This year’s Arctic winter is the warmest on record as levels of sea ice hit record lows for the time of year, new US weather data has revealed.

“It’s just crazy, crazy stuff,” said Mark Serreze, director of the National Snow and Ice Data Center in Boulder, Colorado, who has been studying the Arctic since 1982. “These heat waves – I’ve never seen anything like this.”

The land weather station closest to the North Pole, at the tip of Greenland, spent more than 60 hours above freezing in February.

Scientists had seen the temperature rise above that level on twice before in previous Februarys and then extremely briefly.

Last month’s record-high temperatures have been more like those typical of May, said Ruth Mottram, a climate scientist at the Danish Meteorological Institute.

Of nearly three dozen different Arctic weather stations, 15 of them were at least 5.6C above normal for the winter.

“The extended warmth really has staggered all of us,” Ms Mottram said.

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This February, Arctic sea ice covered 5.4 million square miles, about 62,000 square miles smaller than last year’s record low, the ice data centre reported.

It was 521,000 square miles below the 30-year normal.

Sea ice is frozen ocean water that, in contrast to icebergs and glaciers, forms, grows and melts on the ocean. It is still growing, but “whatever we grow now is going to be thin stuff” that easily melts in the summer, Mr Serreze said.

Loss of Antarctic ice has soared by 75 per cent in just 10 years Show all 2 1 /2 Loss of Antarctic ice has soared by 75 per cent in just 10 years Loss of Antarctic ice has soared by 75 per cent in just 10 years The Lemaire Channel in the Antartic Peninsula David Tipling/Alamy Loss of Antarctic ice has soared by 75 per cent in just 10 years A satellite image of the surface of Antartica uses colours to show the differences in the speeds of flow of glaciers as they drain into the ocean. The pink and red areas show where the glaciers are moving fastest

Something similar has been noted in the Pacific with open water on the normally iced-up Bering Sea, said the data centre senior scientist Walt Meier. To be happening on opposite sides of the Arctic at the same time was unusual, he added.

“Climate change is the overriding thing,” Mr Meier said.