The Vanishing Arctic

One of the most memorable parts of Al Gore’s film 'An Inconvenient Truth' was the cartoon polar bear trying to climb on the last piece of sea-ice in the Arctic, failing, and despondently swimming off into the sunset. With scientists this week reporting that autumn Arctic sea-ice coverage reached a record low this year, Al Gore’s cartoon may not be as far-fetched as it seems.
Arctic sea ice during the 2007 melt season plummeted to the lowest levels since satellite measurements began in 1979. The average sea ice extent for the month of September was 4.28 million square kilometers, the lowest September on record, shattering the previous record for the month, set in 2005, by 23 percent. The September rate of sea ice decline since 1979 is now approximately 10 per cent per decade, or 72,000 square kilometers per year. Arctic sea ice receded so much that the fabled Northwest Passage completely opened for the first time in human memory. At current rates, the Arctic is expected to be entirely free of sea-ice in summer by 2030.

Factors that contributed to this extreme decline include the fact that the ice entered the warmer weather in an already weakened state. An unusual atmospheric pattern, with persistent high atmospheric pressures over the central Arctic Ocean and lower pressures over Siberia also pumped warm air into the region and helped push ice away from the shore.

ice-free Arctic would have dire ecological and economic effects. Already, Russia, Canada and other Arctic nations are limbering up to claim the oil wealth locked beneath the Arctic sea-ice and to assert ownership over the shipping channels opened up as the ice disappears. In August, the Russians planted a flag under the North Pole; the Canadians retaliated by sending their Prime Minister on a trip to the region. 25% of the world’s undiscovered oil and gas is believed to be located under the Arctic sea bed.

As the sea-ice disappears, open ocean is revealed. Dark-coloured water replacing pale-coloured ice has global consequences known as the albedo effect. Pale ice reflects incoming solar radiation and keeps the Arctic cool. Perennial sea-ice, which grows thicker each year, also acts as a blanket, insulating the air above the sea-ice from the ocean below it. When the sea-ice melts, the ocean revealed absorbs rather than reflects incoming radiation and heats the overlying air. As Arctic temperatures rise, more sea-ice melts, exposing yet more ocean.

Al Gore’s polar bear cartoon wouldn’t have been as cute if he’d shown the bear drowning or starving. Polar bears depend on Arctic sea-ice to reach their favoured prey, seals, and depend on seals to get them through a hungry summer. Although polar bears are strong swimmers, prolonged trips through open water in search of food exhaust them, and eventually cause them to drown. Polar bear populations are expected to decline by two-thirds by the middle of next century, as a result of the disappearing ice. Sad as that is these shocking results could mean those predictions are optimistic.

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