Arctic sea ice set to hit record low

By Mark Kinver
Environment reporter, BBC News

image captionArctic sea ice extent on 19 August 2012 (orange line shows the 1979-2000 median)

Arctic sea ice looks set to hit a record low by the end of the month, according to satellite data.

Scientists at the US National Snow and Ice Data Center said data showed that the sea ice extent was tracking below the previous record low, set in 2007.

Latest figures show that on 13 August ice extent was 483,000 sq km (186,000 sq miles) below the previous record low for the same date five years ago.

The ice is expected to continue melting until mid- to late September.

"A new daily record... would be likely by the end of August," the centre's lead scientist, Ted Scambos, told Reuters.

"Chances are it will cross the previous record while we are still in ice retreat."

'Rapid melt'

Sea ice extent refers to a measurement of the area of Arctic Ocean that contains at least some sea ice. Areas with less than 15% are considered by scientists to mark the ice edge.

In its latest summary, the centre said the average rate of ice loss since late June had been "rapid", with just over 100,000 sq km melting each day.

However, it added, the rate of loss doubled for a few days earlier this month during a major storm.

Responding to the latest update, Prof Seymour Laxon, professor of climate physics at University College London, said that he was not surprised that 2012 was set to deliver a record minimum.

image captionThe melt season is expected to continue until the second half of September

"We got very close to a record minimum last year," he told BBC News.

"The fact that Cryosat showed thinner ice last winter, it is not surprising to me that it looks like we will have a record minimum this year."

Cryosat is a radar spacecraft operated by the European Space Agency (Esa) that was launched in 2010 to monitor changes in the thickness and shape of polar ice.

Prof Laxon added that this year's projected record minimum could result in a change in projections of when the Arctic would be sea ice-free during summer months.

"The previous [Intergovernmental Panel on Climate Change] report (published in 2007) stated that the likely date for an ice-free Arctic in the summer - and definitions for this vary a bit - was 2100," he explained.

"When we had the 2007 minimum, that date was brought forward to 2030-2040.

"The fact that we look set to get another record ice minimum in such a short space of time means that the modellers may once again need to go and look at what their projections are telling them."

Arctic sea ice plays a key role in help keep polar regions cool and helps control the global climate system.

The white surface of the ice reflects about 80% of incident sunlight back into the atmosphere, or into space.

When the sea ice melts, it exposes more of the dark ocean surface, resulting in 90% of the sunlight being absorbed, which warms the Arctic ocean.

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