The ARCTOS-Nansen Legacy Polar Front expedition focused on the hydrography and biological processes in the Barents Sea Polar Front region during the highly productive phytoplankton spring-bloom period. 

The science mission was conducted between May 14 to May 22, 2021 and addressed the productivity and biodiversity patterns of phyto- and zooplankton as well as pelagic and benthic invertebrates and fish communities in the Polar Front region of the Barents Sea. The work was organized by the ARCTOS network with partnership from the Nansen Legacy project, and aimed at complementing the field sampling conducted under the Nansen Legacy Seasonal cruise Q2 further north during the same period. The sampling included a wide range of state-of-the-art technologies like gliders and sail-buoys (financed by Equinor).

The Polar Front was crossed twice from the warm Atlantic water in the southern parts into the ice covered Arctic waters north of the Front. The pathway north was sampled mainly by CTDs to estimate the distribution of water masses, while the southern transect provided sampling opportunities to investigate the biological features. The ice cover in May 2021 extended south of the Polar Front, thus providing a unique combination of environmental settings through combined frontal and ice melt effects.

Beyond research, 13 early career scientists with widely varying backgrounds and coming from various institutions and universities participated in the cruise and were introduced to hands-on marine science, for many of them for the first time in their lives. They were offered presentations and discussions sessions during the 10-day pre-cruise quarantine and received training in all scientific approaches used during the cruise.