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 °E, 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 processed current velocities and hydrographic data recorded with Seabird SBE37 microcats, RDI Acoustic Doppler Current profilers and Aanderaa point current meters. Details on data processing can be found in the file description and in Ruiz-Castillo et al. (2022). Instruments types and serial numbers can be found in the attached document.

The records include the processed data from mooring AK4. Current velocities were quality-controlled based on thresholds defined for a variety of parameters. Data points meeting any of the following criteria were discarded: error velocities >10 cm/s, beam correlation <64%, percent-of-good 20°. Bins with >30% of discarded data points were removed entirely. Velocity flags indicate the evaluated quality of the data point (flag=0: good, flag=1: discarded; flag=2: enhanced error velocity (3-10 cm s-1) and or pitch/roll of 10-20°. Velocities were corrected for magnetic declination. The pressure-values provide the actual CTD pressure readings, depth-values provide the nominal instrument depth. Temperature and salinity flags indicate interpolated gaps in the time series. For more details, please refer to Ruiz-Castillo et al. (Structure and seasonal variability of the Arctic Boundary Current north of Severnaya Zemlya. Journal of Geophysical Research-Ocean, under review).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.