Kaktovik, Alaska -- The two shaggy polar bears gnawed on shreds of meat hanging off the carcass of a bowhead whale. They planted their flat furry feet on pieces of blubber and ripped off strips of the rubbery fat with their teeth.
Up onto the spit of sand on Barter Island came two more, A Warming World
Part One: Alarm at the arctic
Part Two: Seashore sea change
Part Three: A way of life threatened
Audio slide show, first part
Audio slide show, second part
a mother and cub rising from the slate-gray Beaufort Sea. They shook off sheets of water and sauntered over to share the feast, greeting the others with a touch of shiny black noses.
Humans don't often see these luminous bears in the wild. They are not land animals, and live nearly all their lives on the vast floating sea ice within the Arctic Circle.
Soon they may not be seen at all. The top of the world is ground zero for global warming, the first part of Earth to show dramatic effects from the heating of the atmosphere and oceans. The bears' frozen habitat is rapidly shrinking.
If a warming world melts nearly all sea ice during summers, as computer models predict will happen by the end of the century, scientists warn that the polar bear is unlikely to survive as a species.
To those who come to watch the scavenging bears on this sand spit, on the edge of the Inupiat Eskimo village of Kaktovik, their growing numbers on land are one more sign that a way of life thousands of years old is melting away.
When polar bears turn up on land, scientists think, it means the sea ice -- their home and hunting ground -- has retreated so far from the shore and its rich coastal waters that they can't find their main prey, ringed and bearded seals.
In the past, as part of the sea ice's yearly short-term melt, there would be open water for only a few weeks. Now the ice breaks up earlier each spring, and the ocean freezes over later each fall. The bears that swim to land must stay there longer, for as long as five or six weeks, where they basically fast because food is scarce on land -- even with the whale carcasses, which Inupiat whaling crews leave on the spit each September after butchering their catch.
As the ice recedes farther each summer and fall, greater numbers of bears swim the 100 or more miles of open water to reach land. There they stay until the ice returns.
The Inupiats see evidence of warming all around them.
Longtime fishing camps are under water. The coastline is eroding. Unfamiliar species of fish are caught in their nets. And the ice that defined their lives is disappearing.
In years past, as migrating whales swam close enough to hunt in September, the open water was already freezing up. Whaling crews scouted the sea by climbing icebergs. The bergs also calmed the sea swells.
"Now it takes longer for the ocean to freeze up,'' and at the whale hunt