کد خبر: 155000تاریخ: 1395/4/25 15:12
Arctic sea ice at record low in June
Arctic sea ice at record low in June
Sea ice cover in the Arctic beat a hasty retreat throughout June, reaching record-breaking levels by month's end.

Data published by the US National Snow and Ice Data Center last week showed average sea ice extent for June was 100,000 square miles smaller than in 2010, the year of the previous June record, UPI reported.

Almost every month this year has set new record lows for sea ice extent.

March, however, was the second-lowest, slightly greater than 2015. The average sea ice extent for June was 4.09 million square miles.

"In 30 years, the area has shrunk approximately by half. There doesn't seem to be anything able to stop this trend," said Christian Haas, an Arctic sea ice geophysicist at York University, Toronto.

As the sea ice melts, the ocean loses its reflective cover, allowing it to absorb more solar heat and causing the water to warm.

This contributes to warmer air temperatures and more sea ice melt.

Ice cover disappeared relatively slowly in early June, following a change in atmospheric circulation.

The high surface pressure that had been over the Arctic Ocean for much of the year shifted to one of low pressure, ushering in more cloud cover.

In addition to reducing the amount of sunlight that reaches the ice, the clouds also summoned below-average air temperatures in the Beaufort Sea area.

Despite this, there was more open water than average in the Beaufort Sea in June, as well as in the Kara and Barents Sea, the NSIDC said. Ocean currents and wind also affect the state of the sea ice, said Haas.

During late April and early May, NASA's Operation Ice Bridge flew aircraft missions to estimate the sea ice thickness between Alaska and the North Pole. It found the first-year ice was generally thinner than typical at the end of the winter, which was consistent with the very high temperatures seen this past winter.

Haas' own studies measuring ice thickness in the Beaufort Sea in April found similar results, using a different technique.

"The first year is more than 50 percent thinner than usual, but the multiyear ice hasn't changed," he said.

Scientists at the University of Washington tallied the volume of Arctic sea ice floating in the ocean.

By their estimates, the total mass of Arctic sea ice is at its second-lowest recorded volume for the beginning of July.

Climate scientist Ed Hawkins, from the University of Reading in the UK, depicted the decline in sea ice volume between 1979 and 2016 in a spiral graphic similar to the one he created earlier in the year for global temperatures.

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