Running over the crown of the globe from the New Siberian Islands in Russia's extreme north to the Canada-Greenland border region via the North Pole, the Lomonosov Ridge, a 1,800 kilometre submerged stretch of continental crust, splits the ocean into the deep Eurasian Basin and Amerasian Basin. The expanses of seawater within these depressions make up the Central Arctic Ocean, itself at the heart of the broader Arctic Ocean and its marginal bodies of water, including the Greenland, Iceland and Norwegian seas (collectively, the Nordic Seas).
The Central Arctic Ocean (CAO), characterized amongst other things by its icy cover and unique life forms, is one of 18 Large Marine Ecosystems (LME) in the Arctic – oceanic regions of more than 200,000 square kilometres which stretch from coastal grounds, river basins and estuaries to the far reaches of continental shelves and coastal current systems, marked by their ecological continuity and such features as hydrography and productivity. The revised boundaries of the current LMEs were mapped by the Ecosystem Approach Expert Group of the Arctic Council's Protection of the Arctic Marine Environment (PAME) working group in 2013, with the ecosystem properties and geographical range contained in the definition essentials for implementing the Ecosystem Approach to Management (EA) in the Arctic.
With the terminology tied to this matchless region often as delicate as the ecosystems and life that it supports, deciding on the parameters for an Integrated Ecosystem Assessment (IEA) of the CAO is a major challenge. For the recent Workshop on Integrated Ecosystem Assessment (IEA) for the Central Arctic Ocean (WKICA) – a joint ICES, Arctic Monitoring and Assessment Programme (AMAP) and Conservation of Arctic Flora and Fauna (CAFF) initiative – the task was to raise and answer questions that would define the geographical and scientific extent of an IEA in the region.
The workshop brought together experts to scope and plan for an IEA, with two of the group's Terms of Reference (ToRs) centring on this need to consider what exactly should be covered by the assessment. With both the Arctic and IEAs high on the ICES agenda, the meeting was not only of strategic importance but added to the pool of ecoregions (often equivalent to LMEs) for which working groups have been set up to perform IEAs, including two of the Arctic LMEs: the Barents and Norwegian seas. In an area now threatened by climate change and other pressures such as transpolar shipping and potential new fisheries, the preparation of an IEA represents a step towards enabling an all-inclusive approach to management of this key ecosystem.
The Central Arctic Ocean LME, set according to ecological criteria rather than political boundaries, essentially comprises the whole Eurasian basin and much of the Amerasian one alongside the deeper slope regions. At 3.5 million square kilometres, it takes in most of the international waters, or High Seas, as well as parts of the Exclusive Economic Zones (EEZs) of the five Arctic coastal states – Russia, Denmark/Greenland, the USA, Canada, and Norway.
One issue for the group, however, was the slope regions that border the basins of the CAO. Whilst the deeper portions of the slope are a constituent of the LME, the shallower ones (down to approximately one kilometre) are not. It was decided that, based on the role played by the inflow of Atlantic water continuing as the Arctic Circumpolar Boundary Current (ACBC) on the adjacent shelf LMEs – the Barents, Kara, Laptev, East Siberian and northern Bering-Chukchi – that they should be considered in the geographical scope.
Indeed, such physical and biological variability is crucial in the group's evaluation of the area. As well as adding the basin slopes into the assessment, it was agreed that some of the surrounding shelf regions should also be included. Relevant processes here include the reproduction of the small crustacean, Calanus glacialis, which is one of the most dominant copepods (group of small crustaceans) in the Arctic, and freshwater influx from rivers. The CAO is also greatly influenced by both Atlantic water entering and passing through from the Barents and Fram Strait and by Pacific water flowing north through the Bering Strait and Chukchi Sea. Indeed, the Arctic Ocean is sometimes referred to in oceanographic terms as part of the Arctic Mediterranean along with the Nordic Seas, as the sea area north of the ridge system between Scotland and Greenland via Iceland.
The interconnectedness of processes of the wider area is evident in the Atlantic gateways between the Nordic Seas and the Arctic Ocean through which seawater moves. In this way, understanding what happens in the Arctic Ocean is paramount for understanding what goes on in the Nordic Seas, especially with regards to the climate fluctuations that drive and impact Nordic and Barents seas fish stocks and ecosystems.
Dynamics such as currents and sea ice distribution were part of a list devised by WKICA to pin down the thematic scope of an IEA, which also included climate variability and change impact, contaminants and pollution, fisheries, industrial activity such as oil exploration, conservation issues, and invasive species.
"There are three main pressures or human activities which should be addressed in an IEA for the CAO: climate change, shipping, and fisheries," explained Hein Rune Skjoldal, who co-chaired the workshop along with Phil Mundy, Alexander Klepikov, and Reidar Hindrum. "What are the biological and ecological consequences of climate change, especially associated with the loss of sea ice? Which ecosystem components and areas are most vulnerable in terms of risk of oil spills and disturbances from future Arctic shipping? The fisheries aspect includes assessment of the existence of harvestable fish resources and the current and future potential for fish reproduction, and also the potential impacts of large scale removal of biomass."
"The CAO is truly and globally unique due to the presence of sea ice and notably the dwindling multiyear ice," added Skjoldal on the distinctive nature of the LME. "The biota associated with the ice includes long flowing beards of colonial ice algae hanging from the underside of the ice, sea ice amphipods (order of crustaceans) and sea ice meiofauna (tiny invertebrates) living in the ice."
On top of these ice inhabitants, the outskirts of the drift are used by larger creatures such as subpopulations of polar bears, ivory gulls, and Ross' gulls, with polar and Arctic cod providing the food base for ringed seals, beluga whales, narwhals and the bears. Monitoring changes in the abundance and form of sea ice biota, therefore, is one trend the group has to keep pace with.
"The changes in sea ice during the last few decades have been pronounced, with a loss of nearly three quarters of the volume of ice in the summer. The loss represents a major change from an Arctic Ocean where much of the ice was multiannual to a situation now where the ice is mainly annual and the multiannual fraction is low," continued Skjoldal.
"A particular challenge in this rapidly changing situation is that the accumulated data and knowledge gained from previous research may no longer be applicable. The area lacks time series monitoring compared to other ecosystems – partly because of the region's remoteness and the fact that there hasn't been much demand – and this, to help bridge the current and previous situations, is part of the challenge."
The Russian scientist Igor Melnikov, who attended the workshop, has personally witnessed very marked changes in the sea ice biota of the CAO over 40 years of work in the region. "Two ecological systems co-exist: multi-year and seasonal sea ice ecosystems of which the composition and function are different. We may be heading soon to a situation with only annually-formed sea ice analogous to conditions in the Antarctic," he stated during his workshop presentation.
Workshop participants also considered the purpose of and practical steps for initiating an IEA and reflected on the availability of data on the area. The worthiness of establishing a CAO IEA working group in collaboration with Arctic Council working groups was agreed, and the potential exists for such a group to be set up going forward.
The WKICA's work also relates to the current US Arctic Council chairmanship, which covers topics such as addressing the impacts of Arctic climate change and stewardship of the Arctic Ocean. As part of these priorities an Arctic Council Task Force has been established – with US, Norway and Iceland as chairs – looking into Arctic marine cooperation and assessing future needs for a regional seas programme or other mechanism for increased collaboration.
A vista of ice, sea, and meltwater in the Canada Basin region of the Arctic Ocean. Photo: Jeremy Potter NOAA/OAR/OER., NOAA Photo Library