With the ice cover down to 14.52m sq km, scientists now believe the Arctic is locked onto a course of continually shrinking sea ice

Melting ice on the Chilkat river near Haines, Alaska, in January 2016. This winter scientists said the Arctic freeze stalled early on, across the polar seas. Photograph: Michele Cornelius/Alamy

A record expanse of Arctic sea never froze over this winter and remained open water as a season of freakishly high temperatures produced deep — and likely irreversible — changes on the far north.

Scientists at the National Snow and Ice Data Centre said on Monday that the sea ice cover attained an average maximum extent of 14.52m sq km (5.607m sq miles) on 24 March, the lowest winter maximum since records began in 1979.

The low beats a record set only last year of 14.54m sq km (5.612m sq miles), reached on 25 February 2015. ...

... The extent of ice cover is a critical indicator of the changes taking place in the Arctic — but the shrinking of the polar ice carries sweeping consequences for lower latitudes as well.

The bright white snow-covered ice reflects about 85% of sunlight back into the atmosphere, compared to the dark surfaces of the open water which absorb most of the heat energy.

"Basically the polar regions are the refrigerator for the Earth," said Dr Donald Perovich, a researcher at Dartmouth. "They are extremely important for being able to keep the Arctic colder, and in turn help keep the rest of the planet colder."

Since 1980, however, the summer sea ice cover over the Arctic has gone into a drastic decline, from 7.8m sq km to 4.4m sq km in 2012, before rebounding slightly. "It would be as if the entire United States east of the Mississippi melted away plus the states from Minnesota down to Louisiana, past North Dakota, South Dakota, Nebraska, Kansas and Oklahoma. It’s huge," Perovich said.