Ecologically or Biologically Significant Areas (EBSAs)
published: 12 Jun 2015
Multi-year Ice of the Central Arctic Ocean
The multi-year ice and associated marine habitats of the central Arctic Ocean beyond national jurisdiction provide a range of globally and regionally important habitats. Projections of changing ice conditions due to climate change indicate that the central Arctic Ocean beyond national jurisdiction and in adjacent Canadian waters is likely to retain ice longer than all other regions of the Arctic, thus providing refugia for globally unique ice-dependent species, including vulnerable species, as the ice loss continues. A shift towards less multi-year sea ice will affect the species composition and production of the primary producers in the area, with potential cascading effects throughout the ecosystem. In a situation with decreasing ice cover, the effects on the ice fauna will be strongest at the edges of the multi-year sea ice. Polar bears (Ursus maritimus) are highly dependent on the sea ice habitat and are therefore particularly vulnerable to changes in sea ice extent, duration and thickness. The multi-year ice habitat is especially important as breeding habitat for polar bears of the southern and northern Beaufort Sea subpopulations. It is noted that the geographic area covered by this description in part overlaps an area meeting the CBD EBSA criteria that was described by the joint OSPAR/NEAFC/CBD workshop in the North-East Atlantic. Following peer-review by ICES, the description of this area is currently under consideration by the Contracting Parties to OSPAR and NEAFC.
The multi-year ice in the Arctic Ocean (the ice that survives summertime melt) is globally unique and has dramatically decreased (in both extent and average thickness) in recent decades (AMAP 2011). Multi-year ice now occupies only the part of the deep area beyond national jurisdiction in the Arctic that adjoins the Canadian Arctic archipelago and the multi-year ice area described there (figure 1). It is noted that the geographic area covered by this description in part overlaps an area meeting the CBD EBSA criteria that was described by the joint OSPAR/NEAFC/CBD workshop in the North-East Atlantic. Following peer-review by ICES, the description of this area is currently under consideration by the Contracting Parties to OSPAR and NEAFC. The multi-year ice that remains is also much younger than previously as the oldest multi-year ice classes have declined more than other classes (AMAP 2011), and even if conditions changed to allow the return of the lost/decreased ice cover were reversed, it would take many years to return to the state of just a few decades ago. The multi-year ice and associated marine habitats of the central Arctic Ocean beyond national jurisdiction provide a range of globally and regionally important habitats. Projections of changing ice conditions due to climate change indicate that the central Arctic Ocean beyond national jurisdiction that adjoins Canadian waters near the Canadian Arctic archipelago are likely to retain multi-year ice longer than all other regions of the Arctic, thus providing refugia for globally unique ice-dependent species, including vulnerable species.
This area comprises the surface ice and related water column features associated with the multi-year sea-ice area. This area is described as a geographically and temporally dynamic feature. The multi-year ice range provided in this description refers to the area beyond national jurisdiction.
DISCLAIMER: The designations employed and the presentation of material in this map do not imply the expression of any opinion whatsoever on the part of the Secretariat concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.
There is limited information about the ecosystems of the central Arctic Ocean—there is more literature describing the shallower, coastal areas. Where appropriate, this description includes some information from these coastal areas. Physical description of the area Multi-year ice is the ice that survives the summertime melt in the Arctic Ocean and so is re-defined each September, when sea-ice is at its minimum extent. It has been declining rapidly over the last 30 years, both in extent and age (Maslanik 2011) and in September 2012, ice more than two years old occupied only 42% of the area beyond national jurisdiction in the central Arctic; very little of this is now greater than five years old (figure 2). The multi-year ice area meeting EBSA criteria is defined by ice greater than two years old. The circulation of sea ice in the Arctic Ocean is wind-forced, and, roughly, flows from the Eurasian side towards Greenland and the Canadian Arctic archipelago. Ice that then flows along the eastern coast of Greenland and through Fram Strait leaves the Arctic and melts. Ice that impinges on the north-western edge of the Canadian Arctic archipelago tends to be compressed there and accumulate, and is thus the oldest sea-ice in the Arctic Ocean and forms the core of the multi-year ice. The multi-year ice in the deep Arctic basins overlays an ocean that is very strongly layered by salinity, comprising nutrient-poor surface waters that are freshened by the huge river runoff, largely from Siberia, and nutrient-rich waters below the seasonal euphotic zone that flow into the Arctic Ocean either from the Pacific Ocean, through the relatively shallow Bering Strait, or the Atlantic Ocean, through the deep Fram Strait and the Barents Sea. The higher strength, thickness and concentration of the multi-year ice tends to shield the underlying waters from the wind and attenuates light. Reduced wind forcing, combined with the high stratification provided by the river runoff, means