Is Global Warming Killing the Polar Bears?

It may be the latest evidence of global warming: Polar bears are drowning.

Scientists for the first time have documented multiple deaths of polar bears off Alaska, where they likely drowned after swimming long distances in the ocean amid the melting of the Arctic ice shelf. The bears spend most of their time hunting and raising their young on ice floes.

In a quarter-century of aerial surveys of the Alaskan coastline before 2004, researchers from the U.S. Minerals Management Service said they typically spotted a lone polar bear swimming in the ocean far from ice about once every two years. Polar-bear drownings were so rare that they have never been documented in the surveys.

But in September 2004, when the polar ice cap had retreated a record 160 miles north of the northern coast of Alaska, researchers counted 10 polar bears swimming as far as 60 miles offshore. Polar bears can swim long distances but have evolved to mainly swim between sheets of ice, scientists say.

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