A polar bear travels submerged under water - a tactic often employed to surprise prey. As part of a fragile Arctic ecosystem, the bears are threatened by the recent dramatic reduction in ice cover. Sea ice - frozen seawater that moves with the ocean currents - provides an important habitat and resting place for many animals. The Artic ice cover reached a record low in 2007. Many attribute this situation to global warming.

Aware of the presence of polar bears, a ringed seal scans the horizon before catching a breath. (Bears grab seals from such ice holes.) Ice is the very essence of the ecosystem of the Artic. Sea ice - frozen seawater that moves with the ocean currents - provides an important habitat and resting place for many animals. In recent years satellite pictures show a dramatic reduction in Artic ice cover, which reached a record low in 2007. Many attribute the situation to global warming.

A bowhead whale cruises the ice edge. With life-spans of up to 200 years, bowheads are among the largest and longest-living animals on earth. They feed on minute creatures such as amphipods. Without ice, this food source will lose the surface on which they live out most of their life cycle, endangering the whales' survival. Ice is the very essence of the ecosystem of the Artic. Sea ice - frozen seawater that moves with the ocean currents - provides an important habitat and resting place for many animals. In recent years satellite pictures show a dramatic reduction in Artic ice cover, which reached a record low in 2007. Many attribute the situation to global warming.

Millions of amphipods swarm under the Arctic sea pack, where they feed on phytoplankton and other micro-organisms. The ice plays a key role in their life cycle, giving them place to feed, have their young, and shelter from strong currents. Animals such as bowhead whales, which can live for up to 200 years, feed on these minute creatures. Ice is the very essence of this ecosystem. Sea ice - frozen seawater that moves with the ocean currents - provides an important habitat and resting place for many animals. In recent years satellite pictures show a dramatic reduction in Artic ice cover, which reached a record low in 2007. Many attribute the situation to global warming.

A kittiwake glides over an iceberg. Fragments of glaciers, ice shelves and icebergs are floating oases for birds, seals and other wildlife. Ice is the very essence of the ecosystem of the Artic. Sea ice - frozen seawater that moves with the ocean currents - provides an important habitat and resting place for many animals. In recent years, satellite pictures have shown a dramatic reduction in Artic ice cover. In 2007, sea ice reached a record low, a situation which many attribute to global warming.

Channels of melt-water funnel into a seal's breathing hole.

In recent years, satellite pictures have shown a dramatic reduction in Arctic ice cover. In 2007, sea ice reached a record low, a situation which many attribute to global warming. Sea ice—frozen seawater that moves with the ocean currents—provides an important habitat and resting place for many animals. A polar bear's tracks cross melting snow. Ice is the very essence of the ecosystem of the Artic. In recent years satellite pictures show a dramatic reduction in Artic ice cover, which reached a record low in 2007. Many attribute the situation to global warming.

A seal freshly shot by an Inuit hunter bleeds on the sea ice. The seal is still alive, so the hunter has pulled it away from its breathing hole so that it cannot escape. Sea ice - frozen seawater that moves with the ocean currents - provides an important habitat and resting place for many animals. Inuit depend on sea ice in their traditional way of life, and complain that there is less of it than only a few years ago. In recent years satellite pictures show a dramatic reduction in Artic ice cover, which reached a record low in 2007. Many attribute the situation to global warming.

A female polar bear and her cub rest on an ice floe after a swim. The bears are not tied to a specific territory, but roam widely in their search for food, often leapfrogging from iceberg to iceberg. Bears fitted with satellite collars have been tracked on swims of up to 240km across open oceans. In some habitats, disappearing sea ice is forcing polar bears to make longer, riskier swims. Ice is the very essence of the ecosystem of the Artic. Sea ice - frozen seawater that moves with the ocean currents - provides an important habitat and resting place for many animals. In recent years satellite pictures show a dramatic reduction in Artic ice cover, which reached a record low in 2007. Many attribute the situation to global warming.

A dead bear lies on sea ice. The cause of death was not apparent, but with diminishing ice, bears have fewer platforms out at sea during their crucial feeding periods. Sea ice—frozen seawater that moves with the ocean currents—provides an important habitat and resting place for animals such as polar bears that hunt and roam there. Ice is the very essence of the ecosystem of the Artic. In recent years satellite pictures show a dramatic reduction in Artic ice cover, which reached a record low in 2007. Many attribute the situation to global warming.

A bear and a glaucous gull feed on the remains of a beluga whale. Probably a large bear had killed the whale and ate its fill, leaving the remains to this smaller one. Sea ice - frozen seawater that moves with the ocean currents - provides an important habitat and resting place for animals such as these. In recent years, satellite pictures have shown a dramatic reduction in Artic ice cover, which reached a record low in 2007. Many attribute the situation to global warming.

A bull walrus squats on a shelf of multi-year ice (ice which has survived at least two summers' melt) off Baffin Island. In recent years satellite pictures have shown a dramatic reduction in Arctic ice cover. In 2007, sea ice reached a record low, a situation which many attribute to global warming. Ice is the very essence of this ecosystem. Sea ice—frozen seawater that moves with the ocean currents—provides an important habitat and resting place for a variety of animals.

A polar bear's tracks cross melting snow. Sea ice - frozen seawater that moves with the ocean currents - provides an important habitat and resting place for animals such as polar bears that hunt and roam there. Ice is the very essence of the ecosystem of the Artic. In recent years satellite pictures show a dramatic reduction in Artic ice cover, which reached a record low in 2007. Many attribute the situation to global warming.

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