that vertical nutrient fluxes are low. Low nutrient input and reduced light levels lead to very low annual primary production in this region. Primary production and lower trophic level communities in multi-year ice Autotrohic and heterotrophic communities Ice algal communities can be divided into communities on the surface, interior and bottom of the ice (Horner et al. 1992). The surface can then be divided into melt-pond and infiltration communities, the interior into diffuse, brine-channel and band communities and the bottom into interstitial and sub-ice communities. All except for the band community occur in annual ice. In addition to microalgae, bacteria are an important component of the ice-algal community, but many other groups of organisms (e.g., archaea, fungi, ciliates, kinetoplastids, choanoflagellates, amoebae, heliozoans, foraminiferans and some protists that belong to no known group) also occur in ice communities (Lizotte 2003). Poulin et al. (2010) reported a total of 1027 sympagic taxa in Arctic waters (including coastal waters). Due to its thickness and construction, multi-year ice is relatively difficult to research. The sub-ice community of two-year-old and multi-year ice is dominated by the centric diatom, Melosira arctica. Widespread deposition of this species has been found on the sea floor at depths of about 4000 m in the central Arctic Ocean, where it is eaten by different benthic organisms or broken down by bacteria (Boetius et al. 2013), thus creating a link between ice and benthic ecosystems. Solitary diatoms increase in abundance in many interior and surface communities, but there is at the same time a decrease in the relative importance of diatoms compared with other algal classes. Ice algae are estimated to contribute to more than 50% of the primary production in the permanently ice covered central Arctic (Gosselin et al. 1997, Sakshaug 2004). The sympagic macrofauna is commonly divided into two groups, the autochtonous and allochthonous species (Lønne & Gulliksen 1991, Arndt & Swadling 2006). The former consists of the species that are believed to live their entire life connected to the sea ice (e.g., nematode worms, rotifers and other small soft-bodied animals within the ice and amphipodes on the underside), whereas the latter consists of species that are connected to the sea ice only during parts of their life cycle (e.g., larvae and juvenile stages of some organisms). Currently the most common amphipod species in the multi-year ice are Gammarus wilkitzkii, Onisimus nanseni and Apherusa glacialis (Werner & Gradinger 2002, Arndt & Swadling 2006). Among these, the former is by far more important in terms of biomass (Arndt & Swadling 2006). These are the important food items for polar cod. Multi-year ice is regarded as a critical habitat for long-lived ice-associated species, e.g., G. wilkitzkii, (Hop & Pavlova 2008). Multi-year ice is also essential for maintaining populations of several sea-ice nematode species, which form trophic chains within the ice environment, with smaller species feeding on autotrophs and the larger ones predating on smaller nematodes (Tchesunov & Riemann 1995, Tchesunov 2006). Fish The fish diversity of the Arctic is described in the Arctic Biodiversity Assessment (Christiansen & Reist 2013, and literature quoted). The Arctic Central Basin has a disproportionately low taxa richness compared with the rest of the Arctic Ocean and adjacent sea regions with only 13 species in four families and a proportion of Arctic species of around 92%. The number of species may be underestimated due to poor sampling, low abundances and unresolved taxonomy. Polar cod (Boreogadus saida), a keystone species in the marine Arctic, and ice cod (Arctogadus glacialis) are endemic to the Arctic and the only fishes in the northern hemisphere that utilize sea ice as habitat and spawning substrate. Polar cod is the most abundant and widespread fish in the Arctic, occurring both in areas with multi-year and annual sea ice. Ice cod is much less abundant than polar cod and is primarily associated with fjords and Arctic shelves. In the Central Arctic, which is covered by thick multi-year ice, the polar cod is usually found as single specimens or in small groups rather than large schools (Melnikov & Chernova 2013, and literature quoted). Mammals: Polar bear Polar bears Ursus maritimus are highly dependent on sea ice and are therefore particularly vulnerable to changes in sea ice extent, duration and thickness. They have a circumpolar distribution, with 19 subpopulations. Polar bears are most commonly on ice over the continental shelves as this is where the preferred prey, young ringed seals, are found. Some also occur in the permanent multi-year pack ice of the Arctic Central Basin (Durner et al., 2009). Recently the number of polar bears in the northern Beaufort Sea was estimated at a density of 0.061 bears per 100 km2 (McDonald 2012). The multi-year ice habitat is especially important as breeding habitat for the southern and northern Beaufort Sea subpopulations. In the last century, a significant proportion of these populations could breed in the multi-year ice, but there are no recent quantitative assessments to confirm if this is still the case (personal communication Stanislav Belikov). The thick, multi-year ice has, in the past, served as a refuge for marine mammals, including polar bears, during summers in years with extensive melt of first-year ice (AMAP 2011). Due to low reproductive rates and long lifetime, it has been predicted that the polar bears will not be able to adapt to the current fast warming of the Arctic and become extirpated from most of their range within the next 100 years (Schliebe et al. 2008).
Production and possible ecosystem effects Reduced sea ice, especially a shift towards less multi-year sea ice, will affect the species composition in these waters. Seasonal/annual sea ice has to be colonized every year, as opposed to multi-year ice. In addition, multi-year ice has ice specialists that do not occur in younger sea ice (von Quillfeldt et al. 2009). In a situation with decreasing ice cover, the effects on the ice fauna will be strongest at the edges of the multi-year sea ice. Sympagic fauna transported with the sea ice from the Arctic Ocean through the Fram Strait will, for example, probably be lost without possibility to re-colonize the ice (Werner et al. 1999). It has, however, been speculated that downwards vertical migrations, followed by polewards transport in deep ocean currents, are an adaptive trait of ice fauna (e.g., Apherusa glacialis) that both increases survival during ice-free periods of the year and enables re-colonization of sea ice when they ascend within the Arctic Ocean (Berge et al. 2012). The transport of organic material out of the Arctic Ocean serves as an important food source for the pelagic and benthic food web in the Greenland Sea (Werner et al. 1999). With a decrease in sea ice cover also the transport of ice to the Greenland Sea will decrease and thus the export of organic material from the Arctic Ocean may diminish and alter the food web structure in the Greenland Sea. Fauna heavily dependant on ice algae will be particularly affected by the reduction of sea ice (Gradinger 1999).
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Areas described as meeting EBSA criteria that were considered by the Conference of the Parties
C1: Uniqueness or rarity High
This is the largest multi-year ice feature of the world’s oceans, making it globally unique. The Arctic multi-year ice is mostly over the deep Arctic ocean basins and contains ice that is more than five years old (Maslanik et al. 2011). This contrasts with Antarctica, which only has small areas of coastal multi-year ice, which is no more than three-years old (Turner et al. 2009). Multi-year ice-dependent communities, fauna and flora, e.g. endemic sea ice nematodes and amphipods (Homer et al. 1992, Werner & Gradinger 2002, Arndt & Swadling 2006, von Quillfeldt 2009, Poulin et al. 2010). Historical records indicate that this was key breeding habitat for a significant proportion of the southern and northern Beaufort Sea subpopulations of polar bear, although the current status of use of multi-year ice by these subpopulations is unknown (personal communication Stanislav Belikov). Multi- year ice normally has ice specialists that do not occur in younger sea ice (von Quillfeldt et al. 2009).
C2: Special importance for life-history stages of species Medium
Historical records indicate that this was key breeding habitat for a significant proportion of the southern and northern Beaufort Sea subpopulations of polar bear, although the current status of use of multi-year ice by these subpopulations is unknown (personal communication Stanislav Belikov) Multi-year ice has autochtonous species that are believed to live their entire life connected to the sea ice (e.g., nematode worms, rotifers and other small soft-bodied animals within the ice and amphipodes on the underside) (Lønne & Gulliksen 1991, Tchesunov & Riemann 1995, Arndt & Swadling 2006, Tschesunov 2006).
C3: Importance for threatened, endangered or declining species and/or habitats Medium
Historical records indicate that this was key breeding habitat for a significant proportion of the southern and northern Beaufort Sea subpopulations of polar bear, although the current status of use of multi-year ice by these subpopulations is unknown (personal communication Stanislav Belikov).
C4: Vulnerability, fragility, sensitivity, or slow recovery High
Extremely vulnerable for a warming climate and human activities in general. Ice algae constitute the second source of primary production in Arctic seas, with the highest relative contribution in the central Arctic Ocean (Gosselin et al. 1997). The increased freshening of surface waters underneath multi-year ice likely impacts the sea-ice biota (Melnikov et al. 2002). Multi-year ice has been declining rapidly over the last 30 years, both in extent and age (Maslanik 2011), and in September 2013, ice older than two years old occupied only 42% of the area beyond national jurisdiction in the central Arctic, very little of which is now greater than five-years old.
C5: Biological productivity Low
Production levels are low, but ice-based production contributes a significant portion of the total multi- year ice ecosystem production Ice algae are estimated to contribute to more than 50% of the primary production in the permanently ice-covered central Arctic, forming a distinct community. (Gosselin et al. 1997, Sakshaug 2004).
C6: Biological diversity Low
Often higher biodiversity compared to annual ice in specific localities (Gradinger 1999, Melnikov et al. 2002, von Quillfeldt et al. 2009, Zheng et al. 2011). The sub-ice community of two-year-old and multi-year ice is dominated by the centric diatom, Melosira arctica, which sinks and forms a link between ice and benthic ecosystems (Boetius et al. 2013).
C7: Naturalness High
Very low impact from human activities (but vulnerable for climate change, already acting) (Meltofte et al. 2013, Eamer et al. 2013).