were deployed during AT2015 and recovered during AT2018.The authors are grateful to the captains, crews and technical/scientific staff of the expeditions. Many individuals have contributed to the conception of the research, the preparation of the instruments, the deployment and recoveries, as well as to the retrieval of the data, which we greatly acknowledge.