An Arctic researcher says the permanent northern sea ice that usually survives the summer has all but disappeared.

David Barber of the University of Manitoba, who is one of Canada's top Arctic scientists, just returned from a research trip to the Beaufort Sea. He said his team was shocked by the state of the sea ice there.

Barber says the thick, multi-year ice that is home to polar bears has been replaced by "rotten" ice that is thin and flimsy.

He says researchers on the expedition watched a multi-year ice floe the size of Winnipeg break up before their eyes.

Experts around the world believed Arctic sea ice was recovering after satellite images showed it was expanding, but Barber says the satellites were misleading because the rotten ice looked sturdy on the surface.