Grizzly bears are a subspecies of the brown bear (Ursus arctos).
Polar bears are a modified and highly specialized brown bear, and their exact species status is a little bit questionable. They can produce fertile hybrids with brown bears, and these hybrids are becoming more and more common. At least one second generation hybrid has been recorded in the wild.
If the sea ice disappears from the arctic ocean, the only future for the polar bear is to be reabsorbed into the more generalist brown bear populations.
