The Nansen Legacy cruise Q2 (Q2: 2nd quarter of the year) was part of the seasonal investigation of the northern Barents Sea and adjacent Arctic Basin. The cruise was conducted during the spring period – a biologically critical time window when a large part of the annual primary production occurs – and focused on comparing the physical, chemical and biological conditions along the Nansen Legacy main transect in open waters and within the sea ice. The cruise addressed objectives of the work packages ‘Physical drivers’ (Research Focus 1), ‘Human impact’ (Research Focus 2), ‘The living Barents Sea’ (Research Focus 3) and ‘Technology and method development’ (Research Activity C).

In total, seven process stations (P1, P2, P3, P4, P5, P6 and P7) were sampled. The station P1 was the only open water station, all other stations were in ice covered waters at the shelf, on the slope and in the deep basin. Sea ice was sampled at stations P2 and P3, but the ice floes were to small and unstable to conduct longer ice stations. The first sea ice station was conducted at P4 and all station north of that. Each process station lasted more than a 24-hour period to allow full daily cycle process measurements (i.e., rates), in addition to extensive biodiversity- and abundance sampling of microbial, plankton and benthic communities. Samples for trophic interaction, ecotoxicology and ocean acidification studies were also collected. At P1, both Unmanned Surface vehicle (USV) and an AUV were deployed to measure the light climate both at the surface and underwater. On the ice stations, remotely operated vehicles were deployed for under-ice optical measurements. Scientific divers collected ice algae and ice fauna and deployed sediment traps and primary production incubations below the sea ice.

Between the P stations, shorter CTD stations (NLEG 1-25) were sampled for hydrographical and biogeochemical parameters to get a higher spatial resolution along the transect. Due to the development of the spring bloom north of Svalbard a series of shorter stations (NLEG A-D), including CTD casts and Bongonet hauls were added to the program on the transit from P7 to Longyearbyen.