The ice cap at the North Pole measured 1.32 million square miles on Sunday. That's 18 percent smaller than the previous record of 1.61 million square miles set in 2007, according to the National Snow and Ice Data Center in Boulder, Colorado. Records go back to 1979 based on satellite tracking. Old records were smashed in a critical climate indicator showing an ever warming world.
"On top of that, we're smashing a record that smashed a record," said data center scientist Walt Meier. Sea ice shrank in 2007 to levels 22 percent below the previous record of 2005.
Ice in the Arctic melts in summer and grows in winter, and it started growing again on Monday. In the 1980s, Meier said, summer sea ice would cover an area slightly smaller than the mainland. U.S. Now it is about half that.
Man-made global warming has melted more sea ice and made it thinner over the last couple decades with it getting much more extreme this year, surprisingly so, said snow and ice data center director Mark Serreze.
"Recently the loss of summer ice has accelerated and the six lowest September ice extents have all been in the past six years," Serreze said. "I think that's quite remarkable."
Serreze said except for one strong storm that contributed to the ice loss, this summer melt was more from the steady effects of day-to-day global warming. But he and others say the polar regions are where the globe first sees the signs of climate change.
"Arctic sea ice is one of the most sensitive of nature's thermometers," said Jason Box, an Ohio State University polar researcher.
What happens in the Arctic changes climate all over the rest of the world, scientists have reported in studies.
The ice in the Arctic "essentially acts like an air conditioner by keeping things cooler," Meier said. And when sea ice melts more, it's like the air conditioner isn't running efficiently, he said.
Sea ice reflects more than 90 percent of the sun's heat off the Earth, but when it is replaced by the darker open ocean, more than half of the heat is absorbed into the water, Meier said.
The melting ice is also affecting the wildlife in the area. Scientists are concerned that Arctic-dwelling ringed seals, who usually need 8 inches of snow to create caves to keep their pups warm, won't have enough cover, LifeScience reported. Arctic ice isn't expected to form until later in the season, which means that even if there is supposed to be an increase in snowfall mid-Winter it might just fall directly into the sea. Scientists predict that during the 21st century ringed seals will lose about 70 percent of the area with enough snow to create their caves.
Scientists at the snow and ice data center said their computer models show an Arctic that would be essentially free of ice in the summer by 2050, but they add that current trends show ice melting faster than the computers are predicting.