Arctic ice hits sixth lowest record as summer draws to a close

US National Snow and Ice Data Center says this year’s sea ice figures are in line with overall warming trend

By Sophie Yeo

The Arctic’s summer sea ice coverage in 2013 fell to a yearly minimum of a little over five million square kilometres, the sixth lowest extent on record.

While there is significantly more ice than last year, when it reached a record low of 3.41 million square kilometres, this year’s figure remains consistent with a broader trend of overall shrinking, suggesting that the days of an ice-free ocean during the summer  are drawing closer.

“This is substantially more ice than observed on the same date last year,” said the National Snow and Ice Data Center (NSIDC), based in Colorado, US, “yet sea ice extent remains quite low compared to the long-term 1981 to 2010 average.”

The extent of the Arctic summer sea ice is keenly observed each year, as it is a key indicator of climate change and global warming.

Over the last thirty years, scientists have observed a decline in the extent of the summer sea ice, with the Arctic having lost about 40% of its cover since 1980.

But the thickness is also declining, meaning that the overall volume of the sea ice is even lower than the declining area of coverage alone would suggest.

Sea ice minimums are based on a five-day average, and the NSIDC is expected to officially confirm this year’s extent in the next couple of days.

A recent spate of articles in the Telegraph and the Daily Mail have picked up on the increase of this year’s Arctic ice based on last year’s record, but NSIDC says this is not surprising.

“Climate models consistently project that there will be large variations in summer ice extent from year to year,” it says.

“A cool summer can help to retain a thin layer of ice, increasing the overall ice extent. Conversely, a warm summer can help to remove much of the thin ice cover.”

This year, they report, saw a cool summer, but ice loss proceeded to accelerate through the first two weeks of September, when air temperatures were 1-3C higher than average over much of the Arctic Ocean.