Ecosystem overviews

Central Arctic Ocean Ecosystem Overview

Climate change impacts

​​​​​​​Observed climate-related changes include decreases in sea ice extent and thickness, salinity and freshwater content affecting water column stratification, and the relative contributions/mixing of North Atlantic and North Pacific water masses in the ecoregion, as well as subregional increases in seawater temperature. These come with associated changes in the distribution and abundance of species, with implications for foodweb structure and dynamics.

A reduction in the extent and thickness of sea ice is the prevailing climate change signal in the ecoregion. Sea ice extent has dramatically diminished in the past decades, leading to an increase in the seasonal duration of open water in the ecoregion (Figure 5). The mean summer minimum of sea ice extent in 2007–2020 was much lower than in 1979–2000 (4.6±0.5 × 106 km2 and 6.9±0.5 × 106 km2, respectively [figures 5 and 6]). Old sea ice (> five years) decreased from 30% to 2%, while first-year ice increased from 40% to 70% between 1979 and 2018. Mean sea ice thickness declined by 65% (from 3.59 to 1.25 m) between 1975 and 2012.

Receding ice has already led to significant changes in both the range and abundance of species in and around the ecoregion, from primary producers to top predators. Primary productivity has increased in areas associated with the loss of summer sea ice. A reduction in multiyear ice and increase of first‑year ice has led to a decline in sympagic algal diversity. Models suggest future increase in sympagic algal productivity because of the thinning of sea ice and enhanced light availability but also limitations by nutrients and ice as a substrate. Sea ice reduction and increasing water temperature were suggested to negatively influence polar cod recruitment in the adjacent Barents Sea. Seabirds and marine mammals that depend on sea ice for habitat and/or food are negatively affected for key processes like reproduction and rearing. The feeding migration of young ringed seals has expanded into the ecoregion over the past decades, concurrent with the sea ice retreat. As sea ice cover heavily influences ambient noise levels both directly (e.g. cracking and vibration) and indirectly (e.g. by limiting shipping activity), the rapid changes in ice conditions also have implications for ambient noise levels.

Since 2000, the stratification in the Eurasian Basin has been reduced, potentially altering nutrient fluxes and primary production. In the Amerasian basin, a stronger influx of Pacific waters has increased heat and freshwater content in the Beaufort Gyre and facilitated the expansion of Pacific species into the ecoregion. The increased seasonal duration of open water is expected to enhance primary production around the basin with subregional differences caused by changes in stratification that affect nutrient availability.

As a potential Arctic refuge, the ecoregion may experience at least short‑term increases in the occurrence and abundance of both Arctic and boreal species that are capable of long-range dispersal. Some pelagic fish that occur in adjacent areas like beaked redfish (Sebastes mentella), Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus), and Atlantic Capelin (Mallotus villosus) may eventually extend their summer feeding migrations into the ecoregion. Ice-dependent fish and marine mammals are experiencing increased competition from boreal species in and around the ecoregion. There is evidence of the occurrence of unusually large abundances of Atlantic cod (Gadus morhua) and other boreal species in the adjacent area (the Atlantic Gateway), which has likely contributed to the decline of polar cod and other Arctic fish species. The long-term success of species' northward migration strategy will depend on the continued availability of key habitat, nutrients, and prey. For example, the distribution, behaviour, and fitness of sympagic species, such as the ivory gull (Pagophila eburnean), are strongly affected by declines in sea ice and associated prey. Bioenergetic modelling suggests that 24 Arctic-breeding seabird species may shift to year-round High Arctic residency.

Increasing freshwater input also leads to the enhanced delivery of terrestrial materials – including carbon, hazardous chemicals, methane, viruses, and bacteria – into the Arctic seas. Permafrost thaw is an important, warming-induced pathway for contaminants such as POPs and mercury into the Arctic Ocean.

Climate change is creating opportunities for the development and expansion of various human activities in the ecoregion. Ship traffic is currently very limited and largely restricted to scientific expeditions and icebreaker activities. In peripheral waters on the Russian side of the ecoregion and the Pacific gateway, however, ship traffic is increasing due to liquid natural gas (LNG[1]) and crude oil transport, as well as trans-Arctic cargo shipping along the Northern Sea Route (NSR). Geoengineering surveys also occur in the adjacent Kara Sea. Increasing shipping will increase underwater noise and marine litter, as well as the risk of the accidental release of hazardous materials and the introduction of NIS.

At present, there are no indications that commercially exploitable fishery resources exist in the ecoregion. With receding ice, exploratory fishing is expected to occur in accessible slope and shelf waters inside the EEZs of the coastal states.

To date, ocean mining interests have primarily focused on areas outside the ecoregion, but may expand further into the Arctic. Similarly, oil extraction is ongoing in adjacent seas, and interest exists for oil exploration in many of the shelf areas surrounding the ecoregion.

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Figure 5: Sea ice extent (the border of 15% ice concentration) in the Arctic Ocean in 1979–2000 (left panel), and in 2012 (right panel). The pink area corresponds to the seasonal minimum in September. The blue area corresponds to the seasonal maximum in March. The white line denotes an isobath of 1000 m, which may be considered a rough approximation of the border of the Central Arctic Ocean. 

Figure 6: Anomaly of the minimum distribution of the Arctic sea ice extent (the border of ice concentration less than 15%) in September (%) relative to the average for the period of satellite observations (1979–2020).

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Central Arctic Ocean Ecosystem Overview

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