Raw physical oceanography data were acquired by a ship-based Seabird SBE911plus CTD-Rosette system onboard Maria S. Merian during research cruise MSM93 to the Fram Strait. In total, 51 hydrographic profiles were acquired as part of 4 main CTD transects, and bottle samples were taken during 44 casts. The installed sensor suite provided duplicate measurements of seawater temperature (SeaBird SBE3plus), conductivity/salinity (SeaBird SBE4) and dissolved oxygen (SeaBird SBE43), along with pressure/depth (SeaBird SBE9), Chl-a fluorescence and turbidity (Wetlabs ECO-FL-NTU), and PAR within the water column. Additionally, a surface PAR sensor was installed on the ship as a reference. Individual sensor pairs suffered from data quality issues throughout most of the campaign, especially in the upper 40 m. In all affected profiles, the duplicate sensor pair was still giving reliable data. The installed PAR did not provide any data.

The authors are grateful to the captain, crew and technical/scientific staff of the expedition MSM93 onboard the RV MARIA S. MERIAN. The work was funded by the Helmholtz infrastructure program "Frontiers in Arctic Marine Monitoring", and the Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung.