The study, published Wednesday in an online science journal, says climate change is on track to push the bears into dire straits throughout the region by the end of the century.
"Under business-as-usual climate projections, polar bears may face starvation and reproductive failure across the entire archipelago by the year 2100," it says.
Even co-author Andy Derocher, a polar bear expert at the University of Alberta who is no stranger to gloomy news, was taken aback by the results.
"I had hung my hopes on the idea that polar bears would persist out to the end of this century, allowing us to go into some sort of conservation mode," he said.
"But now, looking at this work and this modelling, it does not look very good. I'm not as optimistic as I used to be."
The paper, published in PLOS 1, uses the latest data to project what would happen to sea ice in the islands northwest of the Gulf of Boothia if global temperatures increased by 3.5 degrees Celsius. Derocher acknowledges that's a "severe" amount of warming, but it's a level the planet is on track for if significant measures to curb greenhouse gas emissions aren't enacted.
Such warming would lead to more and more years in which waters used by specific polar bear populations would be ice free for more than 180 days, the study says. That would mean more and more years in which the bears couldn't use the hunting platform they need to get their fat-rich seals for at least six months.
At 180 ice-free days, starvation would be likely to kill off between nine and 21 per cent of adult male bears, with females and cubs more vulnerable.
At the same time, the ice would be breaking up earlier and forming later, which would affect how successful females were in raising their cubs. Early breakup can cause reproductive failure in anywhere from half to all of pregnant sows.
Caught between increasingly frequent years of poor sea ice and increasingly poor birth rates, the bears would eventually be squeezed out, the report suggests.
"We find that sea ice conditions may become unsupportive of polar bear population persistence in the (Canadian Arctic archipelago) and its surroundings by the late 21st century."
The study adds urgency to efforts to fight climate change, said Paul Crowley of the World Wildlife Fund, which advocates the High Arctic be managed to give the bears the best chance at survival.
"This study is about business as usual," he said. "Let's hope the grand experiment of business as usual will stop soon.
"If we do have reduction of emissions by 2050, then we're looking at sea ice that could regrow and habitat that could bounce back."
He said that possibility adds importance to WWF's Arctic Home project, which promotes managing impacts of shipping lanes and resource development to protect bears.
"Having conservation in those areas while that transition happens and bottoms out could be even more important."
The study follows a series of similarly dispiriting surveys of two southern bear populations.
Bears in the southern Beaufort Sea area have declined to about 900 from about 1,600 between 2000 and 2010. Inuit and Cree hunters in the southern Hudson Bay area agreed recently to reduce their hunt quota over fears about the population's health.
"We're starting to see the edges fall away for polar bears," Derocher said.Suggest a correction