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It’s the end of the Arctic winter and there’s less sea ice than ever before—ice the size of three Californias is missing.

The Arctic is a big sea surrounded by land: Russia on one side and Canada, the US and Greenland on the other. In summer, in the middle of June, the sun stays pretty much fixed high in the sky. The ice melts back into the sea.

This is normal.

In winter, the opposite happens: sea water turns into sea ice. The Arctic ice cap stretches out to its maximum extent for the year. This year it reached 5.57 million square miles (14.42 million square kilometers), or 471,000 square miles (1.22 million square kilometers) less than the average since measurements began about 40 years ago.

This is not so normal.

“I have been looking at Arctic weather patterns for 35 years and have never seen anything close to what we’ve experienced these past two winters,” said Mark Serreze the director of the National Snow and Ice Data Center.

A record low maximum amount of sea ice doesn’t necessarily mean a record low minimum, given ice melts during the summer, said Walt Meier, a sea ice scientist at NASA’s Goddard Space Flight Center, “But it’s guaranteed to be below normal.”