Arctic lost part of its perennial sea ice in 2005: NASA

Global warming may already be having an effect on the Arctic, says NASA in a recent study.

Global warming may already be having an effect on the Arctic, says NASA in a recent study. The US space agency found that in 2005, the Arctic replaced only a little of the thick sea ice it loses and usually replenishes annually.

NASA scientists used satellite images to analyse six annual cycles of Arctic sea ice from 2000 to 2006.

Sea ice is essential to maintaining and stabilising the Arctic’s ice cover during its warmer summer months. But “recent studies indicate Arctic perennial ice is declining seven to 10 per cent each decade,” said Ron Kwok from NASA’s Jet Propulsion Laboratory in Pasadena, California.

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“Our study gives the first reliable estimates of how perennial ice replenishment varies each year at the end of the summer,” he said yesterday. “The amount of first-year ice that survives the summer directly influences how thick the ice cover will be at the start of the next melt season.”

The team observed that only 4 per cent, which means about 2.5 million square km of thin ice survived the 2005 summer melt to replenish the perennial cover.

This was the weakest ice cover since 2000, and so here was 14 per cent less permanent ice cover in January 2006 than in the corresponding period the year before.

“The winters and summers before fall 2005 were unusually warm,” Kwok said. “The low replenishment seen in 2005 is potentially a cumulative effect of these trends.”

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Records dating back to 1958 have shown a gradual warming of Arctic temperatures which speeded up in the 1980s.