Some polar bear clusters have slowly moved to islands north of Canada's mainland that are retaining the Arctic ice for longer, according to a new scientific study that predicts the migration, linked to climate change, would continue.

The study published earlier this month in the journal PLOS ONE was based on DNA taken from nearly 2,800 polar bears in countries where the animals live — the United States, Russia, Canada, Greenland and Norway.

Researchers tracked the shift through genetic similarity in bears among four regions.

Bear clusters from Canada's eastern Arctic area and a marine area off eastern Greenland and Siberia are journeying to the Canadian Archipelago, also known as the Arctic Archipelago, where ice is more abundant, the study found.

The channels through the islands, known as the Northwest Passages, have come to be seen as a potentially valuable shipping route as Arctic ice melts. 

The region that has attracted a larger number of polar bears sits north of the Canadian mainland, close to Nunavut and the Northwest Territories. It is comprised of more than 36,000 islands and covers more than 1.4 million square km.

The migration has occurred during the last one to three generations of the predators, or between 15 and 45 years, U.S. Geological Survey researcher Elizabeth Peacock, the study's lead author, said in a statement.

The bears choose this area because that is "where the sea is more resilient to summer melt due to circulation patterns, complex geography and cooler northern latitudes," Peacock said.

The Canadian Archipelago could serve as a future refuge for polar bears, who rely on Arctic ice to cross between land masses, to forage and to mate, according to the researchers.

Since 1979, the spatial extent of Arctic sea-ice in autumn has declined by over 9 percent per decade through 2010, the researchers said, adding that recent modelling predicts that nearly ice-free summers will characterize the Arctic before mid-century.