The Great Melt

ICES/PICES/​PAME Working Group on Integrated Ecosystem Assessment (IEA) for the Central Arctic Ocean​
Published: 24 June 2020

​​​Literally placed on top of the world, ​​​the Central Arctic Ocean (CAO) consists of two deep basins (around 4000 m deep) separated by the Lomonosov Ridge which runs 1800 km from the New Siberian Islands to the border area between Canada and Greenland. 

​The CAO ecosystem, a 2.8 million km2 area beyond national jurisdiction, is undergoing substantial change associated with the massive and dramatic loss of sea ice. As a trend over the last few decades, about half the area and three quarters of the volume of the minimum sea ice in summer have been lost with a pronounced change from thick and old multi-annual ice to now mostly thin and young ice. This change has been described as the "Great Melt". Reduced ice cover will allow increased ship traffic, access to reserves of hydrocarbons and minerals, and possible food resources. 

The loss in summer sea ice means a loss in habitat for sea ice biota. There is a specialized and endemic fauna of ice amphipods and some other invertebrates that live associated with the under-surface of the ice. It is anticipated that this fauna component has declined much in response to the Great Melt

Most individuals from the eight subpopulations of polar bear around the CAO (there are 11 more subpopulations further south in the Canadian Arctic) follow the seasonally retreating sea ice into the CAO in summer. With more rapid and extensive melting of sea ice, these polar bears are faced with challenges to cope with the changing conditions and a need to adapt by altering their migratory pattern. 

​​The CAO differs from other large marine ecosystems (LMEs) in having few biological and oceanographic time series available to describe status and changes of the ecosystem. Exceptions to this are satellite-based monitoring of sea ice and oceanographic parameters, such as ocean color and derived information on phytoplankton biomass, composition and production. We foresee the use of 3D physical models to explore and describe water circulation and oceanographic features, and 1D models to assess in more detail the vertical processes and nutrient fluxes which determine rates of primary production in the strongly stratified CAO ecosystem.  

Later in 2020, WGICA will publish “Integrated Ecosystem Assessment of the Central Arctic Ocean: Ecosystem description and vulnerability characterization". In this report, the documented or inferred biological and ecological changes associated with the Great Melt are described through a review of scientific literature and information provided by the WGICA members from ongoing studies.

A second report “Human activities", expected to be published in 2023, will review ongoing and recent changes and events in the CAO, an examination of the effects of climate change on the ecosystem, and an assessment of projected future changes. An assessment of the consequences of climatic and oceanographic changes on transport pathways, the potential effects of contaminants, and a review on new studies on fish as well as other biological components will also be included in the group's work.

The Working Group on Integrated Ecosystem Assessment for the Central Arctic Ocean (WGICA)​​ provides integrated ecosystem assessments (IEAs), including ecosystem overviews, for the Central Arctic Ocean.

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​Polar bear on the ice, north of Svalbard in the Atlantic gateway to the Central Arctic Ocean. 
Photo: Institute of Marine Research, Norway.

Average monthly sea ice extent in March 2019 (left) and September 2019 (right) illustrate the winter maximum and summer minimum extents. The magenta line indicates the mean ice extents in March and September during 1981-2010. 
Image: the National Snow and Ice Data Center, University of Colorado, Boulder (NSIDC) (Fetterer et al. 2017).​

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The Great Melt

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