Washington: Sea ice covering the Arctic has shrunk to its smallest size ever observed in the three decades since consistent satellite observations of the polar cap began, according to NASA scientists.

The extent of Arctic sea ice on Aug 26 was 4.1 million square km or 70,000 square km below what was almost five years ago on Sep 18, 2007, when daily extent of 4.17 million square km was measured.

The area was measured by the special sensor imager on the US Defence Meteorological Satellite Programme spacecraft and analysed by NASA and National Snow and Ice Data Centre (NSIDC) scientists.

The sea ice cap naturally grows during the cold Arctic winters and shrinks when temperatures mount in the spring and summer. But over the last three decades, satellites have observed a 13 percent decline per decade in the minimum summertime extent of the sea ice.

The thickness of the sea ice cover also continues to decline, according to a NASA statement.

"The persistent loss of perennial ice cover - ice that survives the melt season - led to this year's record summertime retreat," said Joey Comiso, senior research scientist at NASA's Goddard Space Flight Center in Greenbelt.

He added: "Unlike 2007, temperatures were not unusually warm in the Arctic this summer."

The new record was reached before the end of the melt season in the Arctic, which usually takes place in mid- to late September. Scientists expect to see an even larger loss of sea ice in coming weeks."In 2007, it was actually much warmer," Comiso said.

"We are losing the thick component of the ice cover. And if you lose the thick component of the ice cover, the ice in the summer becomes very vulnerable."

"By itself it's just a number, and occasionally records are going to get set," NSIDC research scientist Walt Meier said about the new record.

"But in the context of what's happened in the last several years and throughout the satellite record, it's an indication that the Arctic sea ice cover is fundamentally changing."


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