In order to identify physical drivers and ecosystem responses, the Nansen Legacy uses a ‘space-for-time’ strategy, e.g., the investigation of various environmental settings along physical gradients within the limited time available during expeditions along the main transect.

The Nansen Legacy main transect (76-82˚N, 30-34˚E) includes the Atlantic Water influenced regions in the south, the Polar Front and Arctic Water influenced inner shelf, the Arctic- and Atlantic Water influenced northern shelf, and the shelf break adjacent to the deep Arctic Basin. The conceptual idea behind the main transect is to investigate the region nowadays influenced by Atlantic Water, in order to learn about the potential future evolution of the northern Barents Sea, where sea ice is on its retreat and where the Atlantic signal will become increasingly more present.

The main transect is typically investigated with a high spatial resolution for physical and biogeochemical standard parameters, while detailed biological process studies are carried out at key locations (P1-7) along the transect.

The main transect is re-visited several times and at different seasons during the period 2018-2022, allowing for some inter-annual comparisons. In 2021, the Nansen Legacy main transect is extended deeper into the Arctic Basin and Fram Strait in order to extend the observational coverage and to provide a context to the observations from the northern Barents Sea.