Nansen Legacy field campaigns

The Nansen Legacy disposes over 370 days of ship time, primarily using the new Norwegian ice-going research vessel Kronprins Haakon. This allows for collecting unique, synoptic and interdisciplinary seasonal and inter-annual time series data. Beyond-the-state-of-the-art features of this vessel include specialized laboratories with cooling and freezing laboratories for experimental work, a moon-pool for deployment of instruments at high sea or in close pack-ice, a helicopter platform, two sinking keels with the most updated acoustic instrumentation, facilities for sediment coring, trawling, and use of autonomous vehicles.

The approach to identify physical drivers and ecosystem responses includes 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 (see map: black line through the boxes in the map, boxes indicate sites for process studies associated with regions of contrasting physical gradients). The transect includes the Atlantic influenced regions in the south, the Polar Front and Arctic influenced inner shelf, the Arctic and Atlantic influenced northern shelf, and the shelf break adjacent to the deep Arctic Basin.

The transect is investigated annually over five years for time-series studies. High spatial resolving transects are typically been made while going north. Process studies are carried out during the returning south-going transect at key locations identified during the northward transect.

In 2021, the Nansen Legacy main transect will be extended deeper into the Arctic Basin, returning through the Fram Strait to extend the observational coverage (i.e., into the more central Nansen Basin domain and downstream of the Arctic Basin transpolar drift to include the integrated Arctic Ocean signal leaving the high Arctic with sea ice and water masses through the Fram Strait), providing a context to the observations north of the Barents Sea.

During one year (autumn 2019–summer 2020), a major effort will be made to cover all four seasons, including winter, which typically remains a main knowledge gap. This coincides and is coordinated with the international MOSAiC trans-polar drift on regional intercomparison and interdisciplinary processes, and Arctic Amplification (AC)3 on airborne campaigns.

Ship-based data collections are supplemented with time series provided by moorings at strategic locations, and with satellite observations obtained from Synthetic Aperture Radar- (SAR) and optical satellites. The observational effort links to the broad group of modelers involved.

Realizing the Nansen Legacy in the field. The maximum wintertime sea ice extend situation observed from satellite, exemplified for 1981 and 2012 (where the ice-edge is defined as 15% ice concentration), and showing the location of the Shtokman gas field in what has become ice-free water. The color shading indicates sea-ice concentration climatology (mean between 1980-2012) scaled from 0-100% with 5% isolines (based on Årthun et al. 2012). Depth contours show the 500 m and 1000 m isobaths.

Focus areas and sampling transects of the Nansen Legacy fieldwork are indicated. Transects run across gradients in the physical and biological environment, and across the main ocean currents connecting the Barents Sea with the Nordic Seas and the Arctic Basin (see Fig. 2). Black solid lines: transects sampled annually and in every season; grey lines: extended transect into the Arctic Basin with exit through the Fram Strait; yellow lines: proposed transects for Russian-Norwegian cooperation; black boxes: focus areas for process studies; dashed lines: existing transects covered annually by IMR and NPI as part of monitoring programs (mainly sampled in August); white crosses: moorings to be deployed during the Nansen Legacy. Ship-based and mooring-based observations are extended with technologies for multisensory and multidisciplinary field campaigns (Illustration M. Årthun, UiB).