Exploring observation-based management areas for the Central Arctic Ocean

The Central Arctic Ocean is undergoing rapid climate change. As the region warms and sea ice retreats, previously inaccessible areas are opening up, and new economic prospects are being unveiled, paving the way for increased commercial activity. 

Expectations of increased human activity create a need to explore the Central Arctic Ocean to provide the best available knowledge to protect vulnerable areas and secure sustainable management in the years to come.

To maximise relevance for Norwegian management and policy development, the Fram Centre project Sustainable Development of the Arctic Ocean (SUDARCO) focuses on exploring the western ends of the Nansen and Amundsen Basins. Multidisciplinary cruises in 2022 and 2024 with the R/V Kronprins Haakon provided new insights from this little-explored sector (Map 1).

Observation-based management regions

A central challenge in implementing an adaptive approach to governance based on holistic principles is the effective transfer of knowledge across diverse research fields. Summary statistics and generalised trends are easier to communicate between disciplines than detailed information. Defining regions with common characteristics that can be evaluated and described from different perspectives can therefore facilitate interdisciplinary communication.

The Arctic Council working group for Protection of the Arctic Marine Environment (PAME) has defined boundaries for large marine ecosystems (LMEs) in the Central Arctic Ocean and adjacent seas (Map 2). However, the Central Arctic LME is highly diverse, both in its physical environment and its geopolitical situation. SUDARCO aims to build on existing work by subdividing the European sector of this LME into regions with similar physical characteristics and to provide a comprehensive understanding of the conditions within each. The four suggested regions are related to existing regulatory boundaries, new in-situ observations and model results. All regions fall entirely within the Polar Code area regulating shipping in polar waters and (except for a narrow strip along the western boundary of Region 4) within the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR) and the North East Atlantic Fisheries Commission (NEAFC) regions.

These two conventions regulate pollution of the marine environment and fisheries, respectively, and apply in areas within and beyond national jurisdiction. Additionally, both are members of the Collective Arrangement, an effort to coordinate the regulatory activities of competent international organisations with the view of achieving ecosystem-based conservation.

Region 1: Atlantic Inflow

This region is dominated by Atlantic Water from the northward-flowing Norwegian Atlantic Current, which maintains a warm upper 500 m and keeps a significant area perennially ice-free (Maps 3 and 4). However, there are large seasonal differences in sea ice extent, and conditions can change rapidly when strong winds blow ice into the region. This is the only region in which commercial fish species were caught in our 2022 survey. Phytoplankton, zooplankton, cod (Gadus morhua) and capelin (Mallotus villosus) biomasses were all strongly associated with the warm water in the Norwegian Atlantic Current. Region 1 includes parts of the Danish and Russian exclusive economic zones (EEZs) and the Svalbard fisheries protection zone (FPZ), where each country has jurisdiction over both living and non-living resources from the surface to the bottom, but the core of the warm, nutrient-rich Atlantic Inflow, and most associated biomass, exist within the Svalbard FPZ (Map 2).

Region 2: Nansen

Cooler Arctic Atlantic Water occupies most of the Nansen Basin (Fig 1), although pure Atlantic Water is found along the southern boundary adjacent to the inflow and within isolated eddies shed from the inflow region. A thick, cold, fresh Surface Water layer, derived from sea ice meltwater separates sea ice from heat in the Arctic Atlantic Water below, allowing perennial ice cover. Ice extent varies seasonally with the marginal ice zone moving back and forth across the southern boundary with the inflow region. Modelled ice thickness for August 2022 was around 0.5–1.5 m. Echo sounder data revealed a mesopelagic layer at ca 400 m but detected no commercially viable species. However, region 2 is where commercial species might first be expected to appear from the south, given the strong influence of the warm, nutrient-rich Atlantic Inflow. Region 2 includes parts of the Danish and Russian EEZs and the Svalbard FPZ, as well as overlapping Extended Continental Shelf claims from Demark, Russia, and Norway, requesting national jurisdiction of the seabed.

Region 3: Gakkel

The Gakkel region is beyond the reach of the warm, nutrient-rich Atlantic Water described in regions 1-2 (Fig 1). Arctic Atlantic Water there is of a different origin than that in the Nansen region, as evidenced by deep interleaving layers that are not seen in the Nansen region (dark bands from 200–400 m depth in Figure 2). 

A well-mixed layer (light band from 50–100 m depth) exists year-round away from the stratifying influence of strong seasonal sea ice meltwater input (as in Region 2) and large inputs of river water associated with the Transpolar Drift (as in Region 4, described below). The Gakkel region occupies a gap between Atlantic Inflow and Transpolar Drift which does not exist closer to Fram Strait. Modelled ice thickness for August 2022 was 1.5–2.5 m, around a metre thicker than in Region 2 (Map 4). The 2022 acoustic survey revealed large north–south differences in the biomass inventory within the mesopelagic layer in the Gakkel, in correlation with modelled temperature distribution. Around one third of the Gakkel lies within the Danish EEZ and two thirds beyond national jurisdiction. The Gakkel includes ECS claims from Denmark and Russia (Map 2).

Region 4: Amundsen

Surface waters in this region are strongly influenced by the Transpolar Drift which carries fresher water from the Siberian shelves as well as from the Pacific via the Bering Strait (Fig 3). The upper 200 m are more strongly stratified than in the other regions and dissolved oxygen measurements (not shown) indicate that the surface mixed layer remains shallow even in winter, limiting nutrient replenishment. Sea ice thicknesses of 1.5–2.5 m, comparable with those in the Gakkel region, prevail in the Amundsen (Map 4), except along the western boundary where the ice is even thicker (>2.5 m). Mesopelagic biomass was lower in the Amundsen region compared with the Gakkel and Nansen regions (Map 3). The Amundsen includes parts of the Danish EEZ and Danish and Canadian ECSs.

Summary and the way forward

We present these proposed regions with the aim of stimulating discussions on the most effective geographical framework for an integrated ecosystem assessment of the Central Arctic Ocean. In time, the assessment will be delivered to Norwegian authorities as an advisory product from SUDARCO; it will synthesise information on the environment, biology and pressures from human activities within the European sector of the central Arctic LME.