Why don't polar bears move farther north to find ice?
Answered by Dr. Steven C. Amstrup, chief scientist at Polar Bears International and Polar Bear Project Leader at the U.S. Geological Survey for thirty years.
Q: Can't polar bears simply move north where the ice isn't melting? If not, why?
A: We expect polar bears to disappear from more southerly areas as sea ice there is not persistent for long enough to support them. Some of this disappearance will be due to starvation and some to migration of bears to higher latitudes and cooler conditions. But as the world continues to warm, all of the sea ice eventually will be gone and polar bears will have nowhere to go.
It's a law of physics that the world must warm as greenhouse gas concentrations rise. There will be no new stable state or new equilibrium unless we mitigate the rise of greenhouse gases. Hence, without such mitigation, polar bears will be expected to occur only in increasingly northerly climes until they ultimately wink out. Remember, too, there is only so far they can go. When the last vestiges of sea ice are gone, so will the polar bears be gone.
My work has shown conclusively that the only way to save the bears and their sea ice habitats is to control temperature rise through greenhouse gas mitigation. Nothing we can do on the ground will make a difference without such mitigation.