The breakup of the thickest ice in the Arctic will have a potentially catastrophic effect on polar bears and seals, leading scientists have warned.

Satellite images from the first week of August show sea ice along Greenland’s northern shores – some of the oldest and strongest in the Arctic – being broken up and pushed away from the coastline.

Described as the “last holdout” of the Arctic’s multi-year sea ice – that which remains frozen year after year even during the summer months – experts warned its breakup would increase the rate of melting across the continent.

The “highly unusual” phenomenon is the result of warmer temperatures making the sea ice in this region thinner. As a result, the ice is lighter and more fractured and winds blowing from the Atlantic to the Pacific side of the Arctic are able to shift it away from Greenland’s coastline.

“The fact that it has become mobile shows it is thinner than it used to be and this last holdout of heavy ice is now becoming as mobile as any other part of the arctic,” said Professor Peter Wadhams, one of the UK’s leading sea ice scientists who heads the Polar Ocean Physics Group at Cambridge University.

“In the past, most of the ice in the Arctic has been multi-year ice, but that has been shrinking and now nearly all the ice in the Arctic is first-year ice,” he told The Independent.

“The only zone where multi-year ice has survived is north of Greenland, but this last holdout is now opened up and moving away from the coast.”

He said it would have “serious” consequences for wildlife including polar bears, although the full extent of the damage would not be known until next spring when the animals emerge from hibernation.

“The north coast of Greenland, with its very steep cliffs, is a denning area for polar bears,” explained Prof Wadhams.

“They dig holes in the snow and come out in the spring and go hunting. But if the pack ice has moved offshore they come out hibernation and are left without an area to hunt.

“They can’t swim very far. If this becomes a permanent feature with ice away from the coast, polar bears won’t have any ice to hunt on. You would lose the polar bear habitat.”

The Arctic is warming twice as fast as the rest of the planet and this year sea ice in the region is 880,000 square kilometres below the 1981-2010 average.

Sea ice in July was “exceptionally” low in areas of the Arctic nearest the Atlantic, which includes the region north of Greenland, the UK Met Office said.

Professor Martin Siegert, codirector of the Grantham Institute for Climate Change and Environment at Imperial College London, warned the breakup of “really thick and strong” ice in this area was particularly alarming.

“This is not just breaking up of the annual stuff, but the multi-year ice, which is highly unusual,” he told The Independent.

Indigenous populations that require sea ice for traditional fishing methods would be affected, he added, as would seals and polar bears that use ice to access plentiful supplies of fish.

The US-based National Snow and Ice Data Centre said Arctic sea ice declined “rapidly” throughout July but the decline slowed during the first two weeks of August.

But satellite images of Greenland’s northern coastline showed sea ice in that area moving away from the land mass in the first six days of the month.

The centre predicts sea ice this year will fall to between the fourth and ninth lowest level in the 40 years since satellite records began, while 2012 saw Arctic sea ice retreat to its lowest level on record.

Nasa has launched a new mission to record the impact on the ocean around Greenland from its melting ice sheets.