An exceptionally rapid melt this summer has led to unusually high water temperatures in the Arctic Sea, slowing the progress of fresh ice formation

Residents of the Alaskan city of Barrow (due to change its name to Utqiaġvik on 1 December) would normally be looking out across a frozen harbour by now, but this year the sea is reluctant to freeze.

Barrow’s average temperature for October 2016 was a balmy -1C, significantly warmer than the long-term average of around -8C. And over the North Pole the air has been a full 10C warmer than average of late.

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Much of the reason for these warm temperatures and the sluggish rate of sea-ice formation is the exceptional summer sea-ice melt that occurred this year. By 10 September the National Snow and Ice Data Center reported that Arctic sea-ice had shrunk to an area of just 4.14m square kilometres – tying with 2007 for second lowest sea-ice extent on record, and some 740,000 square kilometres short of the record set in 2012.

The rapid melting of this ice earlier in the season gave plenty of time for the surface waters of the Beaufort, Chuckchi, Barents and Kara Seas to warm up, and it is these warm waters, combined with persistently warm dry weather blowing up from the south, that have boosted air temperatures and slowed the progress of fresh sea-ice formation.

Summer sea-ice has been diminishing for a number of years in this region now, and research recently published in Nature Climate Change indicates that this change may be responsible for shunting the Arctic polar vortex towards the Eurasian continent during winter. The resulting change in atmospheric circulation patterns may be causing a cooler end to winter over parts of the Eurasian and North American continents.