Bears rely on sea ice as a hunting platform, waiting by holes in the ice for seals to come up for air.
But as the Arctic has warmed more than twice as fast as the rest of the world over the last three decades, that ice breaks up earlier after each winter and takes longer to form in autumn.
This year's sea ice formation has been particularly slow across the High Arctic due to warmer water temperatures and a record summer heatwave.
In the Hudson Bay area, bears are often staying up to four weeks longer on land than the four months or so they spent there in the 1980s. During that time, they fast and lose about 2 pounds of body fat daily.
"Bears here are not as big as they used to be in their overall frame," said Cassandra Debets, an Arctic ecologist at the University of Manitoba.
Because malnourished bears can experience reproductive failure, scientists have projected that polar bears could disappear from the Arctic almost entirely by 2100 as the sea ice continues to diminish with climate change, according to a study published in July in the journal Nature Climate Change.
Four of the 19 polar bear populations across the Arctic and sub-Arctic are already in decline, including the Western Hudson Bay bears, while the status of others remains unknown.
As the Churchill bears wait for the ice this year, one impatient juvenile male checked out the saltwater slush and then returned to the tundra.
Another young male munched on a pile of kelp - a sign of boredom, scientists say. It will be a few more days before the ice is thick enough for him to head out and hunt again.
