The Arctic lost nearly a quarter of its permanent sea ice cover over the past two winters, space scientists have revealed. The drastic 23 per cent reduction was the fastest ever on record and equivalent to losing an area the size of California and Texas combined.

It was measured by Nasa’s QuikScat satellite combined with observations made by the Arctic Buoy Programme. It leaves the total amount of Arctic ice at its smallest level ever.

A team led by Son Nghiem of Nasa’s Jet Propulsion Laboratory, in California, discovered the latest evidence of the effects of global warming.

The latest severe loss continues a trend of rapid decreases in perennial ice during the current decade, they will report in the journal Geophysical Research Letters this week.

QuikScat can identify and map different classes of sea ice, including older, thicker perennial ice and younger, thinner seasonal ice. The scientists observed less perennial ice cover in March 2007 than ever before, with the thick ice confined to the Arctic Ocean north of Canada.

Consequently, the Arctic Ocean was dominated by thinner seasonal ice that melts faster. This ice is more easily compressed and responds more quickly to being pushed out of the Arctic by winds.

Nghiem said: “Unusual atmospheric conditions set up wind patterns that compressed the sea ice, loaded it into the Transpolar Drift Stream and then sped its flow out of the Arctic.” When it reached warmer waters, it melted.

Our picture is a Nasa artist’s impression of QuikScat in orbit.

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