Arctic ice melting to a record low, scientists warn

Global warming and a huge storm are blamed for the fastest decrease in sea coverage ever seen

The area of the Arctic Ocean covered by floating sea ice is likely to hit a record low next week, with the melting due to continue well into September, according to researchers monitoring the region by satellite.

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Arctic sea ice partially melts each summer and reforms again in the winter, but over the past 35 years of satellite readings the summer retreat has been getting significantly greater, with a record summer minimum recorded in September 2007.

However, scientists at the US National Snow and Ice Data Centre (NSIDC) in Boulder, Colorado, said that this summer's melt season in the Arctic has been so rapid and extensive that 2012 will almost certainly see sea ice coverage reach a new low.

"A new daily record... would be likely by the end of August… Chances are it will cross the previous record while we're still in sea ice retreat," Ted Scambos, a sea-ice specialist at the centre told Reuters. "What you're seeing is more open ocean than you're seeing ice… It just simply doesn't look like what a polar scientist expects the Arctic to look like. It's wide open and the [ice] cap is very small."

The Arctic has seen some of the greatest increases in average temperatures over recent decades due to global warming, resulting in a significant retreat of the sea ice both in terms of surface area and ice thickness, scientists say. "Everything about this points in the same direction – we've made the Earth warmer," Dr Scambos said.

Computer models initially suggested that the Arctic could be completely ice free in summer by the end of the 21st century, but more recent studies suggest that ice-free summers could occur as early as 2035, and possibly even within the next 10 years.

The satellite data analysed by NSIDC looks only at surface area coverage, rather than ice thickness, and the scientists judge that an area is "ice free" when the coverage of the sea surface falls below 15 per cent.

However, other satellite studies using data from the European Cryosat-2, which is able to measure sea ice thickness, have found that the loss of sea ice volume in the Arctic may be 50 per cent greater than previously suspected.

By mid-August, the surface area of sea ice had dipped below that for 2007 and was already among the four lowest for the time of year since satellite records began in the late 1970s.

The sea ice melted particularly rapidly between 4 August and 8 August, which coincided with an intense storm over the central Arctic Ocean. Strong winds associated with the storm could have helped to break up the ice, although scientists could not say whether this had prompted this month's rapid loss of ice.

Dr Scambos said that the speed of melting in recent weeks has been one of the fastest on record for this time of the year. "I doubt there's been another year that had as rapid an early August retreat," he said.

The retreat of the sea ice has led to the possible opening of both sea routes around the Arctic – the Northwest Passage of Canada and the Northern Sea Route across northern Russia